William Eberhard

• Smithsonian Tropical Research Institute

A new bridge between studies of sexual selection and the massive literature on C. elegans behavior and nervous system properties promises to provide important new insights in both fields. This paper shows that mate choice likely occurs in hermaphrodite C. elegans on the basis of stimulation from the male genital spicules, making it possible to appl...

Simple Summary The morphological designs and the behavior (rhythmic brushing, vibrating, scraping, and tapping) of the male genitalia in two species of crane flies indicate that male genital structures in both species function to stimulate the female during copulation. These observations are used to test current theoretical explanations of the rapi...

Orb-web construction behaviour, a classic example of ‘innate’ behaviour, is highly flexible. Determining which cues guide construction behaviour is complicated by the strong correlations between some variables, and the difficulty of manipulating of some web variables in biologically realistic ways. This study utilized a new experimental technique,...

Photographs of the webs of approximately 113 species in 52 genera show that the web architecture of linyphioid spiders (Linyphiidae and Pimoidae) present many variations on a single basic pattern. Nearly all species built webs with a more or less horizontal, continuous sheet with an open space just below the sheet. However, the details in the desig...

Possible functions of several species-specific, sexually dimorphic male structures and of the male genitalia of Lytta eucera were deduced from observations of behaviour in the field and captivity, and were used to test theories of sexual selection. The male rubbed and tapped on the female’s antennae with sexually dimorphic segments of his antennae,...

‘Primary’’ webs of uloborids have large numbers of very fine lines and usually lack sticky cribellum silk. This paper reviews their taxonomic distribution (19 species in 5 genera) and the ontogenetic stages in which primary webs are built (spiderlings newly emerged from the egg sac, older juveniles, mature males, and normal and senile females), exp...

Web designs have long been used to characterize spider taxa and to deduce the relations between them; but systematic documentation of the amount of variation in webs within and between taxonomic groups is rare. This study, based on previously published observations and new observations of 15 species in the family Uloboridae, including two genera, O...

This first-ever extensive review of the construction behaviour of orb webs, of webs secondarily derived from orbs, and of non-orbs shows that the evidence favouring monophyly over convergent evolution of orbs is stronger than previously appreciated. The two major orb-weaving groups, Uloboridae and Araneoidea, share 31 construction behaviour traits,...

Spider webs in general and orb webs in particular are delicate, ephemeral structures that are frequently damaged in nature. Some orb weavers respond to damage by quickly shoring up their webs with non-sticky dragline silk. This study of how Micrathena duodecimspinosa (O. Pickard-Cambridge, 1890) shores up damaged frame lines shows that repairs were...

Linyphiid webs have often been characterized as dense horizontal sheets suspended in aerial tangles. Recent observations indicate that several web traits vary considerably between species, but nearly all information comes from small samples of webs, and little attention has been given to intra-specific variation. This paper documents the intra-web...

Males of the agaonid wasp Heterandrium fallax have wing spots that they display during aggressive encounters near the ostioles of syconia of the fig Ficus pertusa, apparently in competition for the opportunity to copulate with emerging females. In accord with predictions of the “functional allometry hypothesis” for the allometry of structures that...

The large size and slow movements of mature female Trichonephila clavipes (Linnaeus, 1767) permit observations of some seldom-studied details of behavioral processes, such as cutting and initiating silk lines, that help clarify functional morphology. Silk lines were cut after being grasped by the cheliceral fangs; but direct observation and details...

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...

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 we...

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...

Arthropod behaviour is usually explained through ‘hard-wired’ motor routines and learning abilities that have been favoured by natural selection. We describe observations in which two arthropods solved rare and perhaps completely novel problems, and consider four possible explanations for their behaviours: (i) the behaviour was a pre-programmed mot...

Webs of Dictyna bellans Chamberlin, 1919 in captivity included several characteristics seen in other dictynid webs, including a fine-meshed tubular retreat of non-sticky lines with multiple exits, “runways” of dense, fine non-sticky lines that were continuous with the floor of the retreat, and “ladders” of cribellum silk that zig-zagged between mor...

Small swarms of male Leseha vespaSmith & Nishida, 2019 flew during the morning hours searching for the much less abundant females on the upper surfaces of protruding leaves of various plant species at a site where a large population of the host fern Phlebodium pseudoaureum had been recently decimated (probably by L. vespa larvae). Males showed no s...

A recent theoretical model predicts that the allometries of structures under sexual selection vary according to their functions in sexual interactions. Structures that are specialized for exclusive use as courtship devices, and not as weapons or threat devices, were predicted to tend to show low allometric values. Detailed observations of behavior...

The prey capture webs of Emblyna sp. and Mallos hesperius (Chamberlin, 1916) span gentle curves in the surfaces of single, rigid leaves. They share several traits with orb webs: geometrically regular and approximately planar arrangements of strong, non-sticky lines; geometrically regular arrays of sticky lines laid on these non-sticky lines; and fr...

Male courtship signals often stimulate female sense organs whose sensitivities originally evolved under natural selection. In classic female choice models of sexual selection, females can benefit from increasing their sensitivity and responsiveness to male stimuli; but in sexually antagonistic models, increased female sensitivity or responsiveness...

Rapid divergence in external genital structures occurs in nearly all animal groups that practice internal insemination; explaining this pattern is a major challenge in evolutionary biology. The hypothesis that species‐specific differences in male genitalia evolved under sexual selection as courtship devices to influence cryptic female choice (CFC),...

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. Wasp...

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...

Sexually-selected traits often show positive static allometry, with large individuals bearing disproportionately large structures. But many other sexually-selected traits show isometry or even negative allometry, with trait size varying relatively little with body size. We recently proposed that the functions of these traits (as aggressive signals,...

Araneid orb weavers systematically weaken the radii in their orbs by partially or completely removing the provisional radial lines laid during radius construction. Removal of provisional radii by Micrathena duodecimspinosa (O. Pickard-Cambridge, 1890) tended to be less complete for those radii that were attached later during the radius construction...

Orb web construction was originally thought to be highly stereotyped, but adaptive flexibility is now well established in several aspects. This study reviews published data on one behavioural cue and presents new data on flexibility in experimentally modified and control webs of Zosis geniculata and Uloborus diversus . By occasionally ignoring this...

The webs of hahniid spiders are poorly known. Those of Neoantistea riparia (Keyserling, 1887) all included sheets near the surface of the ground, but were more complex and variable than the simple sheets mentioned in previous accounts. Additional components included: sparse tangles of variable size above the sheet; lines below the sheet; small, den...

Many spectacular cases of biological diversity are associated with sexual selection, and structures under sexual selection often show positive static allometry: they are disproportionately large for the size of the animal’s body in larger individuals. Other sexually selected structures, however, show negative allometry or isometry. Theory fails to...

Imperfect knowledge of ancestral behaviour often hampers tracing behavioural evolution. This limitation is reduced in orb weaving spiders, because spider orb web construction behaviour and the cues used by modern orb-weavers are well-studied and highly conserved. Several species in orb-weaving families build non-orb webs that are clearly derived fr...

Funnel webs are common and widespread taxonomically, but little is known about how they are built or details of their structure. Aglaoctenus castaneus (Mello-Leitão, 1942) (Lycosidae) builds horizontal, densely meshed funnel webs of non-adhesive silk, with a tangle of lines above. Web construction behavior was unique in that the spider frequently l...

Spiders are effectively blind with respect to the lines in their own webs. Species in four orb-weaving families solved the problem of finding lines by tapping with their anterior legs, like a blind man with his cane, and then "following" these anterior legs with more posterior legs, which grasp lines that the anterior legs are already holding. Foll...

Traditional views of copulation and sperm transfer supposed that females are passive participants. Recent discoveries suggest, however, that females actively influence the chances that a copulation will result in fertilization of their eggs, and that they sometimes signal to males during copulation in order to elicit male responses. This paper conc...

Behavior can provide useful traits for testing phylogenetic hypotheses, and some details of orb web construction behavior have been especially useful in characterizing higher-level groups in spiders. The cues used to guide construction behavior and behavioral responses to these cues hold similar promise, but have never been used in phylogenetic stu...

A female Micrathena duodecimspinosa (O. P. Cambridge, 1890) used the elasticity of her long dragline to repeatedly jerk her newly constructed egg sac up and down as she lowered it into the leaf litter below. Jerking may reduce the chances that the sac will be entangled in vegetation before it reaches the leaf litter or help insert it deeper into th...

This chapter focuses on descriptive and experimental studies of the sexual biology of two spider species, Leucauge mariana and Leucauge argyra . We examine general questions related to female effects on paternity by taking advantage of several unusual traits: direct female participation in forming copulatory plugs and physical clasping by the femal...

In male spiders, genitalia, sexual behaviour and secondary sex morphology tend to diverge rapidly across species, presumably as a result of sexual selection. In the three Leucauge species for which pre- and copulatory courtship behaviour is known, females clamp the male chelicerae prior to and during copulation. This brings the basal segment of the...

This timely book revisits cryptic female choice in arthropods, gathering detailed contributions from around the world to address key behavioral, ecological and evolutionary questions. The reader will find a critical summary of major breakthroughs in taxon-oriented chapters that offer many new perspectives and cases to explore and in many cases unpu...

A long-standing mystery in morphological evolution is why male genitalia tend to diverge more rapidly than other structures. One possible explanation of this trend is that male genitalia function as “internal courtship devices,” and are under sexual selection by cryptic female choice (CFC) to induce female responses that improve the male’s chances...

This chapter discusses sexual selection by cryptic female choice (CFC) and other possible types of selection on traits involved in male–female interactions during and following copulation. Morphological, behavioral, and probably also physiological traits all show the typical earmarks of sexual selection: puzzlingly extravagant, apparently non-utili...

A long-standing question in morphological evolution is why male genitalia tend to diverge more rapidly than other structures. One possible explanation is that male genitalia are under sexual selection to function as ‘internal courtship devices’. Males of closely related species may provide divergent stimulation using different genital morphologies...

A long-standing question in morphological evolution is why male genitalia tend to diverge more rapidly than other structures. One possible explanation is that male genitalia are under sexual selection to function as ‘internal courtship devices’. Males of closely related species may provide divergent stimulation using different genital morphologies...

Both males and females of the spider Leucauge mariana (Taczanowski 1881) contribute material to the plugs that often occlude the genital openings of females in the field. Males were sometimes unable to remove or penetrate these plugs, but overcame others using three different mechanical mechanisms: snag the plug and pull it off; break and penetrate...

Just before dying, Edessa rufomarginata (Hemiptera, Pentotomidae) individuals that are infected with the fungus Purpureocillium cf. lilacinum (Ascomycota: Ophiocordycipitaceae) move from the leaves onto the stems of their Solanum sp. host and firmly grasp the stems in ways seldom employed by uninfected bugs. These alterations in host behavior proba...

Spider orb webs are impressive for their apparently uniform geometric patterns. There are, however, consistent, substantial and taxonomically widespread periphery-to-hub differences in the distances between both adjacent radii and between sticky spiral lines. Radii in typical orbs were on average about 4–5 times farther apart at the outer edge than...

Sexual selection is thought to be an important force driving the evolution of sexually dimorphic morphology and behavior, but direct experimental tests of the functions of species-specific details of morphology are rare and usually incomplete. The males of most species of the large spider family Tetragnathidae possess large sexually dimorphic cheli...

The wasps Acrotaphus tibialis (Cameron), Eruga ca. gutfreundi Gauld, and Hymenoepimecis tedfordi Gauld induce their host spiders to spin modified "cocoon" webs just before they kill them and pupate. The cocoon webs induced by all three wasp species appear better designed to support and protect the waspsO pupal cocoons than are the normal orbs of th...

Morphological studies have documented the tendency for male genitalia to diverge rapidly compared to other body parts in many animal groups, including spiders. But documentation of how differences in genital structures of closely related species correlate with differences in the behavior of their genitalia during copulation is rare. This study desc...

Direct behavioral observations, plus deductions made from studying the lines in recently built webs, showed that Linothele macrothelifera Strand 1908 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...

Several recent studies emphasize, correctly, that the biomass of prey captured by an orb web is likely more important than the number of prey in driving the evolution of web designs. Using equations that estimate prey mass from the lengths of captured prey, one study concluded that rare, long-bodied prey contribute the large majority of energy obta...

Biodiversity conservation is a global priority where the study of every type of living form is a fundamental task. Inside the huge number of the planet species, spiders play an important role in almost every habitat. This paper presents a comprehensive study on the reliability of the most used features extractors to face the problem of spider speci...

This work presents an improvement of the automatic and supervised spider identification approach based on biometric spider web analysis. We have used as feature extractor, a Joint Approximate Diagonalization of Eigen-matrixes Independent Component Analysis applying to a binary image with a reduced size (20×20 pixels) from the colour original image....

Even for small animals such as spiders, behavioral decisions are sometimes influenced by multiple cues. Orb webs constitute exquisitely precise records of the stimuli the spider experienced and the decisions that it made while building its web. In addition, because spiders appear to sense their webs largely by touch, direct behavioral observations...

Adaptive flexibility in response to environmental variation is often advantageous and occurs in many types of traits in many species. Although the basic designs of the orb webs of a given species are relatively uniform, spiders can adjust their webs to some types of environmental variation. This study of adult female Leucauge argyra tests the extre...

Tiny animals solve problems of housing and maintaining oversized brains, shedding new light on nervous-system evolution. The mechanisms that are responsible for grade shifts are only beginning to be understood. But this combination of generality and variability in Hailer's Rule appears to call into question some basic assumptions regarding the unif...

Philoponella vicina O. Pickard-Cambridge 1899 rests on its orb web in a cryptic posture with its legs folded against its body. While feeding, the spider coats the entire prey with digestive fluid and changes its posture, spreading its anterior legs wide. We tested whether this change in leg position may function to protect against damage to its leg...

Orb-weaving spiders construct webs with adhesive silk but are not trapped by it. Previous studies have attributed this defense to an oily coating on their legs that protects against adhesion or, more recently, to behavioral avoidance of sticky lines. The old evidence is very weak, however, and the behavioral avoidance explanation is inadequate beca...

Summary Although orb web construction behaviour is relatively well studied, there are few studies of the mechanisms with which behavioural decisions are executed, in terms of where the spider grasps lines and attaches them to each other. Video analyses were used here to show that the distance from the previous sticky loop at which the araneid spide...

Summary Several of the cues generally used by orb-weaving spiders to guide sticky spiral placement are missing when the spider lays the first loop of sticky spiral in an orb. This study combines behavioural observations and web measurements to suggest that two species of spiders use the distance between the outer loop of temporary spiral and the fr...

We use a recent wave of data to confirm that Haller's rule of brain–body allometry, for smaller species to have relatively larger brains, holds for invertebrates as well as vertebrates. But different invertebrate taxa fall on several different allometric lines (grades). In the smallest animals in several grades, the brain occupies a large fraction...

Allometric studies of the gross neuroanatomy of adults from nine species of spiders from six web-weaving families (Orbicularia), and nymphs from six of these species, show that very small spiders resemble other small animals in having disproportionately larger central nervous systems (CNSs) relative to body mass when compared with large-bodied form...

Saving earth’s biodiversity for future generations is an important global task. Spiders are creatures with a fascinating behaviour, overall in the way they build their webs. This is the reason this work proposed a novel problem: the used of spider webs as a source of information for specie recognition. To do so, biometric techniques such as image p...

Spiders are effectively blind with respect to the lines in their webs, and they commonly use exploratory leg movements to find lines, just as a blind man finds objects using a cane. Nevertheless, a mature female Leucauge mariana (Keyserling 1881), which spins a relatively open, sparsely-meshed hub and whose legs I and II hold widely-spaced radii ra...

Because of scaling trends in physiology and morphology, very small animals are expected to suffer especially strong selection to reduce the cost of the central nervous system, which may make them more likely to sacrifice behavioural capacities to economize on nervous tissue. This ‘size-limitation’ hypothesis predicts reduced behavioural capabilitie...

There has been a recent burst of studies of the function of genitalia, many of which share several important shortcomings. Given that further studies on this topic are likely (there are probably millions of species showing rapid genital divergence), I discuss the studies critically to promote clear formulation of hypotheses and interpretation of re...

Wendilgarda sp. builds unusually simple webs attached to the surface of water. The simplest design consists of a single vertical line with sticky material near the bottom that is attached at the top to a single horizontal line and at the bottom to the water surface. The spider usually sits immobile waiting for prey as the sticky line skates erratic...

This paper discusses the possible functional significance of the locations of the spigots of different types of silk gland on the different spinnerets of spiders. Deductions are based on recognition that some types of line are initiated by being attached to the dragline, that there is an anterior-posterior asymmetry in how such lines can be initiat...

Shön (200924. Shön , M. 2009 . Why birds should communicate by dynamic optical signal patterns and not by the static signals perceived by man . Ethology Ecology & Evolution , 21 : 161 – 172 . [Taylor & Francis Online], [Web of Science ®]View all references, Ethology Ecology & Evolution 21: 161–172) pointed out that in order to understand the functi...

Published descriptions of egg sac construction behavior in araneids are scarce. We describe egg sac construction and oviposition in one individual of the poorly known araneid Pozonia nigroventris (Bryant 1936) and two individuals of Micrathena sp. These spiders folded dead leaves to protect their eggs. All individuals pulled up and hung a dead leaf...

A long-standing question in morphological evolution is why male genitalia often diverge more rapidly than other structures. One possible explanation of this trend is that male genitalia function as "internal courtship devices", and are under sexual selection by cryptic female choice to induce female responses that favor the male's chances of father...

The evolutionary effects of crowding on male courtship behavior were studied using wild and mass-reared medflies. Mass-reared strains had been raised under highly crowded conditions in mass-rearing facilities for approximately 75, 180, and 238 generations. Pre-mounting courtship was facultatively shortened in both wild and mass-reared males under c...

The hypothesis that the evolutionary origin of novel behavior patterns may be imprecision in the execution of existing patterns is examined using data from spider web construction behavior. Several aspects of orb construction behavior are both extremely invariable intraspecifically, and highly conserved evolutionarily. The behavior of spiders in th...

Young juveniles of L. geometricus fit the strong trend for “ontogeny to repeat phylogeny” previously documented in other web-building spiders; younger spiders were less likely to build the derived silk retreats that occur at the edges of webs of adults. Younger individuals also consistently built more highly organized webs, with radial lines that c...

Female Macrodactylus costulatus, sericinus, and sylphis mated repeatedly while feeding on flowers and fruits as they matured eggs. Courtship in all species occurred both prior to and following intromission, with most courtship being performed after the male had achieved intromission. Females often prevented males from mounting, and often prevented...

Female rejections of males are crucial events in sexual selection by female choice and sexually antagonistic coevolution, but there are few detailed studies of the process of rejection. Female struggles when mounted by males are often assumed to function to dislodge the male. But this study, in which female receptivity was manipulated by using fema...

Uloborus diversus places extra silk (“stabilimenta”) near the hubs of its webs, preferentially on short radii ending near anchor threads. Spiders probably distinguish these radii from others by their relatively low extensibility. The stabilimentum probably functions as a camouflage device, and the orientation of the stabilimentum lines probably aid...

Some polysphinctine ichneumonid wasps induce alterations in the web construction behaviour of their host spiders, and then suspend their pupal cocoons from the resulting “cocoon webs”. Cocoon webs that have been described previously appear to be designed to increase the web's mechanical stability, and thus to protect the wasp's cocoon. This study d...

Males of many animals perform 'copulatory courtship' during copulation, but the possible reproductive significance of this behaviour has seldom been investigated. In some animals, including the spider Physocyclus globosus (Pholcidae), the female discards sperm during or immediately following some copulations. In this study, we determined which of s...

The larva of the ichneumonid wasp Polysphincta gutfreundi induces its host, the orb-weaving spider Allocyclosa bifurca, to build a highly modified, physically stable orb web, to which the larva then attaches its pupal cocoon, and to add an otherwise unusual linear silk stabilimentum to this web that may camouflage the cocoon. The effects of the lar...

SHÖN (2009, Ethology Ecology & Evolution 21: 161–172) pointed out that in order to understand the functional morphology of sexually selected structures that are used as signaling devices in birds, it is crucial to understand how these structures move during sexual interactions. This insight applies not only to bird feathers, but also to many other...

The genital organ of male spiders (the palpal bulb) differs profoundly from the genitalia of other animals in lacking muscles, sense organs, and nerves; nevertheless spider genitalia show the same trend to sustained, rapid divergent evolution that is typical of most animal genitalia. Much of this chapter explores possible consequences of this lack...

The larva of the parasitic wasp Zatypota sp. nr. solanoi induces its host spiders Anelosimus spp. to modify its web in ways not seen in normal webs of this species or in any other species, providing apparent protection and support for the wasp's cocoon by covering the entire web with a protective sheet and adding a central platform and opening a sp...

The male genitalia of many animal groups have elaborate and species-specific forms. One hypothesis to explain why this is so is that male genitalia function as stimulatory devices that are under sexual selection by cryptic female choice. This report is based on a videotaped observation of a single male of an unidentified species of Tipula (Bellarin...

One of the strongest indications that cryptic female choice is an evolutionary phenomenon of general importance is the widespread existence of male courtship behavior during copulation. It has been presumed that such copulatory courtship functions to induce female reproductive behavior that favors the male's reproductive interests, but this functio...