Ventral receptacle in the genus Trichocera: A case of parallel evolution between remote lineages of the Diptera (Diptera: Nematocera: Trichoceridae)

The paper deals with female reproductory system in the Diptera and describes the first case of the ventral receptacle among the Nematocera in the family Trichoceridae. The receptacle is a sperm storage organ alternative to the spermathecae, and was till now described in Brachycera: Schizophora. Herewith, the receptacle appears in a small group of species which present the different stages of evolution from the spermathecae to the receptacle within the genus Trichocera Meigen. The group was formerly known as a rectistylus group of species; herein it is raised to the subgenus level. Three new species are described.The ventral receptacle is a unique character within the genus and the family, whose all species have spermathecae and a similar morphology of the female inner and outer genitalia. Other accompanying modified structures in females of the new subgenus include strongly reduced genital plate and genital fork, and changed shape of the genital segment. Two species show possible evolutionary transition states from the plesiomorphic state of three spermathecae to a new sperm storage system: one new species has both the spermathecae and the receptacle, whereas another, Trichocera polanensis Starý, has three poorly sclerotized spermathecae.