A Comparison of Growth and Developmental Rates of the Parasite Hyposoter exiguae Reared from Two Instars of its Host, Trichoplusia ni1, 2

Abstract

Developmental rate and size of Hyposoter exiguae (Viereck) (Ichneumonidae) were determined in both early and late instar Trichoplusia ni (Hübner) (Noctuidae) larvae. Four larval instars were observed, each lasting about 2, 1½, 1½, and ½ days, respectively. At 26°C, development from egg to adult required 14 days in both 2nd and 4th instar hosts. Parasite larvae and adults reared on 4th instar hosts were significantly larger than those reared on 2nd instar hosts. Larval development progressed continuously throughout all instars, but developmental rate within each depended upon host instar attacked. First and 2nd instar parasites developed faster in older hosts, but 3rd instar developmental rates were about equal. During the parasite's final instar, developmental rate was slower in 4th instar hosts. Larval developmental time ranged from 6½ to 7½ days.