Tachinid flies are mostly robust flies with spiny abdomens. Adult tachinid flies prefer sucking up sweet nectar from flowers, but larvae prefer protein. Of the 1,345 species of tachinid flies in North America, larvae are almost exclusively internal parasitoids of other insects, especially caterpillars. Typically, the females lay eggs on the host, and the larvae burrow inside. They feed within the host, avoiding vital organs until the last stage of their own development (usually killing their host).

Size: Most tachinid flies are larger than a house fly. They range in size from 2–20 mm across the family.

Photo by: Kristi DuBois on 6/17/22 near Clinton, MT