This small, non-aggressive, hermit-like spider prefers avoiding people and lives in dark corners and out-of-the-way places. Occasionally, however, it finds itself in the path of humans and can inflict a nasty bite in self-defense.

The scientific name of the genus is loxosceles (pronounced lox-oss-cell-eze) of which over 50 species are known throughout the world, all poisonous. The loxosceles reclusa, from which the generic name, brown recluse, devolved, is normally found only in the eastern U.S., not in the Southwest.

Southern Nevada is home to two loxosceles species, the l.deserta and l.arizonica. Both of these species are commonly referred to as the brown recluse.

According to Dr. Dale Carrison, UMC's Director of Emergency Services, during the summer months UMC's emergency room treats an average of 2 to 3 recluse bites a week, some of which can get pretty nasty. Multiply that by the number of hospitals in Southern Nevada and the prevalence of recluse bites grows rather large. Taking some common sense precautions, as noted later in this article, can greatly reduce your chances of being bitten.

The adult female varies from 7 to 12 mm in length, averaging about 9 mm. Males are slightly smaller but just as venomous. The recluse has long legs which are covered with tiny brown hairs. Body color varies from light tan to dark brown. Uncommonly, the recluse has 6 eyes, where most spiders have eight. However, if you are close enough to count the eyes, you're too close for comfort.

Immediately behind the recluse's head is a distinctive violin shaped marking with the narrow neck pointing back toward its abdomen. This distinctive feature has resulted in the recluse often being called the "violin" or "fiddle" spider.

The recluse's web is an irregular maze of threads extending in all directions without a definite pattern. The web's main use is as a retreat and not for trapping prey. In winter the spider spins a tube of thick silk as a retreat.

Barring fatal encounters, females tend to live an average of two years and males slightly less. However, under prime conditions, recluse spiders have been known to live for as long as 4 years. Egg production varies between 30 and 300 per female, producing about 50 percent living young each season.

Surveys of the recluse's indoor habitat found the largest majority living in old boxes and papers, with a fair number found in bedrooms, attics, and hallways. The recluse may also be found in old clothes, bedding, and the underside of tables and chairs. Outdoors, the largest number by far were found under rocks, piles of inner tubes, and in abandoned buildings.

According to Dr. Will Pratt, Curator of Invertebrates at UNLV's Barrick Museum, the amount of venom the recluse injects during a defensive bite ranges from 0.25 to 0.62 microliters, with an average of 0.36 ul. Males usually have about half the amount of venom of the female, but it is just as toxic.

However, Dr. Pratt has noted cases where captured recluse spiders were severely provoked and would not bite, indicating the basic non-aggressive nature of this small creature. Biting generally only occurs in self-defense.

A typical reaction to the recluse bite is the decay (necrosis) of the flesh at the bite site. The victim may have an immediate painful reaction, or may not become aware of being bitten for 2-3 hours. When the reaction is immediate, a stinging sensation is usually followed by intense throbbing pain.

In both cases, a small bleb or blister usually arises and the area surrounding the bite becomes congested and swollen. Later reactions include restlessness, feverishness, and difficulty sleeping. The pain is likely to be quite intense, and the area surrounding the bite very sensitive to touch for some time.

There is no antivenom for the recluse's bite. However, its venom, a mixture of enzymes which rapidly destroys both tissue cells and blood cells, appears to be self-limiting in that its ability to destroy cells eventually seems to decrease and cease altogether.

In many cases the flesh in and around the bite sloughs away, gradually exposing underlying muscle tissue (necrosis). Then as the wound heals, the edges thicken and the central area becomes filled with dense scar tissue. Healing is slow, sometimes taking between 6 and 8 weeks. The resulting scar resembles a hole scooped from the body and may range from the size of a penny to half-dollar.

This necrotic process is typical of most bites of the brown recluse. In many cases, the necrosis is so minuscule (usually due to only partial envenomation) that the bite goes unreported and heals on its own. If at all possible, it is recommended that the offending insect be captured and brought to the treating physician for identification.

In some extreme cases a general systemic reaction occurs, usually as the result of complete envenomation by the spider, which can, in rare cases, lead to death. People in poor general health, young children and older people are more apt to have a serious reaction to the recluse's bite.

Both Dr. Carrison and Dr. Pratt agree that successful treatment and prevention of severe necrosis or systemic toxicity depend on early recognition of both the offending insect and the bite symptoms followed by appropriate treatment, which can include antibiotics, tetanus shots, pain medication and possible debridement or surgical excision of the wound area. Follow-up with daily wound care is vital to prevent further infection. Studies have shown that treatment initiated more than 48 hours after the bite is unlikely to have a positive effect.

The picture above (compliments of University of California, Riverside, Department of Entomology) shows the healing sequence of a necrotic wound resulting from the bite of a brown recluse spider. The first panel was taken approximately 48 hours after the bite. Subsequent photographs were at intervals over a period of 58 days. Surgical removal of contaminated tissue occurred as the tissue sloughed off.

As any secluded or seldom-disturbed location provides excellent habitat for the recluse, it is wise to keep your house cleared of undisturbed clutter. The spider does not hang around locales that are frequently disturbed by cleaning or rearranging.

Prime nesting areas such as attics, foundation vents and crawl holes can be sprayed or dusted with insecticides such as lindane, chlordane, diazinon, or resmethrin according to instructions on the package labels.

Since spiders feed on insects, any measures taken to decrease the number of insects in your home will also decrease the number of spiders. Newly hatched spiders can enter the home through screens or around loose-fitting windows and doors, but the older ones can be kept out by careful screening. Spiders can be invade the home with firewood, plants, boxes, and many other items brought in from the outside.

In Southern Nevada it is highly advisable to treat for spiders outdoors as well as in the house. Recommendations include applying a residual-type insecticide coves, porch eaves, low roofs, window wells, around door and window frames, and to a 3- to 5-ft area around the house foundation, as well as the garage, shed, other outbuilding on the premises, piles of old lumber, woodpiles, weedy areas, and fences.

Follow the directions on the insecticide carefully to prevent harm or injury to children, pets, livestock, or any plants in the treated area.