Brown Recluse Spider Information

Published: Nov. 15, 2000 at 8:12 PM CST|Updated: Dec. 14, 2014 at 1:05 AM CST
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BROWN RECLUSE SPIDER, Loxasceles reclusa (Sicariidae). Some 54 species of Loxosceles are known to occur in North America, Central America, and the West lndies. The Brown Recluse Spider, Loxosceles recluse, is one of 13 Loxosceles species now know, to occur in the United States (Breene 1994). At the beginning of the 20th Century, only two species were recognized - L. rufescens and L. unicolor (Comstock 1912). Gertsch and Ennick (1983) report that the brown spiders of the genus Loxosceles (also known as Violin or Fiddle-Back Spiders because of the dusky maculation of the carapace) are known from two principal world areas: temperate South Africa northward through the tropics into the Mediterranean region and southern Europe; and from temperate and tropical zones of North and South America.

In the United States, L. reclusa is considered to be the most widespread and most important species of this group. Of lesser importance are L. arizonica, L. devia and L. deserta, which are native to the Southwest. The Chilean Brown Spider, L. laeta, has a particularly serious bite but is only established in small parts of Southern California. Another imported species, L rufescens, occurs in southeastern states along the coast. This spider's propensity for inhabiting household goods, furnishings, etc. enabled it to be imported in overseas shipments. For example, specimens of L. Laeta were found in the basement of the Museum of Comparative Zoology at Harvard University, Cambridge, Mass., but were subsequently eradicated.

Distribution . The natural range of the brown recluse spider, L. reclusa, is from south- ern Texas, north to Nebraska, and east to eastern Tennessee and Alabama. It appears to be most highly concentrated in the south-central portion of the Midwest. Although there have been reports of Brown Recluse Spiders from Maine to Florida, these are more likely due to transport of commerce or domestic household goods. In addition, many misidentifications occur based upon bite examination. Physicians may be too quick to decide that an open ulcerous wound is the result of a Brown Recluse Spider bite.

Within its range, the Brown Recluse naturally occurs in outdoor situations, living in piles of debris, utility boxes, wood piles, vehicles, and under bark, logs, and stones. It has adapted quite well to indoor habitats where it. is commonly found harboring in storage arm such as closets, attics, crawlspaces, basements, cellars, and other dark recesses, as well as cracks and crevices. They frequently inhabit clothing, boxes, toys, papers, furniture, and other household items and seen to prefer 'layered' situations, such as stacks of items or clutter.

Preying Habits. The brown spiders are nocturnal and search for food such as firebrats, cockroaches, crickets, or other soft-bodied species. At first light, wandering spiders will normally return to their retreat of an irregularly spun, off-white web with their prey. Males wander farther than females (Hedges and Lacey 1995) and are the sex that most commonly crawls into shoes, trousers, or other clothing; or under sheets and covers on beds. Bites occur when a spider hiding in clothing or bedding is accidentally trapped against the skin. The thin, wispy webs of the brown recluse may be seen in drawers, boxes, shelves corners, under furniture, or other undisturbed areas.

Life History. Hite (1966) studied the life history of  the Brown Recluse Spider. After mating, which may occur from February to October within its natural range, 40 to 50 eggs are deposited in off-white, round, 1/4 inch/6 mm diameter silken cases. The summer months of May through August are optimal times for egg production. From one to five egg sacs will be produced during the female's life-time which normally averages from one to two years; however four to five years is not uncommon. The presence of shed skins (exuviae) and subsequent attachment in and around residences may be indicative of infestations and enable accurate identification.  

Recognition of Brown Recluse Spiders . Most Loxosceles possess the characteristic dark brown violin marking on the dorsal carapac, but in some species or individual specimens, this marking may be faded or absent. Six eyes are situated in three pairs arranged in a semicircle pattern.

The body coloration varies from yellowish to light tan to dark brown and is covered with a fine pubescence. The spiderlings resemble adults in structure but have somewhat lighter coloration and may lack the violin-shaped marking on the carapace.