5 Most Poisonous Spiders in California

Most Poisonous Spiders in California
Picture of Israel Alvarez
Israel Alvarez

Owner @ Insight Pest Management

Table of Contents

When it comes to spiders, most people want little to do with them. In fact, many people find these small creatures terrifying. However, in Southern California, some of these small spiders can pack a venomous punch! While people often ask if spiders are poisonous, the correct term is venomous, and in our area, there are five of these spiders you should be aware of.

Key takeaways

  • Learn which Southern California spiders are venomous.
  • Understand how to identify the different venomous spiders in Southern California.
  • Learn how to reduce your risk of a venomous spider bite.

What are the most venomous spiders in California?

In Southern California, there are five venomous spiders that you should be aware of. These spiders have the ability to inject toxic venom through a bite that can cause pain and illness. While most of these spiders are not aggressive and do not seek out humans to bite, they will bite when they are threatened or disturbed.

1. Western black widow spider

The Western black widow spider is found in the Western regions of North America, including California. When considering venomous spiders in our state, the Western black widow is often the most popular and easiest to identify. To identify a Western black widow, you must first understand that the male and females of this species do not look anything alike, and, in the case of this spider species, you only need to worry about the female. male western black widows are not venomous and pose no danger to humans. The females, however, are the ones to look out for. Female black widows are jet black in color, with a distinctive red hourglass-shaped marking on their lower abdomen. In rare cases, this hourglass mark can be yellow or white in color. They typically measure around half an inch.

Even if you do not see a spider, the web can often indicate that you have a Western black widow in your home. Unlike other spider species that create tunnels or spiral spider webs, the Western black widow creates messy, three-dimensional webs that follow no regular pattern. These spiders will often hang upside down in the center of a web waiting for prey to land and once it does, they immediately bite the trapped insect, delivering the venom, before wrapping it up in the web to eat later.

The Western black widow is not an aggressive species and will typically run when they are threatened. However, when a female is guarding eggs or feels trapped, she is much more likely to bite. Thanks to the development of anti-venom, the Western black widow bite is rarely fatal as long as you seek medical attention immediately.

2. Brown widow spider

The brown widow spider is a close cousin to the Western black widow, though smaller in appearance. These spiders vary from light to dark brown or gray to black. On the dorsal side of their abdomen, they have unique black and white patterns, as well as an orangish yellow hourglass shape. Like the Western black widow, only the female brown widow can deliver venom. However, while the bite can still be painful, a brown widow bite does not deliver many toxins and the effects are mainly localized. Like their cousins, the brown widows are not aggressive and will only bite in self-defense or when protecting eggs. The brown widow has very distinct eggs that are covered in spikes, making it easy to identify a potential egg sac.

3. Yellow sac spider

Found mainly in urban areas of Western California, the yellow sac spider is a small beige to yellow venomous spider with dark brown to black markings and an orange-brown stripe running down the abdomen from the top to the center. This small spider measures from ¼ to 1/3 of an inch. They are best known for vertical travel on a silk string in order to catch airborne prey and avoid other predators. While the Yellow Sac spider is venomous, they rarely bite humans. When they do, the bite can cause itching and swelling but will resolve on its own within a few days.

4. Desert recluse spider

The desert recluse spider is often confused with the more popular brown recluse spider. While we don’t have the brown recluse in California, the desert recluse is found in the Eastern desert regions of Southern California and they have the common violin-shape marking, similar to the brown recluse. They are tiny spiders with a body of around ½ inch and a leg span between 1.5 and 2 inches. These spiders are tan or yellowish-tan in color, with a light brown abdomen.

These spiders reside in the desert, most often away from human contact, however, they can be found in and around your home hidden out of site. They are very venomous, and a bite can cause severe lesions, as well as serious symptoms in some cases. The lesions that appear at the site of a bite can be very painful and take weeks to heal. It is important to seek immediate medical attention if you believe you have been bit.

5. Chilean recluse spider

Native to South America and Chile, the Chilean recluse spider is found in Southern California and the Los Angeles area. This spider is similar in size to the desert recluse, is brown in appearance, and has a similar violin-shaped marking on the thorax. The Chilean recluse is considered the most dangerous of all recluse spider species, containing the neurotoxin Sphingomyelinase D, which causes skin and soft tissue necrosis. However, they are very shy and docile, and bites are not very common. If you suspect a bite from a Chilean recluse, it is important to seek immediate medical attention.

How to avoid getting bitten by poisonous spiders

All of these spider species can be found both indoors and outdoors, so you must use care in order to avoid being bitten. In addition to localized pain and swelling, additional symptoms of a venomous spider bite can include:

  • Headache
  • Muscle cramps
  • Nausea/vomiting
  • Convulsions or tremors
  • Increases sweating
  • Skin lesions
  • Fever
  • Chills
  • The appearance of small blisters


Knowing how to identify these spiders or signs that these spiders may be in your home can help reduce your risk of potential spider bites. Other tips can include:

  • Shaking our clothing, shoes, and bed linens before putting them on or getting into bed. Many bites occur when a spider becomes trapped between material and skin.
  • Wear gloves when reaching into dark secluded spaces such as high shelves, into wood piles, and when cleaning out your shed.

Keeping your home free of poisonous spiders

Once you know how to identify these venomous spiders, you can do everything you can to avoid a potential bite. If you find that you have a lot of these spiders in your home or property, professional pest control is recommended in order to best reduce your risk of dangerous spider bites.

The team at Insight Pest specializes in identifying and eliminating dangerous spiders that can pose a risk to you and your family. If you find just one of these spiders, chances are you have more. To learn how our team of experts can help you live spider-free, schedule an appointment today.

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Our expert technicians work to ensure that all potential pest entry points are sealed and offer routine treatment options to help ensure your home or business stays protected from future infestations. You don’t have to share your home or business with pests any longer! If you live in the Ventura County area, let the team at Insight Pest Management help you say goodbye to pests once and for all!

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