The male reproductive organs of the western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) consist of testes, deferent ducts, seminal vesicles and accessory glands. The first 3 have intermediate muscle fibers and pigment cells external to the epithelium, but the accessory glands do not show these cells. The accessory gland cells are engaged in active secretion into the ejaculatory bulb where the spermatozoa are stored. The epithelial cells of the ejaculatory bulb are involved in secretion and osmoregulation. An ejaculatory duct arising from this bulb posteriorly runs the length of a fusiform structure before entering the phallus. This latter consists, from front to back, of: (1) a dorsal phallobase, containing cells with large intercellular lacunae; (2) a medial phallotheca, whose cavity may be filled with hemolymph when the phallus is protruded at mating or with endothecal cuticular folds when the phallus is at rest; and (3) a ventral ductus conjunctus containing spermatozoa. This duct is invaginated ventrally into the phallotheca at the posterior end of the copulatory organ. Contractions of a series of abdominal muscle fibers may convey the hemolymph from the phallobase lacunae to the endotheca, causing the latter to evaginate.