Concerns about brown recluse spiders often lead to questions about their presence in local environments. This article provides factual information about brown recluse spiders in Utah and what to do if a bite occurs.
The Definitive Answer: Brown Recluse in Utah
Brown recluse spiders (Loxosceles reclusa) are not native or established in Utah. Their natural habitat is primarily concentrated in the central and southern United States, including states like Kansas, Oklahoma, Texas, Missouri, and Arkansas. Scientific evidence confirms breeding populations do not exist in Utah.
Isolated brown recluse spiders may rarely be transported to Utah, for example, in luggage or freight from their native range. However, these instances do not signify an established population. Reports of brown recluse sightings in Utah are frequently due to misidentification of other common spiders or misdiagnosis of skin conditions. Some experts suggest that reports of brown recluse spiders in Utah might actually refer to the desert recluse spider (Loxosceles deserta), a closely related species found in parts of southern Utah, though it is also uncommon.
Common Misidentifications and Similar Spiders in Utah
Given the rarity of brown recluse spiders in Utah, many local spider species are frequently mistaken for them. Identifying key features can help distinguish these common spiders. Brown recluses are characterized by a violin-shaped marking on their back, though this can be subtle and often misidentified. A more reliable identifier is their eye arrangement: six eyes grouped in three pairs, unlike the eight eyes most other spiders possess. Brown recluse spiders typically have uniformly colored legs and abdomens, lacking stripes or spines.
One frequently mistaken spider in Utah is the hobo spider (Eratigena agrestis), common in northern Utah. These spiders are brown with chevron markings on their abdomen and build distinctive funnel-shaped webs. Unlike brown recluse spiders, hobo spiders do not have banded legs. Wolf spiders (family Lycosidae) are another group often confused with recluses. These active hunters vary in size, possess hairy bodies, and have a distinct eye pattern with two large eyes facing forward, two on top, and four smaller ones below.
Yellow sac spiders (Cheiracanthium inclusum) are common throughout Utah and, due to their pale yellow or tan coloration, are occasionally confused with brown recluse spiders. However, yellow sac spiders have eight eyes arranged in two rows. Additionally, crevice weaving spiders, primarily found in southern Utah, are large, brown, and possess six eyes, leading to occasional misidentification. These spiders are not considered harmful.
What to Do for a Suspected Spider Bite
If you suspect a spider bite, general first aid measures can help manage immediate symptoms. Begin by thoroughly cleaning the bite area with mild soap and water. Apply a cold compress or ice pack to reduce swelling and discomfort, and elevate the bitten limb if possible. Over-the-counter pain relievers and antihistamines can alleviate pain and itching.
It is often challenging to identify the specific spider responsible for a bite without seeing it. If safe, capturing the spider for identification by a medical professional or entomologist can be helpful, but avoid risking another bite.
Seek medical attention if symptoms worsen, such as spreading redness, increasing pain, or signs of infection like fever or discharge. Prompt medical evaluation is also recommended if the bite is on a sensitive area, or if the individual bitten is a child, elderly, or has a compromised immune system. While most spider bites are not medically significant, professional assessment ensures appropriate care and rules out other potential conditions.