Coadaptation of male aedeagal filaments and female spermathecal ducts of the old world Phlebotomine sand flies (Diptera : Psychodidae)

The morphology of insect genitalia is often highly species-specific, and it s variation has been suggested as an important impetus for evolution. Struc tural variation of the male genitalia and the female spermathecae in Phlebo tomine sand flies is unique among the blood sucking Diptera. We describe th e fine structures involved in mating for Phlebotomus papatasi (Scopoli). Re lationships among the length of the spermathecal duct and aedeagal filament were studied in 26 species of Old World phelebotomine sand flies comprisin g 12 subgenera. In most tara the aedeagal filaments were very long allowing direct insemination into the spermathecae, indicating that intrasexual com petition among males occurs as sperm precedence. There was a positive corre lation between the lengths of the spermathecal ducts and aedeagal filaments , indicating that an evolutionary "arms race" occurs between males and fema les over the control of fertilization The pattern of genitalia variation in phlebotomine sand flies also indicated that differences in the lengths of the spermathecal ducts and aedeagal filaments are distributed unevenly amon g closely related species. Genital differences do not seem to occur in popu lations of the Phlebotomus argentipes Annandale & Brunetti complex, whereas differences showed strongly in closely related Phlebotomus papatasi and P. bergeroti Parrot, and in sympatric Phlebotomus martini Parrot and P. celia e Minter.