The Polysphinctine Wasps Acrotaphus tibialis, Eruga ca. gutfreundi, and Hymenoepimecis tedfordi (Hymenoptera, Ichneumonidae, Pimplinae) Induce Their Host Spiders to Build Modified Webs

Abstract

Abstract The wasps Acrotaphus tibialis (Cameron), Eruga ca. gutfreundi Gauld, and Hymenoepimecis tedfordi Gauld induce their host spiders to spin modified “cocoon” webs just before they kill them and pupate. The cocoon webs induced by all three wasp species appear better designed to support and protect the wasps' pupal cocoons than are the normal orbs of their hosts. The typical cocoon webs induced by A. tibialis were similar to the protected resting webs built by their host spiders Argiope trifasciata (Forskäl) but had more elaborate protective barrier tangles. The other two species of wasp induced the same host spider, Leucauge mariana (Keyserling) to build quite different cocoon webs. The cocoon webs of H. tedfordi varied somewhat, but usually included radial lines and a tangle below. They resembled the resting webs of the host in having a planar radial organization and (often) a tangle below, but lacked a hub and had their lines that were apparently composed of high numbers of individual strands. The three dimensional, radially arranged cocoon web of E. ca. gutfreundi had no clear counterpart in the webs of unparasitized L. mariana. The substantial intraspecific variation in the cocoon webs, especially those of A. tibialis, emphasizes the apparent difficulty of precise host manipulation by these wasps.