Dangerous Spiders in Utah

Funnel weaver (hobo) spider
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  • 01 of 05

    Black Widow

    Black widow spider
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    Black Widow spiders are found throughout North America, especially in the southern and western United States. Mature females are black and shiny, with a distinctive red hourglass marking on the underside of the abdomen. Immature spiders and males may be lighter or duller or may lack the red marking. Black Widows can be found in crevices and undisturbed areas such as woodpiles, rock piles, under eaves, on fences, in outbuildings and in areas where debris has accumulated.

    In many cases, the bite of the Black Widow may cause nothing more than pain and swelling, and you may be able to see two small holes where the spider's fangs have pierced the skin. Individual reaction to spider venom varies, and sometimes spiders may "dry bite" to irritate an intruder without wasting venom. In serious cases, severe symptoms will start to appear within 30 to 60 minutes. These include muscle cramps and spasms, vomiting, severe high blood pressure, stupor or shock.

    Intermountain Health Care...MORE offers these tips for what to do in a case of Black Widow spider bite:

    • Get medical help immediately. Call your doctor, hospital, or poison control center. The number for Utah Poison Control is 1-800-222-1222.
    • Remain calm. Too much excitement or movement will increase the flow of venom into the blood.
    • Apply ice to the bite area.
    • Do not apply a tourniquet. It may cause more harm than benefit.
    • Try to positively identify the spider or catch it to confirm its type.
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  • 02 of 05

    Hobo Spider

    Eratigena agrestis
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    Hobo Spiders are common in the Pacific Northwest but have been known to live in Utah since the 1990s. The bite of the Hobo Spider is often misattributed to the Brown Recluse, which does not live in Utah. Both spiders can cause necrosis, or dying flesh, in the area of the bite.

    Hobo Spiders build funnel-shaped webs in holes and crevices near the ground. They are not good climbers, but they are fast runners.

    The Hobo is considered a dangerous spider, but severe bite cases have been difficult to document. Victims often do not see or catch the spider, and the necrotic lesions attributed to spider bites can be caused by other conditions. It's incredibly difficult for scientists to "milk" spiders for venom, which hampers scientific study of spider bites.

    Dangerous or not? Read about the Hobo Spider controversy.

    Utah State University offers the following information about Hobo Spider bites:

    • The severity of envenomation depends partly on the amount of venom injected, as well as the sex...MORE and age of the spider. The bite of the hobo spider is relatively painless and is reported to feel like a pinprick.
    • Within 15 minutes of the bite, numbing sensations may occur at the bite site or other areas of the body (such as the tongue), and dizziness may occur.
    • After about 1 hour, reddening around the bite begins and enlarges in the area. The bite site becomes hardened and swollen within about 18 hours. Blistering at the bite site, severe headache, visual or auditory disturbances, weakness, and joint pains may occur within the first 36 hours.
    • Within 24 to 36 hours, a discharge of fluids and blistering may occur, and after 2 or 3 days the area around the wound may blacken. A cycle of sloughing and crusting at the ulcerated site may continue for some time, often requiring six months or more for complete healing to occur.
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  • 03 of 05

    Desert Recluse

    Desert Recluse
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    The dangerous Brown Recluse Spider ranges throughout the midwestern and southern United States but does not live in Utah. A related species, the Desert Recluse, can be found in the southwest United States, including the extreme southwest corner of Utah.

    Like the Hobo Spider, the Desert Recluse and other Recluse spider species are frequently blamed for necrotic lesions and skin infections that actually have other causes. The Desert Recluse and other Recluse spiders are difficult for non-experts to identify.

    According to ​​First Aid Expert Rod Brouhard, "Most brown recluse bites heal just fine without any medical intervention or first aid. If you see it happen or suspect that you were bitten, the recommended treatment is to use RICE (rest, ice, compression, and elevation). Wrap the area of the bite with a compression bandage, use ice on it and elevate it. If the bite develops into a boil or an ulcer, see a doctor."

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  • 04 of 05

    Spider Safety

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    Common sense measures for avoiding spider bites include reducing the number of spiders in the home, clearing away clutter, and wearing protective clothing around areas where spiders are likely to be. The Entomology Department at the University of California Riverside offers these tips for avoiding spider bites:

    • Use sticky traps to trap spiders. Every one you catch is one less spider that can bite you.
    • Remove bed skirts from beds. Move the bed away from the wall. Remove everything from under the bed so that the only way the spiders can get up on the bed is to crawl up one of the four legs.
    • Many bites have occurred when people put on clothes that had been lying around for several weeks or months and pressed the spider against their skin. Don't throw clothes on the floor and then wear them the next day. If you do, shake them out or squish them into a ball. Bang out shoes first to see if a spider crawled in during the night.
    • When you store things in the garage, basement or attic, put them...MORE in plastic bags that you can close. This is especially important for things that you stick your hands and feet into like: roller skates, baseball gloves, gardening gloves, boots, raingear. Tape up the edges of cardboard boxes so there is no way a spider can squeeze inside.
    • Be careful when you move things out of storage areas, in particular, cardboard boxes. Spiders like to hang out in the space under folded cardboard flaps.
    • Clean up clutter and junk that is lying around. Spiders love clutter and prefer to live under and between items.
    • Do not stack wood against the house. Move the woodpile as far from the house as possible, stack it off the ground and cover it with a tarp. When you pick up wood, wear gloves.
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  • 05 of 05

    Spider Bite First Aid

    doctor bandaging
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    Most spider bites heal on their own without treatment and only need basic first aid measures such as keeping the wound clean, bandaging and watching for signs of infection. The main dangers of spider bites are allergy, systemic poisoning, and necrosis. About.com's Guide to First Aid, Rod Brouhard, offers this information about treating spider bites:


    Anaphylaxis is always the biggest concern with any type of bug bite. If the victim exhibits any of these signs of allergic reaction or anaphylaxis shortly after a bug bite, call 911.

    • hives
    • shortness of breath
    • wheezing
    • weakness

    Systemic Poisoning

    Victims should seek medical treatment if symptoms appear in parts of the body away from the location of the bite. Black widow spiders have a toxin that affects muscle contraction and nerve function. Severe brown recluse spider bites can also cause some symptoms over the entire body (systemic reaction). Look for:

    • sweating
    • chills
    • headache
    • body aches
    • stomach cramps
    • leg cramps
    • rapid pulse
    • exhaustion

    In...MORE cases where the victim is feeling extremely tired or weak, call 911.


    Necrosis can be associated with Hobo Spider or Desert Recluse bites. Most bites heal just fine without any medical intervention or first aid. If you see it happen or suspect that you were bitten, the recommended treatment is to use RICE (rest, ice, compression, and elevation). Wrap the area of the bite with a compression bandage, use ice on it and elevate it.

    If the bite develops into a boil or an ulcer, see a doctor. This isn't typically 911 worthy, but you'll want to get a physician to take a look. One thing a doctor might do is take a swab from the boil and culture it (test for bacteria). That way, if it can be treated with antibiotics, it will. Antibiotic treatments will only be effective if there is a bacterial infection. The necrosis associated with spider bites can take months to heal.