PROC. ENTOMOL. SOC. WASH. 82(3), 1980, pp. 360-377 THE HABITS AND LIFE HISTORY OF OEDOP ARENA GLAUCA (DIPTERA: DRYOMYZIDAE), A PREDATOR OF BARNACLES' J. F. Burger, J. R. Anderson, and M. F. Knudsen (JFB) Department of Entomology, University of New Hampshire, Dur-ham, New Hampshire 03824; (JRA, MFK) Department of Entomology and Parasitology, University of California, Berkeley, California 94720. Abstract. — Oedoparena f^lauca (Coquillett), a common coastal dryomy-zid fly occurring from Central California to Alaska in the Nearctic Region, is the first known dipterous predator of intertidal barnacles. Adults occur on or adjacent to barnacle beds and mate there. Eggs are deposited on the operculum of barnacle prey and larvae consume several prey during devel-opment. Pupariation occurs in an empty barnacle test. Adults emerge during a morning low tide. The habits of adult flies and the life history of O. glaiica are discussed; illustrations and a description of the second-and third-instar larva in given, and food habits are compared with related Sciomyzoidea. In 1966, fly pupae were discovered by M. F. Knudsen and J. F. Burger in empty tests of the intertidal acorn barnacle, Balaniis gkindiila Darwin, on the central California coast (Sonoma County). Subsequently, larvae were observed inside the tests of living barnacles. Tests containing puparia were returned to the laboratory and one adult fly emerged within 24 hr. This slate gray and brown fly was identified as Oedoparena glaucu (Coquillett). Be-cause this was the first record of a dipterous predator of barnacles, we studied its biology and life history. Schlinger (1975: 442-443) briefly sum-marized O. glauca habits. Oedoparena glauca is a moderately large fly, about 5-9 mm long, inhab-iting that part of the intertidal zone colonized by the Endocladia-Balanus community. Endocladia muricata (Postels and Ruprecht) J. G. Agardh, 1847 is a red alga abundant in the upper tidal zone of California, especially where wave action is moderate. Balanus glandula is a rather small barnacle of diverse habits and usually is found in the middle or upper intertidal levels ' Scientific Contribution Number 1032 from the New Hampshire Agricultural Experiment Station.