Guide to Venomous Biting Spider Species in California

Biting Spiders Found in California

Californias mild climate makes it home to a diverse population of spiders, including some species with bites that can be dangerous. While most spider bites are harmless, a few native California spiders can inflict painful bites that require medical treatment.

Learn how to identify venomous spiders in California, what their bites feel like, and how to avoid them. A little knowledge about the species of biting spiders around your home and outdoors can give you peace of mind.

Black Widow Spiders

The most notorious biting spider in California is the black widow. Found throughout the state, female black widows are distinguished by the red hourglass shape on their otherwise black, shiny bodies. They like to spin their irregular webs in protected spots like woodpiles, under rocks, and in the cracks of logs. People are most often bitten when they accidentally disturb a web.

A black widow's venom contains neurotoxins that can cause muscle cramps, nausea, and difficulty breathing in humans. The bite itself is rarely felt initially and may only cause a pinprick sensation. Pain spreads and intensifies within an hour and abdominal muscle spasms may occur. Though extremely unpleasant, most black widow bites can be treated with antivenom and supportive medical care.

Brown Widow Spiders

A relative newcomer to California, the brown widow spider has a dark brown body with longer legs and a more spindly shape than black widows. The orange hourglass pattern may have a yellow border. Brown widows inhabit similar outdoor areas and can be found under lawn furniture, planters, and patio furniture cushions.

The venom of a brown widow is comparable to that of a black widow, but they tend to inject less during a bite. While still medically significant, their bites cause less severe reactions with pain, redness, muscle spasms, and nausea that normally resolve within 24 hours.

Brown Recluse Spiders

Though not native to California, brown recluse spiders do occasionally hitchhike into the state via transported goods. They can take up residence in man-made structures. Distinguished by a dark brown body and long legs, brown recluses have a characteristic violin-shaped marking on their back. They spin irregular webs in secluded, dry spots like attics and closets.

The venom of a brown recluse destroys skin tissue at the bite site. A blister forms within 8 hours and a painless open sore develops over several weeks, leaving deep scarring. Though rare, severe reactions include fever, chills, and generalized skin rash.

Hobo Spiders

Another spider sometimes accidentally introduced to California is the hobo spider. Aggressive when disturbed, hobo spiders have a distinctive herringbone pattern on their bulbous abdomen. Bites feel like a pinprick and mild initial pain then develops into severe cramping 8-12 hours later.

Unverified reports link hobo spider bites to slow-healing wounds, but other experts assert they are not dangerously venomous to humans. Their bites are likely overdiagnosed due to similarity to other spider bites.

Yellow Sac Spiders

Yellow sac spiders are one of the most common spiders found creeping around California homes and buildings. They have a pale yellow body and darker yellow abdomen. Their painless bites don't always release venom but when they do, redness and mild stinging develops after a couple hours.

Though not medically significant, yellow sac spider bites can become infected if they are scratched open, so monitor for signs of infection like oozing, redness, and swelling.

Fishing Spiders

Two species of fishing spider inhabit the west coast - the raft spider and the dark fishing spider. They are large, hairy spiders that can be found near lakes, rivers, and streams where they hunt for prey on the water surface. Their powerful jaws can inflict a defensive bite if handled.

The venom of fishing spiders is not toxic to humans but contains substances that cause localized pain, redness, and swelling that fades within a few days. The bite may also feel itchy or tingly for awhile.

Wolf Spiders

Large, hairy wolf spiders roam California yards, fields, and forests at night hunting prey. They have camouflage patterns of brown, black, and grey and may have stripes on their legs. Though they rarely bite, wolf spiders will do so if trapped against bare skin.

A wolf spider injects venom that causes swelling and mild pain around the bite site that normally resolves after a few days. The bite may be followed by itching sensations.

Jumping Spiders

Distinguished by their ability to jump, jumping spiders are found around California gardens. Small and sometimes brightly colored, jumping spiders pounce on prey rather than spin webs. Though bites are very rare, they can pinch exposed skin in self-defense.

Jumping spider bites feel like a pinprick followed by mild stinging and localized swelling. The bite may bleed slightly if the skin is broken. The small size of their fangs means reactions are mild.

Recluse Lookalikes in California

Certain native spiders are sometimes mistaken for the more dangerous brown recluse in California. These include the desert recluse, Mediterranean recluse, and apache recluse which all have markings on the body but do not have venom that is medically threatening to humans.

Bites from these recluse lookalikes may cause temporary redness and irritation but have no long-term effects. Experts should identify the spider to keep brown recluse bites from being overdiagnosed in California.

Signs of a Potential Spider Bite

It's not always obvious when a spider has bitten you. Here are signs you may have been bitten:

• Mild stinging or pain at the site developing into severe muscle cramps and abdominal pain.
• Appearance of two fang puncture marks or a raised blister at the bite site.
• Skin redness, itching, swelling, numbness or localized tingling sensation.
• Nausea, sweating, headache or fainting as a reaction to venom.
• A slow-healing open lesion or ulceration at the bite site if infected.

Spider bites require urgent medical attention if you experience difficulty breathing, muscle spasms, fever, vomiting, or dizziness as these can indicate a toxic reaction to venom. Necrotic wounds that won't heal also need medical care.

Treating Spider Bites

Here are some tips for treating spider bites:

• Clean the bite area with soap and water to prevent infection.
• Apply a cool pack or cloth to relieve swelling and pain.
• Keep the bitten extremity elevated if possible.
• Use over-the-counter pain medication if pain is severe.
• Avoid scratching or irritating the bite to prevent infection.
• See a doctor for evaluation of bites that cause systemic symptoms.

More serious bites will require medications like antivenom, antibiotics, pain drugs, and in rare cases surgery. Make sure to get medical care if the bite appears infected, doesn't heal, or causes worrisome symptoms.

Preventing Spider Bites

You can take these steps to avoid spider bites around your home and when outdoors:

• Remove piles of debris and wood from around the exterior of the home.
• Clean up old piles of leaves under plants and trees.
• Store boxes off the ground in sealed plastic containers.
• Clear clutter from garages, attics and basements.
• Shake out shoes, clothing, and equipment before use.
• Seal cracks around doors and windows to block entry.
• Avoid handling spiders and disturbing large webs.
• Wear protective clothing like gloves and closed toe shoes when gardening.

When to Consult an Exterminator

It may be a good idea to contact a professional exterminator if:

• You have frequently encountered spiders or been bitten at your home.
• Significant populations of black widows live around your property.
• Venomous spiders have been spotted indoors repeatedly.
• You keep finding spider eggs sacs around the foundation.

Licensed exterminators have access to stronger and more targeted chemicals to kill and repel spiders. They can treat known infestations and help spider-proof your property against future invasions.

Stay Vigilant for Biting Spiders in California

Though most spiders in California are harmless, a few native and invasive species can inflict painful and potentially dangerous bites. Learn how to identify high-risk spiders like widows, recluses, and sac spiders around your home. Awareness of likely hiding spots, signs of bites, and proper first aid can help prevent and treat spider bites.

With some diligent prevention measures, you can keep your property safe and enjoy California's beautiful outdoors without fear of unwanted arachnid encounters.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.