Caraphractus cinctusis an arrhenotokous mymarid parasitizing the eggs of Dytiscidae under water. In the newly emerged female only fully formed eggs are present in the ovaries and the earlier stages of ovarian development have been studied in the pupa. The two ovaries each contain from 10 to 20 ovarioles depending upon the size of the female. The two lateral oviducts unite to form the vagina which is bent upon itself when laying is not in progress. The eggs are stored in the ovarioles and the female has remarkable control over the deposition of the eggs, since in most cases she rejects host eggs already parasitized, after probing them with her ovipositor. The spermatheca is a rigid capsule and the spermathecal duct at its base has a deep U‐shaped bend. There is a large spermathecal gland opening by its own duct into the spermathecal duct after the bend. The poison apparatus is well developed though the female does not kill the egg or paralyse the embryo host. The poison gland is of unusual shape being compact and rounded distally instead of tubular. Dufour's gland is large and buoyant. The ducts of both glands lead to the base of the ovipositor. The possible effect of their secretions in rendering a once parasitizedAgabusegg generally unacceptable for further laying is discusse