The endoparasitoid Glyptapanteles liparidis (Hymenoptera: Braconidae) injects polydnavirus and venom together with eggs into its Lymantria dispar (Lepidoptera: Lymantriidae) host larvae during oviposition. We studied effects of these parasitoid associated factors by means of g-irradiation-induced pseudoparasitization. The application of radiation for sterilization of female wasps as a tool to study interactions between parasitoid associated factors and the host is demonstrated in this paper. When wasps were irradiated at doses ranging from 24 to 96 Gy and then allowed to oviposit into L. dispar larvae, temporary sterilization was produced. On the first day post irradiation they laid 99% sterile eggs, but fertility recovered partially during the following days. Irradiation had no negative effect on the lifespan of wasps, but total fecundity was significantly reduced. Pseudoparasitization of L. dispar by irradiated G. liparidis caused prolonged larval development with supernumerary molts before pupation in females, and higher pupal weights in both sexes. Only 8 to 20% of pseudoparasitized larvae developed into adults; 20 to 33% died as larvae, 55 to 65% in pupae. Abnormities, such as precocious formation of pupal antennal pads in larvae or incomplete sclerotization of pupal cuticle occurred. Pseudoparasitization impaired the immune reactions of L. dispar larvae. Encapsulation of implanted plastic rods by hemocytes was reduced and hemolymph melanization was significantly suppressed 3 and 5 days post pseudoparasitization.
After leaving their hosts, the larvae of endoparasitic braconid wasps pupate in cocoons. To determine their investment in cocoon silk, the dry weight of newly emerged wasps and that of the empty cocoons were measured for three gregarious braconid species of slightly different sizes: Glyptapanteles liparidis (Bouché), Cotesia glomerata (L.) and Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae, Microgastrinae). These braconids form clusters of cocoons of different types. Glyptapanteles liparidis is significantly larger than either of the Cotesia species, and C. kariyai is the smallest. The ratio of the weight of cocoon silk to the total weight of cocoon silk, wasp body, cast cuticle and meconium is smaller for small species than large species. Small species economise on their use of silk by aggregating cocoons and can therefore invest a larger fraction of their resources in adult body mass. Moreover, the larvae of the smallest species, C. kariyai, additionally reduce their use of silk by constructing a communal airy silk layer beneath which the individual cocoons are formed.