Internal, abdominal structures used for reproduction
In the Schizophora, the abdomen of sexually mature females is taken up mainly with the paired ovaries, filled with eggs. Short oviducts start at the ovaries and unite to form the common oviduct. The common oviduct opens into the vagina. Dorsally two spermathecal ducts and the ducts of the paired accessory glands open on the genital papilla into the vagina. In the schizophoran stem-species pattern there are three spermathecae (Downes 1968, Hennig 1973, J. F. McAlpine 1989). However, the number of spermathecae was frequently reduced to two. The spermathecae consist of a sclerotised capsule surrounded by epithelial gland cells (Kotrba 1993). In the ventral wall of the vagina, opposite the genital papilla, there is an unpaired ventral receptacle in several acalyptrate families (Sturtevant 1925-1926, Kotrba 1993). Like the spermathecae, the ventral receptacle functions as a sperm reservoir. When an egg passes through the vagina, the micropyle is placed next to the entrance of the receptacle and insemination takes place. 
In Milichiidae the ventral receptacle is followed posteriorly by an epithelial pad of unknown function. (ex Brake 2000)