Resource Management in the Orb-Weaving Spider Zygiella x-notata II. Ability to Manage a Set of Various Prey

Management of a set of various prey received ‘simultaneously’ by the orb-weaving spider Zygiella x-notata is investigated in relation to prey species, weight, order of arrival in the web, and factors concerning the spider's state of nourishment. When the spiders encountered several different prey ‘simultaneously’, they subdued all of them, took one of them to begin consumption, and stored the others in the web. The first item for consumption was chosen according to the characteristics of the available prey. Factors concerning previous feeding influenced the spiders's choice of the first item to be ingested. Exploitation of the first item, estimated by the quantity of food extracted and the time necessary for this extraction, depended on the type and the quantity of prey at the spider's disposal. When the spiders received several prey, they spent less time feeding on the first cricket compared with spiders receiving only one cricket, while no difference was found when the first prey item exploited was a fly.     

Are you what you eat? A highly transient and prey‐influenced gut microbiome in the grey house spider Badumna longinqua

Stable core microbial communities have been described in numerous animal species and are commonly associated with fitness benefits for their hosts. Recent research, however, highlights examples of species whose microbiota are transient and environmentally derived. Here, we test the effect of diet on gut microbial community assembly in the spider Badumna longinqua. Using 16S rRNA gene amplicon sequencing combined with quantitative PCR, we analyzed diversity and abundance of the spider's gut microbes, and simultaneously characterized its prey communities using nuclear rRNA markers. We found a clear correlation between community similarity of the spider's insect prey and gut microbial DNA, suggesting that microbiome assembly is primarily diet‐driven. This assumption is supported by a feeding experiment, in which two types of prey—crickets and fruit flies—both substantially altered microbial diversity and community similarity between spiders, but did so in different ways. After cricket consumption, numerous cricket‐derived microbes appeared in the spider's gut, resulting in a rapid homogenization of microbial communities among spiders. In contrast, few prey‐associated bacteria were detected after consumption of fruit flies; instead, the microbial community was remodelled by environmentally sourced microbes, or abundance shifts of rare taxa in the spider's gut. The reshaping of the microbiota by both prey taxa mimicked a stable core microbiome in the spiders for several weeks post feeding. Our results suggest that the spider's gut microbiome undergoes pronounced temporal fluctuations, that its assembly is dictated by the consumed prey, and that different prey taxa may remodel the microbiota in drastically different ways.     

Distinct feeding strategies of generalist and specialist spiders

1. Feeding behaviour of generalist and specialist predators is determined by a variety of trophic adaptations. Specialised prey‐capture adaptations allow specialists to catch relatively large prey on a regular basis. As a result, specialists might be adapted to exploit each item of prey more thoroughly than do generalists. 2. It was expected that obligatory specialist cursorial spiders would feed less frequently than generalists but for a longer time and, thus, that their foraging pause would be longer. First, the feeding frequencies of three generalist spider species (Cybaeodamus taim, Harpactea hombergi, Hersiliola sternbergsi) were compared with those three phylogenetically related specialist species: myrmecophagous Zodarion rubidum, and araneophagous Nops aff. variabilis and Palpimanus orientalis. 3. Generalists captured more prey, exploited each item of prey for a significantly shorter time, and had a shorter foraging pause than was the case for specialists. Generalists also gained significantly less relative amount of prey mass than did specialists. 4. Second, the study compared the prey DNA degradation rate in the gut of generalists and specialists by means of PCR. The degradation rate was not significantly different between specialists and generalists: the detectability half‐life was estimated to exist for 14.3 days after feeding. 5. This study shows that the feeding strategies of cursorial generalist and obligatory specialist spiders are different. Obligatory specialists have evolved a feeding strategy that is based on thorough exploitation of a few large prey, whereas generalists have evolved a strategy that is based on short exploitation of multiple small items of prey.     

Constraints affecting partial prey consumption by a crab spider,Diaea sp. indet. (Araneae: Thomisidae)

Summary The influence of feeding constraints on the feeding behaviour of Diaea sp. indet., was investigated. Diaea is a crab spider which ambushes its prey and practises extraintestinal digestion. A laboratory study was carried out using fruit flies, Drosophila immigrans, as prey. Diaea feeds from two sites on the prey — initially the head, followed by the posterior abdomen, with most of the prey's contents being extracted from the head. If additional prey are available, Diaea will, instead of switching to the posterior abdomen, catch a new prey item. The efficiency with which Diaea can extract food is influenced by changes which occur in the prey as a consequence of it being killed and fed on. Evaporative fluid loss from prey is an important constraint on food uptake because in influences the viscosity of the prey's contents. Regardless of whether a new prey item arrives, Diaea discards the prey item on which it is feeding before all of the available food has been extracted from it. The fluid content of the prey is not only part of the food the spider extracts, it is also a resource enabling efficient transfer of food from prey to predator. The value of the prey's fluid content as a resource decreases as a function of feeding time and as a consequence of the spider feeding on the prey.     

The Effect of Feeding History on Prey Capture Behaviour in the Orbweb Spider Argiope keyserlingi Karsch (Araneae: Araneidae)

The prey capture behaviour of the orb-web spider Argiope keyserlingi Karsch was examined experimentally by subjecting spiders to two different feeding regimes (food deprived and food satiated) and three types of prey: Drosophila, blowflies (Lucilia cuprina) and bees (Apis mellifera). The attack behaviour of the spiders was influenced by both their foraging history and the type of prey. Food deprived spiders attacked Drosophila and bees more frequently than food satiated spiders, and food satiated spiders travelled more slowly to any of the prey types than food deprived spiders. Furthermore, Drosophila were never wrapped in silk but only grasped with the chelicerae, whereas both blowflies and bees were always wrapped. This provides experimental confirmation that feeding history affects the decision of orb-web spiders to accept or reject any given prey.     

Tool Use by Spiders: Stone Selection and Placement by Corolla Spiders Ariadna (Segestriidae) of the Namib Desert

The corolla spider (Araneae: Segestriidae: Ariadna) of the Namib Desert gravel plains typically places seven or eight stones in a circle around its burrow entrance. It was examined whether the spider selects and places stones according to physical characteristics. Circle composition can be explained by the allometric scaling to spider size of the burrow entrance and the stones. The stones were usually placed with the narrowest side or point towards the burrow. Quartz crystals were preferred to four other stone types available. The spiders could detect prey brushing the outside of the circle stones that were about as wide as the spider's path of attack. I conclude that corolla spiders use the selected stones as tools to extend their foraging range.     

Knowing the Risk: Crickets Distinguish between Spider Predators of Different Size and Commonness

Predators unintentionally release chemical and other cues into their environment that can be used by prey to assess predator presence. Prey organisms can therefore perform specific antipredator behavior to reduce predation risk, which can strongly shape the outcome of trophic interactions. In contrast to aquatic systems, studies on cue‐driven antipredator behavior in terrestrial arthropods cover only few species to date. Here, we investigated occurrence and strength of antipredator behavior of the wood cricket Nemobius sylvestris toward cues of 14 syntopic spider species that are potential predators of wood crickets. We used two different behavioral arena experiments to investigate the influence of predator cues on wood cricket mobility. We further tested whether changes in wood cricket mobility can be explained by five predator‐specific traits: hunting mode, commonness, diurnal activity, predator–prey body–size ratio, and predator–prey life stage differences. Crickets were singly recorded (1) in separate arenas, either in presence or absence of spider cues, to analyze changes in mobility on filter paper covered with cues compared with normal mobility on filter paper without cues; and (2) in subdivided arenas partly covered with spider cues, where the crickets could choose between cue‐bearing and cue‐less areas to analyze differences in residence time and mobility when crickets are able to avoid cues. Crickets either increased or reduced their mobility in the presence of spider cues. In the experiments with cues and controls in separate arenas, the magnitude of behavioral change increased significantly with increasing predator–prey body size ratio. When crickets could choose between spider cues and control, their mobility was significantly higher in the presence of cues from common spider species than from rare spiders. We therefore conclude that wood crickets distinguish between cues from different predator species and that spiders unintentionally release a species‐specific composition and size‐dependent quantity of cues, which lead to distinct antipredator behavior in wood crickets.     

The effect of colour variation in predators on the behaviour of pollinators: Australian crab spiders and native bees

1. Australian crab spiders exploit the plant–pollinator mutualism by reflecting UV light that attracts pollinators to the flowers where they sit. However, spider UV reflection seems to vary broadly within and between individuals and species, and we are still lacking any comparative studies of prey and/or predator behaviour towards spider colour variation. 2. Here we looked at the natural variation in the coloration of two species of Australian crab spiders, Thomisus spectabilis and Diaea evanida, collected from the field. Furthermore, we examined how two species of native bees responded to variation in colour contrast generated by spiders sitting in flowers compared with vacant flowers. We used data from a bee choice experiment with D. evanida spiders and Trigona carbonaria bees and also published data on T. spectabilis spiders and Austroplebeia australis bees. 3. In the field both spider species were always achromatically (from a distance) undetectable but chromatically (at closer range) detectable for bees. Experimentally, we showed species‐specific differences in bee behaviour towards particular spider colour variation: T. carbonaria bees did not show any preference for any colour contrasts generated by D. evanida spiders but A. australis bees were more likely to reject flowers with more contrasting T. spectabilis spiders. 4. Our study suggests that some of the spider colour variation that we encounter in the field may be partly explained by the spider's ability to adjust the reflectance properties of its colour relative to the behaviour of the species of prey available.     

Preference for Chemical Cues Associated with Recent Prey in the Wolf Spider Hogna helluo (Araneae: Lycosidae)

In the wolf spider, Hogna helluo , we tested the response to insect and spider prey chemical cues and whether they show a preference for cues associated with prey consumed most recently. Thirty adult female H. helluo were maintained on a diet of either females of a smaller co-occurring wolf spider ( Pardosa milvina ) or domestic crickets ( Acheta domesticus ). A single P. milvina or cricket nymph was maintained on filter paper for 24 h, after which the papers from both prey sources were simultaneously presented to individual H. helluo from each diet treatment group. H. helluo locomotor behavior on each treatment and initial substrate preference was recorded (n = 15/treatment). H. helluo fed crickets showed significantly longer residence time and decreased mobility on filter paper previously occupied by a cricket; spiders fed P. milvina showed longer residence times and decreased mobility on filter paper previously occupied by P. milvina . H. helluo fed P. milvina exhibited an initial preference for substrates previously occupied by P. milvina but H. helluo fed crickets did not show a corresponding initial preference for crickets. Results suggest that H. helluo can detect distant cues associated with P. milvina but not crickets before contacting the substrate and that H. helluo respond to chemical cues from prey and show a preference for those cues associated with their most recent prey.     

Food Intake,Growth and Relatedness in the Subsocial Spider,Stegodyphus lineatus (Eresidae)

One of the presumed benefits of sociality in spiders is an improved foraging success although it has been shown that group feeding is less efficient than feeding alone. In spiders, communal feeding only occurs amongst kin. The effects of relatedness on the consequences of group feeding were investigated in the subsocial spider Stegodyphus lineatus. A significant difference between short-term intake rates and long-term growth rates was shown in a comparison between groups of siblings and groups of non-siblings. Groups of siblings extracted more out of a prey item in a given time and they had higher growth rates than groups of non-siblings.     

Experimental Evidence that a Desert Parasitoid Keeps its Host Cool

The wasp parasitoid Pseudopompilus humboldti (Hymenoptera; Pompilidae) in the Negev desert of Israel stores its paralyzed host, the spider Stegodyphus lineatus (Araneae; Eresidae), at the entrance of the spider's nest. The spider is moved by the wasp from the depth of the nest to the entrance in spite of increased exposure to visually-searching predators, such as birds. We examined the hypothesis that this behaviour has evolved to prevent the wasp's host from overheating in this hot desert. Experimental manipulations of the position of the parasitized spiders demonstrated that spiders and wasp larvae could not survive the heat experienced deep in the spider's nest during summer. By contrast, in the cooler nest entrance, spiders and larvae survived, if they were overlooked by predators. This host-storing behaviour is an adaptive trade-off between thermoregulatory requirements and predation risk. This appears to be the first evidence that a parasitoid manipulates the temperature of its host, albeit for its own ultimate gain.     

Diet of the Critically Endangered Brown Spider Monkey (Ateles hybridus) in an Inter‐Andean Lowland Rainforest in Colombia

Brown spider monkeys (Ateles hybridus) are one of the least known and more threatened primates in the Neotropics. Recognized as a species about a decade ago, field studies on these endangered primates have mainly focused on estimating local population densities. Since 2006, we habituated a group of wild brown spider monkeys at Serranía de Las Quinchas, Colombia, and studied their feeding ecology during 2.5 years using focal “subgroup” sampling, and conducted phenological surveys in order to estimate habitat‐wide fruit availability. Based on 847 hr of behavioral follows, brown spider monkeys spent approximately 25% of their time in feeding activities, and fed from fruits and leaves on at least 123 plant species. Ripe fruits were the most important item in the diet of A. hybridus at Las Quinchas comprising 92% of their feeding time. Probably due to the minor variation in the monthly proportion of fruits in brown spider monkey's diet throughout this study, there was no relation between habitat‐wide fruit availability and the proportion of fruit included in their monthly diet. The diet of brown spider monkeys at Las Quinchas is toward the high end of fruit intake, even within other wild spider monkeys’ populations, suggesting that these endangered primates might also be facing the challenges of being a large bodied fruit specialist under a regional scenario of habitat loss and fragmentation. Am. J. Primatol. 74:1097‐1105, 2012. © 2012 Wiley Periodicals, Inc.     

Prey Luring Coloration of A Nocturnal Semi‐Aquatic Predator

Body coloration serves a variety of purposes in animals. Diurnal and nocturnal predators such as spiders may use their body coloration to lure prey. We predicted here that the white patches on the forelegs on females of the nocturnal semi‐aquatic spider Dolomedes raptor lure prey, explaining why they are primarily displayed when the spider forages along the water edge. To test our prediction, we developed a color vision model assessing whether the patches are visible to pygmy grasshoppers, the spider's primary prey. We conducted a field experiment using cardboard dummies that resemble D. raptor in size, shape, and color, but with half of them lacking leg patches, and we staged interactions between pygmy grasshoppers and D. raptor with and without leg patches in a greenhouse. We found the white patches to be visible to grasshoppers. The dummies with white patches attracted more grasshopper prey than the dummies without the patches. Moreover, grasshoppers were more attracted to spiders when their white patches were present. Our results supported the hypothesis that the white patches of D. raptor lure prey. Our findings, nevertheless, could not be explained as the spider's body coloration acting as a sensory trap but it should not be ruled out. More studies on a wider range of predators and prey will give more meaningful insights into the co‐evolution of predatory lures and prey sensory modalities.     

Hunting Without a Web: How Lycosoid Spiders Subdue their Prey

More than half of all spider species hunt prey without a web. To successfully subdue their prey, they use adapted capture behaviour and efficient grasping mechanisms to interrupt the prey's locomotion, and to restrain it from escaping during the subsequent handling for final envenomation. In this study, we investigated how the prey capture behaviour of different lycosoid spider species is related to leg morphology and venom efficiency; using high speed videography, feeding experiments, stereomicroscopy, scanning electron microscopy and LD₅₀ venom bioassays. We found that different species employed different techniques when grasping their prey and these differences strongly correlate with the distribution and size of hairy adhesive leg pads (so‐called scopulae on pro‐ and retrolateral parts of legs) and erectable spines, which act in a complementary way. Our results indicate that the grasping and handling behaviour and leg morphology is crucial in restricting the prey's movements. However, none of these traits is directly related with venom efficiency.     

Ineffective crypsis in a crab spider: a prey community perspective

Cryptic coloration is assumed to be beneficial to predators because of an increased encounter rate with unwary prey. This hypothesis is, however, very rarely, if ever, studied in the field. The aim of this study was to quantify the encounter rate and capture success of an ambush predator, in the field, as a function of its level of colour-matching with the background. We used the crab spider Misumena vatia, which varies its body colour and can thereby match the colour of the flower it hunts upon. We carried out a manipulative field experiment using a complete factorial design resulting in six different colour combinations of crab spiders and flowers differing in their degree of colour-matching. A rich and diverse set of naturally occurring insects visited the flowers while we continuously video-recorded the spider''s foraging activity. This enabled us to test the crypsis, the spider avoidance and the flower visitor attraction hypotheses, all three supported by previous studies. Flower visitors of different groups either avoided crab spiders independent of colour-matching, such as solitary bees and syrphid flies, or ignored them, such as bumble-bees and honeybees. Moreover, colour-matched spiders did not have a higher encounter rate and capture success compared to the visually apparent ones. Thus, our results support the spider avoidance hypothesis, reject the two other hypotheses and uncovered a fourth behaviour: indifference to predators. Because flower visitors reacted differently, a community approach is mandatory in order to understand the function of background colour-matching in generalist predators. We discuss our results in relation to the size and sociality of the prey and in relation to the functional significance of colour change in this predator.     

Predicting Predatory Outcomes in the Context of Carryover Effects: Interactions between Juvenile Frogs and Spider Predators

As representatives of organisms with complex life histories, frogs provide an ideal system to study predator‐induced carryover effects: how the risk of predation in one life stage can impact predator–prey interactions in a later stage. Invertebrate predation on frogs has been widely reported, although studies of the behavioral mechanisms underlying their interactions in the terrestrial stage have been lacking. We made detailed observations of interactions between a wolf spider (Tigrosa helluo) and Blanchard's cricket frog (Acris blanchardi) to determine factors that predict capture success and to evaluate potential carryover effects from aquatic predation risk. Juvenile frogs, reared with or without dragonfly predator cues, were placed in an arena with or without spider cues and allowed to interact with a spider. Spiders captured frogs, and an interaction between frog size and activity predicted frog survival. We found no evidence that either aquatic or terrestrial cues altered frog behavior or survival. By preying upon a demographically important life stage, spiders may contribute to population dynamics in frogs.     

Wasp Attacks and Spider Defence in the Orb Weaving Species <Emphasis Type="Italic">Zygiella x-notata</Emphasis>

Predator–prey relationships are generally based on arm-race. Wasps and spiders are both predators, which could be potential prey for each other. The orb weaver spider Zygiella x-notata is sometimes a prey for the wasp Vespula germanica. We observed the wasp hunting behaviour under natural conditions, and we tested the influence of the spider’s behaviour on the wasp attack success. Wasps were active predators during the reproductive period of the spider. Results showed that wasps located more easily male spiders than females particularly when they were engaged in mate guarding. Female location depended on the presence of a web, but also of prey or prey remains in the web. On the other hand, their location depend neither on the characteristics and the position of the retreat in the environment nor on the size of the web. After location, males were more often captured than females whatever their behaviour (mate guarding or not). Presence of prey remains or prey in the web did not increase the risk for the spider to be captured. There was also no influence of the retreat’s characteristics or of its position in the habitat on the risk for the spider to be captured; but wasp successful attacks were less numerous when silk was present around the entrance of the retreat or when the spider was completely inside. As prey and prey remains favoured location of spiders by the wasps, we tested spider web cleaning behaviour as a response to wasp predatory pressure. By throwing small polystyrene pellets in the webs, we observed that more 80% of the spiders rejected the pellets in less than one minute. Our data indicated that wasps were significant predators of Z. x-notata and wasp attack could have been a selective pressure that had favoured spider defensive behaviours such as web cleaning.     

Regulation and Non-Toxicity of the Spit from the Pale Spitting Spider Scytodes Pallida (Araneae: Scytodidae)

The pale spitting spider Scytodes pallida (Aranae: Scytodidae) has a unique habit of spitting a glue‐like and possibly toxic substance at its prey to render them immobile prior to envenomation. Quantitative behavioural studies involving the spit, a first for S. pallida, demonstrate that the spider regulates its spit expenditure when offered prey of variable sizes and struggling intensities. This behaviour interestingly mirrors the regulation of venom expenditure according to prey sizes and difficulties exhibited in other non‐spitting spiders. The spit, however, did not appear to have any toxic effects on different prey types exposed to the spit, opposing the long‐standing belief that the spit from scytodids can poison prey.     

Emergent properties in the behaviour of a virtual spider robot

Using a virtual spider robot, we studied hypotheses about the weaving behaviour of orb spiders. Our model spiders built virtual webs that mimicked perfectly the visual architecture of real webs of the garden cross spider Araneus diadematus. The matching of capture spiral and auxiliary spiral pitch was an apparently emergent property in both types of web. This validated our interpretation of the garden spider''s web-building decision rules, which use strictly local interactions with previously placed threads to generate global architecture.     

Cooperation and Prey Capture Efficiency in a Social Spider,Anelosimus eximius (Araneae,Theridiidae)

We studied the efficiency of the hunt and the characteristics of cooperation during the prey capture in a social spider Anelosimus eximius. Two natural types of prey of roughly the same length (20 mm) were used: grasshoppers (Orthoptera) and moths (Lepidoptera); 128 tests were made on 14 colonies, the smallest with 20 and the largest with 1,700 individuals. Test times were 12.00 h, defined as an inactive period for the spiders and 18.00 h, defined as an active period. Overall capture rate of intercepted prey was 66%: it was higher in large colonies or at 18.00 h, when more spider alerts were triggered by the struggling prey. Characteristics of cooperation during capture did not vary with colony size. Capture rate was higher for grasshoppers than moths (73%-58%) in spite of similar number of alerts (76%-87%); so moths must have been more difficult to capture. For both prey types, large colonies capture more rapidly and so had advantages in terms of time gain. We showed that cooperation depended on prey type: more spiders mobilised to attack moths and attack was faster than on grasshoppers. This may be interpreted as an adaptive response of the group to the prey type.