We compared the components of hornet silk - a fibrous protein occurring in the cocoons produced by hornet larvae - among 6 species of the genus Vespa inhabiting Japan: V. simillima, V. dybowskii, V. crabro, V. mandarinia, V. ducalis, and V. analis. From the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), N-terminal amino acid sequence analysis, and 5'-RACE, it was found that the major component proteins composing hornet silk could be divided into 6 groups. Among these 6 proteins, 5 proteins were common to the hornet silks of all 6 Vespa species. The SDS-PAGE major band corresponding to the remaining protein was observed only in the hornet silks of V. mandarinia and V. ducalis. This correspondence between V. mandarinia and V. ducalis can probably be explained in terms of the phylogenetic relationships of the Vespa species.