Once again the larder beetle is on the move inside infested houses. This means homeowners are finding the brown larvae or the black adults crawling throughout the house. The larder beetle is a very common and widespread household insect pest and is especially abundant in houses with an attic fly problem.
The larvae and adults feed on items such as fur, hair, hides, feathers, and occasionally stored products such as dried fish, pet food and cheese. However, the most likely food source for these scavengers is dead insects or other animals (boxelder bugs, attic flies, mice, etc.) that have accumulated inside walls or attics.
The larder beetle adult is slightly longer than 1/4th inch. It is roundly oval and dark brown to black with a characteristic light colored band running across the body. This light band contains 6 more or less prominent dark spots. Larder beetle larvae are up to 1/2 inch long. They are tapered in shape and covered with sparse, stiff hair. There are 2 upward curved spines on the posterior end.
In most situations it appears homeowners cannot isolate a specific source of larder beetles (such as pet food). If a source could be determined control would be much easier (discard or clean infested items). In the more typical, general infestation where the source is probably the dead insects within the innerwall spaces, removal or sanitation is not practical. Cleaning is still recommended. Thoroughly vacuum clean cracks and crevices in the areas where larder beetles are found.
A residual insecticide treatment can be applied following cleaning. Apply small quantities of residual spray or dust to cracks and edges in areas where beetles or larvae are most commonly seen. Readily available insecticides for homeowner use include liquid sprays in an aerosol can or a trigger pump spray applicator (for example, "ant and roach killer"). Dust insecticides such as boric acid and diatomaceous earth are a very fine powders that must be evenly spread in a thin layer or injected into voids and insect hiding places to be effective.
This article originally appeared in the June 27, 1997 issue, pp. 101-102.