Brown Recluse Spiders: Where They Live and How to Tell

The brown recluse lives in the south-central United States, from southeastern Nebraska to southwestern Ohio and south through Texas to northern Georgia, according to a University of California pest note written by spider researcher Rick Vetter. Inside that range it can be common in houses. Outside it, the spider is rare, and most specimens brought in as brown recluses turn out to be other species.

Five traits that identify a recluse

A spider is a recluse only if it shows all five traits listed in the UC Statewide IPM Program’s pest note on recluse spiders:

1. six eyes arranged in three pairs, where most spiders have eight;
2. a uniformly colored abdomen covered in fine hairs;
3. no spines on the legs;
4. legs of one uniform color;
5. a body no more than 3/8 inch long.

The pest note treats the eye pattern as the check that rules out almost all look-alikes. The violin-shaped mark people look for is less reliable. It varies in intensity, fades on preserved specimens, and is faint or missing in several southwestern recluse species. The note adds that people without training in spiders, including physicians and pest control operators, have seen “violins” on harmless spiders.

The University of Kentucky’s fact sheet adds a sense of scale: with legs extended, a brown recluse is about the size of a U.S. quarter, and the neck of the violin points toward the rear of the body.

Where they live, and where they don’t

The brown recluse is established in the south-central range described above and rare elsewhere. UC IPM notes that recluses usually spread beyond their native range only with human help; the few found in California came in with goods shipped from out of state or with people who moved from the Midwest.

The same pest note reports that eleven species of recluse spiders are native to the United States, and two non-native species are established in very limited areas. Of these, the brown recluse, Loxosceles reclusa, is the one with the broad Midwestern and southern range. Other native species live in the Southwest, such as the desert recluse in the Sonoran and Mojave deserts. The non-native Chilean recluse is established in a small part of Los Angeles County.

California shows how far belief runs ahead of the spider. UC IPM reports that fewer than 20 verified brown recluse specimens have been collected in the state over several decades. In a nationwide identification study from 2000 to 2005, nearly 600 spiders sent in from California as suspected recluses included one brown recluse, from a household that had moved from Missouri.

In the Pacific Northwest, the spider with the dangerous reputation is the hobo spider, labeled potentially toxic in the United States in the 1980s. A separate UC IPM pest note places it from British Columbia east to Montana, Wyoming and Colorado, and south through Oregon and northern Utah. It reports that later research questioned that label and states that the hobo spider’s bite is not considered of medical importance.

Where recluses hide indoors

Within their range, brown recluses live close to people. The Kentucky fact sheet lists the places to look: cracks, corners and the joints between walls and floors, especially behind clutter and stored items; behind and under beds and furniture; closets, clothing and shoes; above suspended ceilings; behind baseboards; and inside ducts and registers.

Outdoors, UC IPM notes, recluses shelter in cracks under rocks and beneath loose bark, and around homes they settle under trash cans, plywood, tarps and tires and in storage boxes. They are nocturnal, and as dawn approaches they may crawl into clothing or shoes, while mature males roam in search of females. Those two habits are what bring them into contact with people.

Where they occur, they are rarely alone. UC IPM describes a family in a 19th-century Kansas house that collected 2,055 brown recluses in six months. Over nearly a decade in that house, one person once showed evidence of a bite, a finger that turned red for a few days and healed. The Kentucky fact sheet likewise notes that people often live in heavily infested buildings and are never bitten.

Infestations also persist. UC IPM reports that recluses mature after about a year, live 2 to 4 years on average, with some surviving more than 7 years in the laboratory, and can go 6 to 12 months without food.

Reducing contact at home

UC IPM and the Kentucky fact sheet describe much the same household steps. In the bedroom, move the bed away from the wall, remove bed skirts and ruffles, and clear items stored under the bed, so a spider has no easy route onto it. Store gear used only occasionally, such as gardening gloves and clothes, boots and seasonal clothing, in tightly closed plastic bags or bins, especially in a garage or other dark storage area. Outside, reduce woodpiles, boxes, plywood, tires and other debris kept against the house.

Bites: what the research shows

Most brown recluse bites stay minor. The Kentucky fact sheet says the majority remain localized and heal within 3 weeks without serious complication, while some develop a lesion of dead skin that can spread over days or weeks. UC IPM estimates that about 10% of bites cause moderate or greater tissue damage.

Misdiagnosis is common. UC IPM notes that many medical conditions mimic a recluse bite, including bacterial infections, and cites a national study at 11 university-based medical facilities in which 29% of patients who came in for a “spider bite” had MRSA, a bacterial infection, as the actual cause.

CDC’s National Institute for Occupational Safety and Health advises seeking professional medical attention for a suspected brown recluse bite. Any wound that worsens belongs with a physician; identifying the spider helps the physician but does not replace an examination.

Confirm before you treat

Establish that recluses are present before paying for control. UC IPM advises verifying that recluses are on the property first, and suggests sticky traps along baseboards, out of reach of pets and young children, to catch spiders and gauge how many there are. The Kentucky fact sheet recommends dozens of traps placed throughout the house to show where spiders are concentrated.

If a suspect spider is caught, keep it intact. UC IPM notes that a crushed specimen may be difficult for an expert to identify.

When to call a professional, and what to ask

Call a licensed pest control company once traps or a specimen confirm recluses in the house. The Kentucky fact sheet says treatment is a job for professionals because of the spiders’ secretive habits. It describes insecticide dusts applied into cracks and voids, and sealing cracks and holes in the exterior to reduce spiders moving indoors. Questions worth asking:

• How will you confirm the species before treating?
• Where will you place monitoring traps, and how will you compare the counts after treatment?
• Which cracks and voids will you treat, and with what formulation?
• Which openings, clutter or storage habits should change to remove hiding places?
• How many follow-up visits are included?
• Is your license current for household pest control in this state?