Life History of the Parasite Diolcogaster facetosa (Weed) (Hymenoptera: Braconidae) and Its Behavioral Adaptation to the Defensive Response of a Lepidopteran Host

Abstract

Diolcogaster facetosa (Weed) attacks young green cloverworm larvae in the eastern United States. Development of D. facetosa from oviposition to adult emergence takes 2.5 weeks at constant 30°C to 4 weeks at constant 21°C. Females require ca. 1 day longer than males to complete pupal development at each of four temperatures tested. This solitary parasite passes through three larval stages and emerges from its host through the side of the third, fourth, or fifth abdominal segment; the host dies in the fifth or sixth stadium. Parasitized green cloverworm larvae leave the plant and wander on the substrate before parasite emergence. White cocoons are formed by D. facetosa at or slightly below soil level. Young green cloverworm larvae drop from foliage upon disturbance and hang on silken threads several centimeters below the leaf. Adult D. facetosa females can detect these threads and slide down them to oviposit in the suspended larvae. This behavior of the parasite, the fact that only early instars of the green cloverworm consistently drop on threads, and the inability of the first instar's thread to support the weight of the parasite during descent collectively indicate that under field conditions the most successfully parasitized green cloverworm hosts of D. facetosa are second and third instars. The biology of D. facetosa is compared with the biologies of the two other braconid species most frequently associated with the green cloverworm.