The most familiar stage of the larder beetle (Dermestes lardarius) is the adult. These beetles are up to 9 mm (a third of an inch) long, dark brown to black with a prominent greyish-yellow band roughly across the middle of the body.
Although they are capable of flight, adults are commonly found trapped in a cooking pot or a sink, where the sides are too slippery to escape.
The worm-like larval stages grow up to 13 mm (half an inch long), are dark brown on top with spiky hairs and a pair of short spines at the tail end.
The Problem
Larder beetle females fly in from outdoors during May and June and lay their eggs on or near available food items which may be provided by fat splashed from the back of the stove, grease deposits in a fume hood, spilled food, a bag of dog food, a dead mouse or an accumulation of dead flies in a ceiling light fixture.
Adult beetles eat similar food materials as their young, preferring animal protein, fats and animal skins including dead insects, feathers and woollen materials.
What You Can Do
Beetles that are seen can be caught by hand and killed. Cheese can be used as a bait.
Eliminate food sources, including the removal of old bird nests close to the home and cleaning dead insects from light fixtures, baseboards and windowsills. Seal insect entry points into the house. Vacuum often. Larder beetles in dry pet foods can be killed by heating to 50 degrees Celsius for at least half an hour or by freezing for several days.
If infestations persist, consider the use of crack and crevice applications of diatomaceous earth, a low toxicity insecticide dust that provides effective long-lasting control of these insects.