Copulatory courtship and genital mechanics of three species ofMacrodactylus(Coleoptera Scarabaeidae Melolonthinae)

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Abstract
Female Macrodactylus costulatus, sericinus, and sylphis mated repeatedly while feeding on flowers and fruits as they matured eggs. Courtship in all species occurred both prior to and following intromission, with most courtship being performed after the male had achieved intromission. Females often prevented males from mounting, and often prevented mounted males from achieving intromission. They also probably often prevented male genitalia from penetrating past the vulva, even after they had allowed them into the genital chamber. Males at least sometimes pushed forcefully at structures both on the surface of the female and within her reproductive tract. Copulation probably involved a combination of force and persuasion. It often failed to result in complete transfer of sperm. Males displayed striking virtuosity in both the morphology and behavior of their genitalia, which assumed at least four different morphological configurations. At least five and perhaps up to eight different functions were performed by male genitalia. Small sacs near the tips of the male parameres were probably used by males as “foot-in-the-door” devices to gain access to the female's genital chamber, while the spiney collar and tongue may have helped open the vulva to allow deeper penetration. The energetic and persistent courtship which occurred after intromission was achieved may lunction at least partly to induce the female to allow the male to reach the deeper stage of penetration necessary for spermatophore formation, and perhaps to permit transfer of sperm to her spermathecal duct. Male courtship behavior included movements of his head, vibration and sweeping movements of his middle legs, rubbing with his abdominal bristles against the female's elytra, strong substrate vibrations of unknown origin in the male's body, and tapping and stroking with his genitalia on the external surface of the female's abdomen while he held her with his specialized front legs. Pairings in the field lasted up to several days, but there was no sign of size biases in either paired males or females. Males were more susceptible to predation by a common predator than were females when beetles were paired.