Biology of Agathis gibbosa (Hymenoptera: Braconidae), a Primary Parasite of the Potato Tuberworm1, 2

Abstract

Agathis gibbosa (Say), a primary, solitary, larval endoparasite of Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was studied under laboratory conditions of 26.7 ± 1°C and 50 ± 2%, RH. The egg is deposited in any of the ganglia along the ventral nerve cord of the host larva. The parasite larva develops in the body cavity, emerging after the host larva has spun its cocoon, and then feeds externally on the host larva for 1 to 2 days before spinning its own cocoon inside that of its host. There are 3 instars, the first being mandibulate and the other two hymenopteriform. Total developmental time from egg to adult ranged from 16 to 22 days; average, 18 days. The duration of each developmental stage was: egg 3.5 days, 1st stage 3.5 days, 2nd stage 1 day, 3rd stage 3 days, prepupa 2 days, and pupa 3 days. Adult emergence was stimulated by light, and copulation occurred within a few minutes to several hours later. Males mated several times, females only once. Unmated females produced only males, mated females both males and females. There is essentially no pre-oviposition period. Without food and water, adults died within 2.6 days; with both honey and water, males lived an average of 12.6 days and females 18 days. The highest average daily production of progeny among 10 mated females was 40.5. The females had an average ovipositional period of 9 days and produced an average of 288.5 adult progeny. Longevity of the mated females averaged 10.8 days and the sex ratio (♂ : ♀) of their progeny averaged 1.9:1.