Structures and functions of the endophallic copulatory tube in the family staphylinidae (Insecta: Coleoptera)

Abstract

This paper deals with the structures and functions of the endophallic copulatory tube in Staphylinidae, which has been previously called "copulatory piece," "endophallus," "flagellum," etc. in descriptive studies. First, the general morphology of the copulatory tube and the pseudocopulatory tube is discussed, together with the characterizations and terminology. Second, the distribution of the copulatory tubes in Staphylinidae is described. Third, the structures of the seven basic and some other unique forms of the copulatory tubes in Staphylinidae are described in detail, paying special attention to those of Steninae. Fourth, the functions of the copulatory tubes in Staphylinidae are described or hypothesized, paying special attention to those of Steninae. Namely, the function of the copulatory tube is simply a "spermatophore (or sperm) depositor" in some cases (e.g., some Stenus), whereas it has double function: a "spermatophore (or sperm) depositor" and an "extension tube (or sperm) guiding rod in some other cases (e.g., some Aleochara).