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1 The Journal of
ARACHNOLOGY
OFFICIAL ORGAN OF THE AMERICAN ARACHNOLOGICAL SOCIETY
VOLUME 18
SUMMER 1990
NUMBER 1
THE JOURNAL OF ARACHNOLOGY
EDITOR: James E. Carico, Lynchburg College ASSOCIATE EDITOR: Gary L. Miller, The University of Mississippi EDITORIAL BOARD: J. E. Carrel, University of Missouri; J. A. Coddington, National Museum of Natural History, Smithsonian Institution; J. C. Cokendolpher, Texas Tech University; F. A. Coyle, Western Carolina University; C. D. Dondale, Agriculture Canada; W. G. Eberhard, Universidad de Costa Rica; M. E. Galiano, Museo Argentino de Ciencias Naturales; M. H. Greenstone, BCIRL, Columbia, Missouri; N. V. Horner, Midwestern State University; D. T. Jennings, NEFES, Morgantown, West Virginia; V. F. Lee, California Academy of Sciences; H. W. Levi, Harvard University; E. A.
Maury, Museo Argentino de Ciencias Naturales; N. I. Platnick, American Museum of Natural History; G. A. Polis, Vanderbilt University; S. E.
Riechert, University of Tennessee; A. L. Rypstra, Miami University, Ohio; M. H. Robinson, U.S. National Zoological Park; W. A. Shear, Hampden-Sydney College; G. W. Uetz, University of Cincinnati; C. E. Valerio, Universidad de Costa Rica.
THE JOURNAL OF ARACHNOLOGY (ISSN 0161-8202) is published in Spring, Summer, and Fall by The American Arachnological Society at Texas Tech Press.
Individual subscriptions, which include membership in the Society, are $30.00 for regular members, $20.00 for student members. Institutional subscriptions to The Journal of Arachnology are $70.00. Correspondence concerning subscriptions and memberships should be addressed to the Membership Secretary (see back inside cover). Remittances should be made payable to The American Arachnological Society. Inquiries about availability and current prices of back issues should be sent to Dr. Susan E. Riechert, Department of Zoology, University of Tennessee, Knoxville, TN 37916 USA. Correspondence concerning undelivered issues should be addressed to PrinTech, Texas Tech University, Lubbock, Texas 79409 USA.
Change of address notices must be sent to the Membership Secretary.
Detailed instructions for the preparation of manuscripts appear in the Fall issue of each year, and can also be obtained from the Editor and the Associate Editor. Manuscripts that do not follow those instructions will be returned to the author(s) without benefit of review. Manuscripts and all related correspondence must be sent to Dr. Gary L. Miller, Associate Editor, Biology/ The University of Mississippi, University, Mississippi 38677 USA.
PROOFS, REPRINTS, and CHARGES: Authors will receive a reprint order form along with their proofs. Reprints are billed at the printer’s current schedule of costs. All authors will be billed by The American Arachnological Society for page charges. The charge per journal page will be assessed as follows: $50.00- nonmembers; $45. 00-members acknowledging grant, institutional, or other support; $25.00-full members who do not have support; $20.00-student members who do not coauthor with full members and who do not acknowledge support.
This publication is printed on acid-free paper.
Young, O. P. and G. B. Edwards. 1990. Spiders in United States field crops and their potential effect on crop pests. J. Arachnol., 18:1-27.
SPIDERS IN UNITED STATES FIELD CROPS AND THEIR POTENTIAL EFFECT ON CROP PESTS
O. P. Young1
Southern Field Crop Insect Management Laboratory USDA-ARS, P. O. Box 346 Stoneville, Mississippi 38776 USA
G. B. Edwards
Florida State Collection of Arthropods Division of Plant Industry Fla. Dept. Agric. & Cons. Serv.
P. O. Box 1269
Gainesville, Florida 32602 USA
ABSTRACT
An analysis of 29 faunal surveys of spiders found in nine field crops in the United States indicates the presence of 614 species in 192 genera and 26 families. These species represent 19% of the ca. 3311 species occurring in North America. Five families included 61% of the species reported in field crops: Salticidae (89 spp.), Linyphiidae (78), Araneidae (77), Theridiidae (64), and Lycosidae (62). Considerably more species have been observed in cotton (308 spp.), soybean (262), and alfalfa (233) than in guar (52), rice (75), and grain sorghum (88). Intermediate numbers of species have been observed in peanuts (131), corn (136), and sugarcane (137). The North American spider fauna is estimated at the species level to be 59% web-spinners and 41% wanderers, while those reported from field crops are estimated to be 44% web-spinners and 56% wanderers. These differences may be attributable to guild characteristics associated with dispersal and ability to survive in disturbed habitats. The 42 most frequently occurring spider species were considered in detail and demonstrated that the active wandering guild comprised the largest portion (45%) of this group. Orb-web (21%), sheet- web (19%), ambush-wander (10%), and web-matrix (5%) spiders represented other guilds. The most frequently occurring species in field crops were Oxyopes salticus Hentz (Oxyopidae), Phidippus audax (Hentz) (Salticidae), and Tetragnatha laboriosa Hentz (Araneidae). These three species are prime candidates for augmentation and conservation in field crops or in adjacent habitats as part of a strategy to increase predation on crop pests.
INTRODUCTION
As recently as 1984, a review of spiders as biocontrol agents was able to lament the current failure to consider the potential of spiders in insect suppression programs (Riechert and Lockley 1984). This same review pointed out that generalist predators such as spiders can in certain situations limit exponential increases in insect populations in both natural and agricultural systems. A more recent review of an abundant spider in agroecosystems, Oxyopes salticus Hentz, indicated the considerable potential of this species for suppressing insect pest
'Current address: USDA-APHIS-BBEP, 6505 Belcrest Road, Hyattsville, MD 20782 USA.
2
THE JOURNAL OF ARACHNOLOGY
populations in agroecosystems (Young and Lockley 1985). These reviews and others increasingly point to the importance of spiders as part of a strategy of Integrated Pest Management.
Any investigator, however, who wishes to examine the spider fauna in a field crop faces an immediate problem. The identification of species ia a tortuous process for the novice, and may be close to impossible for many taxonomic groups and for immature spiders. There is no single reference available to identify the approximately 3311 species in North America, and only one regional work (New England) attempts to provide identification aids for all resident species (Kaston 1981). The approximately 470 genera of spiders in North America can be identified with the aid of Roth (1985). The most commonly used North American identification manual for novices considers only 223 genera and, though presenting generalized descriptions of many species, contains no species-level keys (Kaston 1978). Thus the identification of spiders must be performed by (1) use of generic revisions of a highly technical nature, many of which are outdated, (2) comparison with reference collections, most of which are at major urban museums and relatively inaccessible to the agricultural researcher, and (3) consultation with an expert in spider taxonomy, the number of which may be less than 20 in the United States and Canada. Several of these experts are retired or nearly so; all are overworked and reluctant to process large lots of specimens. These factors alone may have discouraged past research in the spider fauna in agroecosystems; they continue to be impediments to present and future research. In this regard it is noteworthy that two agricultural research groups in the United States that actively publish surveys of field-crop spiders are fortunate to have in- house taxonomic expertise (i.e., Dean and Eger 1986, Lockley and Young 1986).
We have failed to detect significant movement in the last 10 years toward implementation of any pest suppression strategy in the United States that specifically includes spiders as part of the suppression strategy, though the TEXCIM model for cotton fleahopper -Heliothis suppression may be a recent exception (Hartstack and Sterling 1988). One possible reason for the slow progress may be due to minimal knowledge concerning the species composition, densities, and distribution of spiders in field crops. In an attempt to facilitate the use of spiders in insect suppression strategies, we here summarize 29 faunal surveys of spiders found in field crops of the United States. We further evaluate the quality of the data base, analyze and interpret the data, and suggest directions for future research.
MATERIALS AND METHODS
The entomological-araneological literature was searched for surveys of spiders in North American field crops. We restricted the database to surveys that included the following information: (1) majority of spiders identified to species, (2) degree of sampling effort specified, (3) method and diel period of sampling specified, and (4) degree of taxonomic assistance indicated. Information from items 2-4 was coded (Table 1) and placed as an annotation after each survey citation (Appendix 2). This format provided criteria to evaluate survey quality.
The nomenclatural problems associated with such a compilation from 29 different sources were particularly difficult to overcome. Many surveys contained
YOUNG & EDWARDS— FIELD CROP SPIDERS
3
Table 1. — Summary of sampling methodologies utilized in 29 field-crop surveys of spiders. Values represent descriptive statistics or number in each category.
A. Number of years of sampling
Range 1-10 Mean 2.7 Mode 1,3
B. Maximum number of months sampled
within a year Range 3-12 Mean 6.2 Mode 4 Not indicated 4
C. Did sampling period
1. Dirunal 29
2. Nocturnal 6
D. Maximum no. fields sampled/ month
Range 1-40 Mean 8.8
Mode 3 Below mean 18 Not indicated 3
E. Methods of sampling
1. Sweep 20
2. Vacuum 1 1
3. Pitfall 18
4. Hand 16
5. Berlese 3
6. Dip net 1
7. Shake-cloth 7
F. Acknowledgment of taxonomic
assistance
1. Yes 17
2. No 12
species names that: (1) recently had been split into several species, or combined with another species name, (2) were no longer valid, (3) belonged in a different family or genus, or (4) were probable misidentifications. The resultant species list is our best estimate of the correct names and placement of species. We followed Roth (1985) as the most current source of information on placement and acceptability of familial and generic names.
RESULTS AND DISCUSSION
Limitations of the data. — Most surveys of arthropods in field crops usually focus on a particular pest or group of pests (e.g., Scott et al. 1983a). When non- pest arthropods are collected they are typically recorded as “beneficials”, or the most common ones may be determined to species (e.g., Scott et al. 1983b; Parencia et al. 1980). This usually is not the case for spiders, which unfortunately are often lumped together into one group (e.g., Smith et al. 1976), or at best subdivided into functional groups (e.g., Lockley et al. 1979). Such generalized categorizations may be due to the identification problems previously mentioned and to the fact that arachnologists typically have not conducted faunal surveys in field crops, preferring more undisturbed areas where spider populations are usually larger and more diverse. The net result is a paucity of information about spiders associated with field crops. Nevertheless, we obtained copies of 29 surveys of field-crop spiders that met our criteria for inclusion. Only 12 of these surveys were published in refereed journals; the remainder appeared in state scientific societal or agricultural experiment station publications (12), or as unpublished theses and dissertations (5).
Assessing the quality of the 29 manuscripts utilized in one analysis was difficult, because established criteria for determination of quality were unavail- able. Six parameters were chosen that we believe should be included when a faunal survey is published: (1) number of years of sampling, (2) maximum number of months sampled within a year, (3) diel sampling period, (4) maximum number of fields sampled per month, (5) method of sampling, and (6)
4
THE JOURNAL OF ARACHNOLOGY
acknowledgement of taxonomic assistance. We then tabulated the manuscripts within categories of each parameter (Table 1).
One survey was conducted over a ten-year period, another over six, whereas 22 surveys lasted three years or less. Surveys <3 years are not likely to demonstrate long-term trends, but should be sufficient to detect most species in an area. Although several surveys were conducted over an entire 12-month period each year, a majority (17) lasted for only 3-6 months. In some cases this short time represented the life-span of the crop, though usually survey duration coincided with the period of crop maturity or with peak arthropod abundance. The number of different sites (fields) sampled each month ranged from 1 to 40; half the surveys included four or fewer sample sites. Small sample sizes may not detect variability within and among sites and may distort the relationship of single-site abnormalities to other more typical sites.
Considerable variability was apparent in the importance that investigators placed on sampling effort and the methods employed; some surveys even failed to mention sampling effort. Most surveys utilized a variety of collection methods, though five surveys used only one method. When methods to obtain both foliage- and ground-dwelling spiders were employed, total number of species obtained were higher than in single-strata surveys. Only six collection programs included methods that specifically obtained nocturnal specimens, though 18 programs included a method (pitfall) that collected ground-dwelling forms both day and night.
Twelve surveys failed to acknowledge taxonomic assistance from specialists. Given the aforementioned difficulties in spider identification, the likelihood that a non-specialist could correctly identify all specimens obtained in a faunal survey is indeed remote. Finally, the variability in methodologies among the 29 surveys is probably less than that of faunistic surveys of spiders in nonagricultural habitats (see review in Young et al., 1989). We conclude that a hypothetical “high quality” survey would employ several collection methods to sample both foliage- and ground-dwelling spiders, day and night, 12 months of the year, for 3-5 years, and at ten or more locations.
Spider fauna of nine agroecosystems. — Faunal surveys were obtained for nine crop systems in the United States, though not all systems were equally surveyed (Appendix 1). Grain sorghum, guar, and peanuts were surveyed only once, whereas multiple surveys were obtained for rice (2), sugarcane (2), corn (2), alfalfa (4), cotton (7), and soybean (9). Species richness of spiders among the nine crop systems can be grouped into three levels. Cotton contained the most species (< 308), with soybean (< 262) and alfalfa (< 233) in the same high diversity group. Guar (< 52), rice (< 75), and grain sorghum (< 88) comprised the group with the lowest number of species. An intermediate group was represented by peanuts (< 131), corn (< 136), and sugarcane (< 137). The wide disparity in numbers of spider species that occur in these crop systems can be attributed to several factors. Those crops surveyed most frequently had the most species, which suggests sampling bias. A more likely explanation, however, involves the structural complexity of plants. The nine crop plants can be separated into two groups based on growth form: (1) multiple-branching dicotyledonous forms include alfalfa, soybean, cotton, peanuts, and guar; and (2) simple-branching monocotyledonous forms include rice, grain sorghum, sugarcane, and corn. Given the known positive correlation between plant structural complexity and numbers
YOUNG & EDWARDS— FIELD CROP SPIDERS
5
of associated spiders (Greenstone 1984; Hatley and MacMahon 1980; Uetz 1976), it is not surprising that cotton, for instance, supports many more spider species than rice. Two apparent exceptions to this trend, guar and peanut, may be due to minimal sampling effort.
Considering all field-crop systems as a whole, the spider community is dominated by only a few of the 48 families that occur in all North American habitats. Species of 26 families occur in field crops; 5 families contained 61% of the total field -crop species — Salticidae (89 spp.), Linyphiidae (78), Araneidae (77), Theridiidae (64), Lycosidae (62). Conversely, 6 families were represented by only 1 species. Several genera were represented by large numbers of species in field crops —Theridion (19 spp.), Lycosa (17), Xysticus (16), Dictyna (15), Phidippus (14). However, of the 192 genera recorded from field crops, 105 were represented by only 1 species (Table 2).
Relation of crop fauna to North American fauna. — Millions of acres annually in North America are occupied by various crop systems. About 22% of the land in the United States is devoted to cropland, with another 8% covered by roads, parking lots, houses, factories, and other structures (Anon. 1987). The remaining 70% is comprised of pastures, rangeland, forests, and margins; these are the sources of spider immigrants to field crops. About 3311 species of spiders in 470 genera and 48 families are found in North America (Roth 1985) (Table 2). Fifty- four percent of the families, 41% of the genera, and 19% of the species also occur in field crops. At least one exhaustive field survey of the spiders of an entire county indicates that these values for North America may be representative of much smaller areas, as 19% of the species collected in Washington Co., Mississippi, also occurred in field crops (Young et al 1989).
The ten largest families of spiders in North America comprise 84% of the total number of species. Some of these families, however, are poorly represented in field crops (Table 2). Only 7% of the 252 agelenid species are associated with field crops; likewise 9% of the 845 linyphiid species and 11% of the 159 dictynid species occur in field crops. Conversely, several families are well represented in field crops, e.g., 40% of the 192 araneid species, 31% of the 288 salticid species, and 31% of the 128 thomisid species. Several factors may account for these considerable differences between families. The most difficult spiders to identify are the small-sized species of Linyphiidae. Some faunal surveys avoid this problem by assigning linyphiids to one undifferentiated category, i.e., Erigoninae. Thus, many more species of Linyphiidae likely occur in field crops than are recognized or reported, particularly given their strong aerial dispersal characteristics (Greenstone et al. 1987). Conversely, three of the taxonomically better known spider families - Araneidae, Thomisidae, and Salticidae - are well represented in field crops and known to be strong aerial or ground dispersers (Greenstone et al. 1987; Young, unpubl. data).
One might expect a larger percentage of the total North American spider fauna to occur in field crops. That such apparently is not so suggests that a selection process is occurring, where only certain spider characteristics lead to increased likelihood of occurrence in field crops. These characteristics probably are associated with dispersal and subsequent survival in a highly disturbed and sometimes noxious environment.
Prey-capturing guilds. — Functionally, spider families can be categorized on the basis of prey capture method, e.g., web-spinning or wandering species (Table 2).
6
THE JOURNAL OF ARACHNOLOGY
Table 2. — Proportions of genera and species of North American spiders that occur in field crops, a = genera and species data from Roth (1985), b = data from Gertsch (1979), Comstock (1940). Percentages in parentheses.
|
Araneomorphae Family |
Genera |
Species |
Prey-capture technique15 |
||||
|
N. A.a |
Field crops |
(%) |
N. A.a |
Field crops |
(%) |
||
|
Agelenidae |
25 |
6 |
(24) |
252 |
17 |
(6.7) |
Web-Sheet |
|
Amaurobiidae |
8 |
1 |
(12.5) |
82 |
1 |
(1.2) |
Web-Sheet |
|
Anapidae |
1 |
0 |
1 |
0 |
Web-Orb |
||
|
Anyphaenidae |
5 |
5 |
(100) |
37 |
13 |
(35.1) |
Wand-Active |
|
Aphantochilidae |
1 |
0 |
1 |
0 |
Wand-Ambush |
||
|
Araneidae |
42 |
30 |
(71.4) |
192 |
77 |
(40.1) |
Web-Orb |
|
Caponiidae |
2 |
0 |
3 |
0 |
Wand-Active |
||
|
Clubionidae |
20 |
11 |
(55) |
193 |
47 |
(24.4) |
Wand-Active |
|
Ctenidae |
3 |
0 |
5 |
0 |
Wand-Active |
||
|
Desidae |
1 |
0 |
1 |
0 |
Web-Sheet |
||
|
Dictynidae |
9 |
3 |
(33.3) |
159 |
18 |
(11.3) |
Web-Sheet |
|
Diguetidae |
1 |
0 |
6 |
0 |
Web-Matrix |
||
|
Dinopidae |
1 |
0 |
1 |
0 |
Web-Orb |
||
|
Dysderidae |
3 |
2 |
(66.7) |
7 |
2 |
(28.6) |
Wand-Active |
|
Filistatidae |
3 |
1 |
(33.3) |
13 |
1 |
(7.6) |
Web-Sheet |
|
Gnaphosidae |
24 |
12 |
(50) |
248 |
38 |
(15.3) |
Wand-Active |
|
Hahniidae |
3 |
1 |
(33.3) |
19 |
4 |
(21.1) |
Web-Sheet |
|
Hersiliidae |
1 |
0 |
2 |
0 |
Wand-Active |
||
|
Homalonychidae |
1 |
0 |
2 |
0 |
Want-Active |
||
|
Hypochilidae |
1 |
0 |
4 |
0 |
Web-Matrix |
||
|
Leptonetidae |
2 |
0 |
34 |
0 |
Web-Matrix |
||
|
Linyphiidae |
152 |
32 |
(21.1) |
845 |
78 |
(9.2) |
Web-Sheet |
|
Loxoscelidae |
1 |
0 |
13 |
0 |
Web-Sheet |
||
|
Lycosidae |
16 |
10 |
(62.5) |
234 |
62 |
(26.5) |
Wand-Active |
|
Mimetidae |
2 |
2 |
(100) |
13 |
7 |
(53.8) |
Wand-Ambush |
|
Mysmenidae |
3 |
1 |
(33.3) |
6 |
1 |
(16.7) |
Web-Orb |
|
Nesticidae |
3 |
1 |
(33.3) |
31 |
1 |
(3.2) |
Web-Matrix |
|
Ochyroceratidae |
1 |
0 |
1 |
0 |
Web-Sheet |
||
|
Oecobiidae |
2 |
1 |
(50) |
7 |
2 |
(28.6) |
Web-Sheet |
|
Oonopidae |
8 |
0 |
24 |
0 |
Wand-Active |
||
|
Oxyopidae |
3 |
3 |
(100) |
20 |
6 |
(30) |
Wand-Active |
|
Philodromidae |
5 |
5 |
(100) |
95 |
28 |
(29.5) |
Wand-Active |
|
Pholcidae |
10 |
2 |
(2) |
31 |
3 |
(9.7) |
Web- Matrix |
|
Pisauridae |
4 |
2 |
(50) |
14 |
9 |
(64.3) |
Wand-Active |
|
Plectreuridae |
2 |
0 |
15 |
0 |
Wand-Active |
||
|
Salticidae |
45 |
33 |
(73.3) |
288 |
89 |
(30.9) |
Wand-Active |
|
Scytodidae |
1 |
0 |
9 |
0 |
Wand-Active |
||
|
Selenopidae |
1 |
0 |
5 |
0 |
Wand-Ambush |
||
|
Sparassidae |
3 |
0 |
8 |
0 |
Wand-Ambush |
||
|
Symphytognathidae |
1 |
0 |
1 |
0 |
Web-Orb |
||
|
Telemidae |
1 |
0 |
3 |
0 |
Web-Sheet |
||
|
Tengellidae |
1 |
0 |
5 |
0 |
Web-Sheet |
||
|
Theridiidae |
27 |
17 |
(63) |
231 |
64 |
(27.7) |
Web-Matrix |
|
Theridiosomatidae |
1 |
1 |
2 |
1 |
Web-Orb |
||
|
Thomisidae |
10 |
8 |
(80) |
128 |
40 |
(31.3) |
Wand-Ambush |
|
Uloboridae |
7 |
2 |
(28.6) |
15 |
3 |
(20) |
Web-Orb |
|
Zodariidae |
2 |
0 |
4 |
0 |
Wand-Active |
||
|
Zoridae |
1 |
1 |
(100) |
1 |
1 |
(100) |
Wand-Ambush |
|
Totals |
470 |
192 |
(40.9) |
3311 |
614 |
(18.5) |
YOUNG & EDWARDS— FIELD CROP SPIDERS
7
Table 3. — Comparison of two prey-capturing guilds, web-spinning and wandering, for North America and for field crops. Each family assigned to a guild based on data from Roth (1985), Kaston (1981), Gertsch (1979), and Comstock (1940). Percentages in parentheses.
Web-spinning (%) Wandering (%)
|
N.A. fauna |
||||
|
Families |
25 |
(52.1) |
23 |
(47.9) |
|
Genera |
307 |
(65.3) |
163 |
(34.7) |
|
Species |
1955 |
(59) |
1356 |
(41) |
|
Field crops |
||||
|
Families |
13 |
(52) |
12 |
(48) |
|
Genera |
98 |
(51) |
94 |
(49) |
|
Species |
271 |
(44.1) |
343 |
(55.9) |
The North American spider fauna is estimated at the species level to be 59% web- spinners and 41% wanderers (Table 3). The spider fauna of field crops, however, is estimated to be 44% web-spinners and 56% wanderers. Such disparity between the North American fauna and the field-crop fauna may be attributable to several factors, which include dispersal (colonization) differences between guilds and survival differences among disturbed (agricultural) habitats.
Dispersal differences between guilds.— Crop fields are assumed to be composed of spider populations that have emigrated from adjacent habitats or are year- round residents (Luczak 1979). Perennial crops such as alfalfa are more likely to have over-wintering populations of spiders than annual crops such as wheat. However, studies in England surprisingly have demonstrated that spider diversity and density on enclosed land freshly plowed and cultivated in the autumn were maintained until early spring as compared to similarly-treated land where spiders were free to emigrate (Duffey 1978). Unfortunately, the ability of spiders to survive autumnal crop harvest and subsequent soil disturbance has not been investigated in the United States. Thus we are left with the assumption that spiders immigrate each year from adjacent habitats into annual field crops, with minimal overwintering in the crop field. Such immigration occurs aerially by floating on silk threads (ballooning), or by silk-thread bridges between plants, or by ambulatory movements on the ground (Gertsch 1979). Most of the spider individuals that undergo aerial movement in field crops are araneids and linyphiids, both families of web-spinners (Greenstone et al. 1987; Dean and Sterling 1985). Wanderers, e.g., Salticidae and Lycosidae, comprised less than 9% of the aeronauts in some investigations (Plagens 1986; Salmon and Horner 1977). Crop fields and adjacent disturbed habitats may generate proportionately more aerial dispersers than other habitats, because species that occupy these “unstable” habitats have greater aeronautic dispersal powers (Greenstone 1982; Meijer 1977).
Survival differences between guilds. — Only those spider species with good dispersal characteristics are likely to appear in a field crop. Their continued presence in the crop, however, is due to other characteristics, such as their ability to avoid predation, tolerate the typically hot and dry environment, adapt to the particular plant structure and spatial pattern, and find food. In general, web- spinners and wanderers exhibit differences in these abilities. Wandering spiders contain few examples of feeding specialists, with most species capable of capturing a wide diversity of prey types and sizes (Nentwig 1986). One of the
8
THE JOURNAL OF ARACHNOLOGY
most abundant spiders in field crops is a wanderer, Oxyopes salticus , which consumes at least 34 species of insects in 21 families and nine orders (Young and Lockley 1985). Web-spinners, however, exhibit considerable specialization on prey types and sizes (Nentwig 1985). This suggests that wandering spiders may be more likely to find suitable food than web-spinners in a field crop.
Habitat characteristics that are particularly important to web-spinners are plant structure and spacing. Increased availability of substrate for web attachment is usually associated with increased spider density (Rypstra 1983). Many of the larger orb-weavers have specific habitat preferences for particular heights above the ground and large distances between plants (Enders 1974). Such conditions may occur in field crops for only short periods of time or not at all Sheet-web and tangle-web weavers also have substrate requirements that infrequently are available in field crops (Rypstra 1983). The movement through a crop field of farming equipment associated with cultivation and chemical applications no doubt damages a considerable proportion of the resident spider webs, but probably has less effect on the wandering spiders. Factors associated with the degree of food specialization, the structure of the habitat, and the differential impact of disturbance may be sufficient to explain the relatively lower numbers of web-spinning species in field crops.
Characteristics of the most frequently occurring spiders in field crops. — The 29
faunal surveys considered herein represent a geographic range from New York to Florida to California and a plant-structural range from rice to soybean. Several spider species occur over a wide geographic range and in a variety of crops. Forty-two species (Table 4) are widely distributed among the crop systems investigated thus far and probably represent the most abundant species found in field crops. At least 1 / 3 of the 42 species average less than 4 mm in body length. Such small spiders probably prey on the smaller pests such as thrips, aphids, and inn natures of Heteroptera and Lepidoptera. The dispersal of the eight small-sized liny p hud species (Table 4) is more affected by the unpredictability of air currents than is that of the larger species (Greenstone et al 1987). Their capture in field crops thus may indicate only recent accidental arrival and not necessarily successful predatory activity. The largest guilds in this assemblage of 42 species are the active wanderers (19 species) and the orb-web spiders (9 spp.), which suggests that active wandering may be the most successful hunting strategy employed by spiders in field crops. Three species — Tetragnatha laboriosa Hentz, Oxyopes salticus , Phidippus audax (Hentz) — have been found in all nine crop systems, usually were the most abundant predators in those crops, and are among the most abundant spiders in North America (K. as i on 1978). Tetragnatha laboriosa is a small orb-weaver that may leave its web to disperse or search for food and is frequently captured in ground pitfall traps (Culin and Yeargan 1983). Other members of the genus Tetragnatha actively seek prey away from the web in ways similar to wandering spiders (Horn 1969). Oxyopes salticus is an active wanderer more tolerant of hot and dry crop situations than some other common predators of the southeastern United States (Mack et al. 1988), and was the numerically dominant predator in several crop systems (Young and Lockley 1985). Phidippus audax is an active wanderer that is large (body length 8-15 mm), hunts on foliage, often is locally abundant, consumes a wide range of prey sizes, and occurs in many habitats (Roach 1987; Young 1989b). These three species — T laboriosa , O. salticus , R audax — are prime candidates for population
YOUNG & EDWARDS— FIELD CROP SPIDERS
9
augmentation by releases of field-captured or lab-reared individuals, or for population enhancement through habitat manipulations of field crops and adjacent plant communities. As an example of their potential importance, P audax and O. salticus are key predators of Heliothis spp. and the fleahopper Pseudatomoscelis seriatus (Reuter) in cotton and adjacent habitats (Dean et al. 1987). By including field counts of these spiders in the TEXCIM cotton insect management model, predictions of pest abundance and subsequent action recommendations have been improved (Hartstack and Sterling 1988).
Prey of common crop-inhabiting spiders. — Prey choices have been documented for several of the abundant species that occur in agroecosystems (Table 4). Oxyopes salticus is known to capture the tarnished plant bug, Lygus lineolaris (Palisot) (Young and Lockley 1988), the imported fire ant, Solenopsis invicta Buren (Nyffeler et al. 1987a), the bollworm, Heliothis zea (Boddie) (Whitcomb 1967), and at least 15 other economically important field-crop pests (Young and Lockley 1985). Crop pests consumed by P. audax , besides the three just mentioned, include the spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber, the three-cornered alfalfa hopper, Spissistilus festinus (Say), the boll weevil, Anthonomus grandis Boh., and numerous others (Young 1989b). Pisaurina mira (Walck.) (Pisauridae) preys on these six crop pests and also consumes the chinch bug, Blissus sp., the leafhopper Chlorotettix sp., the fall armyworm, Spodoptera frugiperda (J. E. Smith), and a variety of other arthropods (Young 1989c). These same crop pests are fed upon by many other common species of wandering spiders, such as Metaphidippus galathea (Walck.) (Salticidae), Misumenops spp. (Thomisidae), Peucetia viridans (Hentz) (Oxyopidae), Pardosa milvina (Hentz) (Lycosidae), and Chiracanthium inclusum (Hentz) (Clubionidae) (Plagens 1985; Howell and Pienkowski 1971; Whitcomb and Bell 1964). Small web-spinning spiders such as T. laboriosa seem to capture only small flies and aphids (Provencher and Coderre 1987; Whitcomb and Bell 1964), and spin a web that is easily destroyed by wind gusts (LeSar and Unzicker 1978). The common large orb-web spider, Argiope aurantia Lucas (Araneidae), spins a strong web capable of capturing large pests such as grasshoppers and scarab beetles, but mostly captures aphids and small flies (Nyffeler et al. 1987b). Thus the various web-spinning spiders that do occur in field crops may have little impact on the “medium-sized” crop pests such as plant bugs, boll weevils, and leaf beetles, and on the non-flying pests such as lepidopterous larvae.
Implications for spiders in IPM programs. — Several management strategies could have immediate positive impacts on spider populations in field crops and lead to increased levels of predation on crop pests. For example, reductions in both chemical applications and cultivation frequencies would kill fewer spiders and destroy fewer webs. Deployment of mulches, non-disturbance of weed covers, and strip planting of diverse crops all increase habitat diversity and consequently would support a larger and more diverse spider community. Augmentation of spider populations by placement of egg sacs in a field also may be feasible. If the pest-management strategy involved reduction of pest numbers in adjacent habitats, then perhaps the most efficient means for accomplishing this would be to conserve and enhance spider populations in these adjacent habitats. Reduction of mowing frequency and herbicide usage in crop margins, as well as the enlargement of such areas, may also result in increased spider populations (e.g., Young 1989a). Of course the easiest tactic to implement is non-intervention, with
10
THE JOURNAL OF ARACHNOLOGY
Table 4. — Size ranges, hunting techniques, and habitats of the 42 most frequently occurring spiders in U. S. agroecosystems, a = data from Kaston 1978, 1981.
Length No. crop
|
Taxon |
of adult $ (mm)a |
Hunting technique |
Habitat & strata3 |
systems (out of 9) |
|
ANYPHAENIDAE |
||||
|
Aysha gracilis |
6.4-7 |
Wand-Act |
On foliage |
6 |
|
ARANEIDAE |
||||
|
Acanthepeira stellata |
7-15 |
Web-Orb |
Tall grass, low bushes |
8 |
|
Argiope aurantia |
19-28 |
Web-Orb |
Tall grass, gardens |
8 |
|
Argiope trifasciata |
15-25 |
Web-Orb |
Tall grass, sunny |
7 |
|
Cyclosa turbinata |
4.2-5 |
Web-Orb |
Bushes |
7 |
|
Gea heptagon |
4. 5-5. 8 |
Web-Orb |
Low grass & forbs |
6 |
|
Glenognatha foxi |
2 |
Web-Orb |
Meadows & wastelands, low |
6 |
|
Larinia directa |
5-12 |
Web-Orb |
Grass, sunny |
7 |
|
Neoscona arabesca |
5-12 |
Web-Orb |
Tall grass, low bushes |
7 |
|
Tetragnatha laboriosa |
6 |
Web-Orb |
Meadows, bushes, long grass |
9 |
|
CLUBIONIDAE |
||||
|
Chiracanthium inclusum |
4.9-9. 7 |
Wand-Act |
On foliage |
8 |
|
Clubiona abbotii |
4-5.4 |
Wand-Act |
On foliage |
8 |
|
Tr ache las deceptus |
3. 4-4. 2 |
Wand-Act |
Under loose tree bark, rolled up leaves |
7 |
|
LINYPHIIDAE |
||||
|
Eperigone tridentata |
2.3 |
Web-Sheet |
Under dead leaves in woods |
6 |
|
Erigone autumnalis |
1.4-1. 7 |
Web-Sheet |
Grass close to ground, under leaves |
7 |
|
Florinda coccinea |
3.5 |
Web-Sheet |
In grass |
7 |
|
Frontinella pyramitela |
3-4 |
Web-Sheet |
Tall grass, bushes in pine woods |
6 |
|
Grammonota texana |
2 |
Web-Sheet |
Low grass & forbs |
6 |
|
Meioneta micaria |
1.9 |
Web-Sheet |
Ground, low forbs |
6 |
|
Tennesseellum formicum |
1.8-2. 5 |
Web-Sheet |
In dead leaves on forest floor |
8 |
|
Walckenaeria spiralis |
2.5 |
Web-Sheet |
Under dead leaves in woods |
6 |
|
LYCOSIDAE |
||||
|
Lycosa helluo |
18-21 |
Wand-Act |
Ground |
7 |
|
Lycosa rabida |
16-21 |
Wand-Act |
Ground |
6 |
|
Pardosa milvina |
5. 2-6. 2 |
Wand-Act |
Ground, herbs, low bushes |
6 |
|
Pardosa pauxilla |
4-4.5 |
Wand-Act |
Ground |
7 |
|
Schizocosa avida |
10-15 |
Wand-Act |
Ground |
8 |
|
OXYOPIDAE |
||||
|
Oxyopes salticus |
5. 7-6. 7 |
Wand-Act |
Low bushes, herbs |
9 |
|
PHILODROMIDAE |
||||
|
Tibellus oblongus |
7-9 |
Wand-Act |
Tall grass, bushes |
6 |
|
PISAURIDAE |
||||
|
Pisaurina mira |
12.5-16.5 |
Wand-Act |
Tall grass, bushes |
6 |
|
SALTICIDAE |
||||
|
Habronattus coecatus |
5.5 |
Wand-Act |
Ground, grass |
6 |
|
Hentzia palmarum |
4.7-6 |
Wand-Act |
Tall grass, bushes & trees |
7 |
|
Metaphidippus galathea |
3. 6-5.4 |
Wand-Act |
Tall grass, bushes |
8 |
|
Metaphidippus protervus |
3. 7-6. 3 |
Wand-Act |
Tall grass, bushes |
6 |
|
Phidippus audax |
8-15 |
Wand-Act |
Tree trunks, under stones, bushes, tall grass, forbs |
9 |
YOUNG & EDWARDS— FIELD CROP SPIDERS 1 1
|
Phidippus clarus |
8-10 |
Wand-Act |
Tall grass, bushes |
6 |
|
Zygohallus rufipes |
3-6 |
Wand-Act |
Dead leaves on ground, |
|
|
herbs, grass, low bushes |
7 |
|||
|
THERIDIIDAE |
||||
|
Latrodectus mactans |
8-10 |
Web-Ma |
Close to ground |
7 |
|
Theridion murarium |
2.8-4 |
Web-Ma |
Trees, bushes, grass. |
|
|
under stones |
6 |
|||
|
THOMISIDAE |
||||
|
Misumenoides |
||||
|
formocipes |
5-11 |
Wand-Amb |
Among flowers |
6 |
|
Misumenops asperatus |
4.4-6 |
Wand-Amb |
In grass & foliage |
8 |
|
Misumenops celer |
5-6.7 |
Wand-Amb |
Grassland flowers |
8 |
|
Misumenops ohlongus |
4. 9-6.2 |
Wand-Amb |
Grass & weeds |
8 |
no inputs of insecticides, biologicals, cultivations, or other manipulations. Non- intervention allows natural enemies such as spiders to develop unimpeded by man and exert natural controls over potential pest populations; such a tactic actually works in many situations (Sterling et al. 1989).
Both theoretical and empirical studies have demonstrated that generalist predators such as spiders can maintain prey populations at low densities (Post and Travis 1979; Kajak 1978). The conservation and enhancement of generalist (polyphagous) predators in field crops recently has been recommended (Luff 1983; Whitcomb 1981). Dean and Sterling (1987), however, point out the possible negative impacts of spiders on other natural enemies of crop pests, and call for detailed ecological studies to determine the roles of spiders in agroecosystems. Nyffeler and Benz (1987), in a world-wide survey of spiders as natural control agents, also point to the need for detailed ecological studies. Our review should provide the basis for further investigations of field-crop spiders associated with U. S. agroecosystems.
ACKNOWLEDGMENTS
The technical assistance of T. C. Lockley and M. S. Oltremari is gratefully appreciated. An exceptionally thorough manuscript review was provided by D. T. Jennings, with additional reviews by D. A. Dean, M. H. Greenstone, M. Nyffeler, D. B. Richman, S. H. Roach, and W. L. Sterling.
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Young, O. P. and T. C. Lockley. 1985. The striped lynx spider, Oxyopes salticus (Araneae:
Oxyopidae), in agroecosystems. Entomophaga, 30:329-346.
Young, O. P. and T. C. Lockley. 1986. Predation of striped lynx spider, Oxyopes salticus (Araneae: Oxyopidae), on tarnished plant bug, Lygus lineolaris (Heteroptera: Miridae): A laboratory evaluation. Ann. Entomol. Soc. America, 79:879-883.
Young, O. P., T. C. Lockley and G. B. Edwards. 1989. Spiders of Washington County, Mississippi. J. Arachnol., 17:27-41.
Manuscript received February 1989, revised May 1989.
14
THE JOURNAL OF ARACHNOLOGY
APPENDIX 1
SPIDERS IN NINE AGROECOSYSTEMS OF THE UNITED STATES
For list of information sources. See Appendix 2.
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
AGELENIDAE |
|||||||||
|
Agelenopsis aperta (Gertsch) |
LA |
||||||||
|
A. emertoni Chamb. & I vie |
LA |
AR |
DE |
||||||
|
A. kastoni Chamb. & Ivie A. naevia (Walckenaer) |
LA |
LA,MS |
IL |
||||||
|
A. pensylvanica (C. L. Koch) A. spatula Chamb. & Ivie |
TX |
AL,AR |
DE,KY |
KY |
|||||
|
Agelenopsis sp. Cicurina arcuata |
OK |
FL,OH |
FL,IA,IL |
NY.VA |
|||||
|
(Keyserling) |
LA |
AR |
|||||||
|
C. pallida Keys. C. robusta Simon |
LA |
IL |
|||||||
|
Cicurina sp. Coras medicinalis (Hentz) |
LA |
AL |
KY |
KY |
|||||
|
C. perplexus Muma Coras sp. Cybaeus sp. |
LA |
KY |
KY |
||||||
|
Tegenaria pagana C. L. Koch |
LA |
||||||||
|
Wadotes hybridus (Emerton) AMAUROBIIDAE Titanoeca sp. ANYPHAENIDAE |
LA |
KY |
|||||||
|
Anyphaena celer (Hentz) |
OK |
LA |
AL,TX |
KY |
|||||
|
A. laticeps Bryant |
AR |
FL |
|||||||
|
A. maculata (Banks) A. pectorosa L. Koch |
TX |
AR |
IL |
VA |
|||||
|
Anyphaena sp. |
AR |
DE,IA |
NY |
||||||
|
Aysha decepta (Banks) |
LA |
FL |
|||||||
|
A. velox (Becker) |
LA |
FL |
|||||||
|
A. gracilis (Hentz) |
OK |
FL |
OK |
TX |
AL,AR, |
DE,FL |
|||
|
LA,MS,TX, IL |
|||||||||
|
Aysha sp. |
AR |
TX |
KY |
||||||
|
Oxysoma cubana Banks Teudis mordax |
IL |
VA |
|||||||
|
(0. P.-Cambridge) |
FL |
TX |
|||||||
|
Wilfila saltabunda (Hentz) |
LA |
FL |
AL,MS,TX |
IL |
NY,VA |
||||
|
Wulfila sp. ARANEIDAE |
DE,KY |
KY |
|||||||
|
Acacesia hamata (Hentz) |
FL |
AL,AR,TX |
FL |
VA |
|||||
|
Acanthepeira cherokee Levi |
TX |
||||||||
|
A. stellata (Walck.) |
OK |
TX |
LA |
OK,TX |
TX |
AL,AR, |
FL,IL, |
KY,NY,VA |
|
|
MS,TX |
KY,LA, MO,NC |
||||||||
|
A. venusta (Banks) Acanthepeira sp. |
FL |
TX |
AR |
DE,NC |
|||||
|
Alpaida calix (Walck.) Araneus guttulatus |
AL |
||||||||
|
(Walck.) |
IL |
||||||||
|
A. juniperi (Emerton) |
DE |
VA |
|||||||
|
A. marmoreus Clerck A. miniatus (Walck.) A. nordmanni (Thorell) |
FL |
AL |
NY |
||||||
|
A. pegnia (Walck.) A. pratensis (Emerton) |
FL |
NY |
|||||||
|
A. thaddeus (Hentz) A. trifolium (Hentz) |
OH |
AR |
NY.VA |
||||||
|
Araneus sp. |
OK |
FL,OH |
TX |
TX |
DE,FL, IA,KY,NC |
KY»NY,VA |
|||
|
Araniella displicata (Hentz) |
OK |
TX |
AL,AR,LA |
IL |
NY.VA |
||||
|
Araniella sp. Argiope aurantia Lucas |
OK |
AR |
LA |
FL,OH |
TX |
TX |
AR,TX |
DE,IA,IL, KY.LA.NC |
VA |
|
A. trifasciata (Forskal) |
OK |
FL.OH |
TX |
TX |
AR,TX |
FL,IL, KY,NC |
KY,NY,VA |
YOUNG & EDWARDS— FIELD CROP SPIDERS
15
Grain Sugar-
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
Argiope sp. Cyclosa caroli (Hentz) C. conica (Pallas) |
TX |
FL |
AL |
FL |
VA |
||||
|
C. turbinata (Walck.) |
OK |
LA |
FL |
TX |
AR,TX |
KY |
KY,VA |
||
|
Cyclosa sp. Eriophora ravilla |
TX |
NC |
NY |
||||||
|
(C. L. Koch) |
FL |
TX |
|||||||
|
Eustala anastera (Walck.) |
FL.OH |
QK,TX |
TX |
AL.AR.TX |
VA |
||||
|
E. cepina (Walck.) Eustala sp. Gasteracantha cancriformis |
OK |
DE,KY |
NY |
||||||
|
(L.) |
FL |
||||||||
|
Gea heptagon (Hentz) |
AR.TX |
LA |
FL |
AL,LA,TX |
DE, FL, KY,NC |
KY,VA |
|||
|
Glenogn&tha foxi (McCook) |
AR |
LA |
TX |
AR,TX |
DE,IL,KY KY,NY,VA |
||||
|
Hypsosinga pygmaea (Sundevall) H. rubens (Hentz) |
LA |
FL |
TX |
TX |
TX |
FL |
|||
|
Larinia directa Hentz |
TX |
LA |
FL |
TX |
AL |
MO,NC |
VA |
||
|
Larinia sp. |
OK |
NC |
NY |
||||||
|
Leucauge venusta (Walck.) |
LA |
FL |
AR,LA |
DE,FL,MO |
|||||
|
Leucauge sp. |
KY |
KY |
|||||||
|
Mangora gibberosa (Hentz) |
OK |
FL.OH |
AR.TX |
DE,NC |
NY.VA |
||||
|
M. maculata (Keys.) |
AL |
||||||||
|
M. placida (Hentz) M. spiculata (Hentz) Mangora sp. Mecynogea lemniscata |
LA |
FL |
AL |
KY |
|||||
|
(Walck.) Metazygia wittfeldae |
LA |
FL |
TX |
AL,AR,TX |
FL |
||||
|
(McCook) Metepeira labyrinthea |
LA |
MS.TX |
|||||||
|
(Hentz) |
OK |
TX |
AR,MS |
VA |
|||||
|
Metepeira sp. Micrathena gracilis (Walck.) |
TX |
TX |
AL,AR, MS.TX |
DE |
VA |
||||
|
M. sagittata (Walck.) Micrathena sp. |
FL |
FL |
|||||||
|
Neoscona arabesca (Walck.) |
AR,TX |
LA |
FL.OH |
TX |
AL,AR, |
DE,FL, |
KY,NY,VA |
||
|
LA,MS, |
IL,KY,LA, |
||||||||
|
TX |
MO,NC |
||||||||
|
N. domiciliorum (Hentz) |
TX |
LA |
AL |
||||||
|
N. hentzii (Keys.) |
LA |
OK |
AR |
||||||
|
N. oaxacensis (Keys.) |
OK,TX |
TX |
CA |
||||||
|
N. pratensis (Hentz) |
TX |
OH |
AL |
||||||
|
N. utahana (Chamberlin) |
TX |
||||||||
|
Neoscona sp. |
OK |
TX |
CA |
FL,MO,NC |
|||||
|
Nephila clavipes (L.) Nuctenea cornuta (Clerck) |
AL |
FL |
|||||||
|
N. sclopetaria (Clerck) Nuctenea sp. Pachygnatha autumnalis |
AL |
KY |
KY |
||||||
|
Keys. |
LA |
LA |
DE,KY |
KY.VA |
|||||
|
R tristriata C. L. Koch Pachygnatha sp. Scoloderus cordatus (Taczanowski) Tetragnatha caudata |
LA |
FL |
TX |
KY |
KY,NY,VA |
||||
|
Emerton T. elongate. (Walck.) |
FL |
AL,AR,MS |
; MO |
||||||
|
T. laboriosa Hentz |
OK |
AR,TX |
LA |
FL.OH |
OK.TX |
TX |
AL,AR, |
DE,FL,IA, |
CA.KY, |
|
LA,MS,TX |
IL,KY, |
NY |
|||||||
|
NC |
|||||||||
|
T. pallescens F.O.P.-Camb. |
AR |
LA |
|||||||
|
T. straminea Emerton |
TX |
AL,LA |
IL |
||||||
|
T. versicolor Walck. |
TX |
AL |
|||||||
|
Tetragnatha sp. |
TX |
CA |
FL,MO,NC |
||||||
|
Verrucosa arenata (Walck.) |
AR |
Wagneriana tauricornis
(O.P.-Camb.) FL
Wixia ectypa (Walck.) VA
16
THE JOURNAL OF ARACHNOLOGY
Grain Sugar-
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
Wixia sp. |
AR |
||||||||
|
Zygiella dispar (Kulczynski) CLUBIONIDAE |
AL |
||||||||
|
Agroeca pratensis Emerton |
AL |
VA |
|||||||
|
A. trivittata (Keys.) Agroeca sp. Castianeira alteranda Gertsch |
TX |
KY |
CA |
||||||
|
C. amoena (C.L. Koch) C. crocata (Hentz) |
TX |
LA |
|||||||
|
C. descripta (Hentz) |
LA |
OH |
TX |
AL,AR |
IL |
||||
|
C. floridana (Banks) |
FL |
||||||||
|
C. gertschi Kaston |
AL,TX |
FL |
|||||||
|
C. longipalpus (Hentz) |
LA |
TX |
AL,AR LA,TX |
FL,LA |
|||||
|
C. occidens Reiskind C. variola Gertsch |
LA |
TX |
VA |
||||||
|
Castianeira sp. Chiracanthium inclusum |
OK |
FL |
TX |
IA.KY |
KY |
||||
|
(Hentz) |
OK |
LA |
FL |
TX |
TX |
AL,AR, |
DE,FL, |
VA |
|
|
MS,TX |
IL,KY,NC |
||||||||
|
C. mildei L. Koch Chiracanthium sp. |
AL |
IL |
NY |
||||||
|
Cluhiona abbotii L. Koch |
OK |
AR |
LA |
FL |
TX |
AL,AR,LA |
DE,IL, KY,NC |
KY,NY,VA |
|
|
C. catawba Gertsch |
AR |
DE |
VA |
||||||
|
C. johnsoni Gertsch |
TX |
AR |
|||||||
|
C. kagani Gertsch |
TX |
||||||||
|
C. maritima L. Koch |
LA |
AL |
|||||||
|
C. obesa Hentz |
LA |
AL |
NY |
||||||
|
C. pikei Gertsch C. plumbi Gertsch C. procteri Gertsch |
TX |
FL |
VA |
||||||
|
C. pygmaea Banks C. riparia L. Koch |
TX |
FL |
|||||||
|
C. saltitans Emerton C. spiralis Emerton |
AR |
DE |
VA |
||||||
|
Clubiona sp. |
TX |
OH |
DE.IA, KY,NC |
KY |
|||||
|
Clubionoides excepta |
|||||||||
|
(L. Koch) |
AL |
||||||||
|
Myrmecotypus lineatus (Emerton) Phrurotimpus alarius (Hentz) |
LA |
FL |
AR |
FL |
|||||
|
P. borealis (Emerton) |
LA |
TX |
|||||||
|
P emertoni Gertsch |
LA |
||||||||
|
P. minutus (Banks) Phrurotimpus sp. |
LA |
FL |
FL |
KY |
|||||
|
Scotinella fratella (Gertsch) |
LA |
AR |
|||||||
|
S. pallida Banks Scotinella sp. Strotarchus piscatoria |
FL |
AR |
KY |
KY |
|||||
|
(Hentz) |
AL |
FL |
|||||||
|
Syrisca afftnis (Banks) |
TX |
TX |
|||||||
|
Trachelas deceptus (Banks) |
AR |
LA |
FL |
TX |
AR.LA.TX |
FL,LA |
VA |
||
|
T. similis F.O.P.-Camb. |
LA |
FL |
LA |
LA |
|||||
|
T. tranquillus (Hentz) |
LA |
AL,AR,MS |
KY |
KY.NY |
|||||
|
T. volutus Gertsch Trachelas sp. |
LA.TX |
KY.NC |
KY |
||||||
|
DICTYN1DAE |
|||||||||
|
Argenna obesa Emerton Dictyna annexa |
IL |
NY |
|||||||
|
Gertsch & Mulaik |
TX |
||||||||
|
D. bellans Chamberlin |
TX |
||||||||
|
D. bicornis Emerton |
OK |
TX |
|||||||
|
D. bostoniensis Emerton |
TX |
||||||||
|
D. consults Gertsch & Ivie D. foliacea (Hentz) |
TX |
NY |
|||||||
|
D. hentzi Kaston |
AR |
NY |
|||||||
|
D. hoya Chamb. & Ivie D. iviei Gertsch & Mulaik D longispina Emerton |
OH |
TX |
TX |
CA |
YOUNG & EDWARDS— FIELD CROP SPIDERS
17
|
Taxon |
Grain sorghum |
Rice |
Sugar- cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
|
D. manitoba Ivie |
||||||||
|
D. reticulata Gertsch & Ivie |
CA |
|||||||
|
D. segregata Gertsch & |
||||||||
|
Mulaik |
OK |
TX |
AR,LA,TX |
|||||
|
D. sublata Hentz |
LA |
TX |
MO |
|||||
|
D. volucripes Keys. |
TX |
TX |
AL,AR,TX |
|||||
|
Dictyna sp. |
OK |
AR |
FL,OH |
TX |
TX |
FL,KY |
Tricholathys hirsutipes
|
(Banks) |
|||||||
|
DYSDERIDAE |
|||||||
|
Ariadna sp. Dysdera crocata C. L. Koch |
LA |
||||||
|
FILISTATIDAE |
|||||||
|
Kukukania hibernalis |
|||||||
|
(Hentz) |
AR.TX |
LA |
|||||
|
GNAPHOSIDAE |
|||||||
|
Cesonia bilineata (Hentz) C. sincere Gertsch & Mulaik Drassodes auriculoides |
LA |
TX |
AL |
||||
|
Barrows |
AR |
||||||
|
D. gosiutus Chamberlin |
AR.LA |
||||||
|
Drassodes sp. Drassyllus creolus |
FL |
AL,TX |
DE,KY |
||||
|
Chamb. & Gert. |
OK |
AR |
|||||
|
D. depresses (Emerton) D. fallens Chamberlin |
AR |
IL,KY |
|||||
|
D. gynosaphes Chamberlin |
LA |
AR |
|||||
|
D. lepidus (Banks) |
OK |
TX |
AR |
||||
|
D. notonus Chamberlin |
TX |
LA.TX |
|||||
|
D. orgilus Chamberlin Drassyllus sp. |
OK |
FL |
TX |
TX |
AL, AR.TX |
||
|
Gnaphosa fonlinalis Keys. |
TX |
||||||
|
G. sericata (L. Koch) Haplodrassus signifer |
LA |
FL |
TX |
AR.TX |
IL,KY |
||
|
(C. L. Koch) Haplodrassus sp. Herpyllus ecclesiasticus |
TX |
TX |
|||||
|
Hentz |
LA |
||||||
|
Micaria aurata (Hentz) |
AL |
||||||
|
M. triangulosa Gertsch M. vinnula Gertsch & Davis |
TX |
AR |
|||||
|
Micaria sp. |
FL |
TX |
|||||
|
Nodocion floridanus (Banks) N. rufithoracicus Worley Sergiolus capulatus (Walck.) S. lowelli Chamb. & |
FL |
TX |
TX |
IL.NC |
|||
|
Woodbury S. minutus (Banks) |
LA |
TX |
AR |
||||
|
S. ocellatus (Walck.) |
LA |
TX |
|||||
|
Sergiolus sp. Synaphosus paludis |
OK |
MS |
|||||
|
(Chamb. & Gert.) |
LA |
TX |
LA |
||||
|
Urozelotes rusticus (L. Koch) Zelotes duplex Chamberlin Z. gertschi Platnick & |
LA |
AR |
|||||
|
Shadab Z. hentzi Barrows |
OK |
TX |
AR,LA |
||||
|
Z. laccus (Barrows) Z. pseustes Chamberlin |
TX |
AR |
IL |
||||
|
Z. subterraneus (C. L. Koch) Zelotes sp. |
OK |
AR |
FL,KY |
||||
|
HAHNIIDAE |
|||||||
|
Neoant istea agilis (Keys.) |
LA |
AR |
IL.KY |
||||
|
N. mulaiki Gertsch N. riparia (Keys.) Neoantistea sp. |
FL |
TX |
TX |
DE |
|||
|
LINYPHIIDAE |
|||||||
|
Anibontes longipes Chamb. & Ivie Balhyphantes albiventris |
FL |
||||||
|
(Banks) |
OH |
Alfalfa
NY
CA
NY,VA
KY
CA
KY
KY
KY
CA.VA
CA
KY
KY
VA
VA
18
THE JOURNAL OF ARACHNOLOGY
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
B. concolor (Wider) |
NY |
||||||||
|
B. palUdus (Banks) |
KY |
KY |
|||||||
|
Bathyphantes sp. Centromerus cornupalpis |
AR |
DE |
|||||||
|
(O.P.-Camb.) Centromerus sp. Ceraticelus bryantae Kaston |
LA |
AR |
NY |
||||||
|
C. creolus Chamberlin |
AR |
||||||||
|
C. emertoni (O.P.-Camb.) |
AL |
NY |
|||||||
|
C. formosus Cros. & Bishop |
OH |
AL |
|||||||
|
C. similis (Banks) |
AR |
FL |
TX |
DE |
NY,VA |
||||
|
Ceraticelus sp. |
AR |
FL |
TX |
FL |
|||||
|
Ceralinella placida Banks Ceraiinops crenata Emerton |
FL |
TX |
KY |
KY |
|||||
|
C. rugosa (Emerton) |
LA |
IL |
|||||||
|
Ceratinops sp. Ceratinopsidis formosa (Banks) Ceratinopsis latkeps |
FL |
NY |
|||||||
|
(Emerton) |
IL,KY |
KY |
|||||||
|
C. nigriceps Emerton C. sutoris Cros. & Bishop Ceratinopsis sp. Collimia plumosus |
AR |
FL |
TX |
IL |
|||||
|
(Emerton) Eperigone albula |
IL |
CA |
|||||||
|
Zorsch & Crosby |
LA |
||||||||
|
K banksi Ivie & Barrows K eschatologies (Crosby) |
AR |
LA |
FL |
TX |
CA |
FL |
|||
|
E. maculata (Banks) |
AR |
||||||||
|
E. tridenlata (Emerton) |
OK |
AR |
LA |
AR |
IL |
KY,YA |
|||
|
E. trilobata (Emerton) Eperigone sp. Eridantes erigonoides |
OK |
TX |
AR |
IL.KY |
KY,VA |
||||
|
(Emerton) |
KY |
KY,NY,VA |
|||||||
|
Erigone atm Blaekwall |
IL |
||||||||
|
B. autumnaiis Emerton |
OK |
LA |
FL |
TX |
AR,TX |
DE.FL, IL,KY |
KY,NY,VA |
||
|
E barrowsi Crosby & Bishop E. blaesa Crosby & Bishop E. denligera O.P.-Cambridge |
OK |
AR |
TX |
TX |
DE,KY |
KY,NY |
|||
|
E. dentosa O.P.-Cambridge |
CA |
CA |
|||||||
|
E. praecwsa Chamb. & Ivie Erigone sp. |
OK |
LA |
AR |
||||||
|
Floricomus sp. |
AR |
||||||||
|
Florinda coccinea (Hentz) |
OK |
AR |
LA |
FL |
AL,AR |
DE,FL, |
KY |
||
|
KY,MOsMC |
|||||||||
|
Froniinella pyramiiela |
|||||||||
|
(Walck.) |
OK |
LA |
FL |
AL,AR,TX |
DE.FL, IL,KY |
KY,VA |
|||
|
Gonatium rubens (Balckwall) Grammonota capitaia |
AR |
||||||||
|
Emerton |
KY |
KY |
|||||||
|
G. inornata Emerton |
OK |
AR |
AR |
DE,IL,KY KY,NY,VA |
|||||
|
G. pictilis (O.P.-Camb.) G. lexana (Banks) Helophora sp. Hypselistes Jflorens |
OK |
AR |
LA |
FL |
TX |
AR/TX |
DE |
NY |
|
|
(O.P.-Camb.) |
NY |
||||||||
|
Handiam jlaveola (Banks) Lepthyphantes nebulosa |
OK |
AR |
DE |
YA |
|||||
|
(Sundevall) L. sabulosa (Keys.) Lepthyphantes sp. Linyphantes aeronauiicus |
LA |
AR |
MO |
||||||
|
(Petrunk.) |
CA |
||||||||
|
Meioneta angulata (Emerton) M. barrowsi Chamb. & Ivie |
DE |
VA |
|||||||
|
M. dactylata Chamb. & Ivie |
KY |
KY |
|||||||
|
M.fabra (Keys.) |
DE,IL |
VA |
|||||||
|
M. maculata (Banks) |
VA |
YOUNG & EDWARDS— FIELD CROP SPIDERS
19
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
M. meridionalis |
|||||||||
|
Cros. & Bishop |
AR |
||||||||
|
M. micaria (Emerton) |
OK |
FL |
TX |
AR |
IL,KY |
KY,VA |
|||
|
M. nigripes (Simon) |
NY |
||||||||
|
M. unimaculata (Banks) |
IL,KY |
KY,VA |
|||||||
|
Meioneta sp. Microlinyphia mandibulala |
OK |
LA |
FL |
TX |
TX |
AL,TX |
NY,VA |
||
|
(Emer.) |
CA,NY,VA |
||||||||
|
M. pusilla (Sundevall) Microneta sp. |
LA |
1L,KY |
KY |
||||||
|
Neriene clathrata Sundevall |
NY |
||||||||
|
N. maculate (Emerton) |
AL,AR |
VA |
|||||||
|
N. radiate (Walck.) Neriene sp. Pimoa sp. Scylaeceus pallidus (Emerton) Spirembolus phylax |
OK |
TX |
AR |
FL |
KY |
||||
|
Chamb. & Ivie Tapinocyba scopulifera (Emerton) Tennesseellum formicum |
CA |
IL |
CA |
||||||
|
(Emerton) |
OK |
LA |
FL |
TX |
TX |
AL,AR |
DE,IL, |
CA,KY,NY |
|
|
KY |
|||||||||
|
Walckenaeria pallida |
|||||||||
|
Emerton |
AL |
||||||||
|
W. puella Millidge |
TX |
||||||||
|
W. spiralis (Emerton) |
OK |
LA |
TX |
AR |
1L,KY |
CA,KY,NY, |
|||
|
VA |
|||||||||
|
LYCOSIDAE |
|||||||||
|
Allocosa absoluta (Gertsch) A. floridiana (Chamberlin) |
LA |
FL |
TX |
||||||
|
A. funerea (Hentz) |
LA |
AR,LA |
DE,KY |
KY,VA |
|||||
|
A. mokiensis (Gertsch) A. sublata (Montgomery) |
AR |
CA |
|||||||
|
Allocosa sp. |
TX |
||||||||
|
Arctosa littoralis (Hentz) |
TX |
LA |
|||||||
|
Arciosa sp. Geolycosa riograndae |
CA |
NY |
|||||||
|
Wallace |
TX |
||||||||
|
Geolycosa sp. |
OK |
||||||||
|
Gladicosa gulosa Walck. |
OK |
AR |
|||||||
|
Lycosa acompa (Chamberlin) L. ammophila Wallace |
LA |
FL |
AR |
||||||
|
L. annexa Chamb. & Ivie |
AR |
FL |
|||||||
|
L. antelucana Montgomery |
OK |
LA |
TX |
AR |
|||||
|
L. aspersa Hentz L. baltimoriana (Keys.) |
OK |
LA |
|||||||
|
L. carolinensis Walck. |
LA |
FL |
AR |
KY |
KY |
||||
|
L. frondicola Emerton L. georgicola Walck. |
LA |
KY |
KY |
||||||
|
L. helluo Walck. |
OK |
TX |
LA |
FL |
AR,LA,TX |
DE,FL, KY,LA |
NY,NY,VA |
||
|
L. lento Hentz L. modesta (Keys.) |
LA |
FL |
FL |
KY |
|||||
|
L. punctulata (Hentz) |
OK |
LA |
AL,AR |
DE,FL,NC |
KY |
||||
|
L. rabida Walck. |
LA |
FL |
TX |
AL,AR, |
DE,FL, |
KY,VA |
|||
|
LA,TX |
KY,NC |
||||||||
|
L. ripariola Bonnet |
KY |
KY |
|||||||
|
L. timuqua Wallace |
FL |
||||||||
|
Lycosa sp. Pardosa atlantica Emerton/ |
OK |
AR |
OH |
TX |
DE,KY,NC |
CA,KY |
|||
|
P. saxatilis (Hentz) |
AR.TX |
LA |
AL,AR |
DE,IA,KY |
KY,VA |
||||
|
P. delicatula Gert. & Wall. |
OK |
LA |
TX |
LA,TX |
|||||
|
P. distincta (Blackwall) |
TX |
AL,LA,MS |
MO,NC |
VA |
|||||
|
P. littoralis Banks |
FL |
AL |
FL |
VA |
|||||
|
P. mercurialis Montgomery P. milvina (Hentz) |
AR,TX |
LA |
FL |
TX |
AL,AR, |
DE,FL, |
KY,NY,VA |
||
|
LA,TX |
IL,KY, LA,NC |
||||||||
|
P. modica (Blackwall) |
NY |
||||||||
|
P. moesta Banks |
LA |
NY |
20
THE JOURNAL OF ARACHNOLOGY
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
P. montgomeryi Gertsch P. parvula Banks |
LA |
FL |
FL |
||||||
|
P. pauxilla Montgomery |
OK |
FL |
TX |
TX |
AR,LA,TX |
FL |
VA |
||
|
P. ramulosa (McCook) |
CA |
CA |
|||||||
|
Pardosa sp. Pirata alachuus |
OK |
TX |
NC |
VA |
|||||
|
Gert. & Wallace |
AR |
AR |
|||||||
|
P. allapahae Gertsch P. insularis Emerton |
TX |
FL |
AL |
DE |
VA |
||||
|
P minutus Emerton |
LA |
DE |
NY,VA |
||||||
|
P. piraticus (Clerck) P sedentarius Montgomery P. seminola Gertsch & |
AR |
LA |
AR |
KY |
KY |
||||
|
Wallace |
AR |
TX |
|||||||
|
P. suwaneus Gertsch |
AR |
LA |
AR |
||||||
|
P sylvanus Chamb. & Ivie |
LA |
AR |
|||||||
|
Pirata sp. |
OK |
FL |
DE |
KY |
|||||
|
Schizocosa avida (Walck.) |
OK |
TX |
LA |
OH |
TX |
AR,LA,TX |
DE,KY |
KY,VA |
|
|
S. bilineata (Emerton) |
OK |
AL |
DE,KY |
KY,VA |
|||||
|
S. crassipes (Walck.) |
LA |
AR |
FL,KY |
KY |
|||||
|
S. ocreata (Hentz) |
OK |
LA |
AR,LA |
DE,FL,LA |
|||||
|
S. retrorsa (Banks) |
AR |
||||||||
|
Schizocosa sp. |
OK |
CA |
VA |
||||||
|
Trabeops sp. Trochosa avara (Keys.) T. shenandoa Chamb. & Ivie |
TX |
AL |
FL |
||||||
|
T. terricola (Thorell) |
TX |
AL |
|||||||
|
Trochosa sp. MIMET1DAE |
OK |
AR |
|||||||
|
Ero leonina (Hentz) Mimeius epeiroides Emerton |
FL |
AR,MS |
IL,KY, |
KY,NY,V, |
|||||
|
NC |
|||||||||
|
M. hesperus (Chamberlin) M. nelsoni (Archer) |
LA |
TX |
TX |
FL |
|||||
|
M. notius Chamberlin |
TX |
FL |
|||||||
|
M. puritanus Chamberlin Mimetus sp. |
FL |
AL,MS |
DE,NC |
CA |
|||||
|
MYSMENIDAE Mysmena guttata (Banks) NESTJCIDAE |
LA |
||||||||
|
Eidmannella pallida |
|||||||||
|
(Emerton) |
OK |
LA |
AR |
CA |
|||||
|
OECOBIIDAE |
|||||||||
|
Oecobius cellariorum (Duges) Oecobius sp. |
AR |
KY |
|||||||
|
OXYOPIDAE |
|||||||||
|
Hamataliwa helia (Chamberlin) Oxyopes aglossus |
FL |
||||||||
|
Chamberlin |
AR |
||||||||
|
O. apollo Brady |
OK |
TX |
TX |
FL |
|||||
|
O. salticus Hentz |
OK |
AR,TX |
LA |
FL |
TX |
TX |
AL,AR, |
DE,FL, |
CA,KY,V/ |
|
LA, MS |
IA,IL, |
||||||||
|
TX |
KY,LA, MO,NC, |
||||||||
|
O. scalaris Hentz |
TX |
AL |
FL,IL |
||||||
|
Peucetia viridans (Hentz) |
TX |
FL |
TX |
AL,AR, |
FL,LA, |
||||
|
MS,TX |
NC |
||||||||
|
PHILQDROMJDAE |
|||||||||
|
Apollophanes texanus Banks Ebo albocaudatus Schick E. latithorax Keys. E. pepinensis Gertsch E. punctatus Sauer |
OK |
TX |
MS |
MO |
CA |
||||
|
& Platnick |
TX |
||||||||
|
Ebo sp. Philodromus cespilum |
TX |
TX |
KY |
KY |
|||||
|
(Walck.) P. histrio (Latr.) P. imbecillus Keys. |
AL |
DE,IL |
CA |
||||||
|
P. infuscatus Keys. |
TX |
YOUNG & EDWARDS— FIELD CROP SPIDERS
21
Grain
Sugar-
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
P keyserlingi Marx |
FL |
TX |
AL |
IL |
|||||
|
P. marxi Keys. P. minutus Banks |
TX |
IL |
VA |
||||||
|
P. pernix BlackwaSl P placidus Banks |
MS |
NY |
|||||||
|
P. pratariae (Schick) |
TX |
TX |
|||||||
|
P. rufus Walck. |
AL |
DE |
NY |
||||||
|
P satullus Keys. |
AR |
||||||||
|
P vulgaris (Hentz) Philodromus sp. |
OK |
TX |
AR,IA |
DE,KY, |
KY,VA |
||||
|
NC |
|||||||||
|
Thanatus formicinus |
|||||||||
|
(Clerck) |
TX |
AL,LA, |
IL |
VA |
|||||
|
TX |
|||||||||
|
T. rubicellus M. Leitas |
AR |
||||||||
|
T. striatus (C. L. Koch) Thanatus sp. |
OK |
OH |
AL |
DE |
VA |
||||
|
Tibellus duttoni (Hentz) T. maritimus (Menge) |
TX |
TX |
AR,TX |
||||||
|
T. oblongus (Walck.) |
TX |
OH |
TX |
AL |
IA,IL, |
CA,KY, |
|||
|
KY |
NY,VA |
||||||||
|
Tibellus sp. |
DE,FL,NC |
VA |
|||||||
|
PHOLC1DAE |
|||||||||
|
Pholcus phalangioides (Fueselin) Psilochorus redemptus |
LA |
||||||||
|
Gert. & Mulaik |
TX |
||||||||
|
Psilochorus sp. PISAURIDAE |
CA |
||||||||
|
Dolomedes albineus Hentz |
LA |
||||||||
|
D. scriptus Hentz |
TX |
LA |
|||||||
|
D. tenebrosus Hentz |
TX |
||||||||
|
D. triton (Walck.) |
AR,TX |
AL,AR, LA,TX |
FL,MO |
||||||
|
Dolomedes sp. |
FL |
NC |
KY |
||||||
|
Pisaurina brevipes (Emerton) P. dubia (Hentz) |
LA |
IL |
|||||||
|
P. mira (Walck.) |
TX |
LA |
TX |
AL,AR,LA |
DE,FL, IL,KY |
KY,NY |
|||
|
Pisaurina sp. SALTICIDAE |
OK |
FL |
DE,KY |
||||||
|
Admestina tibialis (C. Koch) Agassa cyanea (Hentz) Ballus youngii |
TX |
IL |
VA |
||||||
|
G. & E. Peckham |
AL |
||||||||
|
Corythalia canosa (Walck.) Em aurantia (Lucas) |
LA |
FL |
AL,AR,MS |
FL,NC |
VA |
||||
|
E. militaris (Hentz) |
LA |
TX |
AL,LA, MS,TX |
IL,KY,LA |
VA |
||||
|
E. pinea (Kaston) |
AL |
IL |
|||||||
|
Eris sp. |
TX |
DE,MO |
KY |
||||||
|
Euophrys sp. Evarcha hoyi (G. & E. |
VA |
||||||||
|
Peckham) |
AL |
MO |
VA |
||||||
|
Habrocestum pulex (Hentz) Habrocestum sp. |
LA, MS |
DE |
|||||||
|
Habronattus agilis (Banks) |
TX |
AL,LA |
|||||||
|
H. borealis (Banks) H. brunneus |
AR |
LA |
AL,MS |
||||||
|
(G. & E. Peckham) H. calcaratus Banks |
FL |
AL |
|||||||
|
H. coecatus (Hentz) |
OK |
LA |
TX |
AL,AR, LA,MS,TX |
LA,NC |
CA,VA |
|||
|
H. decorus (Black wall) H. mustaciatus |
AL |
NY |
|||||||
|
Chamb. & I vie H. texanus (Chamberlin) |
OK |
TX |
IL |
CA |
|||||
|
H. trimaculatus Bryant H. viridipes (Hentz) |
OK |
FL |
AL,LA,MS |
||||||
|
Habronattus sp. |
AL |
MO |
KY |
22
THE JOURNAL OF ARACHNOLOGY
Grain Sugar-
Taxon sorghum Rice cane
Hentzia mitrata (Hentz) LA
H. palmarum (Hentz) LA
Hentzia sp. OK
Lyssomanes viridis (Walck.)
Maevia inclemens (Walck.)
Marpissa bina (Hentz)
M. dentoides Barnes
M.formosa (Banks) TX
M. lineata (C. L. Koch)
M. pikei (G. & E. Peckbarn)
Marpissa sp.
Metacyrba taeniola (Hentz)
Metacyrba sp.
Metaphidippus castaneus (Hentz)
|
M. exiguus (Banks) M. galathea (Walck.) |
OK |
LA |
|
|
M. insignis (Banks) M. manni G. & E. Peckham M. protervus (Walck.) |
OK |
AR |
LA |
|
M. vitis Cockerell Metaphidippus sp. |
OK |
TX |
Neon sp.
Neonella vinnula Gertsch Peckhamia americana (G. & E. Peckham)
P. picata (Hentz) OK
Peckhamia sp.
Pellenes limatus G. & E. Peckham Phidippus apacheanus Chamb. & Gert.
P. audax (Hentz) OK TX LA
P. cardinalis( Hentz)
P carolinensis G. & E. Peckham
P. clams Keys. LA
P. insignarius C. L. Koch P mystaceus (Hentz)
P. pius Schick P. princeps (G. & E. Peckham)
P pulcherrimus Keys.
P. purpuratus Keys.
P. putnami (G. & E. Peckham)
P. regius, C. L. Koch P. texanus Banks Phidippus sp.
Phlegra fasciata ((Hahn)
Platycryptus undatus (DeGeer)
Plexippus paykulli (Audouin)
Plexippus sp.
Salticus sp.
Sarinda hentzi (Banks) LA
Sassacus papenhoei G. & E. Peckham OK
Sitticus cursor Barrows S. dor sat us (Banks)
|
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
ALSAR, |
DE,FL,NC |
||||
|
TX |
|||||
|
FL |
TX |
TX |
AL,AR, |
DE,FL, |
VA |
|
LA,MS,TX |
IL,NC DE,KY,NC |
||||
|
FL |
TX |
AL,TX AL,LA |
VA |
||
|
FL |
TX |
||||
|
TX |
TX |
VA |
|||
|
TX |
LA |
VA |
|||
|
AL |
|||||
|
AR |
DE |
KY |
|||
|
AL |
|||||
|
TX |
|||||
|
FL |
TX |
TX |
ar,la, |
FL,IL,KY, |
NY,VA |
|
MS,TX |
LA,MO,NC |
||||
|
AL,AR,TX |
|||||
|
CA |
|||||
|
OH |
al,ar, LA, MS |
IA,IL |
NY,VA |
||
|
AR,TX |
DE,FL,KY, |
||||
|
MO,NC |
|||||
|
DE |
|||||
|
TX |
|||||
|
FL |
TX |
AR |
KY |
KY |
|
|
TX |
|||||
|
FL |
TX |
LA |
|||
|
FL |
OK,TX |
TX |
AL.AR, |
FL,IL, |
KY,NY,VA |
|
LA,MS,TX |
KY,LA, MO,NC |
||||
|
TX |
TX |
AR,LA,TX |
|||
|
AR |
|||||
|
FL,OH |
TX |
AL,AR, |
FL,LA, |
VA |
|
|
LA,MS,TX |
MO,NC |
||||
|
AL |
|||||
|
AR |
|||||
|
TX |
|||||
|
OH |
AL |
NY |
|||
|
FL |
AL,AR |
MO |
|||
|
FL |
|||||
|
FL |
AL |
FL |
|||
|
TX |
TX |
||||
|
OH |
QKJX |
AL |
DE,FL, IA,MO,NC |
CA,KY,VA |
|
|
AL,AR, MS.TX |
|||||
|
AL |
MO |
||||
|
TX |
TX |
KY |
|||
|
TX |
TX |
TX |
|||
|
AL |
KY |
VA |
|||
|
TX |
YOUNG & EDWARDS— FIELD CROP SPIDERS
23
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
S. pubescens (Fabr.) Sitticus sp. Synageles sp. Synemosyna formica |
FL |
AL |
DE |
KY |
|||||
|
Hentz |
LA |
AL,AR |
|||||||
|
Talavera minuta (Banks) Thiodina puerpera (Hentz) |
OK |
TX |
TX |
AL,AR,TX |
LA |
NY |
|||
|
T. sylvana (Hentz) |
TX |
AL,MS,TX |
FL,MO |
||||||
|
Thiodina sp. |
FL |
NC |
|||||||
|
Tuteiina elegans (Hentz) |
OK |
AL |
IL |
||||||
|
T. hard (Emerton) Tuteiina sp. Zygoballus nervosus |
OH |
AL |
NY |
||||||
|
(G. & E. Peckham) Z. rufipes |
AR |
AR,TX |
|||||||
|
G. & E. Peckham |
AR |
LA |
FL |
TX |
AL,AR, MS,TX |
DE,FL |
VA |
||
|
Z. sexpunctatus (Hentz) |
AR |
AL,LA,MS |
FL,NC |
VA |
|||||
|
Zygoballus sp. |
IA,MO,NC |
||||||||
|
THERIDIIDAE |
|||||||||
|
Achaearanea globosa (Hentz) |
FL |
AL,AR,TX |
|||||||
|
A. tepidariorum (C. L. Koch) |
LA |
FL |
VA |
||||||
|
Achaearanea sp. |
AR |
FL |
KY |
KY |
|||||
|
Anelosimus studiosus (Hentz) Argyrodes cancellatus |
FL |
TX |
|||||||
|
(Hentz) |
AL |
||||||||
|
A.fictilium (Hentz) A. trigonum (Hentz) |
LA |
FL |
TX |
KY |
NY |
||||
|
Argyrodes sp. |
FL |
DE |
|||||||
|
Chrysso sp. Coleosoma acutiventer (Keys.) |
LA |
FL |
FL |
||||||
|
Coleosoma sp. Crustulina sticta (O.P.-Camb.) Dipoena abdita Gertsch & Mulaik D. nigra (Emerton) |
LA |
AR,LA,MS |
FL |
CA |
|||||
|
Dipoena sp. Enoplognatha marmorata |
TX |
AL |
KY |
||||||
|
(Hentz) E. ovata (Clerck) Euryopis funebris |
AL |
NY |
|||||||
|
(Hentz) |
AL,MS |
KY |
KY,VA |
||||||
|
E. gertschi Levi E. texana Banks Euryopis sp. Latrodectus hesperus |
TX |
DE |
VA |
||||||
|
Chamb. & Ivie L. mactans (Fabr.) |
OK |
LA |
FL |
TX |
TX |
AL,AR,CA |
FL,KY, |
CA |
|
|
LA,MS,TX |
LA,NC |
||||||||
|
L. variolus (Walck.) Paratheridula perniciosa |
LA |
||||||||
|
(Keys.) |
LA |
FL |
|||||||
|
R. fuscus Emerton Robertus sp. Steatoda albomaculata |
LA |
AL,MS |
|||||||
|
(DeGeer) S. americana (Emerton) S. erigoniformis (O.P.-Camb.) S.fulva (Keys.) S. grossa (C. L. Koch) |
LA |
FL |
TX |
MS |
KY |
KY |
|||
|
S. medialis (Banks) S. quadrimaculaia |
TX |
||||||||
|
(O.P.-Camb.) S. transversa (Banks) |
FL |
TX |
|||||||
|
5. triangulosa (Walck.) Steatoda sp. Theridion alabamense |
LA |
TX |
TX |
ALJX |
|||||
|
Gert. & Archer |
LA |
24
THE JOURNAL OF ARACHNOLOGY
|
Grain |
Sugar- |
||||||||
|
Taxon |
sorghum |
Rice |
cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
T. albidum Banks |
LA |
FL |
DE,IL, KY,NC |
KY.VA |
|||||
|
T. australe Banks |
TX |
AR,TX |
DE.KY |
KY |
|||||
|
T. cheimatos Gert. & Archer T. cinclipes Banks |
TX |
DE |
KY |
||||||
|
T. crispulum Simon |
FL |
TX |
AR |
||||||
|
T. differens Emerton |
OH |
AR |
KY.NC |
NY.VA |
|||||
|
T. flavonotatum Becker T. frondeum Hentz |
FL |
AL,AR,MS |
FL.IL, |
KY.NY |
|||||
|
KY |
|||||||||
|
T. glaucescens Becker T. hidalgo Levi |
OK |
LA |
TX |
TX |
|||||
|
T. llano Levi T. lyricum Walck. |
TX |
DE.KY |
|||||||
|
T. murarium Emerton |
OK |
LA |
TX |
TX |
DE.NC |
NY |
|||
|
T. neshamini Levi |
AR |
DE.IL.KY |
KY.VA |
||||||
|
T. pennsylvanicum Emerton T. piclipes Keys. |
FL |
AR |
FL.NC |
VA |
|||||
|
T. rabuni Chamb. & Ivie |
OK |
TX |
AR |
DE.IL |
CA.VA |
||||
|
T. sexpunctatum Emerton |
KY |
||||||||
|
Theridion sp. |
TX |
DE,KY,NC |
KY |
||||||
|
Theridula emertoni Levi |
AL |
DE.KY |
KY |
||||||
|
T. opulenia (Walck.) |
LA |
FL |
AL,AR,MS |
FL.IL, KY.NC |
KY.VA |
||||
|
Thymoites expulsus (Gert. & Mulaik) T. unimaculalus (Emerton) |
LA |
TX |
AL |
IL |
NY |
||||
|
Thymoites sp. Tidarren sisyphoides |
DE |
||||||||
|
(Walck.) Tidarren sp. |
LA |
FL |
TX |
DE |
|||||
|
THERIDIOSOMATIDAE |
|||||||||
|
Theridiosoma gem mo sum |
|||||||||
|
(L. Koch) |
FL |
||||||||
|
THOMISIDAE |
|||||||||
|
Coriarachne floridana Banks |
LA |
||||||||
|
C. versicolor (Keys.) Coriarachne sp. |
OH |
AL,AR,LA |
DE.NC |
||||||
|
Misumena vatia (Clerck) |
TX |
AL,MS |
FL.IL, KY.NC |
NY |
|||||
|
Misumena sp. Misumenoides formosipes |
OH |
NC |
|||||||
|
(Walck.) |
FL |
QK,TX |
TX |
AL.AR, |
FL.IL, |
NY.VA |
|||
|
MS,TX |
KY.LA, MO.NC |
||||||||
|
Misumenoides sp. Misumenops asperatus |
DE |
||||||||
|
(Hentz) |
OK |
TX |
LA |
OH |
TX |
AL,AR |
FL.IA.IL |
KY, NY.VA |
|
|
MS,TX |
KY.MO |
||||||||
|
M. celer (Hentz) |
OK |
TX |
LA |
FL |
OK,TX |
TX |
AL.AR, MS.TX |
FL.LA.NC |
|
|
M. deserti Schick |
CA |
CA |
|||||||
|
M. dubius Keys. M. lepidus (Thorell) |
TX |
CA |
|||||||
|
M. oblongus (Keys.) |
OK |
AR,TX |
LA |
FL |
TX |
AL.AR, LA, |
LA |
CA.VA |
|
|
MS.TX |
|||||||||
|
Misumenops sp. |
OK |
AR |
OK,TX |
DE.KY, MO.NC |
KY |
||||
|
Ozyptila conspurcaia |
|||||||||
|
(Thorell) |
AL |
||||||||
|
O. creola Gertsch O. monroensis Keys. Ozyptial sp. |
OK |
AR |
AR |
KY |
|||||
|
Synaema bicolor Keys. |
AL |
||||||||
|
S. parvula (Hentz) |
AL.AR, MS.TX |
KY.NC |
VA |
||||||
|
Synaema sp. |
DE |
NY |
|||||||
|
Tmarus angulatus (Walck.) Trnarus sp. |
TX |
MS.TX |
DE |
NY.VA |
|||||
|
Xysticus auctificus Keys. |
AR.TX |
IL.KY |
KY.VA |
X. bicuspis Keys. AL
YOUNG & EDWARDS— FIELD CROP SPIDERS
25
|
Taxon |
Grain sorghum |
Rice |
Sugar- cane |
Corn |
Guar |
Peanuts |
Cotton |
Soybean |
Alfalfa |
|
X. californicus Keys. |
CA |
CA |
|||||||
|
X. concursus Gertsch |
TX |
||||||||
|
X. discursans Keys. |
KY |
KY,NY,VA |
|||||||
|
X. eiegans Keys. |
AL,TX |
IL |
|||||||
|
X. ferox (Hentz) |
LA |
1L,KY |
KY |
||||||
|
X. fraternus Banks |
IL |
||||||||
|
X.funestus Keys. |
TX |
AR.LA.TX |
KY |
KY.NY |
|||||
|
X. furtivus Gertsch |
VA |
||||||||
|
X. gulosus Keys. |
TX |
AL |
NC |
NY |
|||||
|
X. luctans (C. L. Koch) |
NY |
||||||||
|
X. pellax O.P.-Camb. |
TX |
||||||||
|
X. texanus Banks |
LA |
TX |
AR,TX |
KY |
KY |
||||
|
X. transversatus (Walck.) |
AL |
VA |
|||||||
|
X. triguttatus Keys. |
AL |
KY,MO |
KY,VA |
||||||
|
Xysticus sp. |
OK |
AR |
FL,OH |
TX |
AL.MS |
DE,IA,KY, |
KY,VA |
||
|
MO,NC |
|||||||||
|
ULOBORIDAE |
|||||||||
|
Hyptioles cava t us (Hentz) |
AR |
||||||||
|
Uloborus glomosus (Walck.) |
LA |
FL |
TX |
AL.AR.LA |
IL |
||||
|
Uloborus sp. |
OK |
FL |
|||||||
|
ZORIDAE |
|||||||||
|
Zora pumila (Hentz) |
AL |
||||||||
|
Totals = 614 taxonomic entries |
88 |
75 |
137 |
136 |
52 |
131 |
308 |
262 |
233 |
26
THE JOURNAL OF ARACHNOLOGY
APPENDIX 2
Information sources for Appendix 1. Letter and number annotations refer to categories as listed in
Table 1.
GRAIN SORGHUM
OK Bailey, C. L. and H. L. Chada. 1968. Spider populations in grain sorghums. Ann. Entomol. Soc. America, 61:567-571.
[A - 1; B - 4; C - 1; D - 1; E - 3,4,5; F - 2.]
RICE
AR Heiss, J. S. and M. V. Meisch. 1985. Spiders (Araneae) associated with rice in Arkansas with notes on species compositions of populations. Southw. Natur., 30:119-127.
[A - 4; B - 3; C - 1; D - 9; E - 1,6; F - 1.]
TX Woods, M. W. and R. C. Harrel. 1976. Spider populations of a southeast Texas rice field. Southw. Natur., 21:37-48.
[A - 1; B - 9; C - 1; D - 1; E - 1,3,4; F - 2.]
SUGARCANE
LA Ali, A. D. and T. E. Reagan. 1985. Spider inhabitants of sugarcane ecosystems in Louisiana: An update. Proc. Louisiana Acad. Sci., 48:18-22.
[A - 3; B - ?; C - 1; D - ?; E - 1,2, 3,4; F - 1.]
LA Negm, A. A., S. D. Hensley and L. R. Roddy. 1969. A list of spiders in sugarcane fields in Louisiana. Proc. Louisiana Acad. Sci., 32:50-52.
[A - 10; B - 6; C - 1,2; D - 8; E - 1,3,4; F - 2.]
CORN
FL Plagens, M. J. 1985. The corn field spider community: Composition, structure, development and function. Ph.D. Thesis, Univ. Florida, Gainesville. 207 pp.
[A - 3; B - 12; C - 1; D - 6; E - 4; F - 1]
OH Everly, R. T. 1938. Spiders and insects found associated with sweet corn with notes on the food and habits of some species. I. Arachnida and Coleoptera. Ohio J. Sci., 38:136-148.
[A - 1; B - 3; C - 1; D - 1; E - 4; F - 1.]
GUAR
OK, Rogers, C. E. and N. V. Horner. 1977. Spiders of guar in Texas and Oklahoma. Environ. TX Entomol., 6:523-524.
[A - 3; B - ?; C - 1; D - ?; E - 1,3,4; F - 1.]
PEANUTS
TX Agnew, C. W., D. A. Dean and J. W. Smith, Jr. 1985. Spiders collected from peanuts and non-agricultural habitats in the Texas west cross-timbers. Southw. Natur., 30:1-12.
[A - 3; B - 4; C - 1; D - 3; E - 1,3,4; F - 1.]
COTTON
AL, Skinner, R. B. 1974. The relative and seasonal abundance of spiders from the herb-shrub MS stratum of cotton fields and the influence of peripheral habitat on spider populations. M. S. Thesis, Auburn Univ., Alabama. 107 pp.
[A - 4; B - 3; C - 1; D - 27; E - 1,2; F - 2.]
AR Whitcomb, W. H. and K. Bell. 1964. Predaceous insects, spiders, and mites of Arkansas
cotton fields. Univ. Arkansas Agric. Exp. Stn. Bull., 690:1-84.
[A - 6; B - 5; C - 1,2; D - 4+; E - 1,2, 3, 4, 5; F - 2.]
CA Leigh, T. F. and R. E. Hunter. 1969. Predacious spiders in California cotton. California Agric., 1969:4-5.
[A - 1; B - 12; C - 1,2; D - 3; E - 1,2,3, 4, 5; F - 2.]
LA Mysore, J. S. and D. W. Pritchett. 1986. Survey of spiders occurring in cotton fields in
Ouachita Parish, Louisiana. Proc. Louisiana Acad. Sci., 49:53-56.
[A - 1; B - 6; C - 1,2; D - 4; E - 1,3,4; F - 1.]
YOUNG & EDWARDS— FIELD CROP SPIDERS
27
MS Lockley, T. C., J. W. Smith, W. P. Scott and C. R. Parencia. 1979. Population fluctuations of two groups of spiders from selected cotton fields in Panola and Pontotoc Counties, Mississippi, 1977. Southw. EntomoL, 4:20-24.
[A -1; B - 4; C - 1; D - 30; E - 2; F - 2.]
TX Dean, D. A., W. L. Sterling and N. V. Horner. 1982. Spiders in eastern Texas cotton fields. J. Arachnol., 10:251-260.
[A - 3; B - 5; C - 1; D - 1+; E - 1,2, 3, 4; F - 1.]
TX Kagan, M. 1943. The Araneida found on cotton in central Texas. Ann. EntomoL Soc. America, 36:257-258.
[A - 2; B - ?; C - 1; D - 3; E - 4; F - 2.]
SOYBEAN
DE Culin, J. D., Jr. 1978. Spiders in soybean fields: Community structure, temporal distributions of the dominant species, and colonization of the crop. M. S. Thesis, Univ. of Delaware, Newark.
[A - 1; B -12; C - 1; D - 7; E - 3,7; F - 2.]
FL Hasse, W. L. 1971. Predaceous arthropods of Florida soybean fields. M. S. Thesis, Univ. of Florida, Gainesville.
[A - 1; B - 4; C - 1; D - 12; E - 1,3,7; F - 1.]
FL Neal, T. M. 1974. Predaceous arthropods in the Florida soybean agroecosystem. M. S. Thesis, Univ. of Florida, Gainesville.
[A - 3; B - 4; C - 1; D - 12; E - 1,2, 3,4, 7; F - L]
I A Bechinski, E. J. and L. P. Pedigo. 1981. Ecology of predaceous arthropods in Iowa soybean agroecosystems. Environ. EntomoL, 10:771-778.
[A - 2; B - 4; C - 1; D - 15; E - 1,3,7; F - 2.]
IL LeSar, C. D. and J. D. Unzicker. 1978. Soybean spiders: Species composition, population densities, and vertical distribution. Illinois Nat. Hist. Surv. Biol. Notes, 107:1-14.
[A - 2; B - 4; C - 1; D - 3; E - 1,2,7; F - 2.]
KY Culin, J. D. and K. V. Yeargan. 1983. Spider fauna of alfalfa and soybean in central Kentucky. Trans. Kentucky Acad. Sci., 44:40-45.
[A - 3; B - 9; C - 1; D - 4; E - 3,7; F - 1.]
LA Goyer, R. A., D. W. Brown and J. B. Chapin. 1983. Predaceous arthropods found in soybean
in Louisiana. Proc. Louisiana Acad. Sci., 46:29-33.
[A - 1; B - 4; C - 1; D - 3; E - 1,3; F - 1.]
MO Bickenstaff, C. C. and J. L. Huggans. 1962. Soybean insects and related arthropods in Missouri. Univ. Missouri Agric. Exp. Stn. Res. Bull., 803:1-51.
[A - 3; B - 4; C - 1; D - 21; E - 1; F - 2.]
NC Deitz, L. L., J. W. Van Duyn, J. R. Bradley, Jr., R. L. Rabb, W. M. Brooks and R. E.
Stinner. 1976. A guide to the identification and biology of soybean arthropods in North Carolina. North Carolina Agric. Res. Serv. Tech. Bull., 238:1-264.
[A - 4; B - 4; C - 1; D - 40; E - 2,7; F - L]
ALFALFA
CA Yeargan, K. V. and C. D. Dondale. 1974. The spider fauna of alfalfa fields in northern California. Ann. EntomoL Soc. America, 67:681-682.
[A - 3; B - 12; C - 1,2; D - 6+; E - 1,2, 3, 4; F - 1.]
KY Culin, J. D. and K. V. Yeargan. 1983. Spider fauna of alfalfa and soybean in central Kentucky. Trans. Kentucky Acad. Sci., 44:40-45.
[A - 3; B - 10; C - 1; D - 4; E - 2,3; F - L]
NY Wheeler, A. G., Jr. 1973, Studies on the arthropod fauna of alfalfa V. spiders (Araneida). Canadian EntomoL, 105:425-432.
[A - 4; B - 7; C - 1; D - 3; E - 1,3,4; F - 1.]
VA Howell, J. O. and R. L. Pienkowski. 1971. Spider populations in alfalfa, with notes on spider prey and effect of harvest. J. Econ. EntomoL, 64:163-168.
[A - 2; B - 12; C - 1,2; D - 1; E - 1,2; F - 1.]
Edwards, R. L. and E. H. Edwards. 1990. Observations on the natural history of a New England population of Sphodros niger (Araneae, Atypidae). J. Arachnol., 18:29-34.
OBSERVATIONS ON THE NATURAL HISTORY OF A NEW ENGLAND POPULATION OF SPHODROS NIGER (ARANEAE, ATYPIDAE)
Robert L. Edwards
Box 505
Woods Hole, Massachusetts 02543 USA and
Eric H. Edwards
868 Teaticket Highway East Falmouth, Massachusetts 02536 USA
ABSTRACT
The surface portion of the tube webs of Sphodros niger Hentz lies hidden at the interface between duff and overlying pine needles in early successional pitch pine-oak woods on Cape Cod, Massachusetts. Males search for females in June. Spiderlings hatch in August and leave the mother the following April. Millipedes appear to be the principal food item. The surface tubes of older juvenile spiders vary from 13 to 15 cm in length and tend down slope. The surface tube has the consistency of thin parchment. The underground portion varies little in length, averaging 13 cm, and is a simple cylinder. The only adult female web found had a surface tube 63 cm in length. This female had at least 73 spiderlings.
INTRODUCTION
Since the revision of Sphodros by Gertsch and Platnick (1980), at which time 47 specimens of Sphodros niger Hentz were examined, the number of S. niger specimens taken by various collectors has significantly increased (Beatty 1986; Morrow 1986). Most of these new specimens are males, taken when they were searching for females, usually during the month of June. One male was picked up by Jonathan Coddington during the American Arachnological Society’s field trip to Martha’s Vineyard in 1987. In this case the specimen was dead, found in the web of a black widow spider. On the same day Vincent Roth and S. Beshers also collected a male at Walden Pond, Mass. Carol Senske, daughter of the senior author, collected a male on her property in Green Lane, Pennsylvania in early June, 1984. Beginning in 1985 we have consistently picked up live males in the Falmouth, Massachusetts area between the dates of 12 to 25 June. The objective of this paper is to report on the results to date of our study of this elusive spider.
30
THE JOURNAL OF ARACHNOLOGY
RESULTS AND DISCUSSION
Habitat and web location. — We are aware of two concentrations of the species in the southwestern corner of Cape Cod. Both are found in early successional pitch pine ( Pinus rigida ) habitat with scattered white oaks ( Quercus alba) and junipers ( Juniperus virginiana). The understory is variable, with only thinly scattered grass under the pines in one area and a considerable amount of low bush blueberry, scrub oaks, reindeer lichen (Cladonia sp.) and grass in the other.
A thorough search of the area for the tube webs followed the first capture of a male in a pitfall trap in 1984. The search was unsuccessful. Further searches were carried out following the observations reported by Beatty, op. cit. The open, grassy areas in the woods were without webs. Almost by accident, a recently vacated web was found in the woods, near where a male had been found (Fig. 1). Efforts were redoubled following this find in and around the barer areas within the woods, in circumstances where the spiders might have portions of their webs under rocks, logs, tree roots, and other objects, again without success. Ultimately we discovered that the preferred situation was one where there was a thick cover of pine needles over duff, in generally bare areas and with the duff thick enough to remain fairly moist through much of the summer. The above-ground capture tubes lie underneath the needles and are therefore completely hidden from view. The soil in this area is a coarse, sandy soil that retains little moisture. To say that this spider is cryptic is an understatement.
Without exception the webs are on the slopes of gently rounded gullies, one to three meters in elevation above the bottom. Webs were considerable distances apart, averaging about 5 m from one another. No concentration such as that described by Beatty (op. cit.) was observed. The majority found were those of larger immature spiders (over 12 mm long). Only one unoccupied tube of a much smaller individual was found, although the remnants of smaller tubes were twice found attached to larger occupied tubes (Fig. 2).
Web architecture. — The webs of these immatures were more or less consistent in their structure and length. In ten of the twelve tubes found so far, the surface portion of the tube paralleled the duff-pine needle interface, averaged 13 cm in length and invariably ran down slope. A relatively sharp, right angle turn led down into the soil for a comparable distance, averaging about 13 cm. The other two webs were found in thickets of low bush blueberries where there were no pine needles but rather a year-round accumulation of leaves with leaf mold underneath. The layout of the webs was otherwise just like those found in the pine needles.
There is no obvious widening of the spider’s retreat at the bottom. Usually at the very bottom a centimeter or more of compacted material had accumulated, including Sphodros exuvia and a quantity of separated scutes of millipedes. The surface portion of the tube (Fig. 4) has attached material comparable to that found in the duff, while the subterranean section has a thin coating of soil. The attached material is exactly what is external to the tube and may have become attached as the web was constructed, not necessarily as a consequence of any deliberate activity on the part of the spider. In our experience thus far with captive S. niger , if the surface portion of the tube is left exposed, the spider makes no attempt to disguise it and will eventually abandon it if left uncovered.
EDWARDS & EDWARDS— OBSERVATIONS ON SPHODROS NIGER
31
Figures 1-3. — Diagrams of the placement of Sphodros niger tube webs and burrows. 1, horizontal portion partially under rotting board; 2, typical web of older juveniles; 3, gap indicates 32 cm of web not shown.
The internal diameter of the horizontal tubes varies from 10 to 12 mm. This is a roomy diameter considering the size of the spider. The inner surface of the horizontal tube is a very light grey in color, smooth and parchment-like in consistency and very strong. If carefully uncovered the tube retains its integrity. The underground portion is soft and flexible, and fairly easily pulled apart. In two cases, the horizontal portion separated from the vertical portion while the pine needle cover was being pulled aside. The horizontal portion of the tube web of an adult female with young, found in August 1988, was unexpectedly long (63 cm; Fig. 3). The vertical portion was exactly like all the others. The end of the horizontal portion of the tube had been collapsed or drawn up by the spider and was compacted into a fairly solid wad.
Behavior of captives. — At the time of this writing (January, 1989) we are keeping several specimens in captivity. It is impossible to make direct observations without disturbing them, since their natural cover has been recreated; consequently we have made only limited behavioral observations. Captive S. niger are quick to make new subsurface tubes, but do not reconstruct the surface portion readily. If the subsurface portion of the original tube is placed in a prefabricated hole with the horizontal portion attached and covered with pine needles, the spider will use the entire tube. Those without horizontal tubes
32
THE JOURNAL OF ARACHNOLOGY
Figure 4. — The surface portion of the web of a mature female Sphodros niger, minus a 7-cm piece and the underground section (13.5 cm). See text for details.
usually do a great deal of excavating, and piles of dirt soon appear at the surface around the upper ends of their tubes. This behavior is reminiscent of an observation of Beatty’s (op. cit.), in which he observed piles of dirt in and at the end of a tube. At first this activity was puzzling, but eventually we concluded that it usually preceded the construction of a new surface tube originating some distance from the original point of entrance of the old tube into the ground. The spider digs a new exit from below — it does not leave what web it has to start an entirely new tube from the surface.
Webs were not found where the duff and leaf cover were thick enough to encourage mice and shrews (esp. Blarina brevicauda and Sorex cinereus) to forage and dig burrows. This could be as much a consequence of predation by mammals as choice.
Food and feeding.— -These spiders seem to be little disturbed when removed from their habitat if they are left in their tube. One spider almost immediately seized and ate a small caterpillar that wandered across its tube while the web was laid out in the bottom of a plastic pail, barely an hour after it had been removed from its natural surroundings. Another juvenile spider, shortly after being placed in its new home, opened its tube to toss out its shed exuvium.
Judging from the debris found in the bottoms of their tunnels, S. niger appears to favor millipedes for food. A few beetle elytra were found as well. It is unlikely that flies, caterpillars or other aerial and surface arthropods would have ready access to the tube. The most abundant insects of any size in the duff-needle interface are various species of carabid beetles, themselves predators. One carabid genus Pterostichus sp., quickly caught and devoured a captive Sphodros that had
EDWARDS & EDWARDS— OBSERVATIONS ON SPHODROS NIGER
33
left its web. Another Pterostichus was found in an unoccupied web. There are a few spiders, notably Steatoda americana (Emerton), Agelenopsis kastoni Chamberlin & Ivie, and some lycosids in shallow retreats that occasionally are found in small numbers at the duff-needle interface. Centipedes and sowbugs occur here in fair number while millipedes are usually abundant. Earthworms are infrequently observed in this situation but cannot be ruled out as potential prey.
Spiderlings. — The one female found with young on 14 August 1988, had 73 spiderlings in the horizontal portion of the web and an unknown number below that in the vertical section. The spiderlings were transferred to the vertical portion along with the adult and placed in an aquarium for observation and study. The newly hatched spiderlings are unpigmented except for the eyes, well stocked with yolk, and possess relatively underdeveloped limbs and spinnerets. In terms of general body size and shape, the newly hatched spiderlings are slightly larger than those that leave in the spring. In the wild the young leave the mother in April, at which time they are moderately pigmented light brown in color, have become more slender, look like miniature adults and measure from 2.5 to 2.6 mm. We have yet to observe any ballooning activity on the part of the young — the few captured in the wild were taken in a pitfall trap.
Behavior of males. — In any particular year males move about for approximately a seven day period, but exactly when this activity occurs, is not predictable. In 1984, 1985, and 1986, movement was during the second to third week in June, and in 1987, the fourth. No observations were made in 1988. So far we have detected no obvious climatic events, such as rainstorms, which trigger this activity. On several occasions we followed males during their mating “walkabout” for considerable periods of time. They move rapidly for short distances, usually only several feet, before they take cover and remain quiet for varying periods of time. They tend to move down slope, but the movements otherwise do not seem to be directed. They were most frequently seen in the early afternoon. Attempts to follow males were unsuccessful and frustrating. They were easily lost in vegetation and debris, or occasionally remained stationary for very long periods of time (hours).
Comparisons with other species of Sphodros. — There are similarities and differences between the webs and behavior of S. niger and those of abboti and rufipes as noted by Coyle and Shear (1981). The males of abboti behave much as niger when in search of mates. They are diurnal and seem to rely in part on a contact pheromone which helps to explain our observations of the behavior of niger males. In addition niger males both move like and have the appearance of pompilid wasps or larger, dark gnaphosids. Our single surface web of an adult female niger , 63 cm in length, was about twice as long as the maximum length of the aerial webs of adult female abboti and rufipes (35 cm). The number of young, 73 plus for our single female niger is comparable to the average of 79.7 for six broods of abboti. The surface portion of the niger web is substantially tougher than the underground portion; the reverse is true of the other two species.
ACKNOWLEDGMENTS
We are grateful to W. A. Shear, F. A. Coyle, and J. A. Coddington for comments and suggestions on the manuscript. H. Guarisco kindly provided some needed literature.
34
THE JOURNAL OF ARACHNOLOGY
LITERATURE CITED
Beatty, J. A. 1986. Web structure and burrow location of Sphodros niger (Hentz). J. Arachnol., 14:130-132.
Coyle, F. A. and W. A. Shear. 1981. Observations on the natural history of Sphodros abhoti and Sphodros rufipes (Araneae, Atypidae), with evidence for a contact sex pheromone. J. Arachnol., 9:317-326.
Gertsch, W. and N. Platnick. 1980. A revision of the American spiders of the family Atypidae (Araneae, Mygalomorphae). Amer. Mus. Nov. (2704): 1-39.
Morrow, W. 1986. A range extension of the purseweb spider Sphodros rufipes in eastern Kansas (Araneae, Atypidae). J. Arachnol., 14:119-121.
Manuscript received April 1989, revised June 1989.
Carrel, James E. 1990. Water and hemolymph content in the wolf spider Lycosa ceratiola (Araneae, Lysoidae). J. ArachnoL, 18:35-40.
WATER AND HEMOLYMPH CONTENT IN THE WOLF SPIDER LYCOSA CERATIOLA (ARANEAE, LYCOSIDAE)
James E. Carrel
Division of Biological Sciences University of Missouri-Columbia Columbia, Missouri 65211 USA
ABSTRACT
Female Lycosa ceratiola, most of whom were gravid when collected in March in Florida, contained significantly less water than males (2.24 versus 2.88 mg water/ mg dry mass, representing 69 and 74% of wet mass, respectively). Both sexes had similar amounts of hemolymph in their bodies (32.4% of wet mass in females and 37.3% in males). The density of hemolymph in male and female spiders at 22- 24° C averaged 1.00 mg/ pi. These results suggest that egg production in female spiders affects their total water content, most likely because ripening eggs gain energy-rich lipids at the expense of water. Two commonly used water content indices, which express water mass as a proportion of either wet or dry body mass, are evaluated.
INTRODUCTION
Water and blood relations in spiders are poorly understood compared to information concerning insects, mites, and ticks. Moreover, the state of the field is heterogeneous: many basic physiological problems in spiders have attracted little attention, whereas a few topics, most notably hemolymph ionic and biological chemistry, have been well investigated (Pulz 1987; Strazny and Perry 1987; and references therein).
Here I attempt to resolve two apparently contradictory concepts underlying variability in water content in spiders (Pulz 1987). The first concept is that there is no consistent difference in water content between the sexes within a species. The second principle is that individual water content depends in part on lipid content, which is high in gravid females compared to males. I hypothesized that water content in gravid females should be significantly less than in males of a given species. Furthermore I hypothesized that the blood content of spiders might also show a similar sexual difference.
I here report on experiments with the wolf spider Lycosa ceratiola Gertsch and Wallace that test these ideas. In addition, I discuss the indices used to express water content in spiders. To my knowledge this is only the second study of hemolymph content in a spider. In this study I express water or hemolymph content as the proportion of spider body mass (Allen 1974).
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THE JOURNAL OF ARACHNOLOGY
MATERIALS AND METHODS
Adult male and female L. ceratiola ( N - 148) were collected in March in xeric scrubby flatwoods at the Archbold Biological Station, Highlands County, Florida. At this time of year, as indicated by preliminary field surveys, reproduction is prevalent in this species (J. E. Carrel, unpublished observations). Spiders were maintained individually in plastic containers as described by Carrel and Eisner (1984). Their wet mass when alive was measured individually to the nearest 0.1 mg shortly before being used in tests. Individual spiders were used only in one test.
Water content of L. ceratiola was determined gravimetrically. Adult spiders (N = eight of each sex) were weighed, placed individually in a tared vial, killed by freezing, and then dried to constant mass in an 80° C oven. Water content was expressed as % wet mass and mg water/ mg dry mass.
To calculate hemolymph content (% wet mass) I determined density and volume of hemolymph in spiders. Hemolymph density was measured in spiders ( N - eight of each sex) as follows: individuals were anesthetized with carbon dioxide gas; a leg was amputated at the base; discharged hemolymph (2.7-11.1 jul) was taken up in a volumetrically calibrated tube previously weighed to 1 ug on a Cahn 28® electrobalance; the filled tube was reweighed and the volume of fluid in it was measured. Density of each hemolymph sample was calculated by dividing its volume by its mass (mg/ /il).
Hemolymph volume in adults ( N - eight of each sex) was determined using the radiolabeled inulin dilution method (Wharton et al. 1965). Injection (5 jul) was accomplished with a micrometer syringe into the pericardial region of the abdomen of a spider anesthetized with carbon dioxide gas. Carboxy- 1 4C-inulin (sp. act. 2.60 mCi/gram, Sigma Chemical Co.) was dissolved in spider saline (Rathmayer 1965) to achieve a dosage of 0.1 yuCi per spider. Each spider was again anesthetized 1 h after injection and hemolymph was collected as previously described. The hemolymph was discharged immediately from the tube into 1 ml deionized water in a scintillation vial. Subsequently 15 ml of Aquasol scintillation fluid was added to each vial and radioactivity was measured in a Hewlett- Packard Tri-Carb 460C® scintillation counter. In a similar fashion the radio- activity in aliquots of the inulin stock solution was measured and used as a reference standard. To correct for counting inefficiencies and quenching effects, the sample channel ratio (SCR) was used to calculate total radioactivity (cpm) in each sample. Hemolymph volume of each spider was calculated as follows:
Vb = -LT, — Vi
Cs
where: Vb = volume of hemolymph in spider Vs = volume of hemolymph sample Vi - volume of solution injected (5 ul)
Q = count of solution injected Cs = count of hemolymph sample
The reproductive state of female L. ceratiola ( N = 100) was determined in two ways. Using the method of Riddle (1985), 50 spiders were killed by freezing and their abdomens were bisected. Specimens with an egg mass greater than one-sixth of the cross-sectional area of the abdomen were considered gravid. To verify this
CARREL— WATER AND HEMOLYMPH IN LYCOSA
37
Table 1. — Dry mass and water content in adult Lycosa ceratiola. Differences between values with the same letter in a column are significant (a = P < 0.001; b = P < 0.01) with Mest. Mean ± SE, (Range).
|
Sex |
Dry mass mg |
Water content |
N |
|
|
% wet mass |
mg water/ mg dry mass |
|||
|
Male |
80.1 ± 8.9a |
74.0 + 0,9b |
2.88 ± 0.1 4b |
8 |
|
(48.3 - 117.2) |
(71.3 - 78.2) |
(2,48 - 3.58) |
||
|
Female |
228.2 + 26.4a |
69.0 + l.lb |
2.24 + 0.1Qb |
8 |
|
(157.5 - 388.4) |
(61.5 - 71.2) |
(1.59 - 2.47) |
procedure, the remaining 50 spiders were inspected at 2=3 day intervals for 4 wk to ascertain whether each had produced an egg sac.
Statistical analyses of the data were performed manually using the methods described in Sokal and Rohlf (1987) or by computer using SAS routines (SAS 1985).
RESULTS AND DISCUSSION
Living adult L. ceratiola exhibited a sexual size dimorphism. Data ( X + SE, N = 24 of each sex) showed female and male spiders weighed 724 ± 56 and 305 ± 29 mg, respectively. This difference, a factor equal approximately to 2.37, was highly significant (Mest, P < 0.001). Female spiders are larger than males, presumably because females invest much more in reproduction than males (Gertsch 1979; Foelix 1982). There was no significant difference (ANOVA, P > 0.01) in wet body mass among spiders used in different experiments.
Female L. ceratiola contained proportionately more dry mass and, therefore, less water than males (Table 1). By either index used in Table 1, water content in female spiders was significantly less than in males. The female/ male dry mass ratio was 2.85, approximately 20% higher than the wet mass ratio.
Whole body water content in L. ceratiola was slightly less than generally reported for adult spiders from a variety of biomes in North America (Stewart and Martin 1970; Vollmer and MacMahon 1974; Riddle 1985). In all of these studies the spiders were well watered in the laboratory, so dehydration should not be a significant factor. Moreover, Vollmer and MacMahon (1974) found no correlation between habitat aridity, body mass, and interspecific differences in water content of spiders. Surely the relationship between water content and physiological ecology in spiders is sufficiently complex that many more data from many more species are needed to discern life history patterns.
Density and relative amount of hemolymph was similar in male and female L. ceratiola (Table 2). Females contained relatively less hemolymph than males, but because of the variability in the data, the difference between the sexes was not significant (Mest, P > 0.05). Whether the high degree of intrasexual variablity in hemolymph content is biologically meaningful or the result of an artifact remains to be determined.
To my knowledge this is the first report of using dilution of radiolabeled inulin injected into spiders. Stewart and Martin (1970), using unlabeled inulin as a blood-born dye, reported the hemolymph in male and female Dugesiella hentzi
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THE JOURNAL OF ARACHNOLOGY
Table 2. — Hemolymph density and content in adult L. ceratiola. Differences between values in the same column are not significant (P> 0.1) with t-test. Mean + SE, (Range).
|
Sex |
Hemolymph density mg/jul |
Hemolymph content % wet mass |
N |
|
Male |
1.003 ± 0.007 |
37.3 ± 2.4 |
8 |
|
(0.97 - 1.03 |
(28.2 - 46.9) |
||
|
Female |
1.000 ± 0.005 |
32.4 ± 6.5 |
8 |
|
(0.98 - 1.02 |
(26.6 - 41.6) |
averages 19.65 and 18.10%, respectively, of wet body mass. Although the hemolymph content in D. hentzi adults is about one-half as much as in L. ceratiola , a difference which in part could result from using different methodologies, nevertheless within each species females tend to have less hemolymph than males.
A majority (74%) of 50 female L. ceratiola examined internally were found to be gravid. This method was verified by the finding that a smaller, but insignificantly different percentage (58%) of 50 females actually produced egg sacs when maintained for 4 wk in the laboratory (chi-square test, P > 0.05). Hence, lipid content of female spiders used in these water and blood content studies presumably was high because most of them contained energy rich eggs. The energy density of spider eggs, expressed as joules/ g dry mass, generally is 11% higher than the average for nongravid adult spiders (Anderson 1978).
e
0)
c
o
o
0)
T3
Water mass (mg)
Figure 1. — Comparison of two indices for water content in a hypothetical spider having dry mass of 1 mg as a function of its absolute water mass. (See text for details). The range of water content values matches those actually found in various spiders under different conditions, as summarized by Pulz (1987). For graphical purposes, water content based on wet body mass is shown at one-tenth scale so that the two lines are similar in scope.
CARREL— WATER AND HEMOLYMPH IN LYCOSA
39
As indicated in Table 1, the water content of whole spiders can be expressed by two different indices, one based on the wet mass and the other based on the dry mass of the animal. Most authors, as cited by Pulz (1987), have used the wet mass index, often refered to as “percent water”. But is one index scientifically more robust than the other? One way to answer this question is to examine how body water content changes as a function of water mass in a spider, under idealized conditions where dry mass is kept constant (say equal to 1 mg) as if the animal is undergoing dehydration or rehydration. As shown in Fig. 1, under these hypothetical conditions the two indices yield two rather different graphs: the wet mass index levels off asymptotically as the spider gains a lot of water, whereas the dry mass index rises in a linear fashion across the same range.
From this graphical analysis, clearly the linear dry mass index is preferable to the curvilinear wet mass index of body water content. An example will illustrate this conclusion. At high moisture levels, a one percent gain or loss in water content based on a spider’s wet body mass translates into a large change approximating 1 mg water/ mg dry mass of the animal.
In conclusion, this study shows that a consistent difference in water content between the sexes of L. ceratiola can be found when females are gravid. The presence of eggs evidently increases the lipid and dry mass contents in female spiders, causing a slight (5%) decline in water content in comparison to male spiders.
ACKNOWLEDGMENTS
I thank Z. Yang and M. H. McCairel for field and laboratory assistance in preliminary studies, M. Deyrup and the staff of the Archbold Biological Station for hospitality and research facilities, J. D. David and G. H. Perrot for technical assistance, and J. F. Anderson and K. N. Prestwich for reviewing the manuscript. Supported in part by Research Incentive Funds from the University of Missouri- Columbia.
LITERATURE CITED
Allen, S. E., ed. 1974. Chemical Analysis of Ecological Materials. Wiley & Sons, New York.
Anderson, J. F. 1978. Energy content of spider eggs. Oecologia, 37:41-57.
Carrel, J. E. and T. Eisner. 1984. Spider sedation induced by defensive chemicals of milliped prey.
Proc. Natl. Acad. Sci. USA, 81:806-810.
Foelix, R. F. 1982. Biology of Spiders. Harvard Univ. Press, Cambridge.
Gertsch, W. J. 1979. American Spiders, 2nd Ed. Van Nostrand Reinhold, New York.
Pulz, R. 1987. Thermal and water relations. Pp. 26-55, In Ecophysiology of Spiders (W. Nentwig, ed.). Springer- Verlag, Berlin.
Rathmayer, W. 1965. Polyneuronale Innervation bei Spinnen. Naturwissenschaften, 52:114.
Riddle, W. A. 1985. Hemolymph osmoregulation in several myriapods and arachnids. Comp. Biochem. Physiol., 80A:3 13-323.
SAS. 1985. SAS User’s Guide: Statistics, Version 5 Edition. SAS Institute, Cary, North Carolina.
Sokal, R. R. and F. J. Rohlf. 1987. Introduction to Biostatistics, 2nd Ed. Freeman, New York.
Stewart, D. M. and A. W. Martin. 1970. Blood and fluid balance of the common tarantula, Dugesiella hentzi. Z. vergl. Physiol., 70:223-246.
Strazny, F. and S. F. Perry. 1987. Respiratory system: structure and function. Pp. 78-94, In Ecophysiology of Spiders (W. Nentwig, ed.). Springer- Verlag, Berlin.
40
THE JOURNAL OF ARACHNOLOGY
Vollmer, A. T. and J. A. MacMahon. 1974. Comparative water relations of five species of spiders from different habitats. Comp. Biochem. Physiol, 47A:753-765.
Wharton, D. R. A., M. L. Wharton, and J. Lola. 1965. Blood volume and water content of the male American cockroach, Periplaneta americana L - methods and the influence of age and starvation. J. Ins. Physiol., 11:391-404.
Manuscript received May 1989, revised June 1989.
Tugmon, C. R., J. R. Brown and N. V. Horner. 1990. Karyotypes of seventeen USA spider species (Araneae, Araneidae, Gnaphosidae, Loxoscelidae, Lycosidae, Oxyopidae, Philodromidae, Salticidae and Theridiidae). J. Arachnol, 18:41-48.
KARYOTYPES OF SEVENTEEN USA SPIDER SPECIES (ARANEAE, ARANEIDAE, GNAPHOSIDAE, LOXOSCELIDAE, LYCOSIDAE, OXYOPIDAE, PHILODROMIDAE, SALTICIDAE AND THERIDIIDAE)
Cathy R. Tugmon1, Judy D. Brown, and Norman V. Horner
Department of Biology Midwestern State University Wichita Falls, Texas 76308 USA
ABSTRACT
Karyotypes are reported for 17 species from eight families of spiders from Texas and Missouri. Chromosomal counts (2N) are as follows: Araneidae — Eustala enter tom, 24; Gnaphosidae — Cesonia sincera, 22 and 24; Nodocion floridanus, 24; Loxoscelidae — Loxosceles reclusa, 18 and 20; Lycosidae— Lycosa rabida, 28 and 30; Oxyopidae — Oxyopes scalaris, 21; Philodromidae — Tibellus duttoni, 29; Salticidae— Mae via inclemens, 27 and 28; Marpissa pikei, 28; Metaphidippus galathea, 27 and 28; Peckhamia americana, 22 and 24; Phidippus audax, 28 and 30; Phidippus texanus , 28 and 30; Platycryptus undatus, 28 and 30; Salticus austinesis, 28 and 30; Tutelina elegans, 27 and 28; and Theridiidae— Steatoda triangulosa, 22 and 24.
INTRODUCTION
A thorough search of the literature indicates chromosomal data (counts) are available for approximately 300 of the more than 30,000 spider species (Gowan 1985; Datta and Chatterjee 1988). Most of these are reported from the Old World and many are identified only at the generic level. This study adds karyotypic data for 14 additional identified species and three that have been previously reported.
MATERIALS AND METHODS
Specimens for the present study were collected from north-central Texas with the exception of Oxyopes scalaris Hentz and Tutelina elegans (Hentz) which were from eastern Missouri.
The meiotic studies were accomplished by examining the ovaries and testes of penultimate and mature spiders. The meiotic procedure used was an air-dry method developed by Cokendolpher and Brown (1985). The only modification was the stain. The commercially available Diff-Quick Solution II was used to stain the chromosomes. This staining solution consisted of 1.25 g/1 thiazine dye mixture, 100% PDC (0.625 g/1 azure A and 0.625 g/1 methylene blue) and buffer.
•Present address: Department of Zoology, University of New Hampshire, Durham, NH 03824 USA.
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THE JOURNAL OF ARACHNOLOGY
Five-day-old eggs (embryos) were used for the mitotic studies. The procedure followed was a modification of Matsumoto’s (1977) method. Substitutions included the use of methanol instead of ethyl alcohol in the fixative, the use of four eggs instead of one, and a pH of 7.0 for the saline solution instead of 7.2. All mitotic preparations were flame dried and stained with Giemsa. The stain was prepared by mixing 2 to 3 ml of Giemsa with 50 ml phosphate buffer (0.469 g sodium dihydrogen phosphate, 0.937 g sodium monohydrogen phosphate/ 1 water).
Chromosome numbers were determined by counting spreads for each species. The most frequent chromosome counts were regarded as the valid number. In mitotic studies, species where two different consistent counts were noted, they were assumed to be due to the sex determining mechanism.
Specimens sacrificed for meiotic studies and females that produced the eggs for the mitotic studies are deposited in the Invertebrate Collection at Midwestern State University.
RESULTS AND DISCUSSION
Eggs are excellent sources of somatic cells that provide good mitotic spreads. At present, spider karyotyping techniques for somatic cells are not sufficient to observe the sex-determining mechanisms. We agree with Matsumoto’s (1977) deductions that meiotic preparations are necessary for determination of the sexing mechanisms.
Tables 1 and 2 list the results of meiotic and mitotic works, respectively. The tables indicate the species studied, diploid (2n) numbers, sex-determining mechanisms in meiotic studies, and geographic location. References are made to previous studies where researchers examined the same or closely related species. Some counts in this study do not agree with the previously reported results (see Table 1). This may be due to counting error, improper identification or even geographic variation. Representative photographs of all species examined are shown in Figs. 1-25 with the exception of Lycosa rabida Walckenaer and Peckhamia americana (Peckham and Peckham) which were unavailable.
Datta and Chatterjee (1988) report that 55 species of Araneidae have been karyotyped. The 2n number ranges from 14 to 46 with 24 being the most common. Our study is the first to report a karyotype for Eustala emertoni (Banks) (Fig. 1). It is 2n=24, as are 81% of the other Araneidae. Since this is a mitotic study no sex-determining mechanism is confirmed.
According to the literature 13 different species of Gnaphosidae have been reported (Painter 1914; Hackman 1948; Suzuki 1952; Mittal 1961). With the exception of Scotophaeus blackwallii (Thorell), which Mittal (1961) reported as having 11 autosomal pairs and an XXO-XXXX sex-determining mechanism, all other Gnaphosidae cytogenetically known have 10 autosomal pairs and an XXO- XXXX sex-determining mechanism (Painter 1914; Hackman 1948; Suzuki 1952; Mittal 1961). Cesonia sincera Gertsch and Mulaik (Figs. 2-3) and Nodocion floridanus (Banks) (Fig. 4) mitotic studies show this same consistency. These two karyotypes are the first reported for their respective genera.
Our figures show Loxosceles reclusa Gertsch and Mulaik (Loxoscelidae) males as 2n— 22 and females as 2n=24 and a sex determining mechanism of XXO-
TUGMQN, BROWN & HORNER— SPIDER KARYOTYPES
43
Table 1. — Meiotic Studies. Species, diploid number, number of individuals examined ( ), sex- determining mechanism, geographic location and selected supportive references.
|
Diploid number |
Sex determining mechanism |
Geopranhic |
|||
|
Species |
Male |
Female |
Male Female |
location |
References |
|
ARANEIDAE |
|||||
|
Eustala sp. LOXOSCELIDAE Loxosceles reclusa |
24 |
xxo |
Asia |
Mittal 1961 |
|
|
Gertsch & Mulaik L. rufipes (Lucas) [prob. |
18(9) |
20(2) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
L. laeta- see text] LYCOSIDAE |
20 |
xxo-xxxx |
S.A. |
Diaz & Saez 1966 |
|
|
Lycosa rabida Walck. |
28(1) |
30(1) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
L. rabida OXYOPIDAE |
28 |
30 |
xxo-xxxx |
N.A. (MS) |
Wise 1983 |
|
Oxyopes seratus (L. Koch) PHILODROMIDAE |
21 |
22 |
xo-xx |
Asia (Japan) |
Suzuki 1952 |
|
Tibellus oblongus (Walck.) |
24 |
26 |
xxo-xxxx |
Asia |
Sokolov 1962 |
|
T. tenellus (L. Koch) SALTICIDAE Maevia inclemen [reported as M. vittata |
28 |
30 |
xxo-xxxx |
Asia (Japan) |
Suzuki 1952 |
|
Hentz] Peckhamia americana |
28 |
30 |
xxo-xxxx |
N.A. |
Painter 1914 |
|
(Peck. & Peck.) |
22(3) |
24(3) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
Phidippus audax (Hentz) |
28(1) |
30(1) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
Phidippus audax (Hentz) Salticus austinensis |
22 |
24 |
xxo-xxxx |
N.A. (TX) |
Pinter & Walters 1971 |
|
Gertsch |
28(7) |
30(3) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
S. cingulatus (Panzer) THERIDIIDAE Steatoda triangulosa |
28 |
30 |
xxo-xxxx |
Asia |
Sokolov 1960 |
|
(Walck.) |
22(3) |
24(5) |
xxo-xxxx |
N.A. (TX) |
Current study |
|
S. bipunctata (L.) |
22 |
24 |
xxo-xxxx |
Europe |
Hackman 1948 |
XXXX (Figs. 5-6). Of the two Loxosceles species previously reported, the sex- determining mechanism is identical but they have a different number of autosomal pairs. Loxosceles rufescens (Dufour) and L. rufipes (Lucus) are reported by Begak and Begak (1960) and Diaz and Saez (1966) respectively as 2n=20. These workers examined only males. Based upon Gertsch’s (1967) revision
44
THE JOURNAL OF ARACHNOLOGY
Table 2. — Mitotic Studies. Species, diploid number, number spreads examined ( ) and geographical location.
|
Species |
Diploid numbers |
Geographic location |
|
|
ARANEIDAE |
|||
|
Eustala emertoni (Banks) |
24(4) |
N.A.,(TX) |
|
|
GNAPHOSIDAE |
|||
|
Cesonia sincera Gertsch & Mulaik |
22(1) |
24(1) |
N.A.,(TX) |
|
Nodocion floridanus (Banks) |
24(4) |
N.A.,(TX) |
|
|
OXYOPIDAE |
|||
|
Oxyopes scalaris Hentz |
21(4) |
N.A.,(MO) |
|
|
PHILODROMIDAE |
|||
|
Tibellus duttoni (Hentz) |
29(3) |
N.A.,(TX) |
|
|
SALTICIDAE |
|||
|
Maevia inclemens (Walckenaer) |
27(4) |
28(4) |
N.A.,(TX) |
|
Marpissa pikei (Peckham & Peckham) |
28(8) |
N.A.,(TX) |
|
|
Metaphidippus galathea (Walckenaer) |
27(8) |
28(3) |
N.A.,(TX) |
|
Phidippus audax (Hentz) |
28(39) |
30(12) |
N.A.,(TX) |
|
Phidippus texanus Banks |
28(3) |
30(8) |
N.A.,(TX) |
|
Platycryptus undatus (De Geer) |
28(3) |
30(8) |
N.A.,(TX) |
|
Salticus austinensis Gertsch |
28(1) |
30(1) |
N.A. (TX) |
|
Tutelina elegans (Hentz) |
27(9) |
28(8) |
N.A. (MO) |
|
THERIDI1DAE |
|||
|
Steatoda triangulosa (Walckenaer) |
22(19) |
24(1) |
N.A.,(TX) |
these reported species, L. rufescens and L. rufipes are probably misidentified and should be L. gaucho and L. laeta respectively.
Gowan’s (1985) survey of the literature revealed karyotypes of approximately 62 different, identified, species of Lycosidae. Diploid counts range from 22 to 30 with 13 autosomal pairs and an XXO-XXXX sex-determining mechanism being the most common. Our findings for Lycosa rabida Walckenaer agree with those of Wise (1983) and match the modal number for the family.
In the Oxyopidae three genera and approximately eight, identified, species have been karyotyped (Painter 1914; Hackman 1948; Bole-Gowda 1950; Suzuki 1950, 1952; Sharma and Tandon 1957; Mittal 1961). All but Oxyopes salticus L. Koch (Painter 1914) and Peucetia viridana Stoliczka (Bole-Gowda 1950) have 10 autosomal pairs and an XO-XX sex-determining mechanism. This study revealed that the mitotic spreads of Oxyopes scalaris (Fig. 7) had a 2n count of 21.
Thirteen autosomal pairs and an XXO-XXXX sex-determining mechanism is the most common number for members of the Philodromidae (Hackman 1948; Sokolov 1960; Suzuki 1952). The 2n count obtained from mitotic spreads for Tibellus duttoni (Hentz) (Fig. 8) is 29. Variation from this count has been reported for T. oblongus (Walckenaer) (Hackman 1948) and T. tenellus (L. Koch) (Suzuki 1952) as indicated in Table 1. Further studies are needed for conclusive counts within the genus and of this species.
Karyotypes from approximately 50 species of Salticidae have been previously reported by Gowan (1985). Maevia inclemens (Walckenaer) (Figs. 9-10), previously known as Maevia vittata Hentz, was karyotyped by Painter (1914). He worked with two morphologically different males but reported no variation in the chromosome numbers. Only one of the diploid numbers obtained in this study agreed with Painter.
TUGMON, BROWN & HORNER— SPIDER KARYOTYPES
45
Figures 1-9. — Chromosome spreads of: 1, Eustala emertoni 2n=24; 2,3, Cesonia sincera\ 2, 2n=22; 3, 2n=24; 4, Nodocion floridanus 2n=24; 5,6, Loxosceles reclusa\ 5, male 2n=18; 6, female 2n— 20; 7, Oxyopes scalaris 2n=21; 8, Tibellus duttoni 2n=29; 9, Maevia inclemens 2n=27. Scale bar-- 10 /tun.
Karyotypes of Marpissa pikei (Peckham and Peckham) (Fig. 11), Metaphidippus galathea (Walckenaer) (Figs. 12-13), Peckhamia americana (Peckham and Peckham), Platycryptus undatus (De Geer) (Figs. 18-19) and Tutelina elegans (Hentz) (Figs. 21-22) are reported for the first time. As these are
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Figures 10-18. — Chromosome spreads of: 10, Maevia inclemens 2n=28; 11, Marpissa pikei 2n=28; 12,13, Metaphidippus galathea; 12, 2n=27; 13, 2n=28; 14,15, Phidippus audax\ 14, males 2n=28; 15, females 2n=30; 16,17, Phidippus texanus; 16, 2n=28; 17, 2n=30; 18, Platycryptus undatus 2n=28. Scale bar=10 /um.
also the first reported for each genus no data on related forms are available for comparison.
Phidippus audax (Hentz) (Figs. 14-15) counts do not agree with those reported by Pinter and Walters (1971). However, the meiotic and mitotic counts in this
TUGMON, BROWN & HORNER— SPIDER KARYOTYPES
47
Figures 19-24. — Chromosome spreads of: 19, Platycryptus undatus 2n=30; 20, Salticus austinesis male n=13 and XXO (the X’s are indicated with arrows); 21,22, Tutelina elegans; 21, 2n=27; 22, 2n=28; 23,24, Steatoda triangulosa", 23, males 2n=22; 24, females 2n=24. Scale bar=10 /im.
research were consistent and supportive for 2n counts of 28 and 30 with a sexing mechanism of XXO-XXXX. These diploid numbers were also found by Maddison (Gowan 1985). Phidippus texanus Banks (Figs. 16-17) diploid counts from mitotic studies were consistent with those of P. audax. Salticus austinesis Gertsch (Fig. 20) diploid counts agree with Salticus cingulatus (Panzer) (Sokolov 1960) and Salticus scenicus (Clerck) (Hackman 1948). Phidippus texanus Banks and Salticus austinesis Gertsch are reported for the first time.
Eight genera and 13 species of Theridiidae have been karyotyped. With the exception of Chrysso venusta (Yaginuma) which has 11 autosomal pairs and an XXO-XXXX sex-determining mechanism (Kageyama and Seto 1979) all reported theridiids have 10 autosomal pairs and a XXO-XXXX sex-determining mechanism. Steatoda triangulosa (Walckenaer) (Figs. 23-24) typifies this pattern.
Many additional species must be karyotyped, and correct identification determined before assessing any inter- and intra-specific chromosomal variation. With the development of consistent banding techniques in spiders, it may be possible to determine homologies and devise a standard numbering system at least within some genera. It could then be possible to determine the diploid number for each sex from somatic cells such as eggs (embryos).
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ACKNOWLEDGMENTS
We want to thank the Biology Department of Midwestern State University for providing the funds, facilities and equipment for this research. This paper is the combined results of separate theses submitted by Tugmon and Brown for their masters degrees. Appreciation is expressed to Jane Lindsey who typed the manuscript. We especially thank James Cokendolpher, Bruce Cutler, Elsa Galbraith, Jon Reiskind and Fred Stangl, Jr. for their reviews and constructive suggestions to improve the paper.
LITERATURE CITED
Bole-Gowda, B. N. 1950. The chromosome study in the spermatogenesis of two lynx-spiders (Oxyopidae). Proc. Zool. Soc. Bengal., 3:95-107.
Begak, W., and M. L. Begak. 1960. Constituicao cromossomica de duas especies de aranhas do genero Loxosceles. Rev. Brasileira Biol., 20:425-427.
Cokendolpher, J. and J. Brown. 1985. Air-dry method for studying chromosomes of insects and arachnids. Entomol. News, 96:114-118.
Datta, S. N. and K. Chatterjee. 1988. Chromosomes and sex determination in 13 araneid spiders of North-Eastern India. Genetica, 76:91-99.
Diaz, M. O. and F. A. Saez. 1966. Karyotypes of South-American Araneida. Mems. Inst. Butantan, 33:153-154.
Gertsch, W. J. 1967. The spider genus Loxosceles in South America (Araneae, Scytodidae). Bull. American Mus. Nat. Hist., 136:117-174.
Gowan, T. D. 1985. The life history and reproduction of the wolf spider Lycosa lentia Hentz.
Gainesville: University of Florida. 259 pp. Dissertation.
Hackman, W. 1948. Chromosomenstudien an araneen mit besonderer berucksichtigung der gechlechtschromosomen. Acta. Zool. Fennica, 54:1-101.
Kageyama A. and T. Seto. 1979. Chromosomes of seven species of Japanese theridiid spiders. Chromosome Inf. Serv., 27:10-11.
Matsumoto, S. 1977. An observation of somatic chromosomes from spider embryo-cells. Acta. Arachnol., 27:167-172.
Mittal, O. P. 1961. Chromosome number and sex mechanism in twenty-one species of the Indian spiders. Res. Bull. (N.S.) Panjab Univ., 12:271-273.
Painter, T. S. 1914. Spermatogenesis in spiders. Zool. Jahrb., 38:509-576.
Pinter, L. J. and D. M. Walters. 1971. Karyological studies. I. A study of the chromosome numbers and sex-determining mechanism of three species of the genus Phidippus (Araneae: Salticidae, Dendryphantinae). Cytologia, 36:183-189.
Sharma, G. P. and K. K. Tandon. 1957. Studies on the chromosomes of the spiders, Oxyopes ryvesii and Oxyopes sp. (Oxyopidae). Proc. 44 Indian Sci. Congr., Ill: 334 (Abstract).
Sokolov, I. I. 1960. Studies on nuclear structures in Araneina. I. Karyological peculiarities in spermatogenesis. The problems of protistology and morphology. Academic Press, Moscow- Leningrad. 160-186 (in Russian).
Sokolov, I. I. 1962. Studies on nuclear structures in Araneina. II. The sex chromosomes. Cytologia (USSR), 4:617-625 (in Russian).
Suzuki, S. 1950. Sex-determining mechanism and karyotypes in spiders. Zool. Mag., 59:57-58.
Suzuki, S. 1952. Cytological studies in spiders. II. Chromosomal investigation in the twenty-two species of spiders belonging to the four families, Clubionidae, Sparassidae, Thomisidae and Oxyopidae, which constitute Clubionoidea, with special reference to sex chromosomes. J. Sci. Hiroshima Univ. Ser. B., 13:1-52.
Wise, D. 1983. An electron microscope study of the karyotypes of two wolf spiders. Canadian J. Genet. Cytol., 25:161-168.
Manuscript received January 1989, revised June 1989.
Fernandez-Montraveta, C. y J. Ortega. 1990. El comportamiento agonistico de hembras adultas de Lycosa tarentula fasciiventris (Araneae, Lycosidae). J. Arachnol., 18:49-58.
EL COMPORTAMIENTO AGONISTICO DE HEMBRAS ADULTAS DE LYCOSA TARENTULA FASCIIVENTRIS (ARANEAE, LYCOSIDAE)
Carmen Fernandez-Montraveta y Joaquin Ortega
Dpto. Psicologia Biologica y de la Salud Universidad Autonoma Cantoblanco, 28049-Madrid Espana
ABSTRACT
Dyadic interactions between adult females of Lycosa tarentula fasciiventris in the laboratory are described. Our results show motor patterns that are not very specific to the context, little ritualized fighting, resulting in a high frequency of cannibalism and a great variability in the duration of the sequences.
RESUMEN
Se describen las interacciones diadicas entre hembras adultas de Lycosa tarentula fasciiventris en el laboratorio. Nuestros resultados muestran la existencia de patrones motores poco exclusivos del contexto y bajo nivel de ritualizacion en la lucha, que se refleja en un indice de canibalismo elevado, asi como una gran variabilidad en la duracion de las secuencias.
INTRODUCCION
El estudio del comportamiento agonistico en las aranas, y en general en todas las especies animates, se ha centrado, fundamentalmente, en las interacciones entre machos adultos (Dijkstra 1969, 1978; Aspey 1976, 1977; Jackson 1982; Halliday 1986). El interes por estos sujetos para tales estudios ha derivado de la funcion que se adjudica al comportamiento agonistico como tecnica de competicion intraespecifica por recursos limitados (Wilson 1975).
En el caso de las aranas las hembras presentan, en general, un repertorio comportamental menos complejo que el de los machos no mostrando, por ejemplo, un cortejo activo. Son los machos los que realizan la busqueda de las hembras, exhibiendo en este contexto una mayor frecuencia de encuentros agonisticos entre ellos, en los que las hembras han sido comunmente consideradas el recurso por el que compiten (Vollrath 1980; Jackson 1982). Por esta razon se han planteado, con relativa frecuencia, estudios sobre competicion, relaciones jerarquicas o relaciones territoriales entre machos adultos (Aspey 1977; Dijkstra 1978; Goist 1982; Austad 1983). Con menor frecuencia, estas mismas cuestiones han sido planteadas con respecto a las hembras adultas (Riechert 1978, 1986; Nossek & Rovner 1984; Hodge 1987). Sin embargo estas podrian ser, en algunos casos, los sujetos idoneos para el analisis de estos problemas.
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En muchas especies de Lycosidos, los machos no se alimentan tras alcanzar la madurez sexual, pierden la vinculacion con un area concreta y vagan en busca de hembras adultas. En Lycosa tarentula fasciiventris Dufour, las hembras, por el contrario, suelen permanecer en el nido, donde se alimentan y aparean. Si se admite que el comportamiento agonistico es una tecnica de competicion por recursos limitados, las hembras podrian ser un buen modelo para su estudio en esta especie, siendo el recurso la ocupacion de un nido o de una localizacion privilegiada para la obtencion de alimento (Riechert 1978, 1982).
Nos hemos propuesto analizar el comportamiento exhibido por hembras adultas de L. tarentula fasciiventris en interacciones diadicas compitiendo por un nido. En este trabajo presentamos una description de la forma en que se desarrolla este comportamiento en dicho contexto, su resultado y sus consecuencias.
MATERIAL Y METODOS
Se han utilizado 40 hembras adultas, recogidas del campo como formas inmaduras, en su antepenultima fase de desarrollo, en las primaveras de 1984 y 1986. Todos los ejemplares procedian de la zona que rodea a la Universidad Autonoma de Madrid. Desde su captura, fueron mantenidas en el laboratorio en condiciones de humedad, temperatura y alimentation constantes, con domination artificial y fotoperiodo de 10 horas de luz y 14 de oscuridad, hasta su observacion durante los meses de marzo, abril y mayo de 1985 y 1987, respectivamente. Durante este periodo, permanecieron en terrarios individuales con aislamiento visual del exterior, realizandose registros periodicos del peso y de la respuesta a las presas, asi como medidas del tamano corporal en cada una de las mudas que sufrieron los animales. A1 alcanzar la fase adulta, los individuos fueron medidos; se utilizo como criterio de su tamano el product© de la longitud por la anchura del prosoma (Aspey 1977).
Las observaciones se realizaron en terrarios de 30x15x15 cm, con paredes lisas y opacas y sustrato de tierra. El nido se construyo artificialmente adosado a la pared anterior, de forma que su interior pudiera ser visible durante los periodos de observacion; fuera de estos periodos, permanecio aislado visualmente del exterior.
Las aranas se observaron por parejas formadas al azar en base a una tabla de numeros aleatorios, de tal manera que una de las dos era colocada en el terrario ocupado por la otra. El criterio de cual de los dos miembros de la pareja era la residente fue tambien por azar, y se utilizaron solo aquellas hembras residentes que habian pasado al menos 7 dias en el terrario, ocupando normalmente el nido y comiendo alii.
Las observaciones tuvieron una duration minima de 30 minutos, y hasta el final de la interaccion en el caso de que esta se produjera. El criterio de inicio y finalizacion de la interaccion fue espacial. Se consider© que una interaccion se iniciaba cuando la distancia que separaba a ambos animales era igual o inferior a 6 cm, existiendo orientation por parte de alguno de ellos hacia el otro, si las aranas se encontraban fuera del nido. Si la interaccion se producia en el interior del nido, a partir del momento en que la intrusa apoyaba el primer par de patas en el. El criterio de finalizacion de la interaccion fue el alejamiento a mas de 6 cm
FERNANDEZ Y ORTEGA— COMPORTAMIENTO AGONISTICO EN HEMBRAS
51
y perdida de orientacion por parte de una de las dos hembras, sin que existiera nueva orientacion durante los 5 minutos siguientes.
Desde el inicio hasta el final de la observacion, se registraron en cinta de video, fotografia seriada y por escrito todas las actividades y movimientos realizados por los animales, transcribiendose posteriormente los datos. La intrusa era retirada tras el registro, no observandose un animal mas de una vez en el mismo dia.
De la observacion de 73 parejas distintas, se obtuvieron un total de 33 secuencias de interaccion. A partir de los datos obtenidos, se ban descrito los patrones motores utilizados, el desarrollo y el resultado de las interacciones. Para cada interaccion, se ha medido su duracion en segundos, calculandose el valor medio, desviacion standard y coeficiente de variation medido por:
C.V. - SD x 100/x
Como variables independientes, se han controlado el tamano de las dos hembras, su diferencia y la situation de residencia previa en la interaccion. Para medir la dependencia entre el resultado y las variables individuals se ha utilizado una prueba de Chi cuadrado. En el caso de la variable “duracion”, se ha calculado el coeficiente de correlation, dado por:
r = sXy/Sx Sy, siendo Sxy la covarianza entre x e y, y Sx, Sy las desviaciones standard de x e y, respectivamente.
RESULTADOS
Cuando se introduce a la hembra intrusa, se observa un periodo inicial de “adaptation” de alrededor de cinco minutos, durante el cual el animal que ha sido trasladado permanece inmovil. Cuando inicia el movimiento, su comportamiento consiste en desplazamientos rapidos y erraticos por el terrario, con el cuerpo en posicion erguida y proximo a las paredes, que intenta ocasionalmente escalar. No se observa direccionalidad aparente en estos desplazamientos.
En el curso de estos desplazamientos las hembras exhiben un movimiento de “sondeo” de palpos, y de “golpear con el primer par de patas”. Tanto uno como otro movimientos no van acompanados de cambios en la direction del desplazamiento con respecto a la posicion del nido.
La localization de este parece producirse por azar. Una vez en contacto con el brocal, la hembra realiza movimientos de palpos y del primer par similares a los mencionados anteriormente (Fig. 1), introduciendose lentamente en el nido. Esta introduction se realiza con el primer par de patas extendido y con movimientos de los palpos sobre las paredes del nido (Fig. 2). Este patron de comportamiento se ha observado en la introduccion a cualquier nido, tanto si estaba ocupado como si no.
La residente suele permanecer inmovil en el interior del nido ante el desplazamiento de la intrusa. En los casos en los que, por alguna razon, no lo ocupa o se encuentra sobre el brocal en el momento de iniciarse la observacion, puede orientarse ante el movimiento de la otra arana a una distancia de hasta 25
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Figura 1. — Sondeo de palpos de la hembra intrusa sobre el brocal. Se observa como la hembra pliega los palpos sobre un hilo de seda del brocal de un nido.
Figura 2. — Introduction de la hembra intrusa en el nido. Se observa el primer par de patas extendido y los palpos plegados sobre el brocal.
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53
Tabla 1. — Tipos de interacciones agonisticas entre hembras. R = secuencias breves, en las que la interaccion se resuelve rapidamente; L = secuencias largas, de resolution lenta.
|
Ocurreecia |
N. inter. |
Secuencias R L |
Capturas |
|
|
Dentro nido |
27 |
9 |
18 |
6 |
|
Fuera nido |
6 |
3 |
3 |
2 |
|
Total |
33 |
12 |
21 |
8 |
cm, sea cual sea la position relativa de ambas. En la Tabla 1 aparece reflejada la frecuencia con la que se han observado interacciones fuera y dentro del nido.
Cuando se encuentra en el nido, la hembra residente no se orienta hasta que la intrusa realiza movimientos sobre el brocal o se introduce en el. Esta introduction se realiza lentamente, y la orientation no suele producirse hasta que la distancia entre ambas se ha reducido a 3-5 cm. El comportamiento de la residente consiste en dar un salto hacia adelante en direction a la intrusa con el primer par de patas extendido y elevado y los queliceros abiertos, most rand o una pauta que hemos llamado “abalanzarse”.
Tras la embestida, algunas interacciones se resuelven rapidamente. En estos casos, a la embestida de la residente y tras el contacto frontal con el primer par de patas, puede seguir la huida de la intrusa o, en algunos casos, su captura. En otras ocasiones, la intrusa responde elevando a su vez el primer par de patas y abriendo queliceros (Fig. 3). Se puede llegar a observar, en estos casos, un contacto de todas las patas (“traba”) similar al que se observa en la captura y
Figura 3. — Exhibicion de queliceros abiertos. En la parte superior se observa a la hembra intrusa con el primer par extendido y los queliceros abiertos. En la parte inferior, se observa una exhibicion de amenaza de la hembra residente.
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sujecion de presas de gran tamano, mostrando ambas arafias los quell cer os abiertos y repetidos intentos de morder a la adversaria. El resultado de la traba puede ser, de nuevo, la huida de una de las dos aranas o, en algunos casos, finalizar con la captura de una por parte de la otra (Tabla 1).
Tambien puede, tras este primer contacto, producirse un retroceso por parte de la intrusa, aun permaneciendo en el interior del nido o sobre el brocal, con sucesivos intentos de aproximacion. En estos casos en que la interaccion no se resuelve rapidamente, el enfrentamiento se puede mantener hasta mas de 8 horas, sucediendose aproximaciones de la intrusa con el primer par de patas extendido hacia adelante, posiciones de inmovilidad con el primer par extendido y los queliceros abiertos y “tamborileo de los palpos” En el interior del nido, la hembra residente suele permanecer inmovil, manteniendo la posicion de primer par extendido y elevado hasta la vertical y queliceros abiertos (“amenaza”). Es de destacar que, en algunas ocasiones, se ha observado que en los mementos en que la hembra residente abandona esta posicion, pierda o no la orientacion hacia la adversaria, esta intenta la introduction en el nido. En algunos casos, la distancia entre las dos hembras en este tipo de interaccion es tan pequena que se observa contacto directo y mantenido entre los queliceros de ambas.
En estos casos la interaccion se resuelve, tambien, tras un ataque, con la huida de una de las dos hembras o su captura (Tabla 1) permaneciendo la otra en el interior del nido; consideramos a esta ultima la vencedora en la interaccion. Tan solo en un caso se observe que las dos aranas se separaran quedando ambas en el interior del nido, una de ellas en el fondo y la otra sobre el brocal, no orientadas una a la otra. La hembra vencedora puede, incluso, perseguir a la otra hasta una distancia de dos o tres cm del brocal, manteniendo la orientacion y la posicion de amenaza hasta varios minutos.
Cuando las interacciones ocurren fuera del nido (Tabla 1), la aproximacion de la residente a la intrusa se produce de forma escalonada, “a saltos”, con xel cuerpo en posicion erguida y un avance casi simultaneo de las patas delanteras, en desplazamientos cortos, rapidos y en linea recta que recuerdan la aproximacion a grandes distancias a presas de gran tamano.
Cuando la distancia entre ambas se reduce a 3-5 cm, se puede producir la orientacion de la hembra intrusa. Una vez ocurrida, el enfrentamiento entre ambas es frontal, desarrollandose la interaccion en la forma descrita anteriormente en el interior del nido: suele resolverse tras el contacto y, en ocasiones, la traba, huyendo una de las dos aranas y permaneciendo inmovil la otra, que mantiene durante algunos minutos la posicion y la orientacion. En otros casos, se observan sucesivas aproximaciones por parte de esta ultima, produciendose repetidos contactos y huidas de la primera (Tabla 1).
En algunos casos, no hay orientacion por parte de la hembra intrusa; puede huir, sin que haya contacto, ante la aproximacion de la residente, o bien resultar capturada tras una embestida a corta distancia.
La comparacion de las frecuencias de las secuencias R y L (Tabla 1) cuando la interaccion tiene lugar dentro y fuera del nido da un x = 1.30 (x2 0.05,1 = 3.84); la comparacion de las frecuencias de captura en ambos contextos da un x2 — LOO.
La captura ha sido el resultado final de 8 de las 33 interacciones observadas. En 5 de estos casos, se produjo tras una interaccion frontal larga, y en los otros tres tras aproximacion lateral o posterior. En todos los casos, el resultado de la
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Tabla 2. — Resultado de las interacciones en funcion de la residencia previa y del tamano. VR = vence individuo residente; VI = vence individuo intruso; VM = vence individuo mayor; Vm = vence individuo me nor.
|
Variable |
Resultado |
|
|
Residencia |
VR |
24 |
|
VI |
9 |
|
|
Tamano |
VM |
23 |
|
Vm |
10 |
captura fue la ingestion total de la congenere. Se observaron, ademas, cuatro intentos de captura en interacciones frontales que resultaron en la mordedura de alguna region no vital (patas) y la posterior separation de las aranas sin resultado final de muerte. En los otros 25 casos, el resultado final de la interaccion consistio en la huida de una de las dos aranas.
En la Tabla 2 se indica cual de las dos aranas resulto vencedora en funcion de las variables “residencia” y “tamano”. A1 aplicar una prueba de Chi cuadrado a los resultados de esta Tabla se obtiene que difieren del azar, tanto con respecto a la residencia x ~ 6.82, p <0.05), como al tamano (x2 = 5.12,/? <0.05).
En la Tabla 3 se presenta el resultado de las interacciones en funcion del tamano de la residente. No existe dependencia significativa entre ambas variables X2 = 3.82), aunque el valor obtenido esta muy proximo al valor significativo (x2 = 3.84, p <0.05). Sin embargo, las aranas de mayor tamano tienden a ganar mas luchas cuando son residentes (x2 = 5.26,/? <0.05).
La duracion de las interacciones observadas es muy variable. El valor medio de la duracion es de 2509.55 segundos, y su desviacion standard 5254.16. Se ha calculado el coeficiente de correlation entre las variables “duracion de la interaccion” y “diferencia de tamano” para el grupo en que el animal residente es el de mayor tamano ( r = —0.36) y el grupo en que el residente es el animal de menor tamano (r = —0.32). Ninguno de estos valores es significativo estadisticamente (p <0.05).
DISCUSION
El comportamiento exhibido por hembras adultas de L. tarentula fasciiventris en interacciones diadicas es similar al descrito por Nossek & Rovner (1984) en otras especies del genero. La estrategia general, asi como los patrones motores del
Table 3. — Resultado de las interacciones en funcion de las dos variables individuales.
|
Tamano residente |
Resultado VR VI |
Total |
|
|
Mayor |
17 |
3 |
20 |
|
Menor |
7 |
6 |
13 |
|
Total |
24 |
9 |
33 |
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comportamiento, no difieren tampoco, de forma significativa, de los descritos para los animales de este sexo y fase de desarrollo en otros contextos (Ortega 1985; Ortega et al. 1986). El nivel de especificidad de los patrones motores exhibidos es, por lo tanto, bajo, y menor que el observado en interacciones diadicas entre machos adultos en esta especie (Ortega et al. 1984).
El nivel de intensificacion de las luchas es mayor que el observado, tanto en encuentros entre machos adultos de esta especie (Ortega et al. 1984), como en los descritos en otras especies (Nossek & Rovner 1984). Este hecho se traduce en el elevado indice de cahibalismo observado.
La mayor parte de las interacciones se han registrado en el interior de los nidos, y su resultado consiste en el abandon© de este por parte de una de las dos hembras. Este hecho nos lleva a postular que estas interacciones pueden interpretarse como competitivas, siendo el recurso en litigio la ocupacion de un nido. Dado el abrigo y la proteccion a temperaturas extremas que proporcionan (Humphreys 1987), puede tratarse de un recurso importante para la supervivencia de los individuos.
El elevado valor de este recurso podria explicar el alto nivel de intensificacion que se observa en los encuentros estudiados. Se ha postulado, de hecho, que la intensificacion de los encuentros se puede producir si el valor del recurso es muy alto (Maynard Smith & Parker 1976; Riechert 1982; Huntingford & Turner 1987).
No hemos detectado diferencias en la frecuencia de interacciones breves y largas o de capturas en funcion de que el encuentro se produzca o no en el interior del nido. En otros estudios no se ha detectado, tampoco, correlacion entre la intensidad de la lucha y el valor del recurso (Hodge 1987).
El elevado riesgo de lesion como consecuencia de la intensificacion podria haber llevado al desarrollo de estrategias de comportamiento que minimizaran los riesgos a los adversaries del tipo de “si eres residente ataca, y si eres intrusa huye” (Maynard Smith 1974; Hammerstein 1981). Esta hipotesis permitiria explicar la predictibilidad del resultado con respecto a la residencia que hemos observado. Sin embargo, no todas las interacciones se resuelven rapidamente en favor del individuo residente.
La existencia de contacto fisico en la mayor parte de las interacciones podria indicar que la resolucion de estos conflictos se produciria, basicamente, tras la evaluation de parametros fisicos del adversario (Turner & Huntingford 1986). Nuestros resultados concuerdan con la hipotesis de que el animal de mayores fuerza o tamano tiene mas probabilidades de resultar vencedor en estos encuentros (Aspey 1977; Riechert 1986).
La interaccion de las dos variables de asimetria no queda clara a partir de los resultados obtenidos, aunque se observa una tendencia a que la probabilidad de veneer de la hembra residente sea mayor cuando es la de mayor tamano. La variabilidad de las secuencias podria reflejar las diferentes situaciones en que se puede encontrar un animal en funcion del tamano y residencia relatives, respondiendo las secuencias lentas a situaciones en las que las probabilidades de veneer de la intrusa, en funcion de su tamano, fueran grandes, y las secuencias rapidas a los casos en que no fuera asi. Estos planteamientos se ajustan a la tendencia a una correlacion negativa que hemos observado entre las variables “diferencia de tamano” y “duration de la interaccion”: las interacciones mas
FERNANDEZ Y ORTEGA - COMPORTAMIENTO AGONISTICO EN HEMBRAS
57
largas corresponden a las situaciones en las que la diferencia de tamario es pequena.
Estos resultados concuerdan con la suposicion de que los animales utilizan las interacciones para obtener informacion acerca de su tarnano relativo. Planteamos que la interpretacion funcional de los patrones motores exhibidos en este contexto no deberia tanto suponer que son senales que informan de la especie y sexo del animal, permitiendo el reconocimiento intraespecifico y disminuyendo el riesgo de que se produzca una respuesta predadora indiscriminada (Krafft 1982), como que son patrones que servirian a los individuos para evaluar la situacion a la que se enfrentan.
AGRADECIMIENTOS
Agradecemos a William Eberhard y a Carlos E. Valerio su revision y sugerencias a este manuscrito. A Jose Maria Calpena, le agradecemos la elaboracion del material fotografico.
REFERENCIAS
Aspey, W. P. 1976. Response strategies of adult male Schizocosa crassipes (Araneae: Lycosidae) during agonistic interactions. Psyche, 83:95-105.
Aspey, W. P. 1977. Wolf spiders sociobiology. I. Agonistic display and dominance-subordinance relations in adult male Schizocosa crassipes. Behaviour, 62, 1-2:103-141.
Austad, S. N. 1983. A game theoretical interpretation of male combat in the bowl and doily spider (Frontinella pyramitela). Anim. Behav., 31:59-73.
Dijkstra, H. 1969. Comparative research of the courtship behaviour in the genus Pardosa (Araneae: Lycosidae). III. Agonistic behaviour in Pardosa amentata. Bull. Mus. Nat. Hist. Nat., 2 ser., 41, sup. 1:91-97.
Dijkstra, H. 1978. Dynamics of dominance in the wolf spider Pardosa amentata (Araneae: Lycosidae). Symp. Zool. Soc. London, 42:403-404.
Goist, K. C. 1982. Male-male competition in the orb-weaving spider Nephila clavipes. Ph.D.
Dissertation. Tulane University, New Orleans, 93 pp.
Halliday, T. R. 1986. Courtship. Pp. 80-86, In The Collins Encyclopedia of Animal Behaviour (P. J. B. Slater, ed.). Collins, Oxford.
Hammerstein, P. 1981. Role of asymmetries in animal contests. Anim. Behav., 29:193-205.
Hodge, M. A. 1987. Agonistic interactions between females bowl and doily spiders (Araneae, Linyphiidae): owner biased outcomes. J. ArachnoL, 15:241-247.
Humphreys, W. F. 1987. The thermal biology of the wolf spider Lycosa tarentula (Araneae:
Lycosidae) in northern Greece. Bull. British ArachnoL Soc., 7:117-122.
Huntingford, F. and A. Turner. 1987. Animal Conflict. Chapman & Hall, London, 448 pp.
Krafft, B. 1982. The significance and complexity of communication in spiders. Pp. 115-66, In Spider Communication: Mechanisms and Ecological Significance. (P. N. Witt and J. S. Rovner, eds.). Princeton University Press, Princeton.
Jackson, R. R. 1982. The biology of ant-like jumping spiders: intraspecific interactions of Myrmarachne lupata (Araneae, Salticidae). Zool. J. Linnean Soc., 76: 293-319.
Maynard-Smith, J. 1974. The theory of games and the evolution of animal conflicts. J. Theor. Biol.,
47:209-221.
Maynard-Smith, J. & G. A. Parker. 1976. The logic of asymmetric contests. Anim. Behav., 24: 159- 175.
Nossek, M. E. & J. S. Rovner. 1984. Agonistic behavior in female wolf spiders (Araneae: Lycosidae). J. ArachnoL, 11:407-422.
Ortega, J. 1985. Quantitative and qualitative analysis of the predatory behaviour of Lycosa fasciiventris Dufour (Araneae: Lycosidae). Biol. Behav., 10: 55-65.
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Ortega, J., C. Fernandez y E. Pablos. 1984. Un ethogramme ouvert du comportement agonistique des males adultes chez Lycosa fasdiventris Dufour (Araneae, Lycosidae). Pp. 309-312. Col. Int. d* Ethologie. SFECA, Barcelona.
Ortega, J., C. Fernandez y E. Pablos. 1986. Comportamiente sexual en Lycosa torentuiu fasdiventris Dufour (Araneae, Lycosidae). Una aproximacion initial Act. X Congr. Int. Arachnol Jaca / Espafia, 1:103-106.
Parker, G. A. and D. I. Rubenstein. 1981. Role assessment, reserve strategy and acquisition of information in asymmetric animal conflicts. Anim. Behav., 29:221-240.
Riechert, S. E. 1978. Energy-based territoriality in populations of the desert spider Agelenopsis aperta (Gertsch). Symp. ZooL Soc. London, 42:211-222.
Riechert, S. E. 1982. Spider interactions strategies: communication vs. coertion. Pp. 281-316, In Spider Communication: Mechanisms and Ecological Significance. (P. N. Whitt & J. S. Rovner). Princeton Univ. Press, Princeton.
Riechert, S. E. 1986. Spider fights as a test of evolutionary games theory. Amer. Scien., 74:604-610.
Turner, A. and F. Huntingford. 1986. A problem for game theory analysis: assessment and intention in male mouthbrooder contests. Anim. Behav., 34:961-970.
Vollrath, F., 1980. Male body size and fitness in the web-building spider Nephila clavipes. Z. Tierpsychol., 53:61-78.
Wilson, E. G., 1975. Sociobiology: The New Synthesis. Harvard University Press, Cambridge, 701 pp.
Manuscript received May 1988, revised June 1989.
Cohn, J. 1990. Is it the size that counts? Palp morphology, sperm storage, and egg hatching frequency in Nephila clavipes (Araneae, Araneidae). J. Arachnoh, 18:59-71.
IS IT THE SIZE THAT COUNTS? PALP MORPHOLOGY, SPERM STORAGE, AND EGG HATCHING FREQUENCY IN NEPHILA CLAVIPES (ARANEAE, ARANEIDAE)
Jeffrey Cohn1
Department of Psychology, Tulane University New Orleans, Louisiana 70118 USA
ABSTRACT
This study investigated the relationship between male size and reproductive success in Nephila clavipes , a neotropical orb-weaving spider. Gross and palpal size variation were examined in relation to copulatory behavior, sperm transfer/uptake, and utilization by the female. The effect of conductor breakage was also evaluated by assessing the timing of its occurrence and its influence on sperm transfer.
There was less variation in palp size of male N. clavipes than in other aspects of male morphology. Gross male body size correlated most highly with how much sperm was produced, transferred to, and stored by the female. Size of the male was not related, however, to the percentage of sperm actually transferred. The number of sperm retained by the female was influenced by the time of mating, but not by copulatory behavior. Approximately twice as many sperm were found in the palps of virgin males as were found in combined totals from mated pairs. This suggests that a substantial percentage of sperm transferred by the male is not stored by the female. None of the variables analyzed in this study greatly influenced the percentage of eggs eventually hatching. Conductor breakage seriously interfered with sperm transfer but occurred less often than expected and did not appear to result from copulatory activity.
INTRODUCTION
Individual differences in invertebrate male morphology may influence copulatory behavior (Jackson 1980; Thornhill and Alcock 1983; Christenson 1984). Male morphological variation may differentially affect internal processes in the female as well. Eberhard (1985) postulated that females in a wide variety of taxa may copulate with many males but discriminate based upon characteristics of the males’ genitalia, fertilizing her eggs with sperm from the most desirable male. This might be accomplished through control of intromission, and differential uptake of sperm, among other mechanisms (Eberhard 1985). Once copulation has begun, females could monitor such variables as intensity or quality of stimuli received, thereby affecting the timing and consequences of copulation including uptake and storage (Jackson 1980; Thornhill and Alcock 1983; Eberhard 1985, 1986).
‘Present address. Environmental Health Sciences Center, P.O. BOX EHSC, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642. This work was part of a doctoral dissertation completed in partial fulfillment of the requirements for the Ph.D. at Tulane University in 1988.
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THE JOURNAL OF ARACHNOLOGY
The genitalia of male golden orb-weaving spiders (Nephila clavipes L.) are not noted for great complexity (Schult and Sellenschlo 1983). One outstanding characteristic, however, is the size of the conductor. Males of similar weight and / or body length, differing in conductor size, will almost certainly differ in the stimulation they provide the female, possibly affecting how much sperm is stored and later utilized by the female. Selective pressures determining conductor size could be open-ended, i.e., continuous pressure for ever larger (or smaller) size, or restrictive, i.e., males with an optimal genitalic size having an advantage over males with larger or smaller conductors. In this study, variation in N. clavipes palpal morphology was first assessed and compared to variation in more gross aspects of male size and sperm production. The relationships of natural and experimentally induced palp variation with transfer/ storage, copulatory behavior, and egg hatching percentage were then evaluated. Because reproductive behavior of N. clavipes differs depending upon the age of the female (Christenson et al. 1985), palpal variation could have different effects on the uptake of sperm by young and mature adult females. Males were therefore mated with females either immediately following the final molt or two weeks post-molt.
METHODS
Study site — The study was conducted at the F. Edward Hebert Center of Tulaee University, approximately 20 km south of New Orleans in Belle Chasse, La. The facility is situated on 500 acres of hardwood, bottomland forest of elm, maple, oak, hackberry, and box elder. The site is transected by dirt roads, drainage ditches, and a series of lagoons.
Subject selection. — One hundred sixty-seven male and 157 female 1 V. clavipes were collected at either the Hebert Center or the Barataria unit of Jean Lafitte National Historical Park in Barataria, La., in July and August 1987. Males were selected based upon coloration, web structure, and the presence of sperm webs, thus ensuring all were approximately the same age, that is, within one or two days after their final molt (Myers and Christenson 1988). Seventeen males, to be included in the virgin male analysis, were selected for very small size (less than 6 mm cephalothorax-abdomen length) or very large body size (greater than 9 mm). Those to be included in the two mated male studies were not selected for size. Females selected were between 18-20 mm in cephalothorax-abdomen length. This ensured that they were in their penultimate instar (Moore 1977), The spiders were housed in 123 X 62 X 62 cm boxes constructed of wood furring strips sided with Fiberglas© screening. Female subjects were presented one or two mealworm larvae each day.
Female N. clavipes were divided into four groups. The first variable was the female’s age at mating: Day of final molt (Day 0) or two weeks post-molt (Day 14). The second variable, was the measure of reproductive success: Number of sperm found in female’s sperm storage sacs (Sperm) or percent of clutch hatched (Egg). This resulted in a 2 X 2 (age vs measure) factorial design.
Initial palp evaluation. — In daily groups of approximately 20, 100 male subjects were brought into the lab before assignment to females. Males were subjected to hypothermia by placing them in a refrigerator for a few minutes and then checked for the occurrence of conductor breakage. Those found to have broken
COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES
61
conductor tips were excluded {N = 4). Males were not kept out of the field for more than 24 hours.
Mating procedure. — Males in the Day 0 groups were housed together until a female’s web showed signs of degeneration, indicating a molt was to occur within a few days. At this time a male was randomly selected from the storage box (similar to female boxes) and placed via a stick near the hub position above the female. Among Day 14 dyads, virgin females were supplied with males 14 days after their final molt. After placing the male, a mealworm was added to the web to facilitate female receptivity (Christenson et al. 1985). Males in both conditions were rarely housed apart from females for more than two days.
Behavioral records. — Serial recording was conducted for a minimum of one hour on the day of the female’s final molt in Day 0 females and following prey capture or the onset of copulation in Day 14 females (whichever occurred first). Specific behaviors recorded included amount of time spent in copula (min per h), the number of copulatory bouts (BOUT - the number of observed palpal insertions of at least 5 sec duration), rates of hematodochal bulb contractions (BC - mean rate per min), number of palp pounding bouts (PP - male rapidly drums his palps on epigynum of the female, 1 sec separating bouts), and number of female fends (FF). The latter was defined as any female behavior which either immediately terminated a copulatory bout or immediately caused a male to move off of or away from her venter. Fends generally included a brisk brushing of the male with the female’s third pair of legs.
Subsequent analyses of male size. — Males were sacrificed by hypothermia. Wet weights were taken and measurements of cephalothorax-abdomen length (CthA) and tibia-patella length (TiPt) were made. Conductors were rechecked to determine frequency of breakage in non-virgin males. Palps were then removed. If not broken, the right palp was measured on a Quantimet 970 Image Analyzer®, otherwise the left palp was used. Four separate measures of palpal length were made (Fig. 1): 1. overall palp length along its retrolateral axis (PLRA); 2. length of conductor along its prolateral axis (CLPA); 3. length of conductor along prolateral axis below the conductor buttress (CLBB); 4. width of conductor at widest point (CndW). Gross and palpal measurements were taken twice on 10 males. Correlations between first and second measurements were greater than or equal to 0.98.
Some slight differences in morphology were found between males assigned to Day 0 and Day 14 females. As males were randomly assigned to these groups, and since both groups were run in equal numbers throughout the summer, these differences were likely due to chance. There were trends toward significantly larger tibia-patella length (FI, 135 = 3.20; p = .076) and greater weight in Day 0 males (FI, 135 = 3.88; p = .051). There was a tendency for Day 0 males to have larger conductors in three of four measures: PLRA (FI, 135 = 2.98; p = 0.086), CLPA (FI, 135 - 3.52; p = 0.063), CLBB (FI, 135 = 0.00; p = 0.973), CndW (FI, 135 = 4.03; p = 0.047).
Conductor manipulation. — To determine the effects of conductor breakage on copulatory behavior and sperm transfer/ storage, conductor tips of 10 males were severed with a scalpel blade. The cuts were made approximately 0.2 mm from the distal end of the conductor, about the length which is occasionally broken off in nature. Males were maintained outdoors in separate boxes for two days after this procedure to await placement on a female’s unrepaired web. Ten additional males
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THE JOURNAL OF ARACHNOLOGY
Figure 1. — Measurements of palp morphology. Retrolateral view on the left, prolateral on the right. 1 = PLRA - Palp length retrolateral axis, 2 = CLPA - Conductor length prolateral axis, 3 = Conductor length below buttress, 4 = CndW - conductor width at widest point (retrolateral axis), B = conductor buttress, Cn = conductor, Cy = cymbium; T = tegulum. Adapted from Levi (1980). Used by permission of the Museum of Comparative Zoology, Harvard University. Scale = 0.1 mm.
serving as controls were similarly handled but not cut. Females mated with these control males were part of the Day 0 Sperm group.
Histological procedure. — Mated pairs in the Sperm groups were brought into the lab five days following their initial copulation, ensuring that female sperm storage sacs had hardened. The storage sacs were removed under a dissecting microscope then placed in a 4 ml centrifuge tube with 200 ml of Ringer’s solution. Following analyses on the image analyzer, male palps were treated in the same manner. The palps (or sacs) were ground thoroughly with forceps and then vortexed for approximately one min. The tubes were then centrifuged for 25 min at 1000 g. The tubes were removed, and the grinding, vortexing, and centrifuging were repeated two more times. The tubes were vortexed one more time, and then 5 ml samples were immediately removed, placed on acid-cleaned gel-coated slides, dried ovenight, and stained with hematoxylin. In the study of sperm availability in virgin males, the procedure was identical.
Sperm counts. — Sperm counts were performed on a Quantimet 970 Image Analyzer®. To facilitate counting, 5 ml samples were used (2.5 percent of the total). The image analyzer was programmed to count all objects with an area of between 3 /x2 and 25 /i2. Within-field editing allowed for the exclusion of extraneous material.
Egg sac analyses. — Following mating, females in the Egg groups were maintained until oviposition. Egg sacs were brought into the lab approximately five weeks after oviposition, sufficient time for spiderlings to have hatched and molted to the second instar. Number of spiderlings, unhatched eggs, and egg sac parasites were counted.
RESULTS
Palpal and gross morphological variation among mated males. — Overall palp length (PLRA) ranged between 1.75 and 2.33 mm, a difference of about 25 percent. The distribution was normal with a skew of well under 1.00 (normality)
COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES
63
Table 1. — Mean (3c) and standard deviations (SD) for Day 0 and Day 14 subjects. The number of sperm found in the male has been omitted from Day 0 data, as only a few sperm were found in only two males. Sperm number refers to sample size (2.5% of the total) in Day 0 and Day 14 Sperm subjects ( n = 35, 36 respectively). Percentage of clutch hatched refers to Day 0 and Day 14 Egg subjects only ( n — 31, 38 respectively). PLRA = Palp length along retrolateral axis; CLPA = Conductor length along prolateral axis; CLBB = conductor length below buttress; CndW = Conductor width at widest point.
|
Day 0 (n |
= 66) |
Day 14 (n |
= 74) |
|
|
Measure |
X |
SD |
X |
SD |
|
Cephalothorax abdomen (mm) |
7.67 |
1.24 |
1A1 |
1.12 |
|
Tibia Patella (mm) |
6.89 |
1.22 |
6.53 |
1.12 |
|
Weight (g) |
0.033 |
0.016 |
0.028 |
0.010 |
|
PLRA (mm) |
2.08 |
0.12 |
2.04 |
0.11 |
|
CLPA (mm) |
1.60 |
0.07 |
1.58 |
0.08 |
|
CLBB (mm) |
1.22 |
0.06 |
1.22 |
0.06 |
|
CndW (mm) |
0.10 |
0.01 |
0.10 |
0.01 |
|
Sperm remaining in male palps |
— |
4401 |
4592 |
|
|
Sperm stored in females |
8037 |
3682 |
1834 |
1404 |
|
Egg hatching percentage |
0.90 |
0.24 |
0.88 |
0.27 |
|
In copula (min/h) |
26.7 |
13.0 |
10.6 |
9.4 |
|
Hematodochal bulb contraction rate (n per min) |
36.2 |
16.0 |
0.4 |
9.1 |
|
Female fends (per h) |
21.4 |
16.2 |
1.7 |
7.0 |
|
Copulatory bouts (per h) |
10.4 |
7.4 |
1.5 |
1.4 |
|
Palp pounds (bouts per h) |
25.9 |
21.2 |
3.1 |
4.9 |
in Day 0 and Day 14 males. In comparison, tibia-patella length varied by over 100 percent, ranging between 4.0 and 9.4 mm. Indices of skewness and kurtosis exhibited trivial differences from normality between all morphological measures. Means and standard deviations for morphological and behavioral data are presented in Table 1 .
Palps were less variable than more general measures of body size. This was determined by calculating coefficients of variation (standard deviation/ (mean X 100)) and testing for significance using log transformations of each of the morphological variables in Day 0 and Day 14 males. Log transformation allowed the variance of each variable to be compared directly (Lewontin 1966). An F- ratio was formed between the coefficient for each palpal measure and each gross morphological measure. Coefficients for palpal measurements were significantly smaller than those for weight, tibia-patella length, or cephalothorax-abdomen length {p < 0.007). Among gross morphological variables, the coefficient for weight was significantly larger than that for tibia-patella length or cephalothorax- abdomen length (p < 0.001). Coefficients and variance of log transformed data are presented for Day 0 and Day 14 subjects in Table 2.
There was a positive correlation between palp size and gross body size. The highest correlation found was between PLRA and tibia-patella length in Day 14 subjects (r = 0.82; p < 0.00001).
Male size and available sperm in virgins. — In virgin males, the amount of sperm found in palps was highly related to gross and palpal morphology. The highest correlation was with weight (r = 0.82; p < 0.0001) and the lowest was with tibia-patella length (r = 0.72; p = 0.002). The various measurements of palp structure correlated equally with the amount of available sperm. Variables PLRA, CLBB, and CndW correlated with sperm at r = 0.75 or 0.76 (p < 0.002). Variable
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Table 2. — Coefficients of variation (C. V.) (Mean/ (Standard deviation X 100)) and variance of gross morphological and palpal measures using log transformation. CthA = cephalotharax-abdomen length; TiPt =Tibia-Patella length; PLRA = Palp length along retrolateral axis; CLPA = Conductor length along prolateral axis; CLBB — conductor length below buttress; CndW = Conductor width at widest point.
|
Day 0 |
Day 14 |
|||
|
Measure |
c. v. |
s2(Log«) |
C. V. |
s2(Log(*)) |
|
Gross |
||||
|
CthA |
15.84 |
5.18X10"3 |
15.03 |
4.36X10~3 |
|
Weight |
50.05 |
6.56X10-3 |
45.05 |
5.62X10-3 |
|
TiPt |
19.05 |
8.12X10"2 |
17.30 |
4.04X10"2 |
|
Palp |
||||
|
PLRA |
6.06 |
6.76X10 |
5.33 |
5.29X10 |
|
CLPA |
4.62 |
4.00X10"4 |
4.91 |
4.41 X10"4 |
|
CLBB |
5.01 |
5.29X10’4 |
4.90 |
4.4 IX IQ-4 |
|
CndW |
7.11 |
5.29X10"4 |
7.71 |
4.41 X10-4 |
CLPA correlated with sperm at r — 0.61 (p — 0.009). Selection bias for very large and very small males resulted in somewhat exaggerated Pearson’s rs.
Male size and sperm storage by females. — Male weight was the best predictor, among male morphological characteristics, of the amount of sperm stored by the female. Stepwise multiple regression performed on collapsed Day 0 and Day 14 data yielded a multiple R of 0.31 for the variable WGT. This score accounted for a significant amount of the variance (F 2,68 = 7.42; p = 0.001). The variable CthA accounted for a significant proportion of the remaining variance. When included in the equation, CthA increased the multiple R to 0.41 ( F2,68 — 6.84; p = 0.002). The relationships between male weight and the amount of sperm stored by the female in Day 0 and Day 14 dyads are presented in Fig. 2.
Male size and proportion of sperm transferred. — When the amount of sperm found in the female was expressed as a percentage of the total available sperm in the female (SP-F) and male (SP-M) combined (SP-F/ (SP-M + SP-F)), no significant relationships were found between the proportion of sperm found in the female and any aspect of male morphology. To test whether males with average- sized palps had an advantage over males of either extreme, proportions of sperm transferred from Day 14 males were converted to z-scores and Pearson rs calculated for the four palpal variables vs the z-scores’ absolute values. Once again, no significant relationship was found.
Male size and copulatory behavior. — To examine whether small males exhibit differences in copulatory behavior to compensate for a deficit in the ability to facilitate sperm storage, the 10 largest (M CthA = 9.50; SD = 0.81) and 10 smallest (M CthA = 5.90; SD = 0.43) males were selected from the Day 0 groups and the 1 1 largest (M CthA = 9.20; SD = 0.38) and 1 1 smallest (M CthA = 6.00; SD = 0.57) from the Day 14 groups. Each group was divided in half again based upon palp size (large or small palps using PLRA as an index), resulting in a 2 X 2 body size vs palp size design. Two-way analyses of variance were conducted to determine whether these divisions resulted in significant size differences.
Day 0 subjects. — As expected, big males had significantly larger palps than small males (FI, 16 = 196.904; p < 0.0001). When the data were collapsed across body size, a significant difference was still found between the largest and smallest
COHN— PALP SIZE AND REPRODUCTIVE SUCCESS IN NEPHILA CLAVIPES
65
Figure 2. — Scatterplot for male weight (g) and sperm (samples) found in female storage sacs in Day 0 and Day 14 dyads with regression lines. Pearson r for Day 0 animals = 0.46 (p = 0.0002). Regression equation is Y = 5125 + 1.0163e+5x. For Day 14 animals the correlation is 0.25 (p = 0.05) and the regression equation is Y = 991.1 + 3.1331e+4x.
palps (PLRA, large bodied males, M = 2.12; SD = 0.05; PLRA, small bodied males, M = 1.81; SD = 0.04; FI, 16 = 44.109; p < 0.0001). The palp size X body size interaction was not significant {p < 0.267). No behavioral differences related to palp size or body weight were uncovered using MANOVA.
Day 14 subjects. — Large and small males displayed means and differences in palp size nearly identical to those found in Day 0 males. Higher rates of some copulatory behaviors were observed in larger males during the one hour serial record: COP (FI, 18 = 5.98; p < 0.025), BOUT (FI, 18 = 4.77; p < 0.043), PP (FI, 18 = 7.82; p < 0.012). The overall multivariate F of behavioral differences based on male weight was significant (F6,13 = 3.83; p = 0.02). Higher rates of palp pounding in large-palped males (FI, 18 = 18.58; p < 0.0004) and more copulatory bouts (FI, 18 = 4.77; p < 0.043) contributed to a trend towards significance in the multivariate F of differences based on palp size (F6,13 — 2.74; p = 0.06). The overall multivariate F for the palp size by body weight interaction was not significant {p = 0.34).
Male size and egg hatching. — Hatching percentage was not dependent upon the size of the male. The highest correlation was with cephalothorax-abdomen length in Day 0 subjects (r = 0.25; p = 0.05). This relationship was not apparent in the Day 14 Egg group.
Female age at mating, sperm storage, and copulatory behavior. — When mating with a newly-molted female, males nearly always transferred their entire supply of sperm (M > 99 percent). When copulation was delayed for two weeks, mated males retained about 24 percent of the sperm found in virgin males. A one-way analysis of variance between Sperm groups indicated that significantly more sperm were found in Day 0 females (FI ,69 = 35.70; p < 0.0001). A mean of 8037 sperm was found in Day 0 samples (SD = 3682), versus 1834 in Day 14 samples
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THE JOURNAL OF ARACHNOLOGY
(SD = 1404). These means reflect sample sizes of 2.5 percent of the total sperm. When the number of sperm transferred to Day 14 females was expressed as a percentage of the total available sperm (SP-F/(SP-M + SP-F)), no relationship was found to exist between any of the behavioral variables and the proportion of sperm transferred.
A MANOVA was performed to determine if any aspects of copulatory activity were related to female age at mating. Due to missing data, three dyads were dropped (for this analysis only) leaving a total of 137. The overall multivariate F was significant (F14,122 — 24.75; p < 0.0001), indicating that the overall pattern of variable scores differed between Day 0 and Day 14 subjects. Subsequent analyses revealed significantly higher rates of copulatory activity in Day 0 subjects: more time spent copulating per one hour serial record (FI, 135 = 68.87; p < 0.0001), a higher number of copulatory bouts (FI, 135 = 105.79; p < 0.0001), higher rate of hematodochal bulb contractions (FI, 135 = 143.50; p < 0.0001), and more palp pounding (FI, 135 — 77.40; p < 0.0001). There were more fends by the female as well (FI, 135 = 87.73; p < 0.0001).
Females fended males more often per unit time spent copulating on Day 0 (FI, 115 = 10.498; p < 0.002); the mean fend/ cop ratio was 1.04 on Day 0 versus 0.33 on Day 14. Cases where no copulations were observed during the one hour observation period were dropped from this analysis ( N = 23) leaving a final N of 117. To determine if females were influencing the number of times a male attempted to mate, 10 Day 0 dyads and 10 Day 14 dyads were randomly selected from those dyads in which at least one mating attempt and fend were observed. The above analysis was then repeated using the ratio of fends to copulatory attempts. A copulatory attempt was defined as occurring when the male descended to the ventrum of the female followed by either successful copulation or insertion of less than 5 sec. No significant difference was found between Day 0 and Day 14 dyads (p = 0.346). Day 0 males were fended a mean of 1.1 times per copulatory attempt. Day 14 males were fended a mean of 0.8 times per attempt.
Do females influence copulation duration? — Gross female activity had little effect on male reproductive behavior. Female fends of males were not correlated with the amount of copulation and only a slight negative correlation was found with the amount of sperm later obtained in the female (Day 0 r = —0.23; p = 0.06; Day 14 r = —0.26; p = 0.05). Fends were positively correlated with BC rates in Day 0 males (r = 0.38; p = 0.001), but this relationship was not found in Day 14 dyads.
Copulatory behavior and sperm storage. — Among Day 0 subjects, total copulation time was the best behavioral predictor of the amount of sperm found in the female. This variable had a correlation with SP-F of 0.47, and was the only variable accounting for a significant proportion of the total variance (FI, 32 = 8.89; p < 0.001). No behavioral variables were related to the amount of sperm found among Day 14 females. The predictive value of behavioral variables were determined by stepwise multiple regression analysis. Because of behavioral differences between Day 0 and Day 14 mating, the analysis was run under each condition.
Amount of sperm transferred during feeding bouts. — Day 14 Sperm dyads were analyzed to determine how much sperm were transferred during each mating bout. These copulations took place almost exclusively after mealworms were added and when females were observed feeding. The numbers of bouts are only
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an approximation as clearly not every one occurring within these dyads was recorded. In three cases, sperm were found in females even though no copulation was observed. Because final molts were observed, it is clear that insemination could only have been carried out by the introduced males. These dyads were included and scored as having the minimum possible one copulatory bout. A mean of 2.8 copulatory bouts were observed among Day 14 Sperm subjects over the 4 days of observations (SD = 1.6). Each bout resulted in the transfer of a mean of 37 750 sperm (SD = 46 886). These were the true numbers, obtained by multiplying the sample size by 40. As the mean amount of sperm found in virgin males (total, not sample size) was 520 898 (SD = 257 779), each bout transferred about seven percent of the male’s total sperm. There was, however, a large amount of variation among