PROC. ENTOMOL. SOC. WASH. 83(2), 1981. pp. 304-315 BIOLOGY AND IMMATURE STAGES OF LYTOG ASTER EXCAVATA, A GRAZER OF BLUE-GREEN ALGAE (DIPTERA: EPHYDRIDAE)' B. A. FooTE Department of Biological Sciences, Kent State University, Kent, Ohio 44240. Abstract. — Information is presented on the life cycle and larval feeding habits of Lytogaster excavata (Sturtevant and Wheeler), a widely distrib-uted species of the ephydrid tribe Hyadini. Larvae are trophically special-ized and apparently restricted to feeding on blue-green algae. In northeast-ern Ohio, the life cycle can be completed in ca. 30 days, and there are probably five generations a year. The egg and mature larva are described and illustrated. The life history strategy of this specialist species is contrast-ed and compared to that of Scatella stagnalis Fallen, a generalist species. The family Ephydridae, with over 1200 described species distributed in all of the major faunal regions, is one of the largest entities within the acalyptrate Diptera (Rohdendorf, 1974). Over 400 species and 68 genera have been recorded from America north of Mexico (Deonier, 1979), and an equally large fauna occurs in the Neotropics (Wirth, 1968). As would be expected in such a large and diverse taxon, considerable adaptive radiation in larval feeding habits has occurred, although the majority of species appear to be microphagous. Larvae are known to utilize a great variety of algae (Brock et al., 1969; Deonier and Regensburg, 1978; Foote, 1979), heterotro-phic microorganisms (Eastin and Foote, 1971), and detritus (Busacca and Foote, 1978; Deonier et al., 1979). However, larvae of particular genera have acquired more specialized feeding habits. For example, larvae of Hy-drellia are leaf miners (Deonier, 1971), those of Platygymnopa utilize de-caying snails (Wirth, 1971), Trimerina larvae prey on spider eggs (Becker, 1926), and those of Ochthera are predators of chironomid and other soft-bodied larvae (Simpson, 1975). This paper is the second of a series that deals with the biology of species Research supported by a grant (DEB 7912242) from the National Science Foundation.