Various shades of—you guessed it—brown. Color varies from tan to dark brown, usually with a darker fiddle-shaped marking on the dorsum or top of the cephalthorax whose neck points towards the abdomen. Immatures very similar to adults except for being smaller and slightly paler..
Varies in size, but an adult with legs extended is about the size of a U.S. quarter. The adult females vary from 7 to 12 mm in length, averaging about 9 mm, and the males are a little smaller, averaging about 8 mm.
Throughout the south central and mid-western United States stretching down into Mexico. Despite sensationalist news headlines, there are no indigenous populations of brown recluse spiders in California. , There are four species of native recluse spiders in Western's service areas. The most common is the desert recluse, found mostly in the Sonora and Mojave deserts, the foothills of the lower San Joaquin Valley, and in adjacent areas of Mexico.
Occasionally, one or a few spiders may be transported to a non-native area in boxes or furnishings, but infestations seldom become established.
Imposteors and wannabes. Due to six eyes arranged in the same pattern, spitting spiders and woodlouse spiders are sometimes misidentified as brown recluse spiders. Many common tan or gray spiders have dark markings on the head region, which convince people they have caught a bona fide recluse spider. These spiders include cellar spiders, pirate spiders, and sheet web spiders. The Public's Health medical journal and entomologists from the University of California have published articles cautioning medical professionals and urging them not to be so quick to blame spiders in general for skin lesions and swelling. Conditions that can cause necrotic wounds and/or that have been misdiagnosed as brown recluse spider bites include: infections with Staphylococcus or Streptococcus species, Herpes Simplex, diabetic ulcer, Lyme Disease, fungal infection, poison ivy/oak, dermatitis, and others.
Word to the wise: check your shoes. The brown recluse lives outdoors in cracks and crevices, in and under rocks. They do not build webs to capture prey, but do use silk to build retreats in which to hide during the day. They emerge from retreats at night and actively hunt down prey, or may wait for prey to land in the small area several inches from retreat.
As dawn approaches, they may crawl into dark places such as clothing, trousers, or shoes. Mature males roam in search of females. These spiders are readily found under trashcans, plywood, tarps, tires, in boxes, etc.
The good news is, they eat roaches. They also prey on firebrats, crickets, and other soft-bodied insects. They forage for food nocturnally, and are well-known for surviving long periods (6-12 months) without food before perishing
After mating, which occurs from February to October, 40 to 50 eggs are deposited in off-white, round, 6 mm, silken cases. From one to five egg sacs are produced in a lifetime, which normally averages from one to two years, or may be up to four years. Spiderlings emerge from eggs in 25 to 39 days and resemble adults but lighter in color
If bitten, people may develop necrosis (dead tissue) at the site of the bite. You may not be aware of being bitten for 2 or 3 hours, or a painful reaction may occur immediately.
A stinging sensation is usually followed by intense pain. Local pain is frequently quite intense, and the area surrounding the bite remains congested and hard to touch for some time. The tissue affected locally by the venom is killed and gradually sloughs away, exposing the underlying muscles. Healing takes place slowly, perhaps 6 to 8 weeks. The end result is a sunken scar resembling a hole punched or scooped from the body. Scars ranging from the size of a penny to less than a quarter have been reported. It is difficult for a physician to accurately diagnose a "brown recluse bite" based simply on wound characteristics. It is absolutely necessary to have the spider for a positive identification. If bitten, remain calm, and immediately seek medical attention. Apply an ice pack directly to the bite area to relieve swelling and pain. Collect the spider (even a mangled specimen has diagnostic value), if possible, for positive identification by a spider expert. A plastic bag, small jar, or pill vial is useful and no preservative is necessary, but rubbing alcohol helps to preserve the spider.
Inside, they will nest anywhere. They prefer warm and hard to reach places like wall voids, behind baseboards, under floors and between linens. Once they find a suitable nesting site inside, they will breed continuously throughout the year. In warmer climates, they will nest outside of the building.
Spider control is a six-step process, which should include:
Inspection - Determine conditions that might need correction.
Identification - Determine target pest and possible treatment strategy based on species habits.
Prevention - Check building conditions allowing entry; lighting that may attract their prey.
Sanitation - Check debris outside, such as wood piles, high weeds, rocks and overgrown shrubs that give shelter. Indoors, eliminate clutter and vacuum areas out of normal access regularly. Removal of webs greatly enhances a control program. Since spiders reuse their silk, a light dusting of remaining webs with a non-repellent insecticide dust will aid in control.
Pesticide Application - Reduce the active population and give overall control when performed along with the above listed recommendations. When using any pesticide, be sure it is registered for the target pest/location. Read the entire label prior to use. Follow all label directions, restrictions, and precautions. For large infestations or multiple sightings of spiders, we recommend using the services of a professional exterminator.