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GRANARY WEEVIL
COMMON NAME: Granary weevil
SCIENTIFIC NAME: Sitophilus granarius (Linnaeus)
CLASS / ORDER / FAMILY: Insecta / Coleoptera / Curculionidae
METAMORPHOSIS: Complete
  
 
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INTRODUCTION. This particular weevil has been a dominant pest for many centuries. It occurs worldwide primarily in cooler climates. In the United Stales, it is usually found breeding from, and including, North Carolina northward.
RECOGNITION. The adults are about 1/8-1/4” long. Their color is usually a shining reddish brown but sometimes it is nearly black. The elytra (wing covers) have no pale markings. Punctures or pits on the thorax are elongated. The wings are vestigial (greatly reduced) and the insect cannot fly. The male's snout / beak is shorter, wider, and has more distinct punctures than that of female's.
The larva are legless and are white in color with a dark head. Thickened in middle (humpbacked), relatively smooth. Labial palp with less than 7 (usually 5) apical sensory palpillae (tiny fingerlike projections).
BIOLOGY. The granary weevil female bores a hole into a kernel of grain and lays an egg, sealing the opening with a gelatinous material. The egg hatches in a few days and the larva feeds on the internal portion of the kernel. A female can lay more than 200 eggs under favorable conditions (range 36-254). There are 4 larval instars which require 19-34 days for development. Pupation occurs within the kernel and requires 5-16 days. The entire life cycle (egg to egg) may be as short as 1 month during the summer or as long as 5 months during the winter, being very dependent upon the temperature. There are usually 4 generations per year. The adults can live for 7-8 months.
HABITS. Because its wings are vestigial, the granary weevil is confined to stored grain and is primarily transported by man. The larva typically requires a whole kernel for development but can develop in caked grain material. It attacks all kinds of grains and grain products. When disturbed, it draws its legs up to its body and plays possum."
Adults are not attracted to light.
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