The confused flour beetle and the red flour beetle, also known as bran bugs, occur throughout the world. The red flour beetle tends to be a southern species, while the confused flour beetle is more common in the northern US. These two species have very similar life histories and are very difficult to tell apart. They are included in the group of Other Live Insects under the federal grain inspection standards.
These beetles fed on flour, fines or broken kernels of many different grains, so they are secondary pests. They also can feed on dried fruits, spices, dried plants, and a variety of other stored products.
Flour beetles can turn flour gray. Their metabolic activity can produce moisture in the grain, causing hot spots and mold growth.
Adults may live for up to 3 years and can be active throughout the winter if the temperature is warm enough. Females lay 2 to 3 small, white eggs per day, a total of about 300 to 400 during their life time. The eggs, which hatch in about 9 days, are laid indiscriminately throughout the food source.
The larva is creamy white to yellow with a dark head. There are a pair of sharp points at the tail end of its body. The number of larval instars varies from 5 to 8. Larval development varies from 22 to 100 days depending upon temperature and type of food. Adults emerge after an 8 day pupal period. The entire life cycle takes about 7 weeks at room temperature.
Red flour beetles are good fliers, confused flour beetles are not. Both are attracted to light.