Male specific protein (MSP) was identified and purified from the hemolymph of Galleria melloneffa L. by electrophoresis and anion exchange chromatography. MSP has a native molecular weight of 55 kDa as determined by gel filtration chromatography and consists of a single unit with the apparent molecular weight of 27 kDa and has the pl of approximately 5.8. MSP is present in the hemolymph from day 8 pupae throughout the male adult. MSP was also found in pupal fat body, adult fat body, and adult testis.