HOST LOCATING BEHAVIOR OF LESCHENAULTIA EXUL AND PATELLOA-PACHYPYGA -2 TACHINID PARASITOIDS OF THE FOREST TENT CATERPILLAR, MALACOSOMA-DISSTRIA

Leschenaultia exul (Townsend) and Patelloa pachypyga (Aldrich & Webber ) (Diptera: Tachinidae) are the principal larval parasitoids of the fo rest tent caterpillar (FTC) Malacosoma disstria (Hubner) (Lepidoptera: Lasiocampidae) in Canada. The response of these two fly species to M. disstria differs depending on the tree species on which the host feed s. In wind tunnel experiments, L. exul spent more time on the side of the tunnel containing volatiles from FTC frass and was attracted to th e FTC-aspen poplar (Populus tremuloides Michx.) complex preferentially to the FTC-balsam poplar (Populus balsamifera L.) complex. Field bioa ssays confirmed that this fly species was preferentially attracted to the herbivore-aspen poplar complex as compared to the herbivore-balsam poplar complex. In field bioassays, P. pachypyga was also attracted p referentially to aspen poplar toes containing FTC larvae? compared to balsam poplar trees with host larvae.