The testis of Anastrepha ludens (Loew) has a special histological structure, which is different from the basic morphological arrangement. The organ consists of a single saclike follicle containing all the development zones of male sexual cells. The base of the follicle is modified as a seminal vesicle where spermatozoa mature. In the testis wall there is a peritoneal sheath of large cells, closely associated with tracheoles. The main feature of these cells is a cytoplasm full of pigment grains. The peritoneum is located on a continuous layer of muscles, not previously reported in insect morphology. There is an apical follicular epithelium supported by a thick basement membrane, and an epithelium at the base of the testis forming a chamber where the spermatozoa are released from the cysts. Most of the mature spermatozoa are inside deep folds of the basal epithelium cells.