Up to 450 eggs are laid singly at a rate of 2-10 per day, depending on temperature. The white eggs are sticky and rapidly become coated with food particles and other debris. At 22-27 'C they hatch in 6-14 days. The larvae are white tinged with yellow and pass through 5-11 moults before reaching a full-grown length of 5mm This process takes 3-9 weeks. Pupae lie naked in the same foodstuff as the larvae. They are initially white, but gradually darken in colour prior to adult emergence after 9-17 days. Adults feed on the same food as the larvae and live for 15-20 months. There may be five generations per year.
Flour beetles are generally recognised as secondary pests of grain and therefore increase the feeding damage done by primary pests. When present in large numbers, flour beetles will:
1. Cause flour to become prone to moulding and will also turn the product grey;
2. Taint commodities with secretions from scent glands.