Granary Weevil

Sitophilus granarius, commonly known as the granary weevil, is a cosmopolitan pest of stored grain, belonging to the family Curculionidae, order Coleoptera. Adults are reddish-brown to black, elongated-oval, hard-bodied beetles, 3-4 mm in length, characterized by a prominent, slender snout (rostrum) and pitted thorax. They are flightless, lacking functional hind wings. Larvae are legless, white, C-shaped grubs, found entirely within grain kernels. Pupae are also found within the kernel. Eggs are minute and white. The life cycle typically takes 30-40 days at optimal conditions (28-300C, 70% RH), but can extend to several months in cooler temperatures. There can be multiple overlapping generations per year.

Granary weevils are primary internal feeders, with the entire larval and pupal development occurring within a single grain kernel (e.g., wheat, corn, rice, barley). The female weevil chews a small hole in a grain, deposits an egg, and then seals the hole with a gelatinous plug. Larvae consume the endosperm, hollowing out the kernel. Adults also feed on grain, chewing small, irregular holes. They are relatively long-lived, up to 7-8 months, and can survive on very low moisture content grains. Dispersal is solely passive, through infested commodities, as adults cannot fly.