none Cocoon fibers of the parasitic wasp Apanteles glomeratus were extracted by aqueous 8M urea to remove glue protein. The resulting fibrous material was dissolved in LiCNS, and then dialyzed to prepare a solubilized wasp fibroin. Amino acid composition analysis showed that it consisted of mainly serine and aspartic acid (containing asparagine). SDS-PAGE of the fibroin indicated a single polypeptide band having molecular mass of -500 kDa, which showed a little decrease of the value after 2-mercaptoethanol treatment. A gel filtration chromatography of the fibroin also gave the similar result. This fibroin was digested to fragment peptides by successive treatments with chymotrypsin and formic acid. Four internal peptides were isolated and identified as ANSN, SNSNANANAN, SNSGANANSN and SYGSANTGSGS. These results suggest that the wasp fibroin is a novel type of fibrous protein. Ecology; Animal constructions Apanteles glomeratus (Braconidae); Cocoons; Characterization of fibroin from cocoon fibres