Grain weevils (Stiophilus granarius) feeding on cereal grain. This weevil infests and feeds on stored grain and is a serious agricultural pest. It has a long rostrum, which is an elongated part of the front portion of the head. The tip of the rostrum contains tiny chewing mouthparts that are used to bore through the outer layer of the grain to the material within, which the weevil feeds on. The female also lay eggs in the holes she makes, ensuring a supply of food for the developing larvae. Weevils form the largest family of beetles (Curculionidae) worldwide, containing 40, 000 known species.