Wolf Spider Research Articles

Age-related female mating decisions are condition dependent in wolf spiders

Female mating behaviors are known to be sensitive to a variety of individual factors both external and internal to a female; however, mating decisions are likely due to a suite of interacting factors. By independently manipulating female and male diet in the wolf spider Rabidosa rabida and testing females across age groups, we demonstrate that, in addition to its independent effect, female nutritional condition interacts with female age to influence female mating behavior. Overall, high-quantity diet (HD) females were more likely to mate than low-quantity diet (LD) females. Within the LD females, older individuals were more likely to mate than younger individuals, while within HD females, mating probabilities were equal across females of different age classes. With respect to mate choice, only female age influenced the likelihood of mating based on male diet. Young females were choosier as they were more likely to mate with HD males than LD males; in contrast, older females were equally likely to copulate with males of each diet treatment. In addition, the likelihood of pre-sexual cannibalism was dependent on both female and male diet. High-quantity diet females were more likely to cannibalize than LD females, and attacks were directed towards LD males most often. We discuss our results in terms of costs versus benefits of female mate choice.

Along Came a Spider: Using Live Arthropods in a Predator–Prey Activity

ABSTRACT We developed a predator–prey activity with eighth-grade students in which they used wolf spiders (Lycosa carolinensis), house crickets (Acheta domestica), and abiotic factors to address how (1) adaptations in predators and prey shape their interaction and (2) abiotic factors modify the interaction between predators and prey. We tested student understanding with pre- and postquizzes, written observations, and interpretations of graphical results.

Modality-specific experience with female feedback increases the efficacy of courtship signalling in male wolf spiders

A male displaying to attract a mate faces the problem of effectively communicating through a complex and variable signalling environment. Many solutions to this problem include flexible adjustments of signaller behaviour that result in improved signal transmission, yet the mechanisms underlying these solutions remain unknown. We propose that males can optimize signal transmission by attending to female feedback cues and adjusting their signalling position accordingly. We test this hypothesis with males of the wolf spider Schizocosa rovneri , which court females with seismic signals transmitted through substrates on the forest floor. In response, receptive S. rovneri females perform a slow pivot display, producing visual and seismic cues. We mimic female receptivity using puppets, manipulated remotely, and ask whether males alter their signalling position, in terms of substrate use, with female feedback. We further ask if adjustment depends upon receiving cues in particular sensory modalities. We found that males receiving visual and/or seismic feedback cues from puppet females increased overall signalling effort. However, only males that received seismic feedback cues altered substrate use when subsequently signalling. Ultimately, males optimized their signal transmission by altering their use of signalling substrate in response to seismic female receptivity cues. Our results demonstrate a behavioural mechanism for how males effectively position themselves in the signalling environment: experience with female feedback. ► We tested whether male wolf spiders adjust signalling in response to female feedback cues. ► We mimicked female visual and/or seismic receptivity cues using puppets. ► Males increased overall signalling effort in response to female feedback cues. ► Males altered their use of signalling substrate in response to seismic, but not visual, female receptivity cues.

Spatial distribution, burrow depth and temperature: implications for the sexual strategies in two Allocosa wolf spiders

Allocosa brasiliensis and Allocosa alticeps are two burrowing wolf spiders that inhabit Uruguayan sandy coasts. Male efficient digging is necessary because copulation and oviposition occur inside their burrows. We examined burrow distribution, density and temperature variation according to burrow depth. Adult burrows were more frequent at the slope of sand-dunes in A. alticeps and at the base in A. brasiliensis. The base provides better digging conditions, whereas A. alticeps adults could prefer the slope to avoid intra-guild predation. Temperature buffering increased with depth, providing thermal stability in such a harsh environment as coastal dunes.

Experience with chemotactile cues indicating female feeding history impacts male courtship investment in the wolf spider Schizocosa ocreata

Male fitness is often determined by the ability of the male to gain access to multiple mates, although in species that exhibit sexual cannibalism, males might increase their likelihood of being cannibalized with each encounter. This risk should create selection for males who are able to perceive potential risks associated with mating encounters. We studied male Schizocosa ocreata wolf spiders to determine whether they use female chemotactile cues (silk, excreta) as indicators of potential risks and how these cues affected subsequent male courtship behaviors. Female treatments included satiated females vs. starved females, as well as a treatment where females had recently cannibalized a male S. ocreata. We performed experiments to assess (1) if males use female chemotactile cues to determine potential risks associated with differing female feeding treatments and alter courtship investment, and 2) how male experience with female chemotactile cues affected courtship investment in subsequent female encounters. At first encounter, males do not vary courtship investment (number of bouts, duration, and vigor) with different female feeding treatments. However, male behaviors during subsequent encounters with female chemotactile cues varied in complex ways, depending on female feeding treatment and male first encounter experience. These data suggest that male experience impacts perception of female chemical cues and offers the male opportunity to avoid sexual cannibalism in high-risk situations.

Anterior lateral eyes ofLycosa tarantula(Araneae: Lycosidae) are used during orientation to detect changes in the visual structure of the substratum

Previous studies in the wolf spider Lycosa tarantula (Linnaeus 1758) have shown that homing is carried out by path integration and that, in the absence of information relative to the sun's position or any pattern of polarized light, L. tarantula obtains information as to the angle it must turn to home through the anterior lateral eyes (ALEs). In the present study, spiders were trained to walk over a black-and-white grating and afterwards tested either over a white substratum, the same substratum used for training or the same substratum rotated 90 deg (two groups: ALEs covered and only ALEs uncovered; they were tested first without their eyes covered and then with their eyes covered). The directional bearing was measured both in training and test conditions. Under the white or the same substratum in test conditions, the directional bearing had the same mean direction and a distribution similar to that of the training sessions. When the substratum was rotated 90 deg, the directional bearing had the same mean direction but the distribution was significantly different from that of the training sessions. Moreover, if ALEs were covered, spiders behaved as if the substratum had not been rotated and the directional bearing distribution was similar to that of the training sessions. But, if ALEs were the only eyes uncovered, spiders behaved as if no eyes were covered and directional bearing distribution was similar to that of the test condition. It is suggested that, when homing, L. tarantula uses both idiothetic information and visual information gathered through ALEs. These findings present the first evidence that spiders can use the visual structure of the substratum to return home.

Experimental evidence for female-driven monandry in the wolf spider, Pardosa astrigera

Females of many species mate multiply, yet some taxon females mate with only one male, also known as monandry. Although the underlying mechanism behind female monandry is poorly understood relative to female polyandry, there are two contrasting hypotheses, male control and female control, for the maintenance of monandry. Since females generally benefit from multiple mating for material and/or genetic benefits, cases of monandry may reflect male manipulation on female remating at the expense of female fitness (male control). Alternatively, monandry may be favored by females, if females maximize their fitness by mating once (female control). Here, we tested two hypotheses by manipulating the number of mating (repeated mating and polyandry) on female fitness in a largely monandrous wolf spider, Pardosa astrigera. We allowed females to be inseminated once, twice with the same males (repeated mating) or with two males (polyandry) and determined female fitness consequences. The number of female mating, regardless of a single mating, repeated mating, or polyandry, had no significant effects on female fecundity, fertility, and survival and size of their spiderlings. However, the fitness cost of female multiple mating may to some extent be underestimated under laboratory conditions. In addition, female survival was adversely affected by induced multiple mating. Therefore, our results suggest that monandry of the wolf spider (P. astrigera) may be under the control of females, rather than under the control of males.

Correlated Morphological, Ecological, and Behavioral Aspects of the Microhabitat Associations inGeolycosaWolf Spiders of Florida (Araneae, Lycosidae)

Abstract Species of Geolycosa (burrowing wolf spider) found in the eastern USA exhibit one of two species-specific microhabitat associations with associated burrow architectures: “turricolous” species burrow in areas covered in leaf litter and construct a distinct turret of silk and debris at the burrow mouth, while “aturricolous” species locate their burrows in more barren areas and do not construct a turret. Our research goal was to document the relationship between spider coloration, burrow-site selection, and burrow-construction behaviors in five Geolycosa species in Florida (G. micanopy, G. hubbelli, G. xera, G. patellonigra, and G. escambiensis). Discriminant analysis of morphological data supports our contention that each ecomorph has a distinct pattern of pigmentation, with the barren-substrata species being paler. Field studies of species pairs at three sites in Florida (Archbold Biological Station, Ocala National Forest, and the Panhandle) documented the species-specific association with one of ...

Effects of a glyphosate-based herbicide on mate location in a wolf spider that inhabits agroecosystems

Chemical communication is important to many arthropod species but the potential exists for anthropogenic chemicals to disrupt information flow. Although glyphosate-based herbicides are not acutely toxic to arthropods, little is known regarding their effects on natural chemical communication pathways. The wolf spider, Pardosa milvina, is abundant in agroecosystems where herbicides are regularly applied and uses air- and substrate-borne chemical signals extensively during mating. The aim of this study was to examine effects of a commercial formulation of a glyphosate-based herbicide on the ability of males to find females. In the field, virgin females, when hidden inside pitfall traps with herbicide, attracted fewer males than females with water. Likewise females in traps with a ring of herbicide surrounding the opening were less likely to attract males than those in traps surrounded by water. We explored the reaction of males to any airborne component of the herbicide in a laboratory two-choice olfactometer experiment. When no female pheromones were present, males were equally likely to select herbicide or water treated corridors and they all moved through the apparatus at similar speeds. When female pheromones were present, the males that selected control corridors moved more slowly than those that selected herbicide and, if we control for the initial decision time, more males selected the control corridors over the herbicide. These data suggest that glyphosate-based herbicides are “info-disruptors” that alter the ability of males to detect and/or react fully to female signals.

Direct and indirect effects of metal stress on physiology and life history variation in field populations of a lycosid spider

1. Under stress, life history theory predicts reduced growth rates and adult sizes, reduced reproductive allocation, production of larger offspring and postponed reproduction. Both direct and indirect effects of metals can explain these trends, mainly linked to energetic constraints. Metallothionein-like proteins (MTLP’s) are believed to be an important defense mechanism against the adverse effects of metals and other stressors. 2. We tested these predictions comparing six field populations of the wolf spider Pardosa saltans, three of which were on sites that are historically polluted with heavy metals. 3. As expected for life histories evolving under energetic constraints, adult size and condition correlated negatively and egg mass positively with Cd concentrations for a subset of four populations. In the population that showed the highest cadmium and zinc body burdens, reproductive output and allocation were lowest and reproduction was postponed. 4. Contrary to our expectation, for all six study populations MTLP concentrations did not increase in exposed populations, indicating that this defense mechanism cannot explain the observed variation in life histories. 5. We conclude that indirect and synergistic effects of metal pollution may be more important than physiological defense mechanisms in shaping life history traits in field populations.

First description of the female of Acantholycosa logunovi (Araneae: Lycosidae)

With 26 named species (Platnick 2011), Acantholycosa Dahl, 1908 is a relatively large Holarctic genus in the wolf spider subfamily Pardosinae Simon, 1898. Acantholycosa was recently revised and 17 species were described as new to science (Marusik et al. 2004). The majority of species occur in Northern Asia and the highest species diversity is known from the Altai-Sayan Mountain System (18 species) (Marusik et al., 2004). Among the newly described species was Acantholycosa logunovi Marusik, Azarkina & Koponen, 2004 from Altai in Russia. The female epigyne of this species was found to be remarkably similar to those of A. norvegica (Thorell, 1872), while male palp was similar to those in A. plumalis species group. While collecting spiders in Altai the senior author collected over a dozen specimens belonging to Acantholycosa of which one pair was in copula. Study of this material revealed that males were conspecific with figures of the holotype of A. logunovi, but that females were different from those illustrated by Marusik et al. (2004). The females described as A. logunovi by Marusik et al. (2004) are instead A. norvegica and therefore females of A. logunovi remained undescribed up until now. Here we describe the female of A. logunovi, provide comparisons with related species and add to the known localities of this species.

Reproductive allocation in female wolf and nursery-web spiders

We collected data on maternal mass, clutch mass (reproductive effort), number of offspring, and mean offspring mass from 28 species of Lycosidae (wolf spiders) and five species of Pisauridae (nursery-web spiders) found in Mississippi, USA. Our primary goal was to test for a trade-off between offspring number and offspring size (mass) among wolf and nursery-web spiders, which are sister families. The regression of reproductive effort on maternal mass was highly significant and explained 94% of the variation in reproductive effort among species and 96% of the variation among genera. The slope of the regression line between maternal mass and total offspring mass was not significantly different from one, suggesting that spiders used a constant proportion of their total energy budget for reproduction regardless of size. Partial correlation and principal components analyses demonstrated a clear trade-off between offspring size and number. Species with large offspring (relative to adult size) produced fewer offspring than expected. Lycosids produced small numbers of large offspring relative to pisaurids, and smaller species of both families are more constrained in the evolution of the offspring size:number continuum than larger ones.

Population Density and Killing Capacity by Predators of Eggs and Larvae of the Diamondback Moth in Nicaragua

The diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a serious pest of economically important brassica crops such as cabbage (Brassica oleracea Linne). To address the current lack of baseline information concerning predators of P. xylostella, and their potential role as biological control agents, especially in Central America, we aimed to 1) identify predators in northern Nicaragua, and estimate their population densities; 2) assess their killing rate of eggs and larvae of P. xylostella; and 3) assess if predators feed more of smaller P. xylostella larvae. Individuals of selected predator groups were offered eggs, second- or third-instar larvae. Our results indicate that there exists a broad spectrum of predators, within and around cabbage fields in Nicaragua that have the capacity to feed on P. xylostella eggs and larvae under laboratory conditions. Predators with the highest killing rates were adult and larval rove beetles (Staphylinidae), sheet weaving spiders (Linyphiidae), and larger jumping spiders (Salticidae). Although all predator densities varied in space and time the consistently most abundant predator groups with the highest consumption or killing rate, and consequently the highest potential for suppressing P. xylostella populations were wolf spiders (Lycosidae) and rove beetles (Staphylinidae), although sheet weaving spiders, jumping spiders, assassin bugs (Reduviidae), and damsel bugs (Nabidae) also can be important. We conclude that those generalist predators exhibiting the highest killing rates in the laboratory should be considered for further study in the field as candidate species with a role in the management of pest P. xylostella.

Contrasting energetic costs of courtship signaling in two wolf spiders having divergent courtship behaviors

Energetic costs of courtship behavior were measured for two sympatric wolf spiders that are reproductively isolated based on distinct male courtship behaviors with different signaling modes and activity levels: Schizocosa ocreata (Hentz 1844) uses multi-modal communication (visual and seismic signals) and an actively-moving courtship display, whereas S. rovneri (Uetz & Dondale 1979) uses only seismic signals produced while stationary. To test for increased energetic expense of more complex multimodal courtship in S. ocreata, we recorded peak CO2 output for male spiders standing, walking, or courting. We found that peak CO2 output while standing or walking was similar between species. Courtship behavior of S. ocreata produced greater peak CO2 output than these other behaviors, and was significantly greater than peak CO2 output of S. rovneri courtship, which was not different from that of locomotion. Hence, unequal energy expenditure related to the modality of the males' courtship displays resulted in different energetic costs for courting male spiders. Male courtship vigor may serve as a criterion for female mate choice in Schizocosa.

Determinants of differential reproductive allocation in wolf and nursery-web spiders

We used data from 33 species of cursorial spiders in northern Mississippi (USA) to investigate the relative contributions of ecology and phylogeny to the reproductive trade-off between number and size of offspring. Sixty percent of the variation among genera for female reproductive allocation was due to differences between the family Pisauridae and the family Lycosidae. Temporal variation in reproductive allocation during the reproductive season was not observed for the majority of species examined. We found significantly different patterns of reproductive allocation among species within genera, suggesting that each species has responded to distinct selection pressures. Preliminarily, this extensive variation appears to be due mostly to interspecific competition and predation risk from other spiders. However, the patterns of reproductive allocation of species within a single guild (i.e., a group of species potentially competing for the same resources) for the two families are very different. Larger species of wolf spiders (family Lycosidae) within a given guild produce smaller numbers of larger offspring relative to the size of the mother, and smaller species produce the reverse. However, in nursery-web spiders (family Pisauridae) the larger species within a guild produce larger numbers of smaller offspring than expected. The current study provides an example of the flexibility of life history evolution despite phylogenetic constraints. It also demonstrates the potential for varying life history strategies to mediate competition, allowing similar species to coexist.

Does allometric growth explain the diminutive size of the fangs of Scytodes (Araneae: Scytodidae)?

Abstract Spitting spiders eject silk and glue from their fangs when attacking prey. The ejection is complete in less than 35 ms and involves high-frequency fang oscillations that can approach 1700 Hz. Because of Newtonian physical constraints, these oscillations, which cause the spit to be dispersed in a zigzag pattern, could not occur at such high frequencies if the fangs themselves were not very small. We hypothesized that allometric neoteny, in which the developmental rate of a structure is retarded relative to the changing overall size of the growing individual, could explain (in an ontological sense) the small fangs of adult spitting spiders. We measured the fangs, chelicerae, carapaces, and sterna of many sizes of spitting spiders, Scytodes thoracica (Latreille 1802a), brown recluse spiders, Loxosceles reclusa Fertsch & Mulaik 1940, and wolf spiders, Varacosa avara (Keyserling 1877), to discover whether the fangs of spitting spiders grow unusually slowly. Using sternum width as our proxy for spider ...

Complex courtship displays facilitate male reproductive success and plasticity in signaling across variable environments

Abstract Effective signal transmission is essential for communication. In environments where signal transmission is highly variable, signalers may utilize complex signals, which incorporate multiple components and modalities, to maintain effective communication. Male Rabidosa rabida wolf spiders produce complex courtship signals, consisting of both visual and seismic components. We test the hypothesis that the complex signaling of R. rabida contributes to male reproductive success in variable signaling environments. We first examine the condition-dependence of foreleg ornamentation (a presumed visual signal) and seismic signal components and find that both may provide potentially redundant information on foraging history. Next, we assessed reproductive success across manipulated signaling environments that varied in the effectiveness of visual and/or seismic signal transmission. In environments where only one signal could be successfully transmitted (e.g., visual or seismic), pairs were still able to successfully copulate. Additionally, we found that males altered their courtship display depending on the current signaling environment. Specifically, males reduced their use of a visual display component in signaling environments where visual signal transmission was ablated. Incorporating signals in multiple modalities not only enables R. rabida males to maintain copulation success across variable signaling environments, but it also enables males to adjust their composite courtship display to current signaling conditions.

Male sexual cannibalism in a sand-dwelling wolf spider with sex role reversal

Sexual cannibalism usually involves females attacking and consuming males before, during or after copulation. Sex role reversed systems may provide insight into the debate about whether it arises as mistaken identity, a spillover in female aggressiveness, foraging decisions, and/or extreme mate choice. In such systems, males may be selective and voracious to compensate for their higher reproductive costs, and thus males may be the sexually cannibalistic sex. Allocosa brasiliensis shows a reversal in sex roles and male-biased sexual size dimorphism (the opposite of the common pattern in spiders). The present study aimed to test whether males cannibalize or mate according to female reproductive status or body characteristics. Each of 20 adult males was consecutively exposed to one virgin and one mated female, alternating the order of exposure. Males preferred to mate with virgin females in good body condition and heavier-mated females. Males attacked 15% of virgins and 40% of mated females and cannibalized 10% and 25% of the total trials, respectively. The astonishing male cannibalistic behaviour best agrees with extreme mate choice hypotheses because attacks were more frequent on mated females of low body condition. This is the first report of male sexual cannibalism in a sex role reversed system. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 68–75.

Nutrient regulation in a predator, the wolf spider Pardosa prativaga

Nutrient balancing is well known in herbivores and omnivores, but has only recently been demonstrated in predators. To test how a predator might regulate nutrients when the prey varies in nutrient composition, we restricted juvenile Pardosa prativaga wolf spiders to diets of one of six fruit fly, Drosophila melanogaster, prey types varying in lipid:protein composition during their second instar. We collected all fly remnants to estimate food and nutrient intake over each meal. The spiders adjusted their capture rate and nutrient extraction in response to prey mass and nutrient composition irrespective of energy intake. Intake was initially regulated to a constant lipid plus protein mass, but later spiders fed on prey with high proportions of protein increased consumption relative to spiders fed on other prey types. This pattern indicates that the spiders were prepared to overconsume vast amounts of protein to gain more lipids and energy. The spiders also regulated protein after ingestion, and ingested protein was incorporated less efficiently into body tissue when the prey was protein rich. Despite both pre- and postingestive nutrient regulation, the body lipid:protein compositions of the spiders were highly affected by the nutrient compositions of their prey, and growth in carapace length and lean body mass increased with increasing prey protein:lipid ratio. Our results demonstrate that prey nutrient composition affects these predators, but also that the spiders possess behavioural and physiological adaptations that lead to partial compensation for these effects.

Enigmatic ornamentation eases male reliance on courtship performance for mating success

Female preferences are frequently invoked to explain the widespread occurrence of elaborate male ornaments, yet empirical data demonstrating such preferences are sometimes equivocal or even contradictory. In the wolf spider Schizocosa stridulans, despite evidence of strong female choice, prior research has been unable to link the conspicuous sexually dimorphic foreleg ornamentation of males to their mating success. We conducted three experiments aimed at determining the function of this previously enigmatic ornamentation. Our first two experiments used males with phenotypically modified foreleg phenotypes in simple and complex mating environments in order to examine the relationship between the presence/absence of ornamentation and male mating success. In both experiments, we found no relationship: courtship rate was the sole predictor of mating success. In a third experiment, we used males with naturally varying foreleg ornamentation in mating trials. Ornamentation was subsequently quantified and we again examined the factors influencing male mating success. As in our first two experiments, we found courtship rate to be a good predictor of mating success. Additionally, we discovered that foreleg ornamentation and courtship rate interact to influence male mating success. At low courtship rates, males with more foreleg ornamentation have a mating advantage, whereas at high courtship rates, males with less foreleg ornamentation have a mating advantage. We discuss several potential explanations for these results. In summary, we provide the first evidence of a benefit of foreleg ornamentation in male S. stridulans and suggest that this benefit is realized by the interaction between ornamentation and courtship rate.