Interspecific relationship between the J apanese horned beetle and two J apanese stag beetle species

The J apanese horned beetle T rypoxylus dichotomus septentrionalis and the J apanese stag beetles L ucanus maculifemoratus maculifemoratus and P rosopocoilus inclinatus inclinatus generally occur syntopically and aggregate on oak tree surfaces that exude sap. Securement of these sap sites might be directly linked to male reproductive success. Among the three species, it is likely that males of T . d. septentrionalis are dominant in occupation of feeding sites because of their larger body size. However, there is no clear evidence of this superiority. Moreover, if T . d. septentrionalis is dominant, the mechanism by which the two stag beetle species secure the feeding sites remains unclear. In the present study, I used body mass to compare the body size among males of T . d. septentrionalis , L . m. maculifemoratus and P . i. inclinatus . Further, to clarify the interspecific relationship between the horned beetle and the two stag beetles, I investigated the seasonality of emergence pattern of males at the feeding sites in the field. Comparison of body mass and observation of fighting behavior revealed that males of T . d. septentrionalis have an apparent superiority over males of the two stag beetle species. The seasonal emergence patterns of the two stag beetle species at the feeding sites showed bimodal distributions, and avoided the peak of emergence in T . d. septentrionalis . My results suggest that the two stag beetle species exhibit mate‐securing tactics by emerging at the feeding sites early and late during the breeding season, in order to avoid encountering T . d. septentrionalis .