Length: typically 8-13 mm
Flies in the genus Trichopoda are believed to be among the more primitive Tachinids. In other genera, eggs undergo development within the female fly’s body, then are placed within the host species by means of a piercing ovipositor. In Trichopoda and several other genera, however, undeveloped, disk-shaped eggs are laid on the surface of the host’s integument. When the embryo is ready to hatch, it burrows into the host. One disadvantage of this type of life history is that the host or another creature may eat the egg, or the egg may be discarded when the host (if larval) molts. (Wood, “Tachinidae,” in McAlpine, 1987.)
In the northern part of its range Trichopoda pennipes parasitizes the Squash bug, Anasa tristis, while in its southern range a common host species is the Southern Green Stink Bug, Nezara viridula. Both are important agricultural pests, thus Trichopoda pennipes is an economically beneficial insect. On the other hand, some researchers have noted that the parasitized bugs often remain active and continue feeding for some time after the the initial paratization.
Other hosts include Leaf-footed Bugs in the genus Leptoglossus, Shield-backed Bugs in the genus Coleotichus, Bordered Plant Bugs in the genus Largus, and the widespread green Stinkbug Acrosternum hilare. In Hawaii, the reported host is a Mantis, Tenodera australasiae (Arnaud, 1978).
Commenting on the parasitizing of Anasa tristis in particular, Susan Mahr, of the University of Wisconsin notes, “The life history of the parasitoid and squash bug are not well synchronized, and host-finding by the fly is not efficient,” so Trichopoda pennipes isn’t able to keep the Squash Bug down to low numbers.
Hokkanen (1983) found that when the Southern Green Stink Bug is the host, Trichopoda pennipes has a strong preference for adult bugs, although nymphs were occasionally parasitized. In his Florida study population, Hokkanen found that the flies emerged from their Hemipteran hosts 15 to 28 days after the eggs were laid. After the flies emerged, 95% of the bugs died within one day.
O’Hara and Woods’ 2004 catalog of the Tachinidae give the Nearctic range of Trichopoda pennipes as California and Idaho to Ontario and Massachusetts, south to Mexico and Florida. They also note the species has been introduced to Washington state.