Sexual behavior in the Japanese beetle, Popillia japonica, and comparative notes on sexual behavior of other scarabs (Coleoptera: Scarabaeidae)

The majority of pairs of Popillia japonica follow the same sequence of sexual behaviors: The male approaches the female, mounts her, intromits, withdraws his genitalia, and remains mounted on her. “Mounted courtship,” that is, courtship exhibited while a male is mounted on the female, also occurs in this beetle. The mean duration of copulation was 132.5 sec for 33 pairs. The leg positions of P. japonica males mounted on females were generally consistent among individuals but varied considerably from those of other scarabs. Males remained mounted on females for up to 2 hr after copulation. Popillia japonica is polygamous in the laboratory and exhibits homosexual behavior. Males comprised 60% of field-collected adults. Sexual and related behaviors, sex ratios, and mating systems are variable in the Scarabaeidae.