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

Araneid spiders of genus Araniella are attacked by three polysphinctine parsitoid wasps Polysphincta boops Tschek, P. tuberose (Gravenhorst), and Sinarachna pallipes (Holmgren). In the present study, the trophic niche of sympatrically occurring parasitoids and the host manipulation they induced were studied. The aim was to identify whether the variation in host response to manipulation is as a result of differences among parasitoids or among host species. It was found that final instar larva forced the spider host to build a three‐dimensional (3D) ‘cocoon web’ to protect the parasitoid during pupation. The behaviour of parasitoid larva and the induced modification of the web architecture differed between wasps of genus Polysphincta and Sinarachna but not among three spider species. The larvae of genus Polysphincta forced the spider host to build the ‘cocoon web’ with a high thread density within which the pupa was positioned horizontally. The larvae of Sinarachna forced the spider host to build web with sparse threads and the pupa was positioned vertically in the middle of the ‘cocoon web’. There seems to be an investment trade‐off in parasitoid wasps: some species manipulate the host to build a dense protective web, while pupating in a sparse cocoon, whereas others make the spider produce a sparse web but build a dense pupa wall.