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Intraguild predation occurs when an organism preys on a competitor. This ecological interaction can have considerable consequences on the population dynamics of predators and indirectly affect their prey. In arachnids, it is a quite common phenomenon, but it has been poorly documented in the Neotropical region. Here, we present records of 16 species feeding on other 14 species of arachnids. The most common families that acted as predators were Buthidae (Scorpiones) and Salticidae (Araneae), while the most common prey were members of the families Araneidae and Ctenidae (Araneae). In our survey, Drake Bay, in Costa Rica, is overrepresented due to years of systematic observations by two of the coauthors. [ABSTRACT FROM AUTHOR]

Optimal foraging and individual specialization theories suggest that different properties of the interactions between prey and predators determine foraging strategies. However, none of these theories consider how the nutritional status of the predators and the risk of being attacked by other predators may affect prey foraging strategy. Shelter-building spiders, such as Metazygia laticeps (Araneidae), build webs as dynamic traps to capture prey and may optimize capture efficiency while adopting strategies to minimize their exposure to predators by building a shelter and staying inside it most of the time. Prey capture, however, involves leaving the shelter, which may contribute to an increased risk of predation. Individuals may be more likely to take risks when they are in poor nutritional status. In this study, we conducted field experiments to assess support for the hypotheses that M. laticeps spiders with poor nutritional status (i) expose themselves to greater risk of predation during foraging and (ii) invest more silk in different web structures to increase prey capture success. Nutritional state was unrelated to exposure to predation and did not restrict web investment in M. laticeps. However, spiders left the shelter more quickly at night than during the day, regardless of their nutritional state. We suggest that individual's nutritional state does not determine foraging, and predation risk can affect general activity of spiders depending on foraging period. [ABSTRACT FROM AUTHOR]

Many orb-web weaving spiders add highly visible zigzagging silk "decorations" to their webs that are thought to function in prey attraction or predator avoidance. Despite the long history of studies on the form, frequency, and function of these structures, little attention has been paid to their mode of construction. Here, we report for the first time the sequence of construction of decorations by Argiope luzona (Walckenaer, 1841), a common species in the northern Philippines. A disc-shaped decoration built by a juvenile was laid as several continuous loops in a modified figure-eight pattern. The resulting asymmetric design is typical of many Argiope spp., hence suggesting that disc decorations are built similarly across the genus. In a full cruciate decoration of an adult female spider -- consisting of four diagonal arms arrayed around the web's hub -- each two-armed diagonal was laid down in turn, each arm being laid from its outermost portion inward, the lower arm first. The mode of construction of the cruciate device suggests that this type of decoration evolved by duplication and diagonalizing the single two-armed vertical decoration seen in presumptively less derived Argiope. [ABSTRACT FROM AUTHOR]

Simple Summary: Orb-weaving spiders can learn to avoid eating unpalatable prey, but what happens when they encounter one that they have never seen before? In the United States, a spider from East Asia has become established (the "jorō spider") in recent years, and their webs are most prominent during the late-summer and fall, which is also when migrating monarch butterflies are in abundance. Since monarch butterflies are unpalatable (because of developing on toxic milkweeds), we wondered if jorō spiders would recognize this and avoid eating them, given that these species do not coexist in East Asia. Using field observations of butterflies deposited into jorō spider webs, we found that these spiders do avoid eating monarchs, and even remove them from their webs in some cases. They readily attack other butterflies, even those that are similarly colored to monarchs. This raises many questions about how they perceive the "distastefulness" of monarchs, even without tasting the butterflies first. An invasive spider from East Asia has established in the U.S. southeast (the "jorō spider," Trichonephila clavata) and is rapidly expanding its range. Studies assessing the impact of this species are needed, including how expansive its diet is. An open question is whether monarch butterflies, Danaus plexippus, are a potential prey item for this spider, given that jorō spiders do not coexist with monarchs in their native range. Since monarch larvae feed on milkweed, they sequester cardiac glycosides into their adult tissues, rendering them unpalatable to many predators. At sites within northeast Georgia, we staged a series of trials (n = 61) where we tossed monarchs into jorō spider webs and, for comparison, performed similar trials with another aposematic species, gulf fritillary (Agraulis vanilla), and a palatable species, tiger swallowtail (Papilio glaucus). We recorded the outcome of the trials, which included whether the spider attacked or did not attack the prey. We also conducted a visual survey during the same fall season to look for evidence of jorō spiders consuming monarchs naturally. Our findings revealed that jorō spiders avoided eating monarchs; spiders only attacked monarchs 20% of the time, which was significantly less than the attack rates of similarly sized or larger butterflies: 86% for gulf fritillaries and 58% for tiger swallowtails. Some jorō spiders even removed monarchs from their webs. From our visual surveys of the surrounding area, we found no evidence of natural monarch consumption and, in general, butterflies made up only a fraction of the jorō spider diet. We conclude that jorō spiders appear to recognize monarch butterflies as being unpalatable, even without having a prior history with the species. This invokes questions about how these spiders can immediately recognize their unpalatability without touching the butterflies. [ABSTRACT FROM AUTHOR]

Globally, arthropod populations are declining at alarming rates, but the causes are rarely understood. Our research details and examines possible causes for fluctuations in the size of a Costa Rican population of golden silk orbweaver spiders (Trichonephila clavipes (Linnaeus, 1767)). Over a seven-year period from 2013–2019, we noted a sharp decline and then partial recovery of the study population during the wet season (June, July), but then failed to locate any spiders during a brief survey in June 2022 when they would otherwise be abundant. We monitored webs daily during 2013–2019 to test whether variation in prey capture, competitors, female size, male availability, predation, temperature, or rainfall related to population fluctuations. We were unable to explain T. clavipes population trends with the collected data. Future studies are needed to determine whether the extremely low population densities we witnessed in 2017 and 2022 can be interpreted as the lowest values of this species' normal population fluctuation cycle or whether these extremes are part of a long-term spider decline. [ABSTRACT FROM AUTHOR]

Simple Summary: Predators and prey have direct interactions that influence their short-term behaviors, including resource allocation and strategies for moving through habitats. However, the presently observed behaviors are the products of coevolutionary interactions, posited to be a history of measures and countermeasures between the predator and prey. We found that Argiope (orb-weaver) spiders in the continental USA appear to use a pheromone lure that mimics the mating pheromone of the day-flying Hemileuca moth (buck moth) to entice male moths into their webs. We found evidence that different phylogenetic groups of Hemileuca moths respond to the Argiope pheromone lure with a broad range of responses, ranging from indifferent to acutely strongly attracted, suggesting a coevolutionary history of predator–prey countermeasures. One of these countermeasures may be the potential evolution of moth developmental timing (adult emergence) to avoid Argiope predation in areas where the ranges of the moths and spiders overlap. Predator–prey coevolution, particularly chemo-ecological arms races, is challenging to study as it requires the integration of behavioral, chemical ecology, and phylogenetic studies in an amenable system. Moths of the genus Hemileuca (Saturniidae) are colorful, diurnal, and fast and often fly well above the vegetation canopy layer. However, several Hemileuca species have been reported as being captured in spider webs, specifically Argiope species (Araneidae). Female Hemileuca are known to produce mating pheromones and spiders of the Araneidae family are known to use pheromone lures to attract lepidopteran prey. We presented primarily female Argiope aurantia, which are attractive to male Anisota pellucida (Saturniidae), to different populations of Hemileuca species across the southern and western United States to categorize the homing response strength of different species of male Hemileuca. When we mapped these Argiope lure attraction strength categories onto the most recently published Hemileuca phylogeny, the behavioral patterns suggested a potential co-evolutionary arms race between predators and prey. Males of Hemileuca maia, H. grotei, and H. nevadensis (all in the same clade) appeared to have no attraction to A. aurantia, while H. magnifica and H. hera (within a different, separate clade) appeared to be strongly attracted to A. aurantia, but H. nuttalli (also within the H. hera and H. magnifica clade) displayed no attraction. Furthermore, Hemileuca eglanterina (yet a different clade) displayed strong, weak, and no attraction to A. aurantia, depending on the population. These apparent clade partitioning patterns of Argiope lure effectiveness and within-species variation in Hemileuca lure responses suggest a predator–prey coevolutionary history of measures and countermeasures. [ABSTRACT FROM AUTHOR]

While surveying operational sex ratios of the giant golden orb weaver Nephila pilipes (Fabricius, 1793) in Singapore, we documented a stunning case of predatory behavior of a jumping spider Viciria pavesii Thorell, 1877. A female V. pavesii invaded a N. pilipes orb web that was occupied by the resident female and four males, and successfully captured, killed, and removed one of the Nephila males. Whether araneophagy in V. pavesii is opportunistic or a predatory ritual remains to be tested more precisely, but because the observed predatory event triggered an aggressive response by the N. pilipes alpha male, it is plausible that V. pavesii may engage in aggressive mimicry. We place our observation into the context of jumping spider cognition and behavioral tactics that are so far well understood only in a few spartaeine genera, notably Portia Karsch, 1878. Viciria Thorell, 1877, we argue, is another such jumping spider taxon worthy of behavioral scrutiny. [ABSTRACT FROM AUTHOR]

Animals may consider both biotic and abiotic factors in foraging site choice. Among the biotic factors, food availability and predation risk are two widely reported important factors in determining foraging site fidelity. Their earlier investments, such as those retreat‐building species' efforts in retreats construction, however, have been largely ignored. The orb‐web spider Cyclosa monticola constructs a long column of masquerading detritus decoration in its web for predator avoidance purpose. This detritus decoration also functions as a retreat. However, the role of the detritus decoration for its foraging site fidelity is unknown. By manipulating three factors, presence of detritus decoration, prey availability and predation risk to the spider webs in the field, we show that the self‐constructed detritus decoration is as important as prey availability and predation risk in mediating foraging site fidelity. In addition, the web area also has a significant impact to the foraging site fidelity of the spider, those with larger webs were more likely to leave after being manipulated. However, other factors such as spider body size, decoration length and rain all have no significant impact. Our study may strengthen the current understanding of the movement and foraging of animals, especially those building retreats. [ABSTRACT FROM AUTHOR]

They mostly come at night: Predation on sleeping insects by introduced candy-striped spiders in North America We rarely observed candy-striped spiders invading other spiders' webs to engage in kleptoparasitism or araneophagy. gl In North America, candy-striped spiders often occur in very high densities (e.g., Tomascik, [13]), and they thrive in a variety of habitats, suggesting that they may have strong impacts on insect communities. Keywords: Enoplognatha latimana; Enoplognatha ovata; foraging ecology; insect sleep; natural history; predation behavior EN Enoplognatha latimana Enoplognatha ovata foraging ecology insect sleep natural history predation behavior 1 6 6 05/03/23 20230501 NES 230501 Candy-striped spiders (two closely related and nearly indistinguishable species: I Enoplognatha ovata i (Clerck, 1757) and I Enoplognatha latimana i Hippa & Oksala, [8]) are, at first glance, unremarkable cobweb weavers in the family Theridiidae. We have also observed candy-striped spiders invading the webs of other spiders to steal prey, consume the host spiders, and/or take over the web and hunt on it (Figure 2c,d, Appendix S1: Table S2). [Extracted from the article]

Simple Summary: Spiders are among the most common predators in terrestrial ecosystems and play a crucial role in ecosystems. However, with changing environments, spiders are under pressure from pollution and habitat destruction. In this study, we collected spiders from five parks with different management histories in the greater Memphis, Tennessee area to explore the extent to which human oversight and management of natural areas, especially invasive plant management, influence spider occurrence. Our results showed that invasive plants might provide a valuable habitat for the humpbacked orb-weaver, which was predominantly found on invasive plant species. These findings may have implications for the management of invasive plants in parks and other protected areas. Land management of parks and vegetation complexity can affect arthropod diversity and subsequently alter trophic interactions between predators and their prey. In this study, we examined spiders in five parks with varying management histories and intensities to determine whether certain spider species were associated with particular plants. We also determined whether web architecture influenced spider occurrence. Our results showed that humpbacked orb-weavers (Eustala anastera) were associated with an invasive plant, Chinese privet (Ligustrum sinense). This study revealed how invasive plants can potentially influence certain spider communities, as evidenced by this native spider species only occurring on invasive plants. Knowing more about spider populations—including species makeup and plants they populate—will give insights into how spider populations are dealing with various ecosystem changes. While we did not assess the effect of invasive plants on the behavior of spiders, it is possible that invasive species may not always be harmful to ecosystems; in the case of spiders, invasive plants may serve as a useful environment to live in. More studies are needed to ascertain whether invasive plants can have adverse effects on spider ecology in the long term. [ABSTRACT FROM AUTHOR]

Differential predation on species with intraspecific colour variation has been explored in various systems and is often implicated as the driving force behind colour polymorphism maintenance.Here, investigation done on whether predation contributes to the maintenance of extensive colour variation in the Neotropical tortoise beetle, Chelymorpha alternans (Chrysomelidae). Recorded predation rates on different colour pattern phenotypes by three common, generalist invertebrate predators, and identified potential chemical signals of unpalatability.Predaceious mantids (Orthoptera, Mantidae) consumed no beetles, regardless of phenotype, whereas the giant orb‐weaving spider (Trichonephila clavipes; Araneidae) consumed all three beetle phenotypes. The carton‐nest ant, Azteca chartifex (Formicidae), displayed differential predation; the rufipennis phenotype of C. alternans was sometimes consumed, the metallic phenotype was never consumed, and the veraguensis phenotype was consumed in the first three encounters and subsequently discarded, suggesting a learned avoidance behaviour.Using gas chromatography–mass spectrometry, it was determined that cuticular hydrocarbon profiles were similar between the metallic and militaris‐a phenotypes. The rufipennis phenotype showed pronounced differences and displayed the greatest among‐individual variation in elytral cuticular profiles.Between‐phenotype variation in chemical cues, and differences in how predators receive those cues, may mediate predator response, and play a role in maintaining colour variation in this species. [ABSTRACT FROM AUTHOR]

Oil palm (Elaeis guineensis) is a tropical crop that produces palm oil: the most traded vegetable oil worldwide. It is principally grown in Southeast Asia, but West Africa – oil palm's native range – is rapidly becoming a hotspot of cultivation. Oil palm in West Africa is cultivated using both traditional (i.e., by local people) and industrial (i.e., by corporations) approaches. Little is known about the relative ecological impacts of these different oil palm cultivation styles on native rainforest ecosystems. Working in Liberia within the framework of the Sustainable Oil Palm in West Africa (SOPWA) Project, we investigated the impacts of traditional and industrial approaches to oil palm cultivation on spiders—important meso-predators that provide pest control services—inhabiting understory vegetation. We sampled spiders in three systems: (1) rainforest, (2) fallowed farmland with wild-growing oil palms, which local people manage and harvest ('country palm'), and (3) industrial oil palm farms. We assessed differences in the abundance of all spiders, adults only, and juveniles only; spider species richness, and spider species-level community composition. Through focussed samples of orb web-building spiders, we also assessed differences in spider web-building (the average web area, total web area, standard deviation of web area) and prey capture (the average captured prey, total captured prey, standard deviation of captured prey) across systems. We found that rainforest had more species in total and on average than country palm and industrial oil palm, and that country palm had fewer spider individuals than rainforest and industrial oil palm. All systems supported distinct spider communities. Our focussed studies on orb web-building spiders indicated that the average web area, total web area, and standard deviation of web area were all higher in industrial oil palm than forest and country palm, which led to higher average and total prey capture. Our findings indicate that conversion of rainforest to country palm and industrial oil palm in Liberia has negative effects on spider biodiversity, with clear "winning" and "losing" species, and levels of spider-associated ecosystem functioning. Our findings also show that industrial oil palm farms can support relatively abundant and speciose spider communities, which may provide important pest control services that could boost oil palm productivity. Future work is needed to identify effective management strategies to conserve spiders and associated pest control services in West African country palm and industrial oil palm systems. • Ecological impacts of oil palm cultivation in West Africa are poorly known. • We compared spiders in forest and oil palm managed traditionally and industrially. • Rainforest had the most species, and systems differed in species-level composition. • Industrial oil palm contained species with larger webs, enhancing prey capture. • Spiders—and their pest control services—should be conserved in oil palm systems. [ABSTRACT FROM AUTHOR]

A prominent question in animal research is how the evolution of morphology and ecology interacts in the generation of phenotypic diversity. Spiders are some of the most abundant arthropod predators in terrestrial ecosystems and exhibit a diversity of foraging styles. It remains unclear how spider body size and proportions relate to foraging style, and if the use of webs as prey capture devices correlates with changes in body characteristics. Here, we present the most extensive data set to date of morphometric and ecological traits in spiders. We used this data set to estimate the change in spider body sizes and shapes over deep time and to test if and how spider phenotypes are correlated with their behavioral ecology. We found that phylogenetic variation of most traits best fitted an Ornstein–Uhlenbeck model, which is a model of stabilizing selection. A prominent exception was body length, whose evolutionary dynamics were best explained with a Brownian Motion (free trait diffusion) model. This was most expressed in the araneoid clade (ecribellate orb-weaving spiders and allies) that showed bimodal trends toward either miniaturization or gigantism. Only few traits differed significantly between ecological guilds, most prominently leg length and thickness, and although a multivariate framework found general differences in traits among ecological guilds, it was not possible to unequivocally associate a set of morphometric traits with the relative ecological mode. Long, thin legs have often evolved with aerial webs and a hanging (suspended) locomotion style, but this trend is not general. Eye size and fang length did not differ between ecological guilds, rejecting the hypothesis that webs reduce the need for visual cue recognition and prey immobilization. For the inference of the ecology of species with unknown behaviors, we propose not to use morphometric traits, but rather consult (micro-)morphological characters, such as the presence of certain podal structures. These results suggest that, in contrast to insects, the evolution of body proportions in spiders is unusually stabilized and ecological adaptations are dominantly realized by behavioral traits and extended phenotypes in this group of predators. This work demonstrates the power of combining recent advances in phylogenomics with trait-based approaches to better understand global functional diversity patterns through space and time. [Animal architecture; Arachnida; Araneae; extended phenotype; functional traits; macroevolution; stabilizing selection.] [ABSTRACT FROM AUTHOR]

Spider webs are iconic examples of extended phenotypes that are remarkably plastic across different environments. Orb webs are not only effective traps for capturing prey, but can also provide information to potential mates and, in some cases, potential predators and prey through silk-based chemicals. As with regular phenotypic traits, variability in the properties of spider webs is thought to be mediated by a combination of genetic and environmental effects. Here, we examined variation in several key features of the webs of the orb-weaving spider Argiope keyserlingi across five geographically disparate populations. We documented variation in web architecture and chemical properties of webs collected directly from the field. We then probed the potential for the underlying environmental driver of local insect abundance to explain this variation, by analysing the properties of orb webs constructed by the spiders from these different populations, but under identical laboratory conditions. We found no evidence of variation across populations in the architecture of webs constructed in the laboratory, despite the large geographic distances. Nonetheless, we discovered between population variation in the composition of chemicals found on the surface of silk and in the taxonomic distribution of available prey. Furthermore, there was a positive correlation between the quantity of nitrogenous compounds in web silks and female body condition. When combined, these findings suggest that environmental mechanisms can drive variation in web traits across spider populations. [ABSTRACT FROM AUTHOR]

Many species – humans included – employ color as an instrument of deception. One intriguing example of this resides in the conspicuous abstract color patterns displayed on the bodies of female orb weaving spiders. These displays increase prey interception rates and thereby function at least as visual lures. Their chromatic properties however vary extensively, both across and within species, with discrete forms often co-existing in the manner of a stable polymorphism. Variation is principally expressed in terms of signal hue (color per se), but it is unclear how attractiveness scales with this property and if extant morphs are maximally attractive relative to a graded range of potential alternatives. We examined these questions by assessing catch rates among color-manipulated females of the dimorphic jeweled spider Gasteracantha fornicata in their natural webs. The manipulation altered dorsal appearance in a manner akin to adding six new variants of their existing white/yellow phenotypes. This magnified the natural variation in stimulus hue independently of chroma (saturation) across a range spanning most of the color spectrum. Catch rate varied across treatments in simple accordance with how greatly stimulus hue deviated from either of the two extant spider phenotypes. Predictions based on fly-perceived chromatic and achromatic background contrast were clearly unsupported despite dipterans constituting ~60 % of identifiable prey. This study supports the importance of signal coloration per se in G. fornicata and suggests that extant lure phenotypes reside in a broadly optimal spectral range for stimulating their aggregate prey community. [ABSTRACT FROM AUTHOR]

Orb-weaving spiders often use their legs to briefly jerk the radii of the web, generating intense vibrations throughout the web. Several functions have been proposed for this behaviour, but there is a lack of empirical evidence. In this study, we conducted a series of experiments on Cyclosa argenteoalba to examine the function and adaptive significance of spider jerks in the context of interactions with prey. First, we used within-individual, inter-individual, and interspecific comparisons (in three co-occurring Cyclosa sp.) to test whether the relation between prey and spider size predict the frequency of jerks that the spider performs. Second, we examined whether jerks prevent prey from escaping the web, whether jerks entangled more spiral threads around the prey, and how prey size affected this result. We found that spiders jerked more as the prey size increased and as spider size decreased. Jerking behaviour reduced the probability of prey escaping from the web and increased the number of spiral threads contacting the prey. The jerk efficiency (the number of additional spiral threads contacted per jerk) was lower in larger prey, which potentially explains why spiders jerk more towards larger prey. Collectively, our results highlight size dependency in the performance of jerks and their role in prey capture. Significance statements: Many orb-weaving spiders show a behaviour that pulls the radii of the web intensively using their legs towards their prey, called jerks. Though this behaviour is common and has been recognised for many decades, the function and their adaptive significance have been surprisingly understudied. Using a series of experiments, we demonstrate that jerks help spiders prevent prey escape and subdue prey by entangling additional spiral (sticky) threads around the prey. We further show that the performance of jerks is size-dependent: spiders jerk more (1) as their size decreases and (2) as prey size increases. Further in-depth analysis suggests that the observed size-dependent jerks seem to be related to spiders' cautiousness and/or reduced jerk efficiency towards larger prey. [ABSTRACT FROM AUTHOR]

Hearing is a fundamental sense of many animals, including all mammals, birds, some reptiles, amphibians, fish, and arthropods. The auditory organs of these animals are extremely diverse in anatomy after hundreds of millions of years of evolution, yet all are made up of cellular tissue and are morphologically part of the bodies of animals. Here, we show that hearing in the orb-weaving spider Larinioides sclopetarius is not constrained by the organism's body but is extended through outsourcing hearing to its extended phenotype, the proteinaceous, self-manufactured orb web. We find that the wispy, wheel-shaped orb web acts as a hyperacute acoustic antenna to capture the sound-induced air particle movements that approach the maximum physical efficiency better than the acoustic responsivity of all previously known eardrums. By sensing the motion of web threads, the spider remotely detects and localizes the source of an incoming airborne acoustic wave, such as those emitted by approaching prey or predators. By outsourcing its acoustic sensors to its web, the spider is released from body size constraints and permits the araneid spider to increase its sound-sensitive surface area enormously, up to 10,000 times greater than the spider itself. The spider also enables the flexibility to functionally adjust and regularly regenerate its external "eardrum" according to its needs. The outsourcing and supersizing of auditory function in spiders provides unique features for studying extended and regenerative sensing and designing novel acoustic flow detectors for precise fluid dynamic measurement and manipulation. [ABSTRACT FROM AUTHOR]

Cicada (Hemiptera) emergence is a major resource pulse that produces diverse effects on terrestrial food webs. Most studies have focused on periodical cicadas; however, little is known regarding the prey–predator interactions and size relationships between annual cicadas and predators, with knowledge being exclusively limited to the cicada–bird systems. Here, we focused on the interactions between annual cicadas and spiders in Japan. Based on direct observations and posts on social networking services and blogs on the Internet, we aimed to (1) reveal the major spider taxa as the predators of annual cicadas, (2) identify the major cicada taxa as the prey of spiders, and (3) characterise the prey–predator body size relationships between annual cicadas and spiders. Large orb-web spiders of the family Araneidae were identified as the major predators of annual cicadas. Spiders preyed on diverse cicada species, and prey species composition varied among the predator species. Regarding body size ratio, spiders tended to prey on cicadas larger than themselves (prey–predator body size ratio >1). We suggest that orb-weavers may function as one of the key predators of annual cicadas. Annual and periodical cicadas may be preyed upon by predators that use different foraging modes (web-builders or cursorial hunters). Further examination of these prey–predator interactions will contribute to the understanding of the cicada–predator systems. [ABSTRACT FROM AUTHOR]

Trophic interactions may strongly depend on body size and environmental variation, but this prediction has been seldom tested in nature. Many spiders are generalist predators that use webs to intercept flying prey. The size and mesh of orb webs increases with spider size, allowing a more efficient predation on larger prey. We studied to this extent the orb‐weaving spider Araneus diadematus inhabiting forest fragments differing in edge distance, tree diversity, and tree species. These environmental variables are known to correlate with insect composition, richness, and abundance. We anticipated these forest characteristics to be a principle driver of prey consumption. We additionally hypothesized them to impact spider size at maturity and expect shifts toward larger prey size distributions in larger individuals independently from the environmental context. We quantified spider diet by means of metabarcoding of nearly 1,000 A. diadematus from a total of 53 forest plots. This approach allowed a massive screening of consumption dynamics in nature, though at the cost of identifying the exact prey identity, as well as their abundance and putative intraspecific variation. Our study confirmed A. diadematus as a generalist predator, with more than 300 prey ZOTUs detected in total. At the individual level, we found large spiders to consume fewer different species, but adding larger species to their diet. Tree species composition affected both prey species richness and size in the spider's diet, although tree diversity per se had no influence on the consumed prey. Edges had an indirect effect on the spider diet as spiders closer to the forest edge were larger and therefore consumed larger prey. We conclude that both intraspecific size variation and tree species composition shape the consumed prey of this generalist predator. [ABSTRACT FROM AUTHOR]

Novel anthropogenic noise has received considerable attention in behavioural ecology, but the natural acoustic environment has largely been ignored as a niche axis.Using arrays of speakers, we experimentally broadcasted whitewater river noise continuously for three summers, and monitored spider abundance and behaviour across 15 sites, to test our hypothesis that river noise is an important structuring force as a niche axis.We find substantial evidence that orb‐weaving spiders (Araneidae and Tetragnathidae) are more abundant in high sound level environments, but are not affected by background noise spectrum.We explore multiple possible mechanisms underlying these patterns, such as loss of vertebrate predators and increased prey capture, and assess spider web‐building behaviour and body condition in noise. Continued research on the natural and anthropogenic acoustic environment will likely reveal a web of connections hidden within this neglected ecological niche axis. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Conspicuous colours in animals are usually explained by mate attraction, predator avoidance and prey attraction. Predators may lure prey by mimicking food or other resources. Alternatively, some animals avoid predation by visually signalling unpalatability to predators. The evolution of a signal is affected by receiver processing mechanisms. Therefore, variation in sensory systems may explain the evolution of colour polymorphism of conspicuous species. We aimed to investigate the role of receivers in the evolution and maintenance of colour conspicuousness and polymorphism in Gasteracantha cancriformis (Araneidae). We tested two hypotheses: (1) conspicuous coloration is a prey lure strategy; (2) conspicuous coloration is a warning signal to predators. Furthermore, we identified the taxonomic order of prey captured and the type of predator (avian versus arthropod). To assess the role of prey, we conducted a field experiment in which webs were assigned to one of four treatments: yellow, red or black spider models, or no model. For each treatment, we counted the number of prey trapped on the webs and calculated the damaged area of the webs. To assess the role of predators, we conducted a second field experiment in which we attached yellow, red and black models to trees using nylon thread and observed the number of attack markings on each model. Our results did not corroborate the prey attraction hypothesis. In the predation experiment, black models had more attack markings, indicating that yellow and red models were less preferred. This suggests that spider coloration may play a role in predator avoidance. Colour polymorphism in this species is possibly a multifunctional attribute, where some morphs benefit from aposematism, whereas others may have alternative fitness advantages. Nonadaptive explanations should also be considered in future experiments of the evolution and maintenance of colour polymorphisms. • We tested whether orb-web spider colour morphs attract prey or deter predators. • There was no difference in foraging success of models (red, yellow, black, none). • Black models bore more attack marks than red and yellow models. • Conspicuous coloration is possibly a warning signal in G. cancriformis. [ABSTRACT FROM AUTHOR]

The observable diversity of antipredator defences across organisms demonstrates predation's impact on trait evolution. The functions of many traits that are presumed to have an antipredator function have never been directly tested. The spiny orb-weaving spider, Micrathena gracilis, for example, stridulates when grasped. While stridulation was first hypothesized to be an antipredator defence nearly 50 years ago, no data exist to support this hypothesis. To explore the form and function of M. gracilis stridulation, we first quantified the behavioural and acoustical properties of sound production. Next, using laboratory assays, we directly tested the effect of stridulation on survival with an avian predator – blue jays, Cyanocitta cristata. Finally, we conducted a large mark–recapture field study in which we compared the natural survival of experimentally manipulated adult female M. gracilis that could not stridulate (silenced) versus could stridulate (control). Stridulatory pulses produced broadband frequency spectra, consistent with acoustic antipredator defences in other taxa. We also observed stridulation by male M. gracilis for the first time. In staged laboratory interactions with captive blue jays, we found no differences in survival between silenced and control M. gracilis. Similarly, in our mark–recapture field study, we found no differences in survival estimates between silenced and control groups, nor an effect of stridulation rate. While M. gracilis stridulation closely resembles antipredator stridulation in other arthropods, our behavioural data do not yet provide solid support for an antipredator function in M. gracilis. • We tested whether M. gracilis uses stridulation in antipredator defence. • We quantified behavioural and acoustical properties of stridulation. • We tested survival of silenced and control adult females in the laboratory/field. • Survival of silenced and control females did not differ. • Stridulation may not serve an antipredator function in M. gracilis. [ABSTRACT FROM AUTHOR]

An organism's ability to identify goals within their environment, orient towards those goals, and successfully navigate to them are critical to all aspects of survival. Long-jawed orb weavers (Tetragnatha elongata) occupy riparian zones and perform orientation behaviors when displaced from this habitat onto the water. Spiders prefer to move toward the closest shoreline, regardless of release location, likely to avoid predation from fish. In this study, we conducted a series of investigations to determine the mechanism by which these spiders rapidly achieve zonal recovery. Occlusion experiments indicate that spiders use visual information to identify characteristics of the riparian habitat and navigate to shelter. While environmental characteristics such as color, contrast, and the sun's position do not appear to factor into this orientation behavior, the polarization of light appears critical. We propose that the polarization of light reflecting off the water's surface acts as a water detector and the absence of such at the edges of the pond (or via experimental induction) serves as a visual reference for the closest suitable habitat. • Vision is critical to orientation in Long-Jawed Orb Weaver spiders when displaced from their web onto the surface of a pond. • Numerous visual conditions were assessed, spiders responded strongly to vegetation height and polarizing film. • Subsequent experiments suggest spiders may perceive polarized light reflecting off the water surface. • The absence of polarized light may serve as an indicator of the closest path to shoreline vegetation. [ABSTRACT FROM AUTHOR]

Color polymorphisms have been traditionally attributed to apostatic selection. The perception of color depends on the visual system of the observer. Theoretical models predict that differently perceived degrees of conspicuousness by two predator and prey species may cause the evolution of polymorphisms in the presence of anti-apostatic and apostatic selection. The spider Gasteracantha cancriformis (Araneidae) possesses several conspicuous color morphs. In orb-web spiders, the prey attraction hypothesis states that conspicuous colors are prey lures that increase spider foraging success via flower mimicry. Therefore, polymorphism could be maintained if each morph attracted a different prey species (multiple prey hypothesis) and each spider mimicked a different flower color (flower mimicry hypothesis). Conspicuous colors could be a warning signal to predators because of the spider's hard abdomen and spines. Multiple predators could perceive morphs differently and exert different degrees of selective pressures (multiple predator hypothesis). We explored these 3 hypotheses using reflectance data and color vision modeling to estimate the chromatic and achromatic contrast of G. cancriformis morphs as perceived by several potential prey and predator taxa. Our results revealed that individual taxa perceive the conspicuousness of morphs differently. Therefore, the multiple prey hypothesis and, in part, the multiple predator hypothesis may explain the evolution of color polymorphism in G. cancriformis , even in the presence of anti-apostatic selection. The flower mimicry hypothesis received support by color metrics, but not by color vision models. Other parameters not evaluated by color vision models could also affect the perception of morphs and influence morph survival and polymorphism stability. [ABSTRACT FROM AUTHOR]

The yellow garden spider, Argiope aurantia Lucas (Araneae: Araneidae), is widespread in North America, whereas the Florida garden spider, Argiope florida Chamberlin & Ivie (Araneae: Araneidae), is restricted to scrub habitats in the southeastern USA. Both orb-weavers occur syntopically in native oak scrub at the Archbold Biological Station in Highlands County, Florida. We hypothesized that female spiders of both species might have a high degree of dietary niche overlap because their orb-webs are located near each other, despite the fact that they may differ in body size and web characteristics. We located 180 side-by-side pairs of mature A. aurantia and A. florida, and assigned them at random into 3 treatment groups of 60 pairs each. Argiope aurantia in group 1 were more heavy-bodied and longer legged than A. florida. In group 2, the orb-webs of both species were hung at the same height aboveground, but A. aurantia webs were larger with fewer sticky spirals than those of A. florida. Over the course of 5 d, the 2 spider species in group 3 captured almost the same number of aerial arthropods (80 for A. aurantia; 76 for A. florida). We identified most prey (94%) to genus or species. Dietary niche overlap at the ordinal level was extensive (70%), but it shrank dramatically when calculated at the generic/ species level (20%). We concluded that not only were A. aurantia consuming substantially larger prey than A. florida, but also that they were feeding on different kinds of aerial insects moving through gaps in oak scrub. [ABSTRACT FROM AUTHOR]

Abstract: Distinct predator groups perceive prey colour and brightness differently because they harbour distinct visual systems. Therefore, the evaluation of the presence of visual‐based mechanisms of action in defensive strategies must be assessed from the perspective of the visual abilities of potential predators. Wixia abdominalis O.P. Cambridge, 1882 (Araneae, Araneidae) is a masquerader species that imitates its substrate, the twigs of trees. Using reflectance spectrophotometry and colour visual models, we tested and subsequently corroborated the hypothesis that colour matching occurs in this species based on how it is perceived by the primary spider predators, hymenopterans and birds. These results provide a theoretical basis on the role of colour and brightness in this defensive strategy, indicating that susceptibility to the two main groups of spider predators can be influenced by these characteristics. Then, we discussed the causes and implications of this defensive strategy in W. abdominalis and similar spider species. [ABSTRACT FROM AUTHOR]

An instance of a female St Andrew's Cross Spider Argiope picta consuming a juvenile Asian House Gecko Hemidactylus frenatus is described. [ABSTRACT FROM AUTHOR]

An orb web’s prey capture thread features tiny glue droplets, each formed of an adhesive glycoprotein core surrounded by an aqueous layer. Small molecules in the aqueous layer confer droplet hygroscopicity and maintain glycoprotein viscoelasticity, causing droplet volume and glycoprotein performance to track changes in environmental humidity. Droplet extension combines with that of a thread’s supporting flagelliform fibers to sum the adhesive forces of multiple droplets, creating an effective adhesive system. We combined measurements of the force on an extending droplet, as gauged by the deflection of its support line, with measurements of glycoprotein volume and droplet extension to determine the Young’s modulus (E) and toughness of three species’ glycoproteins. We did this at five relative humidities between 20–90% to assess the effect of humidity on these properties. When droplets of a thread span extend, their extensions are constrained and their glycoprotein filaments remain covered by aqueous material. This was also the case during the first extension phase of the individual droplets that we examined. However, as extension progressed, the aqueous layer was progresses disrupted, exposing the glycoprotein. During the first extension phase E ranged from 0.00003 GPa, a value similar to that of fibronectin, a glycoprotein that anchors cells in the extracellular matrix, to 0.00292 GPa, a value similar to that of resilin in insect ligaments. Second phase E increased 4.7–19.4-fold. When compared at the same humidity the E of each species’ glycoprotein was less than 5% of the value reported for its flagelliform fibers. This difference may facilitate the coordinated extension of these two capture thread components that is responsible for summing the thread’s adhesive forces. [ABSTRACT FROM AUTHOR]

Daily rhythms occur in numerous physiological and behavioral processes across an immense diversity of taxa, but there remain few cases in which mechanistic links between rhythms of trait expression and organismal fitness have been established. We construct a dynamic optimization model to determine whether risk allocation provides an adaptive explanation for the daily foraging rhythm observed in many species using the orb-weaving spider Cyclosa turbinata as a case study. Our model predicts that female C. turbinata should generally start foraging at lower levels of energy reserves (i.e., should be less bold) during midday when predators are most abundant. We also find that individuals' foraging efficacy determines whether daily rates of encounters with predators or prey more strongly influences boldness under high risk. The qualitative model predictions are robust to variation in our parameter estimates and likely apply to a wide range of taxa. The predictions are also consistent with observed patterns of foraging behavior under both laboratory and field conditions. We discuss the implications of our study for understanding the evolution of daily rhythms and the importance of model predictions for interpreting empirical studies and generating additional hypotheses regarding behavioral evolution. [ABSTRACT FROM AUTHOR]

Background: Theory predicts that colour polymorphism may be favored by variation in the visual context under which signals are perceived. The context encompasses all environmental determinants of light availability and propagation, but also the dynamics of perception in receivers. Color vision involves the neural separation of information into spectral versus luminance channels, which often differentially guide specific tasks. Here we explicitly tested whether this discrete perceptual basis contributes to the maintenance of polymorphism in a prey-luring system. The orb-weaving spider Gasteracantha fornicata is known to attract a broad community of primarily dipteran prey due to their conspicuous banded dorsal signal. They occur in two morphs ("white" and "yellow") which should, respectively, generate greater luminance and color contrast in the dipteran eye. Given that arthropods often rely upon luminance-versus-spectral cues for relatively small-versus-large stimulus detection, we predicted a switch in relative attractiveness among morphs according to apparent spider size. Results: Our experimental tests used colour-naïve individuals of two known prey species (Drosophila hydei and Musca domestica) in replicate Y-maze choice trials designed to manipulate the apparent size of spider models via the distance at which they are viewed. Initial trials confirmed that flies were attracted to each G. fornicata morph in single presentations. When given a simultaneous choice between morphs against a viewing background typical of those encountered in nature, flies exhibited no preference regardless of the visual angle subtended by models. However, when backgrounds were adjusted to nearer the extremes of those of each morph in the wild, flies were more attracted by white morphs when presented at longer range (consistent with a reliance on achromatic cues), yet were unbiased in their close-range choice. Conclusion: While not fully consistent with predictions (given the absence of a differential preference for stimuli at close range), our results demonstrate an effect of apparent stimulus size upon relative morph attractiveness in the direction anticipated from present knowledge of fly visual ecology. This implies the potential tuning of G. fornicata morph signal structure according to a perceptual feature that is likely common across their breadth of arthropod prey, and complements recent observational work in suggesting a candidate mechanism for the maintenance of deceptive polymorphism through the exploitation of different visual channels in prey. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Plant Protection & Pathology is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Receiver biases offer opportunities for the evolution of deception in signalling systems. Many spiders use conspicuous body colouration to lure prey, yet the perceptual basis of such deception remains largely unknown. Here we use knowledge of visual perception in key pollinator groups (bees and flies) to test whether colour-based lures resemble floral signals. We addressed this question at two levels: first according to the spectral reflectance of Australian orb-web spiders and flowers across a broad continental range, and second in reference to polymorphic variation in the species Gasteracantha fornicata. Analysis at the community level supported the hypotheses for broad-scale convergence among spider and flower signals. Moreover, data for G. fornicata indicate that each lure morph presents a signal biased towards the colouration of sympatric flowers. This analysis identified fly- and/or bee-pollinated plants whose flowers are likely to be indistinguishable from each G. fornicata colour morph. Our findings support the hypothesis that deceptive colour-based lures exploit prey preferences for floral resources. Further, the evidence implies a greater role for specific model/mimic relationships over generalised resemblance to flower-like stimuli as a driver of lure colouration and diversity. [ABSTRACT FROM AUTHOR]

Spinosad is a neurotoxic pesticide, which is currently used in IPM and organic agriculture. It can affect the survival and ecological function of spiders, which are natural enemies of important agricultural pests. In the laboratory, we carried out tests to determine lethal and sublethal effects of spinosad on mortality, web building, and web characteristics of Agalenatea redii. Spinosad has a lethal effect at the normal application rate (NAR, i.e., 96 g ha) causing 35 % mortality (vs 0 % for control) after 4 days and 62 % mortality (vs 14 % for control) after 30 days. For the sublethal effects, web building was affected and fewer spiders built webs when exposed to spinosad (10/37 at NAR and 28/39 at half the NAR vs 35/37 for control group). No delay in web building was observed following exposure. Spider webs showed irregularities in the spiral-thread spacing (parallelism) when exposed to higher doses of spinosad (NAR and half of the NAR). Spinosad also affected prey capture: spiders exposed to spinosad (NAR) showed decreased prey capture efficiency (32 vs 73 % for control). These results showed that spinosad affects the spider predatory behavior (agriculture auxiliaries), which could modify their role in pest biocontrol. [ABSTRACT FROM AUTHOR]

Strategies that increase foraging efficiency may also increase predation risk. We investigated how individuals of Hingstepeira folisecens Hingston, 1932, which build shelters at the orb hub, modulate their foraging behaviors in response to the trade-off between capturing prey and becoming exposed by leaving their shelters. We evaluated whether the position of the prey on the web alters the frequency at which spiders leave their shelters. Hingstepeira folisecens spiders were more likely to capture prey positioned below than above the entrance of the shelter. Moreover, when the prey was near the entrance of the shelter, the spider pulled the threads with the entangled prey without leaving the shelter. Conversely, when the prey was distant from the entrance of the shelter, an "attack" behavior (leaving the shelter) was favored. We argue that the "pulling behavior" may be an adaptation to reduce exposure to predators. [ABSTRACT FROM AUTHOR]

Animal body coloration serves several functions such as thermoregulation, camouflage, aposematism, and intraspecific communication. In some orb-web spiders, bright and conspicuous body colours are used to attract prey. On the other hand, there are other species whose body colour does not attract prey. Using a spider species showing individual body-colour variation, the present study aimed to determine whether or not the variation in body colour shows a correlation with predation rates. We studied the orb-web spider ( Cyclosa argenteoalba) using both field observations and T-maze experiments, in which the prey were exposed to differently coloured spiders. Cyclosa argenteoalba has silver- and black-coloured areas on its dorsal abdomen, with the ratio of these two colours varying continuously among individuals. The bright and conspicuous silver area reflects ultraviolet light. Results of both field observations and colour choice experiments using Drosophila flies as prey showed that darker spiders have a greater chance of capturing prey than silver spiders. This indicates that body-colour variation affects predation success among individuals and that the bright silver colour does not function to attract prey in C. argenteoalba. [ABSTRACT FROM AUTHOR]

Conspicuous body colouration in sedentary predators such as orb web spiders seems paradoxical as potential prey can see and avoid the webs. Several studies have demonstrated that rather than deterring prey, the colours act as sensory traps for flower-seeking insects. In chromatically polymorphic species, the existence of more than one colour morph may lead to differing levels of prey attraction. To explore these issues, we studied a neotropical orb web spider, Verrucosa arenata, which shows colour polymorphism with predominantly white or yellow abdomen colours. We asked whether a particular morph is dominant in the population, and whether a particular morph is associated with enhanced foraging success and body condition. Here we showed that although yellow morphs attracted more prey, white morphs were in better body condition. We showed that model prey such as honeybees are able to discriminate between the morphs. We discuss these findings in relation to the functional significance of bright body colouration and colour polymorphism in spiders. [ABSTRACT FROM AUTHOR]

Nephila clavipes golden orb-web spiders accumulate prey larders on their webs and search for them if they are removed from their web. Spiders that lose larger larders (i.e., spiders that lose larders consisting of more prey items) search for longer intervals, indicating that the spiders form memories of the size of the prey larders they have accumulated, and use those memories to regulate recovery efforts when the larders are pilfered. Here, we ask whether the spiders represent prey counts (i.e., numerosity) or a continuous integration of prey quantity (mass) in their memories. We manipulated larder sizes in treatments that varied in either prey size or prey numbers but were equivalent in total prey quantity (mass). We then removed the larders to elicit searching and used the spiders' searching behavior as an assay of their representations in memory. Searching increased with prey quantity (larder size) and did so more steeply with higher prey counts than with single prey of larger sizes. Thus, Nephila spiders seem to track prey quantity in two ways, but to attend more to prey numerosity. We discuss alternatives for continuous accumulator mechanisms that remain to be tested against the numerosity hypothesis, and the evolutionary and adaptive significance of evidence suggestive of numerosity in a sit-and-wait invertebrate predator. [ABSTRACT FROM AUTHOR]

Aging is often associated with reduced behavioral performance such as decreased locomotion or food consumption, related to a deterioration in physiological functions. In orb-web spiders, webs are used to capture prey and aging can affect web-building behavior and web structure. Here, we investigated the effect of aging on prey capture in the orb-web spider Zygiella x- notata. The ability of adult females to capture flies was examined at different ages. The rate of prey capture did not change with age, but older spiders took more time to subdue and capture the prey. Alterations which appeared in web structure with age (increase in the number of anomalies affecting radii and capture spiral) affected prey capture behavior. Furthermore, the analysis of individual performance (carried out on 17 spiders at two different ages) showed that older females spent more time handling the prey and finding it in the web. Our results suggest that, in the laboratory, age does not affect prey capture rates but it influences prey capture behavior by affecting web structure or/and spider motor functions. [ABSTRACT FROM AUTHOR]

Sticky viscous prey capture threads retain insects that strike araneoid orb-webs. The threads' two axial fibers support a series of glue droplets, each featuring a core of adhesive viscoelastic glycoprotein covered by an aqueous solution. After sticking, the glue extends, summing the adhesion of multiple droplets, and dissipates some of the energy of a struggling prey. As a day progresses, threads experience a drop in humidity and an increase in temperature, environmental variables that have the potential to alter thread and web function. We hypothesize that thread droplets respond to these opposing environmental changes in a manner that stabilizes their performance, and test this by examining threads spun by Argiope aurantia, a species that occupies exposed, weedy habitats. We confirmed that decreased humidity increases glycoprotein viscosity and found that increased temperature had the opposite effect. To evaluate the combined effect of temperature and humidity on a droplet's ability to transfer adhesive force and dissipate energy, we extended a droplet and measured both the deflection of the axial line supporting the droplet and the duration of its tensive load. The cumulative product of these two indices, which reflects the energy required to extend a droplet, was greatest under afternoon (hot and dry) conditions, less under morning (cool and humid) conditions, and least under hot and humid afternoon conditions. Although the opposing effects of temperature and humidity tend to stabilize glycoprotein performance, A. aurantia thread droplets appear to function optimally during the afternoon, equipping this species to capture large orthopterans, which are most active at this time. [ABSTRACT FROM AUTHOR]

Search images are perceptual biases acquired through experience that improve an individual's ability to detect the object of their search (e.g., a predator seeking prey). In hymenopterans, examples include floral search images in bees and acquired sensory biases towards specific prey in wasp predators. Mud dauber wasps exhibit individual specialization and consistency in prey preferences through time, often based on visual and chemical cues, that may vary at intraspecific levels. However, the search image concept in wasps has not been evaluated from a visual ecology perspective. Using psychophysical visual modelling from multispectral digital photography, we measured the colour and body pattern of the spiders captured and stored in nests by the wasp Trypoxylon mexicanum. Those visual traits were compared at the community and nest cell levels, according to the nest provisioning sequence, and its relationship with spider diversity. Our results show that the wasps are choosing a small group of orb weavers (Araneidae) with similar coloration and body patterns. These findings highlight the specific visual features that may be the focal trait during search image formation in these wasps. The colour and pattern variables of spider prey were consistent over time, suggesting that individual search images may strengthen with experience. • Mud dauber wasps capture spiders, paralyse and then oviposit on them in sequentially built cells. • Traits used by the wasp, such as spider colour and pattern, can be quantified. • Change in traits across time can be measured. • Wasps show preference for certain colours and patterns which remains constant across time. • This suggests that wasps use a search image strategy in predation. [ABSTRACT FROM AUTHOR]

Abstract: Spiders and birds can greatly decrease insect populations, but birds also limit spider densities in some habitats. Bird predation is thought to be one of the causes behind nocturnal activity in spiders, so night-active spiders that hide in retreats during the day should be less affected by bird foraging than day-active spiders. However, this hypothesis has not yet been tested. We investigated the importance of bird predation on the spider community of a Mediterranean organic citrus grove. We excluded birds by placing net cages over the trees and we conducted visual searches in the canopies to sample web-building spiders. As there are many nocturnal species in the family Araneidae, we conducted searches both by day and by night to compare the abundance of active araneids in these two time periods. We sampled the tree trunks with cardboard bands to collect hunting spiders. In bird-excluded canopies there were more spiders of the families Araneidae and Theridiidae. There were higher numbers of active Araneidae at night, but these were just as negatively affected by bird predation as day-active Araneidae, so there was no evidence of nocturnal activity serving as an anti-predator strategy. We did not find any negative impact of birds on hunting spiders. Our results contrast with other studies reporting a negative effect of birds on hunting but not on web-building spiders. [Copyright &y& Elsevier]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mean populations of spiders in three different places like Thayilpatti, Madathuppatti and Vembakkottai, Virudhunagar district, Tamil Nadu, India were studied. In these areas, twenty common species of spiders belonging to six families from these three selected areas were collected and identified. The collected spiders belonging to the family, Salticidae, Oxyopidae, Araneidae, Lycosidae, Gnaphosidae and Sparassidae. In this study, two species of spiders were observed, one is web weaver and another one is non -- web weaver. The web weaving spiders belonging to the family Araneidae and Lycosidae. The non- web weaving spiders belonging to the family Salticidae, Oxyopidae, Gnaphosidae, Lycosidae and Sparassidae. P. viridana, O. birmanicus, O. hindostanicus, P. latikae and A. anasuja a dominant predator recorded in these three selected areas. The population dynamics of the individual spider species in different months showed that the population of spider species mainly P. vridana, O. birmanicus, O. hindostanicus, A. anasuja, N. lugubris, P. latikae, C. cicatrosa and L. pseudoannulata were very high throughout the study period. The increase in the spiders density suggested that the spider density is influenced by the increase in prey density. [ABSTRACT FROM AUTHOR]

Many orb-weaving spiders decorate their webs with conspicuous ultraviolet (UV)-reflective stabilimenta. The prey-attraction hypothesis suggests that stabilimenta are visually attractive to prey and thus may increase the spiders' foraging success. However, previous studies on the function of stabilimenta have produced conflicting results in Argiope species. Using a combination of field and laboratory studies, we examined whether the linear stabilimentum of Argiope bruennichi contributes to prey interception. We recorded prey interceptions in 53 webs with stabilimenta and 37 equally-sized webs without stabilimenta, classifying captured prey according to their taxonomical group and size. On average, 6.2 ± 4.7 prey items were intercepted in webs with stabilimenta, while 3.2 ± 2.9 items were intercepted in webs without stabilimenta. The effects of stabilimenta on foraging success appear to be due to increased interception of UV-sensitive insect pollinators, including 20 families of Diptera, Hymenoptera, Coleoptera, and Lepidoptera. The mean number of UV-sensitive prey was 4.4 ± 3.6 in webs with stabilimenta compared with 1.8 ± 2.1 in webs without stabilimenta. Webs with and without stabilimenta did not differ in the mean number of UV-nonsensitive prey captured. The linear stabilimentum showed strong positive effects on the interception of large prey: webs with stabilimenta captured more than twice as many large prey (≥5 mm) than webs without stabilimenta, whereas there was only a slight difference in the interception rates for small prey (<5 mm). Comparisons among different Argiope species suggest that the stabilimentum may have different adaptive functions in different species or ecological contexts. [ABSTRACT FROM AUTHOR]

The present work shows predatory behaviour of the social orb-weaver spider, Geratonephila burmanica n. gen., n. sp. (Araneae: Nephilidae) against a parasitic wasp, Cascoscelio incassus n. gen., n. sp. (Hymenoptera: Platygastridae) in Early Cretaceous Burmese amber. An adult male and juvenile of G. burmanica in the same web provide the first fossil evidence of sociality in spiders. The spider is characterised by a pedipalp with a hemispherical tegulum, a subtegulum curved at 180°and an apical spiralled embolas-conductor bent approximately 45°at midpoint. The male wasp is characterised by an ocellar tubercle, 12-segmented antennae with a feeble five-segmented clava, thick sensilla trichodea curvata with rounded ends on the claval antennomeres, a short uncus, a short post-marginal vein and a nebulose radial sector (Rs) vein extending from the uncus to the costal margin of the forewing. This is the first fossil evidence of spider sociality and a fossil spider attacking prey trapped in its web. [ABSTRACT FROM PUBLISHER]

Spider webs are made of silk, the properties of which ensure remarkable efficiency at capturing prey. However, remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider. We explain this paradox by reporting a novel property of the silk produced by the orb-web spider Nephila antipodiana (Walckenaer). These spiders deposit on the silk a pyrrolidine alkaloid (2-pyrrolidinone) that provides protection from ant invasion. Furthermore, the ontogenetic change in the production of 2-pyrrolidinone suggests that this compound represents an adaptive response to the threat of natural enemies, rather than a simple by-product of silk synthesis: while 2-pyrrolidinone occurs on the silk threads produced by adult and large juvenile spiders, it is absent on threads produced by small juvenile spiders, whose threads are sufficiently thin to be inaccessible to ants. [ABSTRACT FROM AUTHOR]

We examined how the web structure of host spiders affects the locomotor ability of the kleptoparasitic spider Argyrodes kumadai. We compared two populations of A. kumadai differing with respect to whether the host used was Agelena silvatica (Agelenidae) or Cyrtophora ikomosanensis (Araneidae). The barrier web of Agelena had a higher thread density than that of Cyrtophora, which presumably constrains locomotion of A. kumadai in Agelena webs. A reciprocal transplant experiment into different webs revealed that, in complex webs, the A. kumadai population using Agelena as a host walked faster than the A. kumadai population using Cyrtophora; however, no such difference was found in simple webs. This suggested that A. kumadai using Agelena are better adapted to the webs of their native host with regard to their locomotor ability than are A. kumadai using Cyrtophora. The prey capture success of A. kumadai, as estimated by the foraging response of the host to prey and the walking speed of A. kumadai, revealed that the population of A. kumadai using Agelena captured larger prey much more frequently than the population using Cyrtophora. Thus, the greater locomotor ability of A. kumadai using Agelena appears to be adaptive for enhancing prey acquisition in Agelena webs where prey-stealing opportunities are severely limited. We conclude that both physical web architecture and the foraging behaviour of the host are important selective agents on locomotor ability in Argyrodes. [ABSTRACT FROM AUTHOR]

Orb webs built by spiders are an extended phenotype, and spiders can modify their morphology when rebuilding them. Internal and external environmental conditions can affect how spiders rebuild. Most spiders that build vertical orb webs wait for prey at the web hub and orient downwards. Moreover, their webs exhibit up-down size asymmetry; specifically, the area below the hub is larger than the area above it. However, some spiders reverse this asymmetry in their webs. To examine the relationship between phenotypic plasticity and web asymmetry reversal and whether spiders elongate their webs upwards in response to prey capture in the upper web, I manipulated prey capture location in two closely related spider species. Cyclosa octotuberculata build webs with typical asymmetry (larger area below the web hub). Cyclosa argenteoalba build webs with reversed asymmetry, a derived phenotype, and wait in a reversed orientation, facing upwards. I found that, when spiders fed in the lower part of the web, both species elongated their webs downwards and that C. argenteoalba webs lost their asymmetry and became symmetrical. In contrast, webs were not elongated in the upward direction when spiders of either species were fed in the upper part of the web. These results provided evidence that the up-down asymmetry of Cyclosa webs is a plastic trait regardless of whether spiders build webs with typical or reversed asymmetry. However, no significant upward elongation of webs indicates that there is no evidence of a relationship between plasticity in the extended phenotype and web asymmetry reversal. [Copyright &y& Elsevier]

A field study was conducted to compare hourly captures by nocturnal adult female orb-web spiders (Eriophora edax) and the insect fauna collected at the same time, using a UV light trap. Predation of the spiders is related to the activity patterns of Lepidoptera, since this order of insects was the dominant prey type of E. edax. Also, E. edax showed a positive selection (Ivlev's index of electivity) for Lepidoptera, which means that the spiders showed a selective over-predation of this prey taxon from the pool of insect prey available in the habitat. Based on our results, we suggest that this spider's behaviour might represent an adaptation to the first step in the evolution of a spider-moth specialisation. [ABSTRACT FROM AUTHOR]