Larder beetle adult (actual size approx. 1/4-1/3 inch)

Larder beetle adult (actual size approx. ½  inch)

Larder beetles were named for their attraction to larders where they fed on cured meats. While this situation is not common today, larder beetles can still be found in homes, where they are primarily a nuisance.

Identification
The adult beetles are dark brown with a cream-colored band across the top of their wing covers. They are about 1/4-1/3 inch in length (see fig. 1). The larvae are worm-like, fairly hairy, dark brown in color, and appear banded. They have a pair of spines on their tail end that curve backwards. Larvae reach about ½ inch in length (see fig. 2).

Biology
Adult larder beetles overwinter outdoors. It is common for them to enter homes in spring through cracks in the home's exterior. They lay eggs if they find an appropriate food source for the larvae. Both adults and larvae eat high-protein materials. Known foods include animal hides and furs, feathers, meat, cheese, dry pet foods, and dead insects.

When the larvae are full grown, they wander about, searching for a place to pupate. It is common for them to bore a short distance, about ½ inch, into wood for protection while pupating. Fortunately damage to wood is slight. Larvae may also bore into other soft materials, such as books,.

It is common for a larder beetle infestation to occur as the result of a cluster fly or face fly problem in homes or cabins. In late summer and fall, these flies seek shelter in buildings. Large numbers of these flies die in wall voids attracting larder beetles to that area the following year. Larder beetles can also feed on animal carcasses, such as a mice or squirrels, that become trapped inside buildings and die.

Control
The presence of a few adult larder beetles does not necessarily mean there is an infestation, especially if found during spring. They may have simply come in from outdoors and not be associated with a food source. Physically remove and discard larder beetles that are found. However, sightings of larvae or large numbers of adults indicates an infestation is present.

Sanitation is the first step in controlling established larder beetle problems. Clean up and remove infested food sources and make uninfested sources inaccessible to larder beetles. Store dry pet food in a metal or heavy plastic container with a tight-fitting lid. Also keep stored fur and feather items in similar containers. Store cheese and dried meats in a refrigerator. Infested materials such as dry pet food or animal pelts can be frozen at 0° F for 48 hours to kill eggs, larvae, and adults.

When flies or dead animals are the source of the infestation, it's often difficult to find and remove the food source. Larder beetles will go away on their own once the food source is eaten. If larder beetles are a problem every year, it's necessary to exclude flies and animals from the building to avoid attracting larder beetles.

To keep cluster and face flies out, seal exterior cracks prior to August and supplement this with an application of a residual insecticide (e.g. permethrin) when flies are first seen on siding, generally in August. To keep animals out, patch holes and gaps which serve as entrance points. Mice can get through holes as small as 3/8 inch wide. Keep bird feeders at least 50 feet from the house to avoid attracting rodents. Also keep vegetation well trimmed around buildings and avoid storage clutter around the foundation.

Insecticides can help control larder beetles. They are most effective in cases when infested material has been removed; larder beetles are easily controlled without an available food source. However, if a food source is still present, insecticides will only provide temporary control of larder beetles.

If an insecticide is necessary, select an aerosol or liquid ready-to-use product that is labeled for indoor use. Spray along cracks and crevices, baseboards, and in corners near the area of the infested material and where larder beetles are seen. Read all label directions carefully before buying insecticides and again before applying them. Information on the label should be used as the final authority. A reputable pest control service can also be hired to treat a home for larder beetles.

E607L
Revised 10/02, Jeffrey Hahn