grain weevil, (species Sitophilus granarius), insect of the family Curculionidae (order Coleoptera), a common pest of stored grain. This small brown weevil is about 3 to 4 mm (0.1 inch) long. The female bores a hole in an individual cereal grain and implants an egg in it. The fleshy white larva feeds on and then pupates inside the grain, which may be of dried corn (maize), oats, wheat, or allied plants. The adults also feed on cereal grains. When disturbed, the adult weevils feign death.