Is That a Dangerous Spider?

A wolf spider hiding in fall leaves.

I've often wondered why a creature as beneficial as the spider looks so horrific. Whenever I encounter one, the feeling of revulsion is often followed by an immediate need to find a sound-hearted sole to take it outside and far away from me. However, the reality is that spiders are extremely helpful critters, especially in our homes. They control the populations of other bugs such as mosqiutoes, ants, flies and gnats that can be a nuisance inside. And outside, they protect our gardens from aphids, mites and beetles. Just a few of the thousands of types of spiders are considered a danger to humans. So, by learning to distinguish the dangerous from the beneficial, we can better understand which spiders pose a real threat, and which are just here to help.

In general, insects (and arachnids) that carry a dangerous venom display certain physical traits such as a bright color, unusual pattern, or large size. These traits warn predators, “Do not mess with me!” However, there are plenty of exceptions to the rule, such as the writing spider, which is large and brightly colored, but not venomous or aggressive at all. Although plenty of deadly spiders exist, most are native to tropical climates and remote locations. There are a few, however, that live in temperate climates where run-ins with humans are commonplace. The three types of dangerous spiders to look out for in your homes and yards are the black widow, brown recluse, and hobo spider. These spiders rarely harm humans, but are highly venomous and can live in a variety of locations.

Black Widow

The black widow is notorious for its macabre mating ritual, in which the female sometimes devours the male. And, of course, for its venom, said to be stronger than that of a rattlesnake.

Is That a Dangerous Spider, black widow

Luckily, the black widow has a distinct coloration: jet black with a bright red hourglass, or grouping of red spots, on the underside of its abdomen. They also commonly display red markings on the top of their abdomen. The black widow is just a little larger than a paperclip. Although there are established black widow populations in all states, they are reclusive and avoid contact with humans. Usually, they are found under wood piles or inside quiet sheds and boxes. The black widow builds a messy and irregular web, waiting upside down at the center for prey to become entangled in it. Though their poison is strong, they are not aggressive and will only bite in self-defense when fleeing is impossible. When they bite, the black widow secretes an unusual neurotoxin, called latrotoxin, which causes pain, nausea, paralysis of the diaphragm and difficulty breathing. Despite common belief, those bitten rarely suffer lasting damage, let alone death. However, to young children, the elderly, or household pets, a black widow bite could be fatal.

Brown Recluse

The brown recluse, unfortunately, has no eye-popping color to warn predators of its danger. However, they have an unusual pattern on the top of their abdomen resembling a stretched out violin, with the neck of the instrument towards their back end.

Is That a Dangerous Spider, brown recluse

Although all brown recluse spiders are brown, the shade of brown can vary widely. Their bodies are only the size of a green pea, but their long spindly legs can span a space larger than a quarter. The brown recluse population is concentrated in the center of the country, and these spiders are rarely found outside of it. In residential areas, they are found in undisturbed locations such as garages and tucked away closets. They build an asymmetrical web that includes a messy shelter made from disorderly strings of web. Like the black widow, the brown recluse is very shy and would rather run away than fight. Bites from this species are uncommon. In 2001, over 2,000 of these arachnids were removed from an infested home in Kansas, with the family of four inside never having been bitten, despite many encounters. When it feels cornered, however, the brown recluse will bite. It carries a deadly hemotoxic venom that causes vomiting, fever, rash, and muscle and joint pain. In severe cases, the venom will cause a necrotizing ulcer which will eat away at the surrounding healthy tissue and leave deep and lasting scars. Again, the young, elderly, and sickly are most susceptible to severe bites.

The Hobo Spider

The hobo spider is, perhaps, the most difficult venomous spider to identify. It is small, never exceeding two inches in leg span, and a nondescript medium brown.

Is That a Dangerous Spider, hobo spider

The only real identifying characteristic are two thin black zigzag lines running down the spider's abdomen. The hobo spider was introduced into the United States from Western Europe in the 1920s through the port of Seattle. Since then, the population has spread as far as the eastern edge of Washington state, as far south as Oregon, and as far north as Vancouver. Although the population within this area is large, the spiders are rarely found outside of it. These arachnids build funnel-shaped webs in cracks and crevices and lie in wait at the narrow end of the funnel for prey to walk inside. The strength of the hobo spider's venom is still debated, but has been known to cause headaches, dizziness and lesions that can take months to heal.


If you encounter what you believe be a dangerous spider, leave it alone! If you see one in nature, do nothing but alert the property owner. If you find one at home or on your property, call an exterminator. It may seem silly to call someone for a single spider, but a professional will check your property for any other poisonous and unwelcome visitors. Where there is one, there may be two (or 2,000).

Bite Care

If you have been bitten by a potentially dangerous spider, the first step is to make sure you keep the bite elevated and press it with ice. Next, if possible, safely capture the spider (preferably alive, but certainly not crushed). Then, have someone drive you and your new friend to an urgent care center. Do not panic. Severe spider bites are common and fatalities are very rare. Having the spider with you will aide in identifying the venom, but don't worry too much if you can't catch it. Likely, you will be given a steroid, antibiotic, and in severe cases, an antivenom.

It may be a bit cliché, but it is always true that spiders, even the most deadly, are more afraid of us than we are of them. So, be cautious and knowledgeable when approaching any spiders and remember that even the poisonous ones serve an important, albeit unsavory, function in nature.

(By the way, the dramatic looking fellow at the top is a wolf spider. Often confused with the brown recluse, they are nonaggressive and not dangerous.)