Possible host-determined strains of Trichopoda pennipes from Anasa tristis, Nezara viridula, or Leptoglossus phyllopus

Trichopoda pennipes is a tachinid fly that parasitizes species of Heteroptera in certain geographical areas. It parasitized the bordered plant bug, Largus cinctus, a Largid, in California but not the local squash bug, Anasa tristis, despite occurring with each other in the same squash field. Even when the two hosts were caged together, flies from the bordered plant bug never parasitized the squash bug. However, T. pennipes collected from A. tristis in New York and transported to California immediately parasitized A. tristis on squash. Trichopoda pennipes also parasitizes A. tristis and other coreids in the Southeast, along with the southern green stinkbug, Nezara viridula, and additional species of pentatomids. It frequently oviposits on the eastern leaffooted bug, Leptoglossus phyllopus, another coreid, as well. Therefore, three host-determined strains of T. pennipes were assumed to occur in different geographical areas: one from coreids in the Northeast, a second from pentatomids in the South, and a third from the bordered plant bug in California. We observed recently, however, that several species of coreids and pentatomids were parasitized by T. pennipes at the same southern farms. To determine if the T. pennipes from these host species are host-determined strains, mated females were given a choice between A. tristis, N. viridula, and L. phyllopus adults for oviposition. The females oviposited primarily on their parental host species for at least one generation. Mitochondrial DNA analysis revealed separate markers for two parasitoid lineages, one from both N. viridula and L. phyllopus and another from only L. phyllopus.