Papers by William Eberhard
Journal of Arachnology, Aug 1, 2017
Journal of Arachnology, Apr 1, 2013
Direct behavioral observations, plus deductions made from studying the lines in recently built we... more Direct behavioral observations, plus deductions made from studying the lines in recently built webs, showed that Linothele macwlhelifera Strand 1 908 lays swaths of lines in relatively stereotypic ways that differ during sheet web and tube construction. Sheet construction occurs in brief bursts interspersed with returns to the retreat. The legs are not used to manipulate lines; the spinnerets attach lines to the substrate and are probably used as sense organs. Asymmetrical use of the spinnerets during sheet construction results in an increase in the variety of orientations of lines in the sheet.
Journal of Arachnology, Apr 1, 2011
Princeton University Press eBooks, Dec 31, 1996
Journal of Arachnology, 1986
Ethology Ecology & Evolution, Dec 21, 2022
Journal of Arachnology, Aug 1, 2017
The Journal of Arachnology
Abstract. Studies of web evolution in spiders generally focus on the overall designs of webs in t... more Abstract. Studies of web evolution in spiders generally focus on the overall designs of webs in the field. As has been typical for dictynids and several other cribellate families with “irregular” webs, this study detected few discernable patterns in the field regarding the spatial organization of the highly variable, three-dimensional and largely aerial webs of the dictynid Dictyna meditata Gertsch, 1936. Nevertheless, there were three consistent sub-unit designs in the additions that spiders made to their webs in captivity, and in webs that they built from scratch in captivity: “silk ladders”, with a cribellum line that zig-zagged between a pair of approximately parallel non-sticky lines; “twig ladders”, with a cribellum line that zig-zagged between a non-sticky line and the substrate; and long non-sticky lines that each supported a long, slightly looped cribellum line. I suggest, using examples from dictynids and other families with long-lived, geometrically irregular webs, that this pattern of using consistent behavior patterns to add geometrically regular “modules”, is widespread and ancient, but has often been missed due to damage and additions to webs in the field, and to lack of direct behavioral observations. Recent attempts to link web evolution to studies of spider phylogeny could benefit from a change of emphasis, focusing on the additions that spiders make to their webs, rather than on the currently common but necessarily vague characterizations of overall web designs seen in the field.
The Journal of Arachnology, 2021
Abstract. In previous studies, the “cocoon” webs built by spiders of the genera Cyclosa Menge, 18... more Abstract. In previous studies, the “cocoon” webs built by spiders of the genera Cyclosa Menge, 1866 and Allocyclosa Levi, 1999 under the influence of Polysphincta spp. wasps resembled molting webs built by unparasitized spiders; this behavioral manipulation was associated with increased concentrations of the molting hormone ecdysone. The present study documents an additional aspect of the cocoon webs of Allocyclosa bifurca (McCook, 1887) built under the influence of the wasp Polysphincta gutfreundi Gauld, 1991. Molting webs were more likely to have an associated barrier web than were prey capture orbs; and cocoon webs were even more likely to have barrier webs. The similarity between molting and cocoon webs accords with previous indications of ecdysone use by the wasps. The accentuation of molting web traits in the cocoon webs (also seen in other species) implies that the wasps manipulate the spiders using mechanisms other than simply replicating hormonal stimuli involved in normal molting.
Journal of the Kansas Entomological Society, 2019
Wasps of the Polysphincta clade are known to manipulate the behavior of their web-building spider... more Wasps of the Polysphincta clade are known to manipulate the behavior of their web-building spider hosts by injecting psychotropic chemicals, but the methods they use to hunt spiders are poorly documented. In 25 attacks observed over several years in the field in the Valle Central of Costa Rica, Polysphincta gutfreundi showed great flexibility. Wasps employed three basic hunting tactics to subdue the host spider Allocyclosa bifurca: strike the spider at its resting site at the hub of its orb web; land in the sticky spiral of the web, struggle, and then attack the spider when it approached; and wait immobile at the hub to await the return of a spider that had fled. The wasps moved and oriented agilely on their hosts' orbs. The only repeatedly effective spider defense was to drop immediately from the web and remain away for many minutes. Parasitism was strongly clumped spatially, suggesting that female wasps may learn where to hunt. Nearly all the details of P. gutfreundi attack behavior have also been observed in other species of the Polysphincta clade. They include the use of multiple attack strategies, surprise attacks from the air on spiders resting on their webs, attacks through the hub, agile movements on the spider's web, inducing the spider to approach by apparent imitation of prey, waiting for long periods in the web poised to strike, and inserting the ovipositor into the anterior end of the spider's cephalothorax. One unique detail of attack behavior in P. gutfreundi was to shuttle rapidly to the other side of the hub to reach the spider. Few of the spider's defensive traits were effective against these wasps. Species in the Polysphincta group are behaviorally flexible, but as a group these wasps utilize relatively uniform tactics to subdue their hosts.
Journal of Arachnology, 1983
... (ARANEAE, ULOBORIDAE) Brent D. Opell Department of Biology, Virginia Polytechnic Institute an... more ... (ARANEAE, ULOBORIDAE) Brent D. Opell Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 and William G. Eberhard ... Figs. 5-6. Zosis geniculatus (Olivier) female: 5, ventral view; 6, lateral view. Page 4. 372 ...
Biological Journal of the Linnean Society, 2019
Wasps in the Polysphincta group of Ichneumonidae induce their web-spinning spider hosts to constr... more Wasps in the Polysphincta group of Ichneumonidae induce their web-spinning spider hosts to construct modified 'cocoon' webs that support and protect the wasps' cocoons, but the mechanisms used by wasps to manipulate their host spiders have been unclear. We evaluate the hypothesis that wasps manipulate spider ecdysteroid moulting hormones, using the taxonomic distribution of the hosts and cocoon web types of different wasp lineages in the Polysphincta group, with new data comparing cocoon webs with the moulting webs of non-parasitized host spiders. Several predictions were confirmed: wasp and spider species have not co-evolved in a strict sense, with wasp lineages jumping between host lineages; cocoon web designs induced by closely related wasps varied widely in spiders with differing natural histories; cocoon web designs were consistently adjusted to the natural history of the spider in ways promoting wasp survival; and cocoon web designs often resembled those of moulting webs of non-parasitized spiders. Several other types of data did not fit the predictions of simple versions of the ecdysteroid hypothesis, however. We conclude that the use of ecdysteroids by the wasps to manipulate host spider behaviour is probably widespread, but that some wasps might also use other mechanisms.
InTech eBooks, Aug 29, 2012
Bulletin of The Museum of Comparative Zoology, May 12, 2023
Journal of Evolutionary Biology, Feb 1, 2010
Journal of Evolutionary Biology, 2003
We contrast some recent uses of the concept of male-female conflict, with the type of conflict th... more We contrast some recent uses of the concept of male-female conflict, with the type of conflict that is inherent in traditional Darwinian female choice. Females in apparent conflict situations with males may suffer reduced lifetime reproduction, but nevertheless benefit because they obtain sons with superior manipulative abilities. Female defences against male manipulations may not be 'imperfect' because of inability to keep pace with male evolution, but in order to screen males and favour those that are especially good manipulators. We examine the consequences of these ideas, and of the difficulties of obtaining biologically realistic measures of female costs, for some recent theoretical and empirical presentations of male-female conflict ideas, and find that male-female conflict in the new sense is less certain than has been commonly supposed. Disentangling previous sexual selection ideas and the new conflict of interest models will probably often be difficult, because the two types of payoffs are not mutually exclusive.
Journal of Arachnology, Dec 1, 2004
I argue that several unusual aspects of spider sexual biology make them extremely promising subje... more I argue that several unusual aspects of spider sexual biology make them extremely promising subjects for future research on sperm competition and cryptic female choice, and outline promising lines for future research. The important traits include: double, bilaterally symmetrical genitalia (allowing the use of the same animal as experimental and control and thus providing unusually complete controls for experimental manipulations); isolation of male ejaculates in pure form during sperm induction (allowing experimental determination of the effects of sperm and male accessory glands on female reproductive physiology, and separation of their effects on the female from those of copulatory courtship and copulation); frequent venter-up orientation and genitalic meshes in which most of the male genitalia is outside rather than inside the female (allowing unusually complete observations of male genital behavior during copulation); immobile sperm (allowing confident deductions about male and female movement of sperm without complications from motility of the sperm themselves); a huge data set on female as well as male genitalic morphology from previous taxonomic studies (enabling, in combination with studies of the fit between male and female genitalia, studies of the details of how rapid genitalic divergence occurs). Studies of spider sex should be in the forefront of the next generation of studies of sperm competition and cryptic female choice.
PLOS ONE, 2021
The brains of smaller animals are smaller than those of their larger relatives, but it is not cle... more The brains of smaller animals are smaller than those of their larger relatives, but it is not clear whether their adaptive behavioral flexibility is more limited. Previous interspecific comparisons found that aspects of web construction behavior of very small orb weaving spiders (0.005 mg) were no less precise than those of much larger related orb weavers (30 mg), but the behaviors tested were relatively simple. Here we perform a more sensitive intraspecific test involving the multiple behavioral adjustments of orb web designs made by Leucauge argyra to confinement in very small spaces. Web adjustments of spiderlings as small as ~0.1 mg were compared to previously published observations of ~80 mg conspecific adults. Spiderlings in constrained spaces made all of the complex adjustments made by adults in at least seven independent web design variables, and their adjustments were no less precise. Rough estimates based on previously published data on total brain volumes and the mean dia...
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Papers by William Eberhard