Over a period of about 3 weeks the female Biscuit beetle will lay, singly, about 100 eggs, either in the foodstuff or in the surrounding areas. At 19-24'C they hatch in 1-2 weeks to produce very tiny, active larvae which wander about and may penetrate packaging to infest the foodstuffs inside. Development takes 2-5 months, during which time the larvae go through four moults to reach a full-grown length of 5mm Eventually they become incapable of movement and construct cells of food particles and saliva in which to pupate. The pupal stage lasts 9-18 days, but the adults may then remain in the cocoons for up to two weeks before emerging. on emergence, the adults disperse, living (without feeding) for up to 8 weeks.
Stegobium paniceum is a pest of cereal products, e.g. flour, bread, breakfast cereals, spices, beverage concentrates and even drugs - indeed there have been reports of it infesting poisonous substances such as strychnine, belladonna and aconite. infested products may lose value or cause contamination of other products and packaging may be damaged, the larvae reputedly being able to penetrate tinfoil and sheet lead. Books and manuscripts may also be attacked.