Sexual Behavior of the Horned Beetle, Allomyrina dichotoma septentrionalis (Coleoptera, Scarabaeidae)

Sexual behavior of the horned beetle, Allomyrina dichotoma septentrion-alis in plastic boxes was observed under three conditions : male-female, male-male, and female-female interactions. The courtship behavior showed the same pattern and consisted of the following five phases under any condition : approaching, abdomen shaking, mounting, licking, and abdomen bending. The male-male and the female-female courtship behavior were "homosexual" behavior. There were significant differences in the one-cycle time of abdomen shaking among the observed individuals. None of the males courted by the "homosexual" ones used their horns as weapons. The horns may be useless in preventing the courtship of "homosexual" males. Both males and females often fought against individuals of the same sex. However, none of the individuals courted by the "homosexual" ones attacked these "homosexual" ones. In A. d. septentrionalis, the "homosexual" behavior may inhibit the fighting behavior of individuals of the same sex.