SALT LAKE CITY, Utah (ABC4) — As summer ends and turns to fall, keep a watchful eye out for things that crawl. There are several species of spiders to be found in Utah, and ABC4 breaks down what to know about each type.
According to Utah State University Extension, this includes Black Widows, Hobo Spiders, Wolf Spiders, and Yellow Sac Spiders. The brown recluse spiders do not occur in Utah. “Some of these spiders are improperly labeled as dangerous, while others truly pack a venomous punch,” the press release states.
Black Widow Spiders
The Utahn Black Widow Spider (Latrodectus hesperus) is one of several “widow” spiders within the Latrodectus genus. There are 31 widow spiders within that genus, but the most commonly seen in Utah is the Western Black Widow.
The female Black Widow spider can be easily recognized by its jet-black exoskeleton and flaming red hourglass shape on its under-abdomen. Male Black Widows are tan with small oval-shaped abdomens. According to USU, the average size of the female is about 1/2 an inch, whereas the males average 1/4 an inch. Black Widows tend to build irregularly shaped webs with no pattern, and prefer dark spaces, as they are nocturnal.
The Black Widow gained its name due to the fact that some females eat their male counterparts after intercourse, also known as sexual cannibalism. According to USU, this behavior is rather rare in the wild.
While many are aware of the potent venom that comes from Black Widows, it is important to note that only female widows have this venom. The venom is a type of neurotoxin and comes with pain, nausea, sweating, swelling, goosebumps, and in some cases fatality.
According to USU, fatalities in the U.S. are relatively low, usually impacting only young children, the elderly, and immunosuppressed populations.
The Hobo Spider (Eratigena agrestis) is well known in Utah as a dangerous foe, but is it really that bad? It is classified within the Genus Eratigena known as Funnel Web Spiders. These are not the same as the Australian Funnel Web Spiders who are from a different Genus, USU reports.
According to USU, Hobo Spiders were introduced to the North American continent in the 1930s on the Eastern coast but have since spread into most of Northern and Eastern Utah.
Hobo Spiders are difficult to identify without the use of a microscope, as many spiders look similar in Utah, such as the Barn Funnel Weaver, and some species of the Wolf Spider.
The Hobo Spider is nicknamed “The Aggressive House Spider,” likely due to the species name agrestis. However, it should be known as the field house spider, because agrestis is Latin for “of the field.”
While researchers originally believed Hobo Spiders contained “necrotic” venom, which would mean the death of cells around the site of the bite, or blisters, lesions, or inflammation, which cannot be reversed. However, within the last 10 years, studies have suggested that the Hobo Spider bite is not necrotic, USU reported. In fact, there have been no scientifically confirmed cases of necrosis caused by a Hobo Spider bite.
According to USU, confirmation of such a bite would require sufficient study, of which all reported cases have not been, and therefore could be a case of blaming the spider who was in the wrong place at the wrong time.
The Hobo Spider may OR may not be dangerous to humans. According to USU: “More and more evidence is being mounted against the idea that they are [dangerous]”
There are several species of Wolf Spider that can be found in Utah within the Hogna Genus. They are the larger types of wolf spiders. They are the largest species, Hogna carolinesis has been sighted occasionally in Utah.
According to USU, Wolf Spiders are unique due to the fact they do not form webs. Instead, they stalk and run down their prey. These spiders are usually larger, reaching up to 1.38 inches in length. These spiders are also unique because they carry their hatching offspring on their backs to protect them from predators.
Their bodies are tan with brown and black patterns on the thorax and are most easily recognized by their larger set of eyes (two large eyes atop four small eyes in a row.) In fact, their eyes are large enough that when hit with a source of light, such as a flashlight, they will shine back.
Although large and scary looking, the Wolf Spider’s venom is not considered dangerous to humans outside of severe allergic reactions. The bite typically causes mild pain, swelling, and localized itchiness.
Yellow Sac Spiders
The Cheiracanthium inclusum, or American Yellow Sac Spider, is known for their larger oval-shaped thorax that has a yellowish/tan appearance. They are sighted most during the summer months.
These spiders, approximately the size of a nickel, can also be recognized by a small “heart-mark” found on the cephalothorax where it meets the abdomen (above where the spider heart is typically located.) The heart-mark is a dark line that goes down its back.
These spiders are a real threat if bitten, as their venom is confirmed to be cytotoxic (causing tissue death) and in the worst cases necrotic. Necrotic venom can cause tissue death, which can be identified when the skin develops an ulcer, becomes black in color, and forms a crust that eventually falls off. According to poison.org, the venom can penetrate deeper in the tissues sometimes affecting the fat and muscles. It can also spread to the rest of the body and become life-threatening. Often, a necrotic bite can leave a crater-like scar, even after it has healed.
Yellow Sac Spiders are also more aggressive than some spiders, possibly biting more than once if kept in close proximity to exposed skin. The first sign of a bite from a Yellow Sac Spider is localized burning for up to an hour, nausea, fever, stomach ache, and lethargy. It may then develop a dead-skin cap called an eschar, that will fall off after 7 to 10 days. This should be monitored, as it can cause serious health issues if it turns out to be necrotic.
If worse symptoms arise, such as difficulty breathing/swallowing, severe vomiting, or apparent death (black/grey skin tissue, loss of tissue), seek medical attention immediately.
Bite Protection and Management
If bitten by a spider: capture it for identification, USU reports. This will assist professionals in treating the bite, and further research.
One way to avoid spider bites is to check storage areas frequently, this includes garages, basements, attics, storage facilities, pantries, workshops, etc. where items may be left alone for long periods of time.
According to USU, some other ways to keep spiders away, and avoid bites include the following:
- Use gloves when handling firewood, hay/straw, or other debris where spiders might hide.
- Do not walk barefoot in areas where spiders will likely hide.
- Triple-check that doors and windows are properly sealed, including the use of window screens.
- Use a pest control spray service once or twice a year to keep spiders away.
If you, or someone you know, has been bitten by one of the venomous spiders as outlined above, seek medical attention immediately, wash the wound, and use ice to reduce swelling.