Host locating behaviour of Leschenaultia exul and Patelloa pachypyga: Two tachinid parasitoids of the forest tent caterpillar, Malacosoma disstria

Leschenaultia exul (Townsend) and Patelloa pachypyga (Aldrich and Webber) (Dipiera: Tachinidae) are the principal larval parasitoids of the forest tent caterpillar (FTC) Malacosoma disstria (Hubner): (Lepid0ptera: Lasiocampidae) in Canada the response of these two fly SpeCies to M. disstria differs dependingon the tree Species on which the host feeds. In wind tunnel experiments, L. exul Spent more time on the side of the tunnel containing volatiles from FTC frass and was attracted to the FTC-aspen poplar (Popalus tremaloides Michx) complex preferentially to the FTCbalsam poplar (Populus balsamifera L.) complex. Field bioassays 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 atttracted preferentially to aspen poplar trees containing FTC larvae, compared to balsam poplar trees with host larvae.