[Illustration: Fig. 96.--Diagram to show the theoretical (upper figure) and actual position of the hinder abdominal sterna in the female Cockroach. _U_, uterus; _s_, spermatheca. The nerve-cord is introduced into both figures.] The external reproductive organs of the female Cockroach belong to the 7th, 8th, and 9th somites. The 7th sternum is incompletely divided into anterior and posterior sections, and the posterior section is split into lateral halves. These are joined by a flexible membrane, which admits of the wide separation of the halves, when copulation or the passage of the large egg-capsule renders it necessary. The vertical faces of the membrane, which are pressed together when the parts are at rest, are stiffened by chitinous thickenings. If the succeeding sterna retained their proper place, as they do in some Orthoptera (_e.g._, the Mole Cricket), the 8th and 9th sterna would project beyond the 7th, while the rectum would open beneath the last tergum, and the uterus between the 8th and 9th sterna. In the adult female Cockroach, however, the 8th and 9th somites are telescoped into the 7th, and completely hidden by it. Their terga are reduced to narrow bands. The 8th sternum forms a semi-transparent plate which slopes downwards and backwards, and is pierced by a vertical slit, the outlet of the uterus. The upper edge of this sternum is hinged upon the projecting basis of the anterior gonapophyses (to be described immediately), and the parts form a kind of spring joint, ordinarily closed, but capable of being opened wide upon occasion. The 9th sternum is a small median crescentic plate, distinct from the 8th; it supports the spermatheca, whose duct traverses an oval plate which projects from the fore-edge of the sternum. [Illustration: Fig. 97.--Hinder end of abdomen of female Cockroach. In the upper figure the halves of the 7th sternum are closed; in the lower figure they are open.] By the telescoping of the 8th and 9th somites the sterna take the position shown in fig. 96_B_, and a new cavity, the genital pouch, is formed by invagination. This receives the extremity of the body of the male during copulation, while it serves as a mould in which the egg-capsule is cast during oviposition. Its chitinous lining resembles that of the outer integument. The uterus opens into its anterior end, which is bounded by the 8th sternum; the spermatheca opens into its roof, which is supported by the 9th sternum and the gonapophyses; while its floor is completed by the 7th sternum and the infolded chitinous membrane.