Brown Recluse Spider
The color varies from golden brown to dark brown. They have long legs and a body length that ranges from 1/4 – 3/4 inch. The most identifiable characteristic is the dark violin-shaped mark that begins right behind the eyes. Unlike most spiders that have 8 eyes, the brown recluse has only 6 eyes. The eyes are arranged in pairs, one pair in front and a pair on each side can be readily seen under low magnification.
Brown recluse spiders generally occupy dark, undisturbed sites, and are found indoors as well as outdoors. In favorable habitats, their populations are often dense. They thrive in human-altered environments. Indoors, they can be found in attics, basements, crawl spaces, cellars, closets, and ductwork or registers. They may seek shelter in storage boxes, shoes, clothing, folded linens, and behind furniture. They also may be found in outbuildings such as barns, storage sheds, and garages. Outdoors, brown recluse spiders may be found underneath logs, loose stones in rock piles, and stacks of lumber. There is no evidence to suggest that the brown recluse spider is established in Utah.
The brown recluse spider mainly feeds on insects. They can survive long periods of time (about 6 months) without food or water.
Life Cycle & Reproduction
The female brown recluse will lay eggs primarily from May through July. The female lays about 50 eggs which are encased in an off-white silken sac that is about 2/3-inch diameter. Each female may produce several egg sacs over a period of several months. Spiderlings emerge from the egg sac in about a month. Their development is slow and is influenced by weather conditions and food availability. It takes an average of one year to reach the adult stage from the time of egg deposit. Adult brown recluse spiders often live one to two years.
The bite of the brown recluse spider can result in a painful, deep wound that can take a long time to heal. Death from a brown recluse spider is extremely rare, but bites are most dangerous to young children, the elderly, and those in poor physical condition. When there is a severe reaction to the bite, the site can erupt into a “volcano lesion” (a hole in the flesh due to damaged, gangrenous tissue). The open wound may range from the size of an adult’s thumbnail to the span of a hand. The dead tissue gradually sloughs away, exposing underlying tissues. The sunken, ulcerating sore may heal slowly up to 6 to 8 weeks. Full recovery may take several months and scarring may remain. It is difficult for a physician to accurately diagnose a “brown recluse bite” based simply on wound characteristics. It’s absolutely necessary to have the spider for a positive identification.
The brown recluse spider is not normally aggressive, and generally bites when crushed, handled or disturbed. Some people have been bitten in bed after inadvertently rolling over onto the spider. Others have been bitten after accidentally disturbing the spider when cleaning storage areas. Some bites occur when people put on seldom used clothing or shoes inhabited by a brown recluse.