A Guide to Venomous Spiders in Utah: Black Widows, Brown Recluses, Hobos and More

Introduction to Venomous Spiders in Utah

Utah is home to a diverse range of spider species. Only a small number of these spiders are potentially dangerous to humans. Spider bites are quite rare, and very few ever require medical treatment. However, it is still important to learn how to identify Utah's venomous spiders and understand the risks they pose.

This article covers the main types of poisonous spiders found in Utah. It includes:

• Black widow spiders
• Brown recluse spiders
• Hobo spider
• Yellow sac spiders
• Tarantulas

For each spider, we will explore its appearance, habitat, bite symptoms, and first aid recommendations. With some basic knowledge, you can coexist safely with these fascinating creatures.

Black Widow Spiders in Utah

Black widow spiders are among the most venomous spiders in North America. Two species occur in Utah - the western black widow (Latrodectus hesperus) and the northern black widow (Latrodectus variolus).

Identification

Female black widows are distinctive spiders that are easy to identify. They have a spherical black or dark brown abdomen with a reddish hourglass shape on the underside. Their legs and cephalothorax (head region) are also black.

Male widows are smaller with lighter markings. Juveniles may have additional red or white spots on the abdomen.

Western black widows grow to around 1.5 inches (35 mm) long while northern widows reach over 2 inches (50 mm).

Habitat

Black widows favor dry, dark, undisturbed places. Common habitats in Utah include:

• Woodpiles
• Rodent burrows
• Hollow logs
• Dense vegetation
• Outdoor toilets
• Unused sheds and garages
• Old mining tunnels
• Rock walls and piles
• Under porches and decks

Their webs are irregular, tangled cobwebs with a few thicker anchor threads. Western widows often nest near the ground while northern widows build webs in vegetation up to 3 feet high.

Bites and Symptoms

Widows tend to be timid and non-aggressive. They only bite in self-defense when disturbed or trapped against bare skin. This mostly occurs when people reach into dark hidden areas.

Bites inject potent neurotoxic venom that causes severe muscle pain and spasms. Other possible symptoms include:

• Intense pain at bite site
• Rigid abdominal muscles
• Nausea and vomiting
• Profuse sweating
• Headache
• Hypertension

Though alarming, most widow bites do not require antivenom. Supportive treatment for pain and muscle spasms is usually sufficient. Seek prompt medical attention if bitten.

First Aid

For black widow bites, recommended first aid steps include:

• Wash bite area with soap and water
• Apply cool compress to relieve swelling
• Take pain relievers like acetaminophen
• See a doctor for evaluation and monitoring
• Note timing of bite and progression of symptoms

Avoid any folk remedies like cutting or sucking the bite. Just seek medical assistance as needed.

Brown Recluse Spiders in Utah

The brown recluse spider (Loxosceles reclusa) has a venomous bite that can damage skin tissues. It is uncommon in Utah but occasionally found in the southwestern part of the state.

Identification

Brown recluses are usually light to dark brown. They have a dark violin-shaped marking on the cephalothorax with the neck of the violin pointing backward toward the abdomen.

The legs are uniformly colored with no bands or stripes. Brown recluses grow to 0.5-1 inch long (12-25 mm) with a legspan around 1 inch.

Habitat

This spider favors quiet, dry, undisturbed places indoors. Common habitats include:

• Attics
• Basements
• Closets
• Sheds
• Barns
• Wood and rock piles
• Cellars

Their webs are loose, non-sticky, and irregular.

Bites and Symptoms

Most brown recluse bites are minor and heal without complications. In some cases, their venom causes tissue damage and necrosis at the bite site called loxoscelism.

Possible symptoms include:

• Sharp stinging pain
• Itching
• Nausea
• Fever and chills
• Skin lesions, blistering or ulcers
• Purple-black wound crust

Healing can take 6-8 weeks or longer. Seek medical care if the bite area expands or does not heal properly.

First Aid

Recommended first aid for brown recluse bites includes:

• Wash bite with soap and water
• Apply cold pack to relieve pain and swelling
• Elevate bite area if possible
• Avoid ice directly on skin
• See a doctor, especially if symptoms persist

Hobo Spider in Utah

The hobo spider (Eratigena agrestis) is a funnel-web spider found in parts of Utah. It has long been feared as a dangerous spider but recent research suggests its bite poses low risk to humans.

Identification

Hobo spiders have an elongated oval abdomen and a distinctive pattern on their cephalothorax. The top is yellowish-brown while the sides are bordered in white with grey chevron markings.

Adults grow up to 14-20 mm long (over 0.5 inches). Their legspan reaches around 2 inches.

Habitat

Hobo spiders live in sheltered spots in homes and buildings. Common habitats include:

• Corners of rooms
• Window and door frames
• Woodpiles
• Basements
• Garages and sheds
• Crawlspaces

They make funnel-shaped webs in undisturbed places.

Bites and Symptoms

Though once blamed for causing necrosis, most researchers now agree hobo spider venom does not significantly affect humans. Bites may cause:

• Mild pain
• Itching
• Reddened skin
• Slight tissue damage in rare cases

Their bite is considered less harmful than a bee or wasp sting.

First Aid

To treat hobo spider bites:

• Clean bite area thoroughly with soap and water
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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.