Morphological association between spermatophores and male genitalia in carabid beetles of the tribe Pterostichini (Coleoptera: Carabidae).

A morphological association between genitalia and ejaculates could provide insight into the function and evolution of genitalia. In this study, the morphologies of the ejaculates and male genitalia of 15 species of Pterostichini and two species of Platynini (Coleoptera: Carabidae) are described. All the species examined formed a spermatophore, the morphology of which could be classified into three types based on its relative volume in the female vaginal cavity and the presence or absence of a pluglike conformation. Male genital morphology could be divided into two types by the direction of the endophallus and gonopore. Species with a strongly bent endophallus invariably formed a pluglike spermatophore. The results suggest that the peculiar shape of endophallus found in some species of Pterostichini may function in forming the pluglike structure of the spermatophore.