Modification of Tetragnata montana (Araneae, Tetrafnathidae) web architecture induced by larva of the parasitoid Acrodactyla quadrisculpta (Hymenopteram Ichneumonidae, Polysphincta genus-group)

Background: The polysphinctine wasp, Acrodactyla quadrisculpta, is a koinobiont ecto-parasitoid of spiders and is narrowly associated with the biology of its spider hosts. The larva, attached to the dorsal side of the abdomen, develops while the spider continues foraging. Shortly before pupation, the parasitoid larva manipulates the web-building activity of the host in order to construct a safe shelter against natural elements and predators during parasitoid pupation. Results: A. quadrisculpta was associated exclusively with the orb web weaving spiders Tetragnatha montana, with a parasitism incidence of 19%. The manipulated spider constructed a unique cocoon web that provided strong mechanical support for the parasitoid's pupal cocoon. The cocoon web consisted of one highly reinforced main thread, tensioned in 60% of cases by a reinforced side thread. The wasp cocoon, square in cross-section, was fastened along its length to the main cocoon thread. Conclusions: The wasp A. quadrisculpta was exclusively associated with an orb-weaving spider T. montana in the family Tetragnathidae. The alteration of the web architecture of T. montana induced by the larva A. quadrisculpta was unique and species specific