THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Larvae of aquatic Empididae may be found in streams and at the margins of streams, ponds and marshes. These small, predatory flies are usually tan to white with 7 or 8 pairs of well-developed prolegs on the underside of their abdominal segments. There are various shapes, sizes, and numbers of hairs on their posterior end. Head parts are often visible through the skin at the anterior end, but are reduced to a few long, dark rods.

There is some variance in tolerance levels among the different genera in the Empididae. Thus, a survey of this family may be a good indicator of the condition of a water body.

This family gets its name from the movements of the adults when swarming. Dance fly adults are predatory; males may present potential mates with prey and be chosen by females on the basis of their offering.