The Rice Weevil, a Stored Product Pest


Adult rice weevils (approximately 1/8 inch long) are easily recognized by their long snout and by the four pale spots on their wing covers. Rice weevils typically infest whole kernel foods, such as corn or Indian corn.

Rice weevils, Sitophilus oryzae, are dark, reddish brown beetles and can be identified by the presence of a pair of large, pale spots on each wing cover. The faint spots can be highlighted by slight moistening of the wing covers. Notably, the weevil’s body is covered with small, round pits or indentations. As is common in weevils, they also have a long snout (Figure 4). The larvae generally require a food source with a hard or semihard coating in which to develop properly (e.g., corn kernels, rye, barley, cereals, wheat, dried peas, beans, nuts, bird seed, or rice). Adult female weevils lay eggs in whole kernel grains, such as corn, by first chewing a small depression in the kernel, depositing an egg in the depression, and then sealing the egg inside with a gelatinous plug that they produce. When the larva hatches from the egg, it starts consuming the inside of the kernel. The larva continues to feed and grow inside the kernel. All larval stages of the beetle are spent inside the kernel, obscured from the naked eye. The last larval instar pupates, and the adult weevil emerges from the kernel several days later, leaving a small, round hole in the kernel. Like drugstore beetles, rice weevils can be found both in food and nonfood areas of homes because of their mobility (adults readily fly) and the variety of items they are capable of infesting, including decorative items containing grains and nuts. Adults are long-lived (3 to 6 months) and feed on a wider variety of items than larvae. They sometimes play dead when disturbed.

“Stored Product Pests in the Home” is a production of the Department of Entomology and Plant Pathology, University of Georgia. The original authors of this content are Daniel R. Suiter, Michael D. Toews and Lisa M. Ames.
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