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.     

Oviposition behavior of Zatypota albicoxa (Hymenoptera, Ichneumonidae), an ectoparasitoid of Achaearanea tepidariorum (Araneae, Theridiidae)

Oviposition behavior of Zatypota albicoxa (Walker) is described. This wasp parasitizes the house spider Achaearanea tepidariorum (Koch), which weaves irregular, three-dimensional webs. Based on field observations, two modes of oviposition behavior were recognized. In one, the wasp hung on the web, pulling the thread with its fore leg, until the spider lifted it up (ambush-style). In the other mode, the wasp climbed the web (climbing-style). Under laboratory conditions in an aquarium, the wasp hung on the web in mid height of the gumfoot thread as in the former style, then flew toward unaware spider and paralyzed it. After paralyzing, the wasp usually rubbed the spider's abdomen with its ovipositor and tip of metasoma repeatedly at short intervals for several minutes. In all cases they adopted the same posture in which they grasped the spider abdomen with fore and mid legs during oviposition. As female wasps emerged from larger hosts and male wasps emerged from smaller ones, the ovipositing wasp apparently assesses the size of the spider and chooses whether to lay a fertilized or an unfertilized egg. In addition, it was confirmed that Z. albicoxa expelled the eggs not from the tip of the ovipositor but from the tip of its abdomen, as in other species of the Polysphincta group (e.g. Hymenoepimecis argyraphaga , Reclinervellus tuberculatus and Schizopyga circulator ).     

The Trochidae and Turbinidae of the Kermadec Ridge (Mollusca: Gastropoda)

Abstract

Taieria erebus (Gnaphosidae) was found to be a versatile predator: it captured insects both cursorially (away from webs) and kleptopar-asitically (on alien webs); it captured spiders in both the presence and absence of webs; and it also ate the eggs of host spiders (oophagy). When T. erebus invaded webs, it was as an aggressive mimic — it performed a repertoire of vibratory behaviours to lure the host spider. Although T. erebus pursued and captured spiders on diverse web-types, it was more effective as a predator when invading densely (rather than sparsely) woven cribellate and non-sticky webs, and was especially effective on non-cribellate sticky webs. Gnaphosids are traditionally referred to as hunting spiders, but T. erebus built a small prey-capture web. T. erebus also preyed on segestriid spiders, then used their webs to catch more prey, this being an unusual example of a spider using, as a tool for predation, the spinning-work of another species from an unrelated family. T. erebus used specialised behaviours to prey on nesting cursorial spiders. Prey was either grasped or stabbed; the venom of T. erebus was highly potent against spiders. Experiments indicated that vision was of little or no importance in the predatory behaviour of T. erebus. The behaviour of T. erebus is compared to that of Portia, a web-building salticid spider which is very versatile in its predatory behaviour and has acute vision. T. erebus is discussed in relation to hypotheses concerning gnaphosid and salticid evolution.     

Behavioural modification of a social spider by a parasitoid wasp

1. Manipulation of host behaviour by parasitoids has long captured the imagination of ecologists. Parasitoid wasps in the Polysphincta group of genera develop as external parasitoids of spiders. 2. In the present study, the previously undescribed interaction between a Zatypota sp. wasp (Ichneumonidae) and a social spider Anelosimus eximius (Theridiidae) is described. The larva of this Zatypota wasp is found to induce its host to disperse from their communal web and build an entirely enclosed web consisting of densely spun silk. 3. The wasp is observed to target primarily immature A. eximius individuals, with 37.5–44% of nests in a given area being parasitised. Of those nests, approximately 1.3–2.0% of individuals are hosts to the parasitoid larvae. Larger spider colonies had a significantly higher probability of harbouring parasitoids. 4. This interaction results in unusual behaviours for A. eximius induced by the parasitoid: (i) leaving the protection of the social nest and (ii) building a unique, altered web that it would not otherwise build. It is suggested that the wasp may be tapping into ancestral dispersal behaviours in its host and that a social species provides this wasp an evolutionary advantage by allowing a stable host source.     

Opportunistic Egg Feeding in the Kleptoparasitic Spider Argyrodes gibbosus

Argyrodes gibbosus is a kleptoparasitic spider in the web of spiders. It generally steals freshly captured prey from the web of its host. In Sicily, Argyrodes gibbosus parasitizes webs of the spider Cyrtophora citricola, a facultative colonial species. When a C. citricola female was present in its web, Argyrodes caught small prey in the web or tried to rob prey captured by the host; in that case, we never observed successful attacks on host egg-sacs. When the host disappeared from its web, the kleptoparasite modified its foraging strategies and attacked the host egg-sacs and ate the eggs. The exploitation of this new resource could ensure rapid development for the kleptoparasite which was characterized by the presence of larger females and a higher mating rate.     

Kleptoparasites influence foraging behaviour of the spider <Emphasis Type="Italic">Stegodyphus lineatus</Emphasis> (Araneae,Eresidae)

Prey captured by a predator may attract kleptoparasites which could significantly reduce the amount of food consumed. Stegodyphus lineatus, a cribellate spider, builds an energetically costly web. Ants raid the webs of S. lineatus to steal prey and behave as kleptoparasites. We investigated ant raids in a natural population of S. lineatus and their influence on the spider’s foraging behaviour. Considering spiders that had captured a prey, 31.2% suffered an ant raid within 24 h after the prey capture. Experimental tests showed that the response to ant raid is to delay web rebuilding and this was independent of a spider’s previous foraging success. There was a tendency for spiders that were exposed to ants to build larger webs. Neither prey-handling duration nor prey consumption was modified after exposure to ants. These results suggest that Stegodyphus lineatus adapt its web-building behaviour in response to the risk of kleptoparasitism.     

Parasitoid genus‐specific manipulation of orb‐web host spiders (Araneae,Araneidae)

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The biology of New Zealand and Queensland pirate spiders (Araneae, Mimetidae): aggressive mimicry, araneophagy and prey specialization

Mimetus sp. indet. and Mimetus maculosus , from New Zealand and Australia, respectively, were studied in the laboratory and in nature. Behaviourally, the two species were very similar. Each was found to be primarily an araneophagic spider which invaded alien webs, acted as an aggressive mimic by performing a variety of vibratory behaviours to which the prey-spider responded as it normally would to its own prey, and attacked by lunging at close range, subduing its victim with a strong, apparently spider-specific venom while holding the spider in a 'basket' formed by its spine-covered legs. In nature, these mimetids were observed to feed on a restricted range of spiders: orb web-building araneids and space web-building theridiids. Sometimes, they occupied other types of webs, but in the laboratory they captured only araneids and theridiids efficiently. They captured non-cribellate amaurobiids considerably less efficiently, and never captured other types of spiders. Occasionally, the mimetids fed on insects ensnared in araneid and theridiid webs and on eggs of theridiids. Experimental evidence indicated that vision was of little or no importance in the predatory behaviour of these mimetids. The behaviour of the mimetids is compared to that of Portia , an araneophagic web-invading salticid, and the results of this study are discussed in relation to hypotheses concerning salticid evolution.     

Chemical Mediation of Prey Recognition by Spider-Hunting Wasps

Predator–prey interactions are important in maintaining the structure and dynamics of ecological communities. Both predators and prey use cues from a range of sensory modalities to detect and assess one another; identification of these cues is necessary to understand how selection operates to shape predator–prey interactions. Mud-dauber wasps (Sphecidae) provision their larval nests with paralyzed spiders, and different genera of wasps specialize on particular spider taxa. Sceliphron caementarium (Drury 1773) wasps preferentially capture spiders that build two-dimensional (2D) webs, rather than those that construct three-dimensional (3D) webs, but the basis of this preference is not clear. Wasps may choose spiders based on an assessment of their web architecture, as 3D webs may provide better defenses against wasp predation than do 2D webs. However, because many hymenopterans use chemical cues to locate and recognize prey, it is also possible that mud-dauber wasps rely on chemical cues associated with the spider and/or the web to assess prey suitability. When we offered foraging S. caementarium wasps 2D and 3D spiders both on and off their webs, we found that in both cases the wasps took 2D spiders and avoided 3D spiders, demonstrating that the web itself is not the impediment. Results of a series of behavioral choice assays involving filter paper discs containing spider cues and chemically manipulated spiders or spider dummies corroborated the importance of spider chemical cues in mediation of prey recognition by mud-dauber wasps. We also discuss the relative importance of visual and chemical cues for prey recognition by wasps, examine the anti-predator behaviors of 2D and 3D spiders, and consider the role of wasp predation in spider diversification.     

Comparative biology of Portia africana,P. albimana,P. fimbriata,P. labiata,and P. shultzi,araneophagic, web-building jumping spiders (Araneae: Salticidae): Utilisation of webs,predatory versatility,and intraspecific interactions

Abstract

Portia is a behaviourally complex and aberrant salticid genus. The genus is of unusual importance because it is morphologically primitive. Five species were studied in nature (Australia, Kenya, Malaysia, Sri Lanka) and in the laboratory in an effort to clarify the origins of the salticids and of their unique, complex eyes. All the species of Portia studied were both web builders and cursorial. Portia was also an araneophagic web invader, and it was a highly effective predator on diverse types of alien webs. Portia was an aggressive mimic, using a complex repertoire of vibratory behaviour to deceive the host spiders on which it fed. The venom of Portia was unusually potent to other spiders; its easily autotomised legs may have helped Portia escape if attacked by its frequently dangerous prey. Portia was also kleptoparasitic and oophagic when occupying alien webs. P. fimbriata from Queensland, where cursorial salticids were superabundant, used a unique manner of stalking and capturing other salticids. The display repertoires used during intraspecific interactions were complex and varied between species. Both visual (typical of other salticids) and vibratory (typical of other web spiders) displays were used. Portia copulated both on and away from webs and frequently with the female hanging from a dragline. Males cohabited with subadult females on webs, mating after the female matured. Adult and subadult females sometimes used specialised predatory attacks against courting or mating males. Sperm induction in Portia was similar to that in other cursorial spiders. Portia mimicked detritus in shape and colour, and its slow, mechanical locomotion preserved concealment. Portia occasionally used a special defensive behaviour (wild leaping) if disturbed by a potential predator. Two types of webs were spun by all species (Type 1, small resting platforms; Type 2, large prey-capture webs). Two types of egg sacs were made, both of which were highly aberrant for a salticid. Responses of different species and both sexes of Portia were quantitatively compared for different types of prey. Many of the trends in behaviour within the genus, including quantitative differences in predatory behaviour, seemed to be related to differences in the effectiveness of the cryptic morphology of Portia in concealing the spider in its natural habitat (‘effective crypsis’). The results of the study supported, in general, Jackson & Blest’s (1982a) hypothesis of salticid evolution which, in part, proposes that salticid ancestors were web builders with poorly developed vision and that acute vision evolved in conjunction with the ancestral spiders becoming proficient as araneophagic invaders of diverse types of webs.     

Attack Behavior of Two Wasp Species of the <Emphasis Type="Italic">Polysphincta</Emphasis> Genus Group (Hymenoptera,Ichneumonidae) on their Orb-Weaver Spider Hosts (Araneae,Araneidae)

Species in the Polysphincta genus group, as far as is known, are exclusively koinobiont ectoparasitoids of spiders. These wasps attack their hosts, inflicting a temporary paralysis, and then lay one egg on the host’s abdomen or prosoma. Parasitoid attack behavior is highly variable among species, including occasions where the wasp darts directly and holds the spider, as well as instances involving complex behavioral sequences. In the present study, we describe the attack behavior of Polysphincta sp. nr. purcelli and P. janzeni on Cyclosa fililineata and C. morretes, respectively. All attacks occurred at night. Initially, the female wasp landed on the web hub at the position occupied by the spider, with the spider always escaping from this initial attack. Subsequently, the wasp waited for up to 14 h at the web hub for the spider’s return. The wasp then inserted its ovipositor into the mouth of the spider, after which the spider became paralyzed and remained motionless for at least 30 min. The wasp laid one egg on the surface of the host’s abdomen and remained on the web for at least 1 h thereafter. The lie-in-wait and attack only after the return of the host to the web hub, as well as the permanence of the wasp on the web after the attack are not frequent behaviors described for polysphinctines. Behavioral idiosyncrasies, such as those observed here, are common among polysphinctines, suggesting a high level of specific adaptive matching of polysphinctine parasitoid behavior to their hosts’ biological characteristics.     

Anti-predator defences of Pholcus phalangioides (Araneae, Pholcidae), a web-building and web-invading spider

The behaviours used by Pholcus phalangioides (Fuesslin) (Araneae, Pholcidae) to evade its predators were studied with particular attention being given to a special defence behaviour, whirling. To whirl, this long-legged web-building spider swings its body around in a circle, with its legs remaining on the silk. Experiments were carried out to determine the types of stimuli that elicited whirling. Touching the spider or its web elicited whirling, as did air movement over the spider, but there was no evidence that chemical stimuli from potential predators were important. Small juveniles differed from adult females and larger juveniles by more often dropping from the web instead of whirling when confronted by a potential predator. Besides catching prey on its own web P. phalangioides invades other spiders' webs to catch the other spiders. By whirling in alien webs, P. phalangioides could deter attacks by the resident spider, but P. phalangioides was less inclined to whirl when in an alien than when in its own web.     

Competition for a limited space in kleptoparasitic Argyrodes spiders revealed by field experiments

Most kleptoparasitic Argyrodes spiders rely exclusively on host spider webs for obtaining their food. Because their densities occasionally reach high levels within a restricted area, competitive interactions may be important for determining the density of these unique spiders. Here I used two Argyrodes species commonly found on webs of the large orb-web spider Nephila clavata to clarify whether inter- and intraspecific competition influences abundance and within-web distribution by using observational data and field experiment. Removing Argyrodes flavescens from the host webs induced a remarkably high immigration of that species while density on control webs remained almost at the same level, which is evidence for strong intraspecific competition. Larger individuals of A. flavescens were located more frequently at the capture area of the host webs where it is easy to access prey ignored by the host spider, and spiders immigrating into webs from which that species had been removed were smaller in body size, suggesting interference competition for space among conspecific kleptoparasites. Argyrodes bonadea increased in number on webs from which A. flavescens had been removed, and the increase was correlated with the number of A. flavescens removed. This finding is evidence for interspecific competition that is rarely reported in spiders. A multiple regression model including numbers of a conspecific parasite as well as web and body sizes of the host spider could not detect competitive interactions between species, suggesting the importance of experimental approaches. Received: May 22, 2000 / Accepted: December 1, 2000     

Host behavior modification of Achaearanea tingo (Araneae: Theridiidae) induced by the parasitoid wasp Zatypota alborhombarta (Hymenoptera: Ichneumonidae)

Behavioral manipulation involving Zatypota (Ichneumonidae: Pimplinae) parasitoids and their spider hosts is usually associated with an increase in web complexity at the location where the parasitoid larva builds its cocoon. A higher number of web threads at this location may improve stability and provide a physical barrier against potential predators. However, we observed that parasitized individuals of Achaearanea tingo attacked by Z. alborhombarta change the three‐dimensional structure of their webs to a very simple and strong structure composed of two cables attached to the surrounding vegetation. This structure holds the curled leaf formerly used by the spider as a shelter. The parasitoid larva remains protected within this shelter after killing the host. The architectural pattern of the cocoon webs of A. tingo indicates that host manipulation is characterized by the repetition of one specific subroutine involved in web construction. Similar alterations have been previously described for cocoon webs constructed by parasitized orb‐weavers, but not for the three‐dimensional webs of theridiids.     

The parasitoid wasp Eruga unilabiana Pádua & Sobczak,sp. nov. (Hymenoptera: Ichneumonidae) induces behavioral modification in its spider host

Some polysphinctine parasitoid wasps can alter the web building behavior of their host spiders. In this paper, we describe and illustrate a new species Eruga unilabiana sp. nov. and report for the first time, to the best of our knowledge, the interaction between this parasitic wasp and the linyphiid spider Dubiaranea sp. We investigated the wasp's host selection, development, and manipulation of host behavior. We found that most of the parasitized spiders were intermediate‐sized adult females that probably provide sufficient resources for parasitoid larvae and are less vulnerable for parasitoid females than larger host individuals at attack. The cocoon web of Dubiaranea sp. consists of a complex three‐dimensional tangle structure with several non‐stick radial lines that converge at the cocoon. In addition, E. unilabiana individuals construct their cocoons horizontally, which differ from cocoons of the majority of polysphinctine wasps. This study provides important information and discussion to further understand the evolution of parasitoid wasp–spider interactions.     

Effect of abiotic factors on the foraging strategy of the orb‐web spider Argiope keyserlingi (Araneae: Araneidae)

Abstract Environmental conditions such as light level, background contrast and temperature might influence a spider's prey capture success and risk of predation. Thus it may often be advantageous for spiders to adjust web‐building behaviour in response to variation in these environmental conditions. This hypothesis was examined in a study of the construction of webs and web decorations (conspicuous strands of silk at the hub of the web) of the orb‐web spider Argiope keyserlingi. Web decorations are thought to have one or more separate functions. They may attract prey, deter predators or advertise the web to oncoming birds, thus preventing web damage. In this series of experiments, relationships between weather parameters and the construction of webs and web decorations were considered. In complementary laboratory experiments, A. keyserlingi spiders were exposed to two different light levels (700 and 90 lx), background contrasts (black and white) and temperature conditions (20 and 26°C). Of the available weather parameters, only temperature was significantly related to web decorating behaviour but not to web size. In the laboratory, temperature also influenced web‐decorating behaviour, and spiders in dim light (700 lx) constructed larger webs and longer decorations. Background contrast did not significantly alter web size or web decorations. These data suggest that when prey availability is reduced at low temperatures, spiders may use web decorations to attract prey to the web. Similarly, in dim light, spiders may build more and larger decorations to increase the visual signal to approaching prey or to advertise the web to oncoming birds.     

Predatory behaviour of the social orb-weaver spider,Geratonephila burmanica n. gen., n. sp. (Araneae: Nephilidae) with its wasp prey,Cascoscelio incassus n. gen., n. sp. (Hymenoptera: Platygastridae) in Early Cretaceous Burmese amber

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.     

Female false black widow spiders,Steatoda grossa,recognize webs based on physical and chemical cues

Females of the false black widow, Steatoda grossa CL Koch (Araneae: Theridiidae), invest significant energy and time weaving cobwebs. We tested the hypothesis that S. grossa females select sites for their webs based, in part, on the presence of con‐ or heterospecific webs, sensing both physical and chemical web cues. In bioassays, we offered female S. grossa a choice between an empty control frame and a frame bearing the web of a conspecific female or that of a female common house spider, Parasteatoda tepidarium CL Koch (Araneae: Theridiidae), recording (1) the time she spent, and (2) the time she spent inactive (a proxy for settling behaviour) on each frame. We also tested the effect of (1) silk micro‐ and macrostructure (wrapped‐up silk or intact web, each semiochemical‐deprived), (2) plastic webs, and (3) silk semiochemical extract on the responses of S. grossa females. Females settled on both con‐ and heterospecific webs and chose test stimuli based on their chemical and physical characteristics. Even plastic webs in cobweb‐like arrangement readily prompted settling behaviour by females. Our results suggest that web architecture, rather than web silk, mediates settling responses by female S. grossa on pre‐existing webs which may provide structural support for a new web and indicate habitat suitability.     

Building a better insect trap; An experimental investigation of prey capture in a variety of spider webs

Summary Web-building spiders (Araneae; Theridiidae, Linyphiidae, Araneidae) are catagorized as searchers because they devote a large amount of energy to the construction of the web which constitutes the search phase in the foraging sequence. In this study search energy is equated with the density of threads in a web and the effectiveness of a variety of webs in three broad catagories (tangle webs, sheet webs & orb webs) is tested in the light of current foraging theory. Within each web type there is a distinct thread density at which the number of approaching Drosophila (Diptera; Drosophilidae) that are captured is maximized (Figs. 1, 2, 3). That maximum results from a combination of factors that are a function of the density of threads in the web. The visibility of the web to an approaching Drosophila increases which acts to decrease the number of flies that enter the web (Tables 2, 3, 4). The ability of the web to detain a Drosophila that contacts it (capture efficiency) increases to an asymptote as a function of thread density (Fig. 4). These data support an assumption of many optimal foraging models that with increasing investment in search the predator receives a diminishing return.More Drosophila intercept orb webs than intercept sheet or tangle webs. In addition orb webs detain a greater proportion of the flies that contact them (Fig. 4). Sheet webs are intermediate between orb and tangle webs in their relative abilities to contact and detain Drosophila.     

A preliminary molecular phylogeny for New Zealand sheet-web spiders (Cambridgea) and comparison of web-building behaviour

ABSTRACT

Spider webs vary in size to meet the nutritional requirements of the resident spider with the resident’s body size strongly informing these requirements. In this way, the effect of body size on web-building behaviour should be apparent across species. To determine whether the size of analogous web structures scales with body size across closely related species, we first measured mainsheet area and adult female body size of 12 sheet-web spider species (Cambridgea). Using these species, we then generated alignments from the cytochrome c oxidase subunit I (COI) and histone 3 (H3) gene regions. These alignments were phylogenetically analysed using Bayesian inference and maximum likelihood methods. While phylogenetic trees for the COI gene suggested that Cambridgea is monophyletic relative to sampled outgroups, H3 did not. Combining our COI phylogenetic tree’s branch lengths with data on web-building behaviour, we used phylogenetic least squares to determine whether web size scales with spider size across species. While we found evidence that larger species generally build larger webs, the variation in web size across even similarly sized species suggests that environmental characteristics which influence site selection and prey type may play a role in determining the optimal web size for different species.