Reproductive morphology, copulation, and inter-populational variation in the diamondback moth, Plutella xylostella (L.) (Lepidoptera : Plutellidae)

Copulatory mechanisms and internal reproductive systems of male and female Plutella xylostella (L.) were investigated. Both male and female specimens exhibited characteristics typical of ditrysian Lepidoptera, with some pecul iarities. Female structures appear to be relatively simple: the bursa copul atrix lacks cuticular signa within, the spermatheca lacks lagenar arms exhi bited in some Lepidoptera, and colleterial glands have secretory system and reservoir combined. Male accessory gland ducts are joined distally, a cond ition that has not been described in other Lepidoptera. Genitalia of both s exes appear simple; females possess a posterior cuticular extension of abdo minal sternites that houses the bursal duct and accomodates the needle-like aedeagus of a male during copulation. Despite the apparent simplicity, con figuration of genitalia is highly specific in shape, angle, and size, which is likely to be important in maintaining reproductive isolation within the species. However, a population of P. xylostella from Australia showed some modification to both aedeagal and bursal structures. These variations sugg est some important implications for considering species with worldwide dist ributions. (C) 1999 Elsevier Science Ltd. All rights reserved.