Stored Grain Insects



Confused Flour Beetle

Tribolium confusum



Adult confused flour beetle (Tribolium confusum)
Courtesy of Degesch Inc.

The confused flour beetle (Tribolium confusum) is red-brown in colour and about 3-4 mm in length. The confused flour beetle was named because of the confusion over its identity. It resembles the rust-red flour beetle, except for the antennae which is four segmented and gradually thickens towards the tip. Another slight difference is in the shape of the thorax. The sides of the rust-red flour beetle are curved, whereas the thorax of the confused flour beetle is straighter. It has well developed wings but seldom flies. When agitated or crowded, they may secrete chemicals called quinones. These chemicals can cause the infested feed to turn pink and have a pungent odor. Confused flour beetles have been reported to prefer and aggregate in flour exposed to quinones. The larvae are a light honey colour and about 6 mm long. The head and a distinctive forked process at the tip of the abdomen are slightly darkened.


Developmental stages in confused flour beetles
Courtesy of Degesch Inc.

Life cycle
Average fecundity is 400 - 500 eggs per female, with peak oviposition occurring during the first week. Adults may live longer than 3 years, and females may lay eggs for more than a year. Eggs are deposited directly in flour, other food material, or attached to the surface of the container. They are white or colorless and covered by a sticky material to which flour can adhere. Eggs hatch in 3 - 5 days at 32 - 35?C. Larvae burrow into kernels of grain but may leave their burrows in search of a more favorable food. There are 5 - 11 larval instars (7 - 8 is usual); the variation a result of environment, food, temperature, humidity, or the individual insect. Larvae are fairly active but generally hide within the food, away from light. The pupae are naked, without protection of any form. Development time from egg to adult varies with conditions, however the average is 26 days at 30 - 33?C and >70% rh. Limits of development are imposed mostly by larval mortality, especially among early instars.

Damage caused by confused flour beetles
Courtesy of Degesch Inc.

Confused flour beetles can be found infesting a variety of grain and food materials. They have been reported in grain, flour, and other cereal products, beans, cacao, cottonseed, shelled nuts, dried fruit, dried vegetables, drugs, spices, chocolate, dried milk and animal hides. They cannot feed on whole grain, but can feed on broken kernels that are usually present. In general, fungi may play a significant role in the nutrition of confused flour beetles.

Confused flour beetle
? Agriculture Western Australia

Grain insects are declared under the Agriculture and Related Resources Protection Act. Limited chemical controls are available to farmers and emphasis is placed on clean hygienic storage and cleaning of machinery. Farmers are encouraged to purchase and maintain sealed farm silos to increase the effectiveness of fumigation.