Behavior of larvae and adults of Campoletis sonorensis (Hymenoptera: Ichneumonidae), with special reference to Heliothis virescens (Lepidoptera: Noctuidae) as a host

Abstract

Studies were conducted on the morphology, feeding behavior, and cocoon spinning behavior of the larvae and on host acceptance and oviposition behavior of adults of Campoletis sonorensis (Cameron). Morphological studies indicated that C. sonorensis passed through five larval stages in the course of its development. The various larval stages were described and illustrated. First instar larvae of C. sonorensis initially feed on hemolymph, but later feed on adipose tissue. The second and third instars feed on hemolymph, but use adipose tissue and Malpighian tubules as their primary source of food. The fourth instar larvae feed extensively on all tissues, while the fifth instar larvae are essentially non-feeding. The mode of feeding is similar for all instars; food materials, including hemolymph, are ingested by means of an esophageal pump. The mandibles are not used in the actual feeding process. In the first of three stages of cocoon spinning, C. sonorensis spins the loosely woven outer layer of the cocoon. The second stage of spinning begins when the parasitoid begins constructing the more closely woven inner layer. During the third stage of spinning, the inner layer is lined with a transparent sheet of silk. Parasitoid larvae are incapable of repeating spinning operations when removed at various stages of spinning. Cocoon spinning and adult emergence are affected by substrate moisture content, but not by atmospheric moisture. In a study of physical stimuli on host acceptability and oviposition, shape had the greatest effect on host acceptance; a straight cylindrical shape was more acceptable than a round or flat one. Movement and size of hosts were of lesser importance to the oviposition process..