Copulatory Mechanism Of Terrobittacus Implicatus And Bittacus Puripennis

Mating behavior is vital for sexual reproduction in insects.The elaborate genitalia play an important role in the success of sperm transfer in mating behavior.Insect genitalia have rapidly evolutionary rate and show the rapid divergent evolution in sexual conflict.However,the studies on the functional morphology of male genitalia and copulatory mechanism are far from satifactory thus far.Bittacidae in Mecoptera are commonly known as hangingflies.The Bittacidae have interesting nuptial feeding behavior and assume a unique belly-to-belly hanging mating position.However,limited research was focused on copulatory mechanism and functional morphology of Bittacidae.In this study,the mating behavior and copulatory mechanism of hangingflies were investigated by the observation of intersexual behaviors in Terrobittacus Tan&Hua,2009 and Bittacus Latreille,1805 in combination with light and electron microscopy.We have revealed the functional morphology of hangingfly genitalia,compared the differences in the mating behavior and copulatory mechanism among different genera of Bittacidae.The hangingfly Terrobittacus implicatus(Huang&Hua,2006)was investigated for its mating behaviors and functional morphology of the small epandrial lobes.It is the first behavioral study of the genus Terrobittacus.The male provides a prey as a nuptial gift to the female and twists his abdomen about 180~o to form a belly-to-belly hanging mating position.During the penisfilum-entering process,the male epandrial lobes clamp the female subgenital plate with the aid of the female abdomen swelling.Then the male locates the female copulatory pore through his upper branch of proctiger,and inserts his penisfilum into the female spermathecal duct in the cooperation of the short setae on the groove of proctiger.The female subgenital plate where the epandrial lobes clamp is strongly sclerotized and melanized.The copulatory mechanism of Terrobittacus is briefly discussed.Based on the observation of the courtship and copulation behaviors in Bittacus puripennis Cai&Hua,2006,we investigated the functional morphology of genitalia and copulatory mechanism.The results show that,similar to the mating behaviors of other hangingflies,the male of B.puripennis also provides a live arthropod as a nuptial gift to the female during mating and assumes a belly-to-belly hanging mating position.The translucent upper branch of male proctiger can closely grasp the female abdomen.The curved direction of lower branch of proctiger and aedeagal lobes is opposite.The lower branch of proctiger and aedeagal lobes can closely contact during mating to ensure that the male penisfilum fully enters the female spermathecal duct.Our study also found that the male B.puripennis has a prey-stealing behavior.Having compared the mating behaviors between T.implicatus and B.puripennis,we found that the mating behavior are distinctive between different genera.The copulation duration of T.implicatus is longer than that of B.puripennis.Due to the difference morphology of epandrial lobes,the way of male abdomen twisting and the degree of sclerotization of female subgenital plate are different between T.implicatus and B.puripennis.