Utah’s most common and dangerous spiders

spider pest control

Black Widow

black widow spider on webThe black widow is considered the most venomous spider in Utah as well as all of North America. Known for their distinctive appearance, females are typically about half an inch long, shiny black with a large globular abdomen and a red hourglass on their underside. Only female black widows bite and it is typically when they are disturbed or protecting their eggs. The females also eat the males (which are typically half the size of females) after mating which gives them their name. Being nocturnal creatures, they are most active at night and can be found in dark corners and crevices especially in garages, sheds, or other areas on the near the exterior of a home.

The bite can cause severe effects to humans since it alters the victim’s nervous system. When first bitten, there may be two small holes from the fangs. The center of the bite may be light red with some darker red around that. The first symptoms occur within 20 minutes to an hour after the bite: there tends to be local pain in the area of the bite followed by general muscle cramps and spasms, abdominal pain, chest pain, weakness, tremor, as well as possible stiffness, chills, nausea, dizziness, fever, difficulty breathing, and/or an increase in blood pressure and heart rate. Get more information on the black widow here.

Hobo Spider

Hobo SpiderHobo spiders are fairly common in Utah. They are part of the funnel web spider family which means they have long legs and make funnel or cone-shaped, non-sticky webs. Varying in size but never more than two inches long, they have a brown cephalothorax (the body part above the abdomen that the legs are connected to) with darker brown markings. Their abdomen is grey with yellow markings which is often difficult to spot without magnification. Since they look similar to several other types of spiders, a distinguishing factor is that they DO NOT have bands or rings around their legs. Hobos are very fast but are not climbers and therefore aren’t often found above ground-level. They prefer the outdoors and may be found in fields, around brush, wood piles, rock piles, foundation gaps, or other areas that give them adequate shelter. They are also found in homes which gave them the common name of “aggressive house spider” and may be hidden in window wells and sills, dark basements, between objects, or in other protected and undisturbed areas.

The severity of the bite depends highly on whether it is a dry or wet bite. If dry (meaning no venom was released), the bite should not be serious. If wet, immediate redness will most likely develop around the bite which generally goes away within a few hours and, for the first 24 hours, doesn’t look like anything more than a mosquito bite but may feel warm in temperature. Then, after a day or two, the blister breaks and creates an open, oozing ulceration. If serious and not treated, they can cause an erupting lesion that spans from a pea size to larger than a half dollar or a flesh hole which can lead to dead tissue. For more information on hobos, go here.

Wolf Spider

wolf spiderOften mistaken as a tarantula or nursery web spider, wolf spiders are another spider that can be dangerous to Utah residents. The best way to distinguish them is by their eyes. These rather robust, dark brown spiders have eight eyes arranged in three rows: four small ones on the bottom row, two large on the middle row and two medium ones on the top of the head. They vary greatly in size depending on the species and sex. Females are generally larger than males. Also, females carry their egg sac and babies on their backs.

When bitten, fang marks and tearing of the skin may be present if the wolf spider is large enough. Often though, only redness, swelling and pain occurs which can last up to 10 days. Swelling of the lymph glands occurs often as well. Sometimes, the skin around the area will become dark in color. The wolf spider is not as dangerous as the black widow or the hobo but can lead to further complications if not properly cared for. Learn more about the wolf spider here.

Yellow Sac Spider

yellow sac spiderThe Yellow Sac spider is a common species throughout the U.S. and quite abundant in Utah. The yellow sac spider is somewhat unique for dangerous spiders in that they don’t create spider webs; instead, they create a sac (thus the name), which they may place in the corner of two walls and a ceiling.

Yellow sac spiders will remain hidden in leaves, cords of wood, or in underbrush. They prefer the outdoors until the weather begins to cool, at which time they’ll move indoors.

The yellow sac spider bite is quite painful from their fangs, and they are quick to bite if they find themselves in a newly occupied shoe or clothing. A bite from the yellow sac spider won’t lead to death, but it can be confused by the bite of a brown recluse. Redness and inflammation is a common side effect, along with the irritating pain.

For more information on Yellow Sac Spiders, click here.

If you suspect that you or a loved one has been bitten by one of these three spiders, you should consider seeking medical help especially if it is a black widow or hobo spider bite. If it is a less serious bite that doesn’t require medical help, check out these home remedies for spider bites.



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