Some new cases of ectoparasitoid wasps from the Polysphincta genus-group manipulating the behaviour of host spiders have been described in recent years, indicating that the modification of normal web structure is the rule rather than an exception as the outcome of these interactions. In most cases, orb web diameter and the number of adhesive spirals are reduced, which decreases the probability of web damage from the interception of insects on the viscid threads during the development of the parasitoid within the cocoon. In this study, we describe a new interaction between the host spider Leucauge volupis and the recently described parasitoid Hymenoepimecis jordanensis. Web modifications induced by larvae in their last instar, in this case, are different to those described for two other Leucauge species attacked by Hymenoepimecis spp., L. argyra and L. roseosignatha. The cocoon webs constructed by the parasitized L. volupis are similar to those webs constructed by immature individuals, presenting a lower tangle, which may increase the stability of the web or offer additional physical protection for the cocoon. As in other previously described cases, sticky spirals are absent from cocoon webs. However, the photographs of webs constructed by spiders carrying second instar larvae indicated that the reduction in spirals begins before the construction of the cocoon web. These webs remain functional, being substantially modified only when the larvae reach the third instar. Variation among cocoon web designs of congeneric hosts attacked by distinct Hymenoepimecis species indicate that the substance used for host manipulation may vary in concentration and/or composition. Alternatively, distinct host responses may occur to the same substances.
Individual specialization (IS) in resource use is common within populations of several animal species because some individuals can be more efficient than others in obtaining specific food items. Spiders are usually classified as euryphagous predators, but the broad diet of populations may result from many individuals specializing in capturing different types of prey. Empirical evidence supporting this pattern, however, is still scarce. In this study, we hypothesized that (1) the diet of individuals of Tidarren haemorrhoidale is more restricted than the population's diet and (2) individual diet restrictions are not determined by the spatial distribution of prey types. We collected the prey remains of 74 webs of females in a conservation area of the Atlantic Forest. Our results indicated that T. haemorrhoidale could be considered a euryphagous predator because its diet comprised Opiliones, Diplopoda, and eight orders of insects. However, spiders exhibited moderate and high degrees of IS for prey size and taxa, respectively. There was no modularity for both prey attributes in the food web, but there was a medium nestedness. Most individuals captured ants, but additional prey taxa were of different orders. There was no correlation between the dissimilarity of prey taxa and the distances between the webs, suggesting that IS did not occur based on the spatial distribution of their potential prey. The diversity of prey defensive strategies may induce spiders to perform specific behavioral routines after prey interception. If this occurs, cognitive constraints may limit their ability to use different capture routines efficiently. Our study supports the predictions of individual niche specialization theory for a euryphagous spider species and highlights the potential of spiders as a study model to investigate the underlying mechanisms.
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