Legend has it that Dr. Harold "Tiny" Gunderson, the popular and well-known ISU Extension Entomologist between 1936 and 1971, had a standing bet that he could find carpet beetles in any house in Iowa. He probably wasn't taking much of a risk with that wager, based on what we know about this very common and widespread insect.
Only in the house do carpet beetles become pests. In the "real world" they are valuable "recyclers" that feed on the dried remains of dead animals (a thankless but important task). Carpet beetles are everywhere and their scavenger existence keeps them on the move. It is only logical that sooner or later they would enter the house, and upon finding a cache of suitable food such as dead flies or boxelder bugs in the attic or a mouse carcass in the wall, they would establish populations indoors.
The name carpet beetle comes from our early household experiences when carpets were made of real wool, an animal protein quite suitable as carpet beetle food. Carpet beetles used to be quite destructive in homes as the larvae fed on the woolen carpet fibers. Modern synthetic carpets are not attacked by carpet beetles, though we still have plenty of valuable animal-based products that they can damage: leather, furs, woolen and silk clothing, taxidermy specimens and certain stored food materials. Of personal interest is the persistence with which carpet beetles get into insect collections and ruin the preserved insects (which are, after all, just another dead animal food source to the carpet beetles).
There are many different species of carpet beetles but only four species of dissimilar appearance are common in the house. The adults of all species are generally oval-shaped and about 1/8 inch long. One common species, the black carpet beetle, is shiny black. Adults of other common species are marked with mottled patterns of white, brown, yellow and orange scales. Carpet beetle larvae are about 1/4 inch long, dark brown in color and covered with hairs or bristles. Only the larval stage feeds on fabric and causes damage.
Carpet beetle controls include eliminating the beetles by cleaning or destroying infested items (clothing, food products, etc.). Often, the source may be difficult to find or there may not be a single source. A major part of carpet beetle prevention and control is thorough vacuum cleaning to prevent the accumulation of lint, hair, and other carpet beetle food materials. Close attention should be given to radiators and registers, corners, cracks and other hard to reach places.
If beetles are found throughout the house localized applications of residual insecticides may be needed. Treatment should be lightly applied to those surfaces upon which the insects are likely to crawl, such as along the edges of carpeting, in closets, behind radiators, baseboards and moldings, and in corners, cracks, and so forth. Ready-to-use residual insecticide products such as "ant and roach killers" and boric acid dusts are appropriate for this purpose. Cases of heavy, widespread infestation may require the services of a professional pest control operator.
Woolens and other susceptible fabrics should be dry cleaned or laundered before being stored for long periods. Cleaning removes perspiration and stains that are attractive to carpet beetles and kills any eggs or larvae that may be present. Store cleaned articles in tight-fitting containers (garment bags, storage boxes, etc.). Moth balls or flakes and cedar wood products may or may not be of benefit. The air-tight quality of the storage container and the pre-storage cleaning are probably more important than "moth" prevention products.
This article originally appeared in the March 27, 1998 issue, p. 29.