Please refer also to the following links for details on this group:
Empididae = Link 1
Description & Statistics
Empidids or "dance flies" are commonly found in damp places, such as along streams. The adults are predators, and larvae are either predators or scavengers, living in the soil, decaying vegetation and wood, under bark, and in water. The adult flies are all predaceous on other insects of small size, and the larvae are either predators or scavengers.
The complete biological control of an infestation of Phytomyza aconiti Hendel was reported through the attack of Tachydromia minuta Meig. on the adult flies (Whitfield 1925). There is a very unusual feeding habit associated with mating in the genera Empis, Hilara and Rhampomyia. The male captures its prey, carrying it about until mating occurs, at which time it is transferred to the female. Males of several species envelop the prey in a frothy web before presenting it to the female (Lundbeck 1910, Clausen 1940).
Cole, F. R. 1969. The Flies of Western North America. Univ. Calif. Press, Berkeley & Los Angeles. 693 p.
Frey, R. 1956. Die Fliegen der Palaearktischen Region 4: 231-6.
Kessel, E. L. 1955. Syst. Zool. 4: 97-104.
Kessel, E. L. 1959. Wasmann J. Biol. 17: 221-30.
Melander, A. L. 1927. Genera Insectorum, Fasc. 185. 434 p.