Effects of azinphosmethyl, an organophosphate, and chlordimeform, a formamidine, onBracon mellitorSay, a parasitoid of Coleoptera and Lepidoptera, were studied. Both were much more toxic to adultB. mellitorthan to adult boll weevils and affected male parasitoids more severely than females. At low doses, both insecticides reduced the number of eggs deposited on boll weevil larvae. These effects were more severe with chlordimeform exposure. Up to 4 days after initial chlordimeform exposure,B. mellittorparalyzed, but did not oviposit on most hosts. Chlordimeform doses below the LC50also caused females to imbibe honey water to such extent that the abdominal cuticle was distended and split.