It is difficult to separate these two beetles. Under magnification, the sawtoothed grain beetle has exposed eyes, whereas the merchant grain beetle has the eyes more protected by small knobs behind the eyes. Also, the head is more triangular in the merchant grain beetle. Males can be separated from females by observing a tooth on the femur of the hind leg. Eggs, larvae, and pupae of both beetles are similar.
Eggs are white, microscopic, and elongated.
The head is brown with three pairs of legs. The pupal case is a capsule of glued foodstuff fragments. Both beetles lay eggs singly or in small batches in the food material where the life cycle is completed. The sawtoothed grain beetle cannot fly, but the merchant grain beetle can fly. Adults usually live about 6 to 10 months, with some living as long as 3 years and 3 months.