Flour Beetles

Tribolium confusum and Tribolium castaneum

Red and confused flour beetles attack stored grain products such as flour, cereals, meal, crackers, beans, spices, pasta, cake mix, dried pet food, dried flowers, chocolate, nuts, seeds, and even dried museum specimens. These beetles have chewing mouthparts, but do not bite or sting. The red flour beetle may elicit an allergic response, but is not known to spread disease and does not feed on or damage the structure of a home or furniture. These beetles are two of the most important pests of stored products in the home and grocery stores. The confused flour beetle apparently received this name due to confusion over about its identity as it is so similar to the red flour beetle at first glance.

The red flour beetle is of Indo-Australian origin and is found in temperate areas, but will survive the winter in protected places, especially where there is central heat. In the United States, it is found primarily in the southern states. The confused flour beetle, originally of African origin, has a different distribution in that it occurs worldwide in cooler climates. In the United States it is more abundant in the northern states.

Although small beetles, about 1/4 of an inch long, the adults are long-lived and may live for more than three years.

The red flour beetle is reddish-brown in colour and its antennae end in a three-segmented club. Whereas the confused flour beetle is the same colour but its antennae end is gradually club-like, the "club" consisting of four segments.

The red and confused flour beetles live in the same environment and compete for resources. The red flour beetle may fly, especially before a storm, but the confused flour beetle does not fly. Eggs, larvae, and pupae from both species are very similar and are found in similar environments. The eggs are white, microscopic and often have bits of flour stuck to their surface. The slender larvae are creamy yellow to light brown in colour. They have two dark pointed projections on the last body segment.

These beetles can breed throughout the year in warm areas. The life cycle takes from 40 to 90 days, and the adult can live for three years. All forms of the life cycle may be found in infested grain products at the same time

The red and confused flour beetles may be present in large numbers in infested grain, but are unable to attack sound or undamaged grain. The adults are attracted to light, but will go towards cover when disturbed. Typically, these beetles can be found not only inside infested grain products, but in cracks and crevices where grain may have spilled. They are attracted to grain with high moisture content and can cause a grey tint to the grain they are infesting. The beetles give off a displeasing odour, and their presence encourages mould growth in grain.

Keep in mind that these beetles may infest areas other than the pantry. Be sure to inspect spices, pet food, and flower arrangements. Also keep in mind that some stuffing in furniture or stuffed animals may have natural products that these beetles could feed on. Also be aware of areas in which any of these products may have spilled, like under the refrigerator or stove. These beetles are able to locate very small bits of food. Once all of the infested material has been removed, be sure to vacuum and clean up the area around the infestation. If you have shelf paper, it would be wise to remove it, thoroughly clean under it with soap and hot water, and replace it with new paper. Be sure to pay close attention to the cracks and crevices of any cabinets. To prevent re-infestation, all grain products should be stored in containers with tight fitting lids, or stored in the freezer. Also consider where the infestation came from. It is likely that you could have a re-infestation by purchasing infested grain products from the same business. When shopping, look for those "leaky packages". If you suspect a beetle infestation, don't buy the product.