Biology of Hyposoter exiguae (Hymenoptera: Ichneumonidae), A Parasite of Lepidopterous Larvae1

Hyposoter exiguae (Viereck), a Nearctic ichneumonid, is a solitary endoparasite of the larvae of several species of Lepidoptera. It prefers to oviposit in late first- and second-instar larvae and emerges from the third. Three larval instars have been observed, the last leaving the host body to spin its cocoon. At 72° to 76° F. the insect spends 2 days in the egg stage, 7 days as a larva, and 7 to 8 days in the cocoon. Females mate only once, but males mate with more than one female. Mated females produce about equal numbers of both sexes; unmated females produce males only. Temperature was found to be the main factor influencing the life cycle and longevity of the parasite. Developmental time at 60° to 80° F. ranged from 33.8 to 14.6 clays. Longevity at 40° to 80° F. ranged from 50.5 to 6.5 days. Percent emergence from cocoons was also related to temperature. Those held longest at 40° F. prior to removal to 72° to 76° F. showed emergence of only 20% as compared with 100% for those held for the shortest period. Spilochalcis albifrons (Walsh) was the most frequent hyperparasite reared. It oviposits in the cocoon of H. exiguae, and its life cycle requires 23 days at 72° to 76° F.