In this article, you’ll learn about seven brown spiders you’ll likely come across in Arizona and how you can easily identify each one.
Arizona Brown Spider
The Arizona brown spider is a small brown spider native to Arizona and is closely related to the popular brown recluse spider of the midwestern United States. Arizona brown spiders can be identified by dark brown markings on top of the head, which resemble the shape of a violin; hence they are commonly referred to as “violin” spiders. These markings are less obvious than in the brown recluse spider, an important distinguishing feature for both species. Arizona browns are ¼ to ½ inches long and have eight long slender legs. Though primarily an outdoor species, the Arizona brown spider is reclusive by nature. This spider may sometimes be seen hiding in cracks or crevices and can be found nesting in basements, drop ceilings, attics, crawl spaces, closets, and behind baseboards. The bite of an Arizona brown spider is potentially dangerous to humans, but symptoms are often not as severe as those of the brown recluse spider. The most common symptom when bitten is a spreading sore at the site of the bite that may result in necrosis (decaying of tissue due to cells dying) or permanent tissue damage if untreated.
Western Desert Tarantula
The western desert tarantula is a brown, large-bodied, burrowing spider commonly seen in southwestern deserts during the summer or rainy season. These spiders are known to be distributed in New Mexico and Arizona within the United States. An adult individual of this species has a body length of 3 to 5 inches (8 to 13 cm), with females being larger than males. The female western desert tarantula is usually a uniform tan or light brown color, while the male has a reddish-brown abdomen and black legs. As its name depicts, this spider often lives in desert soils and is resistant to harsh weather. It can also build burrows, surrounding the entrance with strands of silk, allowing this spider to detect prey while hiding in the burrow. The venom of the western desert tarantula is not dangerous to humans, and it is one of the least dangerous tarantulas within the family Theraphosidae.
Common House Spider
Another brown spider in Arizona, the common house spider, is a small brown spider that lives in and near human dwellings. Common house spiders vary in color from tan to nearly black, often with patterns of varying shades on their body. House spiders are easily identified by the papery brown egg sacs deposited in their webs. Females reach 0.20 to 0.24 inches long, while males are generally smaller, between 0.15 and 0.19 inches long. Females also have a distinctly rounded abdomen, more bulbous than males. Though these brown spiders live in constant proximity to humans, their size and color allow them to blend into the background and escape being seen easily. House spiders are often mistaken for the much more dangerous brown recluse spider because of their similarity in appearance. However, house spiders are not known to be dangerous to humans. They are rarely aggressive but will only bite humans occasionally in self-defense when grabbed or squeezed. Their bites heal quickly, unlike the brown recluse, which persists for days to weeks.
Brown Recluse Spider
Brown recluse spiders are not common throughout Arizona, so you’re unlikely to encounter any because of their solitary nature. They’re identifiable by their small size, light brown or tan color, and the violin-shaped pattern on their back. These shy spiders avoid human contact at all costs, so they like to build webs and hide in dark and secluded places such as attics, closets, sheds, garages, wood piles, and foliage. You’re also likely to find brown recluse spiders in cluttered areas around homes and commercial buildings, where piles of debris can provide harborage. They are one of the most common Arizona spiders known to be venomous to humans. The spider’s bite can be severe, and symptoms can worsen quickly if medical attention is not sought immediately.
Carolina Wolf Spider
Wolf spiders can be found in many habitats, including wet coastal forests, woodlands, shrublands, suburban gardens, and human dwellings. Among the wolf spider species in the U.S., the solid dark brown Carolina wolf spider is the largest wolf spider species found in North America, growing up to more than 1 inch (2.5 cm) long. Female wolf spiders are larger, 0.3-1.38 inches long, and males are 0.25-0.75 inches long. The Carolina wolf spider has a distinct solid black underside and eight eyes arranged in three rows. Unlike most other arachnids with poor vision or are generally blind, wolf spiders have impressive eyesight. This species makes deep, tubular burrows that hide most of the time– they don’t spin webs. Though people are often intimidated by their terrifying name and large size, wolf spiders are not actually a threat to humans, and they don’t often bite people unless provoked. Even when they do, their bite isn’t usually dangerous. It may cause a small red bump, mildly itchy and swollen, which usually doesn’t require medical treatment. These brown spiders hunt bugs and other spiders, so they often try to hide under chairs or tables inside a home.
Huntsman Spider
Huntsman spiders (family Sparassidae) are also called giant crab spiders because of their large size and unique crab-like appearance. Large species of huntsman spiders can often be confused with tarantulas. Still, they can mainly be identified by their legs, which, rather than being jointed vertically relative to the body, are twisted so that they extend forward in a crab-like fashion. Their legs have somewhat prominent spines, but the rest of their bodies are smoothly hairy or furry. Different species of huntsman spiders appear in varying shades of brown. The body of a huntsman spider measures about 0.7 in (1.8 cm) long on average, and its leg span alone can reach up to 5 inches (15 cm). Huntsman spiders are native to tropical and warm temperate regions and tend to live under rocks and in the crevices of tree bark. But they sometimes wander into people’s homes, so you’re likely to encounter them in sheds, garages, and other less disturbed areas. These brown spiders do not build webs but forage and hunt insects and other invertebrates. Huntsman spiders have been known to bite humans in defense, particularly in females aggressively defending their egg-sacs and young against perceived threats. However, bites cause mild symptoms and usually do not require hospital treatment.
Grass Spider
Grass spiders are harmless brown spiders found in Arizona. They are easily identified by their two prominent hind spinnerets and the arrangement of their eight eyes into three rows. There are two eyes in the top row, four in the middle row, and two in the bottom row spaced wider than the ones on the top row. Grass spiders have two dark brown bands running down both sides of their cephalothorax and lighter bands on their legs. Larger individuals can grow to about 19 mm in body length. Generally, spiders are known to use their webs to catch prey, but that is not the case for grass spiders. They weave sheet webs with funnel shelter on one edge and lack adhesive ability. Thus, the grass spider’s web is not sticky, but these spiders make up for that by running very fast to hunt prey.
