Grain weevil. Coloured scanning electron micrograph (SEM) of the head of a grain weevil (Sitophilus granarius). This beetle infests and damages stored grain, using the mandibles at the end of its elongated snout, or rostrum, to cut through the shell of a wheat grain and gain access to the food within. Females lay their eggs inside wheat grains, so that their larvae can have a food supply. It can be controlled using fumigants. The grain weevil measures about 3-4mm long.