Host-Searching Kairomones Alter Behavior of Chelonus sp. nr. curvimaculatus , 1 a Hymenopterous Parasite of the Pink Bollworm, Pectinophora gossypiella (Saunders) 2

Abstract

This study examines the role of behavior-modifying chemicals in host location for the braconid egg-larval parasite, Chelonus sp. nr. curvimaculatus Cameron (Hymenoptera: Braconidae). The scales of one natural and two factitious lepidopterous hosts were found to contain kairomones that released an intense and stereotyped searching response that included locomotory arrestment, antennation, ovipositor probing, and inverse klinokinesis upon antennal contact in female Chelonus , responsiveness persisting during their entire reproductive life. The chemicals were soluble in hexane and methanol, being perceived by parasites over a range of 0.1 to 0.00004-mg scale equivalents. Scales shed by ovipositing moths around deposited eggs are thought to act as odorous extensions of host eggs for Chelonus , signaling for their presence over a larger area than would be possible by host egg-derived cues alone and leading to concentrated search in probable host-infested areas. When other Lepidoptera cohabiting cotton fields scatter their body scales over a broader area of the cotton plant, the result may diminish the percent parasitization of Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) by Chelonus species.