Comparative studies of ovarian histopathology and the mating behaviour of Periplaneta americana, Linn. (Orthoptera) treated with sublethal concentrations of BHC and DDT.

Cockroaches are familiar pests of grain stores. They are prolific breeders and can also transmit various diseases. Adult females were therefore treated with sublethal BHC and DDT concentrations to control their fecundity and viability. Ovulation was arrested as a result of damage to and resorption of the terminal oocytes. Histopathological changes were clearly expressed in the follicular epithelium of pathological oocytes and also in immature oocytes. Vitellogenesis was arrested and protein yolk precursors were broken down and destroyed by the pycnotic follicular epithelium. Fibrosis and thickening of the tunica propria gradually diminished. Prolonged treatment resulted in atrophy of the ovaries, together with a large number of immature and pathological oocytes. Since the effect of DDT is cumulative, the histopathological changes it caused were severer than those induced by BHC. Treated adults kept in pairs showed prolonged duration of mating, followed by a 2-3 days' delay in ootheca formation; no first instar nymphs emerged from these oothecae, however, owing to the failure of fertilized eggs to develop any further in the oothecal lumen.