Dangerous Spiders and How to Avoid Them

Mike Bonds is the technology director for NYC Pest Pros, a NYC based pest control company that focuses on education, awareness and green sustainability.

There are literally thousands of spider species in North America, all of which are important parts of a healthy ecosystem. While most pose no threat to humans and pets, there are a handful of species that are considered pests and can cause serious health problems or death. Here are some of the most common dangerous spiders and what to do about them.

Widow Spiders

Black Widow spider

Widow spiders (Latrodectus) are members of the comb-footed spider family and can be identified by their messy, tangled webs. The black widow is the most familiar widow species and is typically found in the American South and Southwest. However, there are also other varieties of the black widow that can be found in Northern states. Two other widow species, the false widow and the brown widow, are also located in many portions of the country.

All but the false widow posses the characteristic hourglass pattern on their undersides. Interestingly, only the females are dangerous. The small, drab-colored males are harmless. That said, any pest control company will tell you that the female widows bite can cause serious problems. These include severe pain, fever, nausea, vomiting, dizziness, headaches and severe muscle cramps. In small children, the elderly and those with compromised immunity, the bite can be fatal.

Recluses

Brown recluse spider

The most well-known species in this group (Loxosceles) can be identified by the telltale violin pattern on its head, or cephalothorax. These spiders are mainly restricted to the Southern states. However, there are other recluse varieties in many portion of the US that pose little or no threat. True to their name, recluses prefer to stay hidden and aren’t aggressive.

They’re wandering hunters, which means that they don’t spin webs. The danger of these spiders, while real, is dramatically over-blown. It’s common for people to mistake insect bites, MRSA and certain skin conditions as recluse bites, even when these cases occur outside of the spiders’ natural range.

Even if you live in an area where the recluse population is abundant, few actual bites occur. In one case, exterminators found more than 2,000 brown recluses in a family’s home. In the eight years the family had been living there, not a single bite occurred. Even if someone is bitten, the bite doesn’t always result in infection and necrosis. In healthy individuals, little more than time and an ice pack may be all that’s needed.

Hobo Spider

hobo spider

The hobo spider (Tegenaria) is restricted to the Pacific Northwest and is part of the funnel-web family, not to be confused with Australia’s Sydney Funnel Web. They look strikingly similar to the average wolf spider, with the exception that they build and inhabitsheet-like webs with a funnel at the end. There are many other types of funnel-web builders that are harmless, however, so learning to properly distinguish them is important.

Asking a pest control company how to distinguish them is a good start. With hobo spiders, the males are more toxic than females, particularly the subadults. Bite symptoms can include pain, fever, nausea, vomiting, swelling and necrosis.

If these spiders or any of their variants are in your area, it’s important to be cautious. Never put your hands in places you can’t see into, and always wear thick leather gloves when handling wood or debris. Keeping clutter out of corners and eliminating entry points is also recommended. It’s also a good idea to call in a pest control service to spray your home against this pest problem.

Controlling Spiders

trapped spider

It’s best to take preventative measures instead of having to deal with one of these intimidating creatures in person. Avoid having piles of junk or clutter in your house or garage. Never stick your hand into boxes or anywhere where you can not see into the space. These are prime places where spiders take up residence. It’s best advised to not deal with these types of spiders on your own as they are no easy feat for the average homeowner.

Seek out professional help from a local company. If you are dealing with a spider situation in an outdoor garden, there are some excellent eco-friendly pest control techniques that you may employ. Additionally, there is no shortage of excellent resources online where you can find more helpful information on dealing with these dangerous spiders and other pests.

Hobo Spider Myth

Last night I was scrolling through my Facebook news feed when I stumbled upon a supposed “USA Spider Chart.” The chart, which is shown below, has numerous false and erroneous spider accusations; something the spider must be well acquainted with by now. One such error happened to be that the Hobo Spider is a deadly and dangerous spider, grouped together with the Black Widow spider and the Brown Recluse spider. See for yourself:

USA Spider Chart
Source: (Facebook.com)

 

THIS INFORMATION IS WRONG! The Hobo spider that is found in the United States is not deadly, and is not as dangerous as the Black Widow or Brown Recluse. Let’s clear up this common misconception about the misunderstood Hobo spider.

Are Hobo Spiders Dangerous?

Many of us cower in fear at the thought of a spider. If there is even an inkling that the spider might be lethal, we’d run screaming the other direction looking for the nearest flamethrower to take the spider out. It is misconceptions, like that of the Hobo spider, that lead many of us to feel the way we do about spiders.

Hobo SpiderHobo spiders are not deadly. Hobo spiders are not dangerous. In fact, a recent study from The National Center for Biotechnology Information and The US National Library of Medicine states that the Hobo spider is relatively harmless.

It was believed for a long time that Hobo spider bites can leave a necrotic (rotting flesh) wound that progresses over several days—similar to that caused by a Brown Recluse spider bite. In the study entitled The Misdiagnosis of Spider Bites, the venom from a Hobo spider was shown to not produce necrosis in humans, and in didn’t even produce necrosis in rabbits; which was believed to be the case after an earlier study on rabbits was released decades earlier.

Additionally, the study found Hobo spider venom was not deleterious, harmful, dangerous, or toxic to ANY vertebrate red blood cells.

It’s important to note that the Hobo spiders mentioned in the studies and in this blog post are the Hobos that are commonly found in the United States. Hobo spiders found in Australia can have a nasty bite.

How The Hobo Spider Myth Got Started

It’s believed that the Hobo spider myth started after the spider’s venom was injected onto a rabbit decades ago, and it caused necrosis of the rabbit’s skin. The above mentioned study proved the rabbit’s necrosis to be false, as the more recent study performed with up-to-date technology caused no such necrosis. The study also suggests that human related Hobo spider bites do not cause necrosis.

Hobo Spider Close UpI searched medical literature on Hobo spider bites, looking for instances in which a Hobo spider has caused necrosis or death, and found very little. I did find one case of a verified bite by a Hobo spider that resulted in a necrotic skin lesion, and this was in a person who had a pre-existing medical condition which can also lead to necrotic skin lesions.

The funny thing is that mites, fleas, bed bugs, soft ticks, hard ticks, conenose bugs, and kissing bugs would be far more likely to cause necrotic-type wounds than a Hobo spider bite; pests that don’t have the same rap as spiders do.

As far as I can tell, this Hobo Spider myth got started by fear mongering arachnaphobs perpetrating more spider hate.

Identifying A Hobo Spider

If you are resident of the Pacific Northwest, you are very well acquainted with the Hobo spider… or at least you think you are. The fact is that most people in the states of Washington, Oregon, Idaho, and Utah, in which the species is commonly found, refer to any big spider they see as a Hobo spider. As spider control professionals, we have found that many well-intentioned people call non-Hobo spiders as Hobo spiders. Giant House spiders are commonly confused for hobo spiders.

The truth is that Hobo spiders are very difficult to identify by the naked eye. Some people use a spider’s coloration to determine the species. The problem with this is that similar spider species often times overlap in their appearance with Hobos. Even experienced arachnologists have a difficult time identifying Hobo spiders, and rely heavily on hand lenses and microscopes to identify them.

True Hobo spiders are brown, with a large abdomen, and measure in length from 1/4th to 5/8 of an inch long. One of the easiest ways to determine if a spider is indeed a Hobo spider is to look at it’s web-building. Hobo spiders build funnel webs. To identify a Hobo spider with 100% accuracy, the spider in question must have its eyes and reproductive structures examined by an experienced entomologist.

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Pest Of The Week: The Hobo Spider

 

Hobo Spider Close Up

Grayish brown in color, with dark zigzag stripes, the Hobo spider is an aggressive spider found in the Pacific Northwest (Washington, Oregon, Northern California, Idaho, and British Colombia). It is suggested that these spiders are so aggressive because they have such poor eyesight. They have to attack things that move, or else they would starve.

With their impressive leg span, these spiders can reach a diameter of 1 ½ inches. They build funnel shaped webs, with oval openings, near the foundation of your home; and will aggressively attack anything that disturbs its web.

Although Hobo spiders aggressively bite, their bites are not as dangerous as once believed. There are many misconceptions out there regarding the lethality of the Hobo spider; comparing it to the more dangerous Black Widow spider and Brown Recluse spider. These rumors have recently been debunked.