Adult : Reddish-brown, 3-4mm, antennae gradually enlarged towards the tip, flightless adult (T. confusum), reddish-brown, 3-4mm, elongate body with antennae with enlarged last three segments, able to fly (T. castaneum).

Eggs (300-400), larvae are brownish-white, 13mm long. Entire life cycle takes between 1-4 months.

Both beetles look very similar and share similar habits. They are very common pests infesting many flourmills, warehouses, and grocery stores, also feeding on grain, beans, dried fruits, nuts, chocolate, and other foods in the house. They can also enter homes through infested flour and can build up into large populations on food accumulations in cabinet cracks and crevices and in furniture.