Spider beetles are small oval or cylindrical beetles that often resemble small spiders. Although they are not common pests, they can be important pests in homes, warehouses, grain mills and museums.
When found in structures, larvae may infest dried vegetable or animal substances such as flour, wool, hair, and feathers, as well as textile fabrics and old wood. Larvae infesting stored food or grain may tunnel into wood surrounding such foods to form pupal chambers, causing damage to some kitchen cabinets. They seem to be particularly attracted to old or out of condition products such as pet food.
Infestations may be found in floor cracks and expansion joints. These beetles are scavengers, attracted to moisture and excrement and are found in the nests of animals. Adult beetles have been known to be active at freezing temperatures.
As with any stored product pest, the location of the infestation is extremely important, which may be difficult to accomplish with spider beetles as they wander about only at night and feed on such a variety of materials. Most spider beetles avoid light and are hard to locate, hiding deep inside cracks or inside packages. They are often located by the webbing that the larvae make or by cast skins. Control begins with a thorough cleaning, including removing bird and rat nests and inspecting stored food containers and cupboards. Old packages of pet food should be discarded.