Perhaps several thousand species remain to be described, particularly in the tropics. Adult tachinids range in size from 2 mm to over 20 mm and display a wide variety of shapes, colours and sizes. All tachinids are internal parasitoids of other arthropods during their larval stage.
Hosts are primarily immatures of moths, sawflies and beetles, and adults of beetles and bugs.
Hosts include many of the major insect pests of economic concern to the agricultural and forestry industries in Canada. Since hosts are usually killed by their tachinid parasitoids and tachinids have rather narrow host preferences, tachinid flies constitute an important resource in terms of biological control of pest insects. Naturally-occurring species help keep populations of potential insect pests in check, while certain exotic species have been introduced into North America as part of biological control programs aimed at controlling targeted pests. Photo courtesy of Robert W. Mitchell. Tachinid flies are not well known at the species level in America north of Mexico.