The disaccharide trehalose is a major substrate for energy production and macromolecular synthesis in many insects (Friedman, 1978). As the principle hemolymph sugar, the utilization of trehalose and the maintenance of hemolymph trehalose concentrations have been implicated in a diversity of physiological processes, including flight metabolism (Clegg and Evans, 1961), cold tolerance (Wyatt, 1967), and chitin synthesis during moulting (Candy and Kilby, 1962). Catabolic utilization of trehalose in insect tissues is initiated by the enzyme trehalase (a,a-glucoside-l-glucohydrolase; EC 3.2.1.28), which catalyzes the hydrolysis of trehalose into two glucose moieties. This enzyme has a broad distribution among insect tissues and may occur as more than one isozyme (Friedman, 1975; Yanagawa, 1971). Talbot and Huber (1976) found that abdominal and thoracic trehalases in Drosophila melanogaster differed in pH optima and electrophoretic mobility, although the existence of distinct trehalase isozymes in this species has been disputed (Oliver et al., 1978; Bargiello and Grossfield, 1979). One approach to clarifying the dispute concerning multiple trehalase isozymes is to map genetically the structural gene(s) involved. Using segmental aneuploidy and trehalase activity assays, Oliver et al., (1978) found evidence for only a single trehalase structural gene (Treh) in D. melanogaster. They mapped Treh to the right arm of the second chromosome, in the region of bands 55B-E. Because no electrophoretically detectable trehalase allelic variation has been previously reported in D. melanogaster (Bargiello and