Earwig-parasite
Guides
Triarthria setipennis
European earwig parasitoid fly
Triarthria setipennis is a tachinid fly native to Europe that was introduced to North America in the 1920s as a classical biological control agent for the European earwig (Forficula auricularia). It is ovolarviparous, depositing eggs near potential hosts rather than on them. First-instar larvae actively seek out earwigs and attempt to penetrate through intersegmental membranes, though only about 16.7% succeed. The species overwinters as pupae and produces one complete and one partial generation annually in temperate regions. It has established populations in British Columbia, Washington, Oregon, California, Idaho, Nevada, Utah, Newfoundland, New Hampshire, and Massachusetts.