What Kind of Spiders Are Poisonous in Arizona?
Arizona, like the rest of the U.S., is home to innumerable species of spiders. Types of Arizona spiders include large tarantulas to small, inconspicuous web spinners. Of all the spiders in the state, only two types of spiders are considered dangerous or medically significant: black widow spiders and brown spiders. Some people may be sensitive to the bites of other types of spiders, although this is rare.
Black Widow Spiders
Although several species of black widows live in the United States, Arizona has seen an increase in the population of the western black widow (Latrodectus hesperus).
The female black widow has a description many are familiar with: a shiny, black, globular body with red hourglass markings on the abdomen. Females reach approximately 1 1/2 inches with their legs extended. She spins irregular webs in protected areas; in urban areas, ideal web locations include in outbuildings, around spigots, under stairs and other protected areas near the ground. In arid, desert locations, ideal web locations occur nearly everywhere as small rock crevices provide protected hideaways.
The brown spiders (Loxoceles spp.) are sometimes called recluse spiders, fiddlebacks or violin spiders. Perhaps the most well-known of the brown spiders, and the most potentially dangerous, is the brown recluse (Loxoceles reclusa). While the state is not home to established populations of brown recluses, Arizona has established populations of five native recluse spiders: Loxoceles arizonica, Loxoceles deserta, Loxoceles apachea, Loxoceles kaiba and Loxoceles sabina.
Most recluse spiders have a dark violin-shaped marking behind the head, although many Arizona species are more uniform in color. These distinctive spiders have six eyes instead of eight, and most grow to 1/3-inch long in body, or approximately 1-inch long including the legs.
True to their colloquial name, recluse spiders prefer to stay hidden and are nocturnal. Most Arizona species prefer to live outdoors in dark, dry places such as scraps of wood or wood piles, dead cacti or rats' nests.
Because the western widow is showing an increase in population in urban areas, it is important to be cautious while gardening. Although shy, widow females are particularly protective of their webs and egg sacs. Always look where you are placing your hands or bare skin to prevent coming in contact with a web. Wear gloves when handling wood or debris outdoors, as many recluse spiders prefer to live in these dark, dry places. Move wood piles away from homes and keep all clothes or similar materials off of floors as recluses will find shelter in them if they manage to make it indoors.
The widows and recluses have very different venom and bites show different symptoms. A widow bite generally feels like a pin-prick if it is felt at all. Following the bite, the bite area will become red and start to swell. The venom is a neurotoxin that affects the nerves. Many people experience intense pain or stiffness, followed by abdominal cramping.
A recluse bite, on the other hand, often goes unnoticed. The bite area may start to sting. Within eight hours of the bite, the bite area will begin to show redness and pain, followed by a dark area forming around the bite. Recluse venom produces a necrotic wound, meaning the tissue begins to die, leaving a crater-like wound.
In the case of a spider bite, clean the bite area with a mild soap and water. Fill a wet cloth with ice and place it over the wound to reduce swelling and pain. Over-the-counter pain relievers can help.
Seek immediate medical care if you are concerned you may have been bitten by one of these dangerous spiders or if you begin to develop symptoms of either of these types of spiders' venom.
If at all possible and safe to do so, capture the spider to send to an arachnologist for proper identification.
- Arizona State University Julie Ann Wrigley Global Institute of Sustainability: The Western Black Widow Spider: Urban Pest
- The University of Arizona College of Agriculture and Life Sciences: Venomous and Poisonous Animals in Arizona
- The University of Arizona College of Agriculture and Life Sciences: Black Widow Spiders (Theridiidae:Lactrodectus sp.) in the Low Desert
- The University of Arizona College of Agriculture and Life Sciences: Pest Press: Recluse Spiders
- Mayo Clinic: Spider Bites: First Aid