The Brown Recluse Spider

Common Name:
Brown Recluse Spiders
Scientific Name:
Latrodectus spp.


The brown recluse or fiddleback/violin spider gets its common names from its coloration and reclusive habits, or the dark violin/fiddle-shaped marking on the top of the cephalothorax. Members of the genus Loxosceles occur in southern Europe, temperate Africa, and in North, Central, and South America. Brown recluse spiders occur pretty much throughout the United States and of 1 1 species recognized, 7 are of public health importance. Recognition of the brown recluse species group is sufficient for PCO purposes.


Adults usually about 1/4-1/2" (6-12 mm) in body length (L. laeta about 1 "/25 mm). Color tan to dark brown with a darker fiddle-shaped marking on dorsum or top of cephalothorax whose neck points towards abdomen. Uniquely, with 6 eyes arranged in 3 groups of 2 (diads) in a semicircle. lmrnatures very similar to adults except for being smaller and slightly paler.


All other spiders lack a darker fiddle-shaped marking on the top of cephalothorax and 6 eyes arranged in 3 groups of 2.


Because several species are involved and species separation is primarily by differences in male genitalia, species identification should be left to experts. Those of public health importance are:

  1. Loxosceles arizonica Gersch & Mulaik which occurs in Arizona.

  2. Loxosceles deserta (Gersch) which occurs in the southwest.

  3. Loxosceles devia Gertsch and Mulaik which occurs in southern Texas.

  4. Loxosceles laeta (Nicolet) which has been found in Massachusetts and occurs in southern California.

  5. Loxosceles reclusa Gertsch and Mulaik, the brown recluse, which occurs in the eastern United States.

  6. Loxosceles rufescens (Dufour) which occurs sporadically from New York to Illinois and throughout the southeastern states.

  7. Loxosceles unicolor Keyserling which occurs in Arizona, New Mexico, and western Texas.


This discussion is based on L. reclusa. The female deposits 40-50 eggs in a silken egg sac which is off-white, with the outer covering loosely woven. The sac has been described as either flat beneath and convex above (5/8"/17 mm in diameter and 1/8"/3.7 mm high) or as round (1/4"/6 mm in diameter). From 1 to 5 sacs are produced, each containing 31-300 eggs. The eggs hatch in 25-39 days and the spiderlings undergo at least 1 molt within the sac before emerging. The spiderlings typically go through 8 instars, and the development period (egg to adult) averages 336 days (range 266-444). Indoors, males live an average of 543 days, and females live 628 days, but 4-5 years is not uncommon. The female spins an irregular web in undisturbed areas. The web is not used to ensnare prey, but mostly as a retreat for the spider.

Both male and female brown recluse spiders can inject venom, and must be considered dangerous to humans. Injection of their venom may produce necrosis or dead tissue, resulting in an ulcerating type of sore. The bits is usually not felt, but it may produce an immediate stinging sensation followed by intense pain or this reaction may be delayed for 6-8 hours. A small blister usually appears and the surrounding bite area becomes swollen. Symptoms include restlessness, fever, and difficulty in sleeping. The killed tissue gradually sloughs away during the next 10-14 days, leaving an open ulcer and possibly exposing the underlying muscles and/or bone. Healing is very slow and usually takes several weeks, resulting in dense scar tissue. In severe cases, plastic surgery may be required. An antitoxin has been developed but it is NOT available. Call a physician or go to an emergency room immediately if bitten, and take the spider along for identification purposes. It should be noted that not all brown recluse bites result in ulcer formation and that bites of other arthropods may cause similar reactions in people.


Outside, brown recluse spiders are typically found around rocks, piles of inner tubes, utility boxes, woodpiles, under bark, etc. These spiders have been found in such places as outside rodent bait stations and infesting cedar shake roofs.

Inside the home, they can be found in almost any undisturbed area to which they can gain access. They are most commonly found in boxes, among papers, and in seldom- used clothing and shoes, although they can be found in corners, underneath tables and chairs, or in crevices such as those found along baseboards, doors, and window moldings. Hence, storage areas such as closets, bedrooms, attics, crawl spaces, and basements are the areas of greatest occurrence. They typically run for cover when disturbed. Bites have been reported to occur when putting on seldom-used clothing or shoes, when cleaning out storage areas, or by rolling on the spider while in bed. In commercial buildings, the usual places to find brown recluse spiders include heat tunnels, boiler rooms, attics, basements, storerooms, and garages.