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.
Many spider species build webs and remain resting on this structure to capture prey. In addition, the transmission of vibrational stimuli on webs is involved with the identification of sexual partners and the silk may act like a physical barrier that minimizes predation risk. Nevertheless, the web can be used by intruder, kleptoparasite spiders, and may allow access to araneophagic predators. In this study we observed an araneophagic species, Gelanor zonatus, and two species usually considered as kleptoparasites, Faiditus caudatus and Argyrodes elevatus, invading webs of Manogea porracea. We tested hypotheses on trophic position of intruders and their nutritional preferences. We also evaluated factors that influence their occurrence on host webs and the biomass acquired by the araneophagic predator after the consumption of different prey items. We conducted tests with nitrogen and carbon stable isotopes, field observations and laboratory experiments. Gelanor zonatus shows higher values of nitrogen isotopes when compared with other species found in the same area. It can, consequently, be considered as a secondary carnivore predator. This species shows diet selectivity based on their prey nutricional content. Furthermore we observed that the increase in predator body mass, when it consumes different prey items, varies not only with the prey mass, but also with prey species. Kleptoparasites show nitrogen isotopes values similar to Gelanor zonatus and higher than host spider species. The presence of males, females or both and the egg sacs on M. porracea webs did not explain the kleptoparasite occurrence. Finally, A. elevatus exhibit preference for prey consumption instead of eggsacs on the invaded webs.
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