Reference:

Brown Recluse Spiders: Facts, Bites & Symptoms

Brown Recluse Spider
Venomous brown recluses exist within a smaller range than many realize, and their existence may be threatened by climate change.
Credit: Rick Vetter

Well-known for its appearance and poisonous bite, the brown recluse spider is commonly found in the south and central United States, in states such as Kansas, Arkansas, Missouri, eastern Texas and Oklahoma. It is a common house spider in these areas, but contrary to popular belief does not live outside of them.

The brown recluse gets its name from its color and habits. It is solitary in nature and often hides in dark, secluded places like under porches or deep in closets.  The brown recluse thrives in man-made areas, and may be found under trashcans, tires, etc. It is primarily nocturnal and lays its eggs from May to July.

It is part of the recluse (Loxosceles) genus of spiders. Members of this group are well known for their violin-shaped markings on the top of their cephalothorax (fused head and thorax) and may be casually referred to as fiddleback or violin spiders.

Appearance

The brown recluse’s well-known violin marking can vary in intensity depending on the age of the spider, with mature spiders typically having dark violin shapes. The violin shape points toward the spider’s bulbous abdomen. The violin shape is easy to misinterpret, so it is best to look at the eyes when determining if a spider is a brown recluse.

Other types of spiders have eight eyes arranged in rows of four. Recluses, however, have six equal-sized eyes, which are called dyads. The dyads are arranged in three pairs in a semicircle around the front of the cephalothorax.

Other distinguishing characteristics of the brown recluse spider are: a uniformly colored abdomen (though the shade of brown varies from spider to spider) covered in fine hairs to give it a velvety appearance; long, thin legs that are also covered in fine hairs but do not have spines; and uniformly colored legs. The scientific name Loxosceles means “slanted legs,” and refers to the fact that recluse spiders hold their legs in a slanting position when at rest.

The brown recluse is typically about three-eighths of an inch long and about three-sixteenths of an inch wide (about 1 cm long and half a centimeter wide), with males being slightly smaller than females but possessing longer legs.[Gallery: Spooky Spiders]

A spider bite from a brown recluse spider
After being bitten by a brown recluse spider, a 10-year-old girl in Mexico required two medical procedures to remove blackened, dead tissue from her leg.
Credit: The New England Journal of Medicine ©2013

Brown recluse bite

The brown recluse has a venomous bite. Typically, the spiders only bite when disturbed —though it is possible to inadvertently threaten them. There are reports of bites after rolling over on a spider in bed, accidentally touching it while cleaning dark cabinets, or finding it in a rarely worn shoe.

Reactions to a brown recluse bite vary depending on the amount of venom injected and the individual’s sensitivity levels. Some people may experience a delayed reaction, others an immediate reaction, and others no reaction at all. Many brown recluse bites leave a small red mark that heals quickly, and the vast majority of bites do not leave scars.

For those with higher sensitivity levels, a small white blister appears at the bite-site soon after the bite. The tissue may become hard. Lesions are dry, blue-gray or blue-white patches with ragged edges surrounded by redness. This color pattern has yielded the nickname “red, white and blue.” In severe reactions, the bite-site can develop a “volcano lesion.” The damaged tissue becomes gangrenous and leaves an open wound that can be as large as a human hand. It can take eight weeks or longer for full recovery, and scars may result. [Related: Girl's Brown Recluse Spider Bite Turns into Open Wound]

There are infrequent cases of victims experiencing restlessness, generalized itching, fever, chills, nausea, vomiting or shock after a bite. Fatalities are extremely rare, but the bites are more dangerous to young children, the elderly, and those in poor health.

If bitten, go immediately to a medical profession and bring the spider if possible, for identification purposes. There is no effective commercial antivenom, though other treatments are available.

For the latest information on brown recluse spiders and other arachnids, visit:

More from LiveScience