Sperm transfer in the Japanese queenless ant Diacamma sp (Hymenoptera: Formicidae)

Sperm transfer in the Japanese ponerine ant Diacamma sp. was studied by making histological sections through copulating pairs. Males of this species remain attached to the female by their genitalia for several hours, during which they are killed by the gamergate and her nestmates. Our sections revealed that males clasp the female's last sternite with two chelate appendices of the male copulatory organ, called volsellae. We also found that the male inserts his sharp sclerotised penis valves in the female bursa copulatrix, a dorsal evagination of the genital chamber. The penis is inflated inside the female genital chamber, possibly strengthening the connection between the partners. We noticed that the male transfers his sperm to the female in a sheath of gelatinous material, called a spermatophore. Eventually the male's abdomen is removed by the gamergate. Prolonged copulations are viewed as an effective male strategy to ensure unique fatherhood.