The maggot pupates about an inch down in the soil in a dark reddish-brown puparium formed from the last larval skin, and an adult fly emerges about two weeks later. There can be three generations per year depending on location. The fly overwinters as a second instar larva within the body of the overwintering host bug. Adult flies emerge in late spring or early summer. The only bugs large enough to parasitize at this time are overwintered adults.
Subsequent generations develop on both nymphs and adults of the next generation.
But because the bugs continue to feed after parasitization, T. pennipes will not always prevent crop damage. However, the reproductive organs of the host bug begin to atrophy when the parasitoid reaches the second instar, so pest population increase will be reduced somewhat. The life history of the parasitoid and squash bug are not well synchronized, and host finding by the fly is not efficient, so T. pennipes is not able to maintain this pest at low densities.