Two spiders matter medically in California: the western black widow and its milder, non-native relative, the brown widow. UC IPM calls the black widow the most common harmful spider in the state. Both live outdoors around Los Angeles homes and usually bite only when trapped or touched. The brown recluse and the hobo spider do not live in California. Here is how to identify them, what a bite does, and how to keep them away.
How do I identify a black widow?
An adult female is shiny jet black, with a red marking on the underside of the abdomen. The marking is usually an hourglass, but it can be two separated triangles, a triangle and a bar, faint red, or absent. Males and immatures are tan or olive-gray, with a white stripe down the abdomen and diagonal stripes on the sides. UC IPM says adult females are the most common spider capable of seriously injuring people in California, and almost all medically important bites come from them.
- Low webs, usually within three feet of the ground, leading back to a sheltered retreat.
- Yellowish, teardrop-shaped egg sacs with a tough covering, each holding about 300 eggs.
- Favorite sites: garages by doors and vents, woodpiles, rock walls, trash can grips, lawn chairs and picnic tables.
How do I tell a brown widow from a black widow?
A brown widow is a mottled mix of tan, brown and gray, and its hourglass is usually orange rather than red. The surest sign is the egg sac, covered in silk spikes like a very large pollen grain. UC IPM says the sac alone confirms the species, even when no spider is seen.
Brown widows became established in Southern California in the early 2000s. They pick more exposed spots than black widows: the undersides of cheap plastic patio furniture, chain-link fences, mailboxes and eaves. UC Riverside's Center for Invasive Species Research says they may be supplanting native black widows in some habitats.
UC IPM states that "the bite of the brown widow is much milder than that of the western black widow." Drop for drop the venom is at least as potent, but the smaller spider likely injects much less. If you cannot identify the spider, treat it as a black widow bite.
Are there brown recluse spiders in California?
No. UC IPM is unambiguous: the brown recluse does not live in California. Fewer than 20 verified specimens have been collected here over several decades.
California's native desert recluse (Loxosceles deserta) lives in the Sonoran and Mojave deserts and the lower San Joaquin Valley foothills. UC IPM calls it "the only California species of concern, and a minor one at that."
The Chilean recluse has lived in Alhambra, Sierra Madre, Monterey Park and San Gabriel for at least 80 years. All four are cities we serve from El Monte. UC IPM reports it is usually found only in dark commercial storage basements, not in homes.
To rule out a recluse, ignore the violin mark; UC IPM says it is not a reliable identifier. Recluses have six equal-sized eyes in three pairs; most spiders have eight in two rows of four.
The "California brown recluse bite" persists because wounds get blamed on spiders no one saw. UC IPM lists the more likely causes: MRSA and strep infections, bed bug and flea bites, shingles, diabetic ulcers, poison oak and chemical burns.
What about hobo spiders and yellow sac spiders?
The hobo spider does not live in California, and UC IPM reports no specimen verified by a qualified arachnologist. A 2001 study found its venom caused no necrotic wounds in rabbits, and UC IPM now considers the spider of minor medical importance.
The yellow sac spider, light yellow with a darker stripe on the upper abdomen, spins a small silk sac in ceiling and wall corners indoors. Bites usually happen when it is trapped against skin in clothing or bedding. UC IPM describes initial pain like a bee sting, redness and sometimes swelling. Yellow sac spiders are a job for routine general pest control.
What does a black widow bite feel like and what should I do?
The bite site often shows little more than redness and swelling; the venom is a neurotoxin, so the real symptoms are internal. CDC describes pain starting at the bite and spreading to the chest, abdomen or the entire body. UC IPM lists these symptoms:
- Rigid stomach muscles, which some doctors have misdiagnosed as appendicitis.
- Sweating, sometimes only of the bitten limb.
- Pain that is local, radiating or regional, and urine retention.
- Less often, numbness, agitation, fever and patchy paralysis.
Symptoms most often resemble the flu. Death is very unlikely, and medical treatment relieves many symptoms. First aid, from CDC and UC IPM:
- Stay calm, and identify the spider if you can do so safely.
- Wash the bite with soap and water.
- Apply a cold, damp cloth or wrapped ice, and elevate the bite if possible.
- Do not try to remove the venom.
- Seek medical attention right away, or contact a physician, hospital or poison control center.
When and where do widow bites happen in Los Angeles?
Usually when a hidden spider is trapped or touched. UC IPM says black widow bites are quite rare even where the spiders are very common, because they are shy and retreat when disturbed. Widows come out at dusk, and spiderlings arrive by ballooning on warm days with an updraft, so web removal needs repeating throughout the year.
The usual scenarios:
- Cleaning out a garage or shed.
- Handling firewood or reaching into a woodpile without gloves.
- Putting on gloves, clothing or shoes stored in the garage or outdoors.
Shake out gloves, clothing and shoes before use, wear gloves when handling stored items, and look before you reach.
How do you keep widows away from the house?
Habitat removal beats spraying. UC IPM is direct: "Insecticides do not provide long-term control." In a 2016 study it cites, water-based sprays had no significant effect on the eggs inside brown widow sacs. Three steps matter most:
- Stack woodpiles away from the house, clear debris along walls, and store garage items in zipper bags or taped boxes off the floor.
- Sweep, hose or vacuum webs and spiders off eaves, fences and outdoor furniture regularly.
- Keep outdoor light fixtures pointed away from doors and windows; lights draw the insects widows eat.
Our spider control service removes existing spiders, clears webs, creates perimeter barriers, and addresses the insects that attract them. For the gaps and lights that bring spiders indoors, read why spiders are in your home.
Spiders fall under the second tier of our 30-day guarantee: another visit within 30 days costs 30% of the original price. The written quote is free, and same-day service is available for an extra fee that depends on the day's route. Request a quote or call (323) 472-5329 anywhere in our Los Angeles and San Bernardino County service areas.
Frequently asked questions
Are brown widow bites dangerous?
Rarely. In 15 verified South African bites cited by UC IPM, the main symptoms were pain and burning at the site. None developed the body-wide effects of a black widow bite. One American case required hospitalization, so seek medical advice if pain spreads beyond the bite.
Do black widows come inside the house?
Rarely, and almost never to stay. UC IPM notes that widow spiders usually will not find enough prey to survive inside homes, so they nest outdoors and in garages, woodpiles and clutter. Strays usually arrive on plants, firewood or boxes carried in from outside.
Can a doctor confirm a spider bite?
Not from the wound alone. UC IPM points out that people and their physicians often blame spiders for skin lesions with no proof of spider involvement. In California, MRSA and other insect bites are more likely causes than a recluse bite. Bring the spider or a clear photo if you have one.