Please refer also to the following link for details on this group:
Dolichopodidae = Link 1
Description & Statistics
The immatures and adults of Dolichopodidae are predators on other insects. The adults are often found on foliage in shaded areas. Larvae occur in wet or muddy soil, under bark, in decaying organic matter and in water. Adults of some species are able to skim over the water surface. The females move quickly and often have a crab-like manner of locomotion. Williams (1933) noted that the adults of a few species of Campsicnemus are active on the surface of water pools in Hawaii and that they feed extensively on the collembolan, Salina maculata Fols. It was also observed that the adults of Hydrophorus pacificus V.D. pulled Chironomus larvae out of shallow water along muddy shores and in marshes.
In the genus Medetera, the hosts of which are mainly the larvae, pupae and adults of bark beetles, M. signaticornis Lw. is predaceous on larvae and adults of Scolytidae (Hubault 1925). M. aldrichii Wh. De Leon (1935a) found it to be an important natural enemy of the mountain pine beetle, Dendroctonus monticolae Hopk. in western North America. The eggs are laid beneath bark scales or in crevices, and young larvae work their way into the inner bark for immature host stages. They also feed on dead larvae and various other insects that they find in the burrows. Pupation occurs in a cell in the bark, which is lined with a silk-like substance. The larvae of several species are aquatic and feed on a variety of aquatic animals (Clausen 1940/62).
Dolichopodidae is a large, cosmopolitan family with more than 2,502 species known by 2000. Diagnostic characters include a 3-segmented antenna, usually with a dorsal arista; branches of R-s usually do not branch further; vein M-2 atrophied or absent; male genitalia complex, turned under remainder of abdomen. The body is small, often a bright or dull metallic green. The legs are long, somewhat bristled. In the male the forelegs are may have tufts of hair.
Becker, T. 1922. Zool.-Bot. Gess. Wien, Abhandl. 13: 1-394
Cole, F. R. 1969. The Flies of Western North America. Univ. Calif. Press, Berkeley & Los Angeles. 693 p.
Wirth, W. W. & A. Stone. 1956. Aquatic Insects of California, with Keys to North American Genera and California Species. R. L. Usinger, ed. Berkeley, CA. 508 p.