Kairomone-mediated host finding by spruce budworm egg parasite,Trichogramma minutum.

The host-finding responses of the egg parasite,Trichogramma minutum Riley, reared from its natural host,Choristoneura fumiferana (Clemens) and a laboratory host,Sitotroga cerealella (Oliver), to hexane extracts of scales of these hosts were compared in laboratory experiments. When presented withC. fumiferana eggs on filter papers treated with hexane and hexane extract of grain moth scales, egg finding byT. minutum was random. When presented with budworm eggs on filter papers treated with hexane and hexane extract of budworm scales,T. minutum found significantly more eggs on extract-treated filter papers, indicating the presence of kairomones on the scales of spruce budworms.T. minutum responded to kairomone-treated patches with a localized search behavior characterized by intense antennal tapping, decreased locomotion and increased turning within the patch, and repeated returns to the patch. In the absence of successful host finding, this response slowly waned. No significant difference in behavior ofT. minutum reared on eitherC. fumiferana orS. cerealella was observed.