In North America there are thirteen species known in the brown recluse genera Loxosceles. The brown recluse (Loxosceles reclusa) is the most infamous species and has been reported in 29 states in the continental US.
Violin pattern on cephalothorax
The brown recluse (Loxosceles reclusa) is a small tan-colored spider (length of female body averages 9 mm) with long slender legs. They are relatively hairless spiders with a smooth sleek appearance. Because of violin-like dark pattern on their back (dorsal side of the cephalothorax) they are also known as fiddle or violin spiders. Another characteristic to use in identifying brown recluse spiders from other common house spiders is their eye number and arrangement. They have 6 eyes arranged in three doublets unlike most spiders which have eight eyes.
Face of L. reclusa showing three pairs of eyes
Venom
The physcial bite of the brown recluse is fairly painless with maybe only a slight stinging sensation being felt. In contrast, the venom is ultimately quite destructive. The symptoms from the venom appear about six to eight hours after the bite. Local reaction includes redness of the skin, tenderness and possible blistering. About 12-24 hours after being bitten one may feel maliase, chills, fever and nausea. The venom contains the enzyme sphingomyelinase which is a necrotic substance. The localized cell death from this enzyme can result in large open wounds that take a long time to heal. The poison also destroys red blood cells (hemolytic) and may cause death by liver and/or kidney failure. If you are bitten by a spider, kill (with minimal smashing) the spider and bring it with you for identification when you seek medical attention.
Natural History
Brown recluse build irregularly shaped webs under logs, stones, or piles of lumber. It is not uncommon for them to move into a house where they prefer dark corners found in trunks, piles of stored clothing, or inside garage and basement storage areas. They feed on a variety of prey items found in the home/basement (e.g., silverfish, camel crickets). Brown recluse can survive on very little food. One published laboratory experiment reported brown recluse surviving up to five months with no food or water.
