Spider beetles are named so since they are Beetles that look like a Spider in a glance. These are general scavengers. They feed on a variety of items, such as cereals, seeds, flour, meat, dried fruits and vegetables, fish food, dead insects, rodent droppings, old wood, cayenne pepper, roots, cocoa, sugar, drugs, and spices. Common sites of infestation in the house include wall voids and drop ceilings. Spider beetles are primarily warehouse pests, attacking various seeds and certain whole grains, such as wheat, barley, rye, and flax.
Also, serious infestations have been found in flour and feeds, such as bran shorts and meal preparations. Larvae cause a typical “scarring” of the wood in buildings in the formation of pupal cells prior to pupation. Spider beetles sometimes become prominent cereal pests in Canada and the northern United States. Some have been found quite active even during freezing weather. They do not bite or sting humans or pets, spread diseases, or feed on or damage the house or furniture.
Spider Beetle Appearance
Adult spider beetles are minute oval or cylindrical insects with long legs resembling giant mites or small spiders. The head is often hidden when viewed from above. They are 1/16- to 3/16-inch long with long filamentous antennae (usually 11 segmented) arising on the front of the head close together at the base. Most are brownish-black with a large, globe-like abdomen and the prothorax (first segment behind the head) constricted at the base of the wing covers. Larvae are C-shaped or grub-like and cream-colored with short legs. The segmented abdomen contains many long hairs.
The hairy spider beetle is reddish-brown with two irregular- shaped white patches on each wing cover. The whitemarked spider beetle has a reddish-brown body covered with yellow hairs; the females have two white patches on each wing cover that join to form two transverse bands. The brown spider beetle is uniformly dark brown without scales on the wing covers. The American spider beetle is dark, reddish-brown to nearly black with a shining subglobular body. The Australian spider beetle is dark reddish-brown and the wing covers are covered with golden brown or yellowish hairs.