Flour Beetles

Flour beetles are pests of flour and cereal products. They are among the most important pests of flour and stored products. They are common in homes and grocery stores. They also infest mills and food processing facilities.

Two of the most common flour beetles are the confused flour beetle, Tribolium confusum (duVal), and the red flour beetle, Tribolium castaneum (Herbst). These are small beetles. The adults are about 1/8” long. They are reddish brown in color. There are differences between the antennae of these two beetles. Since these insects are so small, it usually requires a magnifying glass to recognize these differences.

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The red flour beetle originally came from Asia. In the United States it is most common in the south. The red flour beetle is a good flier.  It sometimes flies from fields into buildings.

Some people suspect that the confused flour beetle got its name from being confused with the red flour beetle. The confused flour beetle originally came from Africa. In the United States it is more common in the northern states. Although it has wings, no one has ever reported seeing it fly.

The flour beetles are a large group of insects. Some of the other flour beetles are the black flour beetle, the false black flour beetle, the broad-horned flour beetle, the slender-horned flour beetle, the depressed flour beetle, the small-eyed flour beetle, and the longheaded flour beetle. These do not occur as often as the red and the confused flour beetles.

Flour beetles do not attack whole grains. The female beetle deposits eggs directly on flour, cereal, dry pet food, or other similar product.  The females deposit a few eggs each day in the food that she is eating. The egg laying can last several months. The eggs are hard to see in flour or meal.

Adult flour beetles can crawl into packages that appear to be sealed. Infestations can easily spread from one product on a shelf to several different products. People can transport infested products from place to place. As they eat, the beetles cause flour to become discolored and develop a disagreeable odor.

The larvae hatch and begin to eat the material where they hatched. The larvae are about ¼” long. Flour beetles can develop from egg to adult in as little as seven weeks.    In warm environments, there can be 4 or 5 generations per year.

Controlling flour beetles starts with a thorough inspection. Every infested package should be thrown away. Vacuum the pantry and cabinet shelves. This will remove food particles. Store new food products in sealed containers to prevent new infestations.

Insecticide application is the last step. The insecticide should go into cracks and crevices. The object is to eliminate any flour beetles that may be hiding. The crack and crevice application requires special application equipment. It is advisable to call a pest control professional.