Both the confused and red flour beetles are similar in appearance. Also, the confused flour beetle has a straight-sided thorax, while the thorax of the red flour beetle has curved sides. The eggs, larvae, and pupae are similar in both beetles. Eggs are whitish or colorless and microscopic in size, with food particles adhering to the sticky surface. Larvae have six legs and two-pointed or forked projections at the last rear body segment.
Pupae are white to light brown.
Within 5 to 12 days, these eggs hatch into slender, cylindrical, white larvae tinged with yellow. Fully grown larvae transform to naked pupae, and in a week adults emerge. The life cycle requires 7 to 12 weeks, with adults living for 3 years or more. Adults are very active, quickly running for cover when disturbed, and can be found either on the surface or deep within the food material. Because of their small size and shape, they can frequently invade storage containers.