Large numbers of small, brown, hairy larder beetle larvae often appear suddenly in the spring, alarming homeowners. Larder beetles attack all products of animal origin, including feathers, horn, skins, ham, bacon, dried beef, hides, hair, beeswax, and similar products. In recent years, they have been found in increasing numbers in dry pet foods containing a mixture of cereal and animal products. Adult beetles are occasionally found on flowers, where they feed on pollen.

Description:

The adult is a small, black beetle, 6 to 9 mm (1/4 to 1/3 inch) in length, with a pale, yellowish-brown to reddish band across the anterior half of its wing covers. On this band are six black dots, three on each side of the middle line. The larder beetle larva tapers towards both ends and may reach 16 mm (5/8 inch) when fully grown. The larva has a brown, hairy body, white undersurface, and two short, curved stiff spines on the top of the last abdominal segment.

Life Cycle:

Larder beetles usually enter homes in May and June seeking food on which to deposit their eggs. If no food can be found, the beetles deposit their eggs in cracks and crevices about the pantry and other areas where the larvae will be able to find food. Larder beetles frequently follow heavy cluster fly infestations, as the beetles readily feed and lay their eggs on the fly carcasses. Large numbers of nearly full-grown larder beetle larvae consume the last of the cluster flies or other food upon hatching, work their way out of the partitions in the house, and wander about, ending up in sinks, tubs, bureaus, beds, etc. This invasion can last from two to four weeks. Similar problems can result from mice, birds or squirrels nesting in the walls. Under favorable conditions, there may be more than one generation per year. The larder beetle can complete its life cycle in 40 to 50 days.

Control:

• Controlling cluster flies is often helpful in reducing larder beetle infestations (see URI Greenshare Factsheet on cluster flies). Seal baseboards and other possible openings into attics and partitions.
• Keep smoked meats in cold storage. Farm-cured meats should be carefully wrapped in cloth or paper immediately after smoking.
• Store all meat products in sealed containers.
• Catch the beetles and larvae by hand and destroy. Use cheese as a bait to trap the beetles.
• Infestations in dry pet food may be controlled by heating to 135 degrees F for 30 to 45 minutes or by freezing for several days. Microwaving should be equally effective.

Adapted from G.R. Nielsen, University of Vermont Extension, 1999