Abstract
Male giant water bugs (Abedus herberti Hidalgo) brood eggs attached to their backs by their mates. Brooders risk being "cuckolded" because females store sperm from previous matings. Males always copulate with females prior to receiving their eggs and mate repeatedly during oviposition. Experiments with a genetic marker reveal almost complete sperm precedence for the last male to mate with a female. The male's behavior therefore assures his paternity of the eggs he broods.