Abstract.Dissection of the ovaries of the mosquitoAedes aegypti(Diptera: Culicidae) revealed, in each ovariole, a group of seven to nine specialized epithelial cells in a region of the calyx wall that is enclosed by the end of the ovariolar sheath. This group of cells is termed the basal body. During ovulation, the mature oocyte passes from the ovariole into the calyx lumen through the basal body. Subsequently, granulation occurs in the basal body cells. The granular basal bodies differ from all previously described ovarian structures. In multiparous females the size and optical density of the granular basal bodies increase after each ovulation. Examination of the granular basal bodies in intact ovaries, stained with neutral red, provides an easy method for distinguishing parous from nulliparous females, and has potential as a new method of age grading.