5 Venomous (Poisonous) Spiders in California in 2024

Yellow Sac Spider sitting in a tree.
Rainer Fuhrmann/Shutterstock.com

Written by Taiwo Victor

Updated: October 9, 2023

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Most people generally regard spiders as terrifying creatures. Luckily, there are only five types of venomous spiders to be worried about in California. These spiders are; western black widow, brown widow, desert recluse, Chilean recluse, and yellow sac spiders. They are venomous spiders capable of injecting toxic venom into bitten prey or humans. In actuality, most of these spiders are not aggressive –they will not bite if left alone or undisturbed. This article looks into how you can easily identify these spiders in California and where you can find them.

Western Black Widow Spider

Adult female black widows can harm humans with their bites.

The western black widow is a venomous spider found in the western regions of North America, including California. Like other black widow spiders, it is a common notorious species in the state, so it’s important to know how to identify this spider. First, be aware that males and females of this species look nothing alike. The female western black widow spider is jet black, often with an hourglass-shaped red marking on the lower abdomen. However, the “hourglass” pattern can be yellow or, sometimes, white. The female’s body is about ½ inch (14–16 mm) long. On the other hand, the male western black widow spider is around half the length of the females. They typically have a tan color with lighter-colored stripes on the abdomen.

As with other spiders of the genus, western black widow spiders can also be identified by the irregular or “messy” webs they build. Their webs do not take the spiral or tunnel-shaped pattern of other spiders. In addition, female black widows are also reputable for being the dangerous of the two sexes, with a potent venom containing neurotoxins. Symptoms of this venom in humans include pain, nausea, and sweating. Treatment including antivenom is recommended if the toxicity is severe enough. 

Brown Widow Spider

brown widow spider vs black widow spider

The brown widow spider has a neurotoxic venom.

Also a member of the genus Latrodectus, the brown widow spider is a close cousin of the black widow, though smaller and lighter in color. The brown widow is one of the spiders in California, also found in many areas of the U.S. Unlike the black widow spider, this spider’s color can range from tan to dark brown to grey or black. The brown widow can be identified by the black and white patterns on the dorsal sides of its abdomen and a prominent orange-yellow colored hourglass shape. Brown widow spiders have distinct eggs, easily recognized by pointed projections all over the egg sacs described as spiky in appearance. 

Though painful, the brown widow’s bite is not considered dangerous; they are usually much less dangerous than the black widow’s because they deliver little venom. The spider has a neurotoxic venom, and the effects of the toxin are usually confined to the bite area and surrounding tissue. The affected skin might turn red, and the victim may feel pain, so it is important to seek medical attention when bitten. However, brown widow spiders are shy and avoid human contact, so they only bite in self-defense. 

Desert Recluse Spider

Desert Recluse Spider

The desert recluse spider resides in areas largely uninhabited by humans.

The desert recluse is a brown spider commonly misidentified as the brown recluse spider. It is a common type of recluse spider found in hot and humid areas of southern California’s eastern desert regions. In contrast, the brown recluse is relatively rare in the state. Male and female desert recluses are small and may be hard to spot, with a body length of about ½ inch and a leg span between 1.5 inches and 2 inches. They are typically tan or yellowish-tan in color, with a light brown abdomen. Common with most recluse spiders, their identifying feature is the “violin-shaped” or “fiddle-shaped” mark, with six eyes rather than eight.

As implied by its name, the desert recluse spider resides in areas largely uninhabited by humans, especially among thick vegetation and close packrat dens. The spider hunts at night and eats small insects – dead or alive. The bite of the desert recluse is venomous, and the symptoms can vary from virtually no effect to death, though very rarely. Symptoms usually start between two to six hours after receiving a bite. The bite can damage the skin and the surrounding tissues of the bitten area. These lesions can take weeks to heal, and they can cause serious problems if medical attention is not sought.

Chilean Recluse Spider

Chilean Recluse Spider

Though Chilean recluse spiders are venomous and have a reputation of being the most dangerous of all recluse spiders, they are shy.

Though native to Southern America’s Chile, the Chilean recluse spider can be found in Southern California and the Los Angeles area of California. It is a larger species of recluse spider, with its body length (including legs) ranging from 0.31-1.57 inches (8–40 mm). Similar to other recluse spiders, Chilean recluses are typically brown with violin-shaped markings on the dorsal side of their thorax. They have six eyes arranged in pairs. 

Though Chilean recluse spiders are venomous and have a reputation of being the most dangerous of all recluse spiders, they are shy and docile. They don’t bite unless frightened or startled, such as when pressed against human skin. However, it is a spider of medical significance because its venom contains Sphingomyelinase D, a dermonecrotic agent which affects the skin. Symptoms range from mild skin irritation to severe skin necrosis with the destruction of soft tissue, which may take months. Medical treatment is highly recommended if you suspect a Chilean recluse has bitten you.

Yellow Sac Spider

Yellow Sac spider (Cheiracanthium) with prey in a pine tree. These dangerous spiders are prolific at night, and have similar venom to the Brown Recluse spider, only a milder dose.

Yellow sac spiders are dangerous spiders prolific at night and have similar venom to the brown recluse spider, only a milder dose.

The yellow Sac spider is one of the spiders in California that are venomous. This tiny spider can be found in western California, especially in urban areas. True to its name, the spider is beige or yellow, with dark brown or black markings on its palps, chelicerae (jaws), and feet. It also has an orange-brown stripe running down the abdomen from top to center. The body of a female yellow sac spider measures between 0.2 and 0.35 inches, while males tend to have a narrower body and a larger leg span than females.

Yellow sac spiders are venomous and capable of biting humans, though they rarely bite. The venom from a bite causes moderate pain followed by itching and swelling. Symptoms usually resolve within 7–10 days, and bites are rarely fatal. These venomous spiders are popular for their vertical traveling attached to a silk string, which they use to catch airborne prey. They also use this to avoid attack from predators such as ants, centipedes, or larger spiders.

Bonus: What Keeps Spiders Away

dried herbs and essential oils

Essential oil scents like lavender are repugnant to spiders.

One of a person’s worst nightmares is having spiders wind up in their home–especially the poisonous kind! The best way to avoid getting bitten by a spider is to try and prevent them from entering your house in the first place. As spiders can get into your home through holes and cracks, you can check for possible entryways with a flashlight. If the light gets through from the inside to the outside, you should fill that hole or crevice with an appropriate product.

Keeping your yard free of debris and overgrown vegetation helps cut down on areas spiders would gravitate to. Caulking doors and windows is also a good strategy to keep them out.

Spiders hate certain scents, so scented essential oils can help deter them like peppermint, tea-tree, lavender, and rose. You can add 15-20 drops of a particular oil in a water bottle mixed with water and spritz it around your house. They also hate the smell of cinnamon and vinegar, so these scents can be used similarly.

Rubbing lemon or orange peels on the baseboards along your walls, on window sills, and on other surfaces can also repel spiders, who dislike citrus smells. Furniture polish and cleaning products with lemon scent can also help.

Regular cleaning inside your home, especially in areas that are dark or less frequented, is necessary to keep spiders from setting up residence. It’s also important to keep an eye on fruit bowls, as they can attract spiders.


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About the Author

For six years, I have worked as a professional writer and editor for books, blogs, and websites, with a particular focus on animals, tech, and finance. When I'm not working, I enjoy playing video games with friends.

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