Tachinid Flies

Tachinid Flies

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"Though often little noticed, these flies have an important role in controlling phytophagous Insecta" (Arnaud 1978). Previous ICEL research has shown that tachinids usually exploit the pheromones of Heteroptera as host-finding kairomones, and recent GC-EAD analyses indicate that, in general, tachinids are 5-10 times more sensitive to the pheromones of bugs than are the bugs themselves. We found that geographically isolated populations of Trichopoda pennipes (Diptera: Tachinidae) give dramatically different antennal responses to pheromone extracts of N. viridula and certain native host species. This is the first experimental verification that kairomone-strains of tachinids exist. These data help explain why T. pennipes introduced into Hawaii from Florida failed to parasitize N. viridula, and T. pennipes fails to attack the squash bug, Anasa tristis (Coreidae), in California although A. tristis is the most common host of this parasitoid in the northeastern U.S. In the future, electrophysiological screening of parasitoids prior to classical biological control introductions could avoid inevitable failures. Additional studies of tachinid chemical ecology showed that a species (Euclytia flava) attracted to pheromones of the spined soldier bug and certain other indigenous species, when given a choice, prefers to oviposit on exotic hosts. Thus, invasive species may be more vulnerable to native parasitoids than are native host species yet go unrecognized as potential hosts.