Adult beetles are about 1/8 inch long with skinny, flat bodies. They have saw-like projections on the prothorax, a characteristic that is easily distinguished. Mature larvae are 1/8 inch and yellow white. They are long and straight (not C-shaped like other beetle larvae) and possess functional legs.

Adult females lay hundreds of eggs in the larval food, with eggs hatching in 1 to 3 weeks depending on temperature. Development is fastest at temperatures of 86 to 95°F and the life cycle can be as short as 1 month. Adults may live as long as 3 years.

Saw-toothed and merchant grain beetles feed on cracked grains and the dust from whole grains, cereals, pasta, dried fruit, sugar, chocolate, drugs, tobacco, and many other items. Neither adults nor larvae can penetrate whole seeds or kernels. Despite that, these beetles are widely destructive worldwide and can easily get into packaging that is not airtight.