Tachinid flies

By Alicia Alexander, IPM Intern

The tachinid fly (family Tachinidae) is a parasite of other insects. In most cases these flies are beneficial because they are pest controllers. Some flies are host specific. Most species of these flies parasitize caterpillars and beetles. A few other species will parasitize grasshoppers and other insects. Most hosts are still in their immature stage.

What are probably Tachind eggs on a whitelined sphinx caterpillar. Photo credit: Alicia Alexander. 

There are a variety of methods different species of these flies use when laying their egg. The eggs of these flies are small, oblong, and a white/gray color. Some female tachinid flies will lay their eggs on leaves so that a host, such as a caterpillar, can ingest them. Other species directly insert the eggs into the host’s body. The eggs consumed by the host or inserted into the host will hatch into maggots inside the host. Another way the female tachinid fly ensures readily accessible food for her young is attaching the eggs onto the back of a host. These eggs will hatch and the maggots will bore into the body of the host. Once inside, the maggots develop and consume their host as they grow. Not much is seen of the maggots since they develop inside of a host insect. They maggots slowly feed on the host’s internal parts then once the maggots are well developed they feed on the necessary organs leaving the host to soon die. These maggots can be seen when exiting its host. They dig into the ground where they will pupate. The pupa is usually a small oblong dark reddish case.

 The adult tachinid fly can be diverse in appearance and can some can be quite large. There are many species of the tachinid fly and these can vary in color. Many have long distinct sparse bristles on their bodies. The adult tachinid fly is usually found in gardens and other landscapes visiting flowers. They feed on nectar and pollen. They are also known to feed on aphid honeydew.

A Tachinid fly. Photo credit: Alicia Alexander.