How to Identify Venomous House Spiders

What and What Not to Be Afraid of

“Oh my God, kill it! KILL IT!”

Outbursts like these are common throughout much of the United States and, indeed, the world, when a spider’s cover is blown and it is forced to skitter this way and that along the wall or across the living room carpet to avoid being, as suggested above, speedily smashed.

It is unfortunate that so many of these harmless eight-legged critters have to pay such a price for our unfounded fears and instinctive squishing behaviors, especially since they work so hard to rid our homes of ever creepier (in the author’s personal opinion) pests such as silverfish, fleas, bed bugs, gnats, and flies.

I find that the basis for most fears of spiders is the fact that most people don’t know the difference between those that are harmful to humans and those that are perfectly capable of coexisting with us peacefully. And so, in the spirit of enlightenment, I have devised a way to help any and all who are curious learn about which spiders pose a danger and which do not.

"Be careful of me. I don't want to bite, but if I do, I can pack quite a punch!"
“Be careful of me. I don’t want to bite, but if I do, I can pack quite a punch!”

. Biggest Threats

The leading ladies and gentlemen on this list are of course the ever-beautiful female Latrodectus hesperus (black widow spider) and her renowned accomplice the Loxosceles reclusa (brown recluse spider). The runner-up to and lesser known than these two is Tegenaria agrestis (hobo spider).

Female black widows are perhaps the most easily identifiable spider in human history. The striking red markings on their undersides are a dead giveaway to their species. Whether the red mark is in the shape of an hourglass or a simply a dot, it is safe to assume that any shiny black spider with a bulbous abdomen falls under this category. The males of this species are smaller, shyer, and less venomous than their female counterparts. In fact, there has been much speculation as to whether or not they are more deadly than the common garden spider! Also, they look nothing like their women; they’re thin and usually mottled brown or gray.

Black widows, like cockroaches, can be found anywhere in the United States providing there is:

  • A stable source of heat (such as a human dwelling)
  • An ample supply of food (flies, woodlice, other spiders, etc.)
  • Dark places (the space under your bed, in your shoe closet, etc.)

They are more prominent in warmer states because they can breed and catch food outside. Natural enemies of this spider do exist and consist mainly of wasps such as the blue mud dauber and the spider wasp.

Black Widow Bites

Source

Two red marks are the first sign of a black widow bite. Some spider bites are “dry” and no venom is injected. However, if venom is injected, then the following symptoms are often muscle cramps and spasms near the site of the bite, fever, and nausea. If this happens, see a doctor immediately. Stay calm and apply concentrated heat to the bite to minimize the spread of the venom and alleviate pain.

Brown Recluse

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Brown recluses have a distinctively smooth appearance compared to most other spiders their size.
Brown recluses have a distinctively smooth appearance compared to most other spiders their size.
Brown recluses have a distinctively smooth appearance compared to most other spiders their size.

While the black widow is easily identified by her shiny black exterior, large abdomen, and red shape on the underside, the brown recluse is less easily recognized because of his dull colors. The famed ‘violin shape’ (the base of the violin starts near the eyes, and the neck of the instruments points down toward the abdomen), which is supposed to be the telltale sign for this species is sadly not confined to brown recluses, nor do all brown recluses possess it. Perhaps the only foolproof way of identifying these tricky arachnids is to count their eyes. It’s true! While most spiders have eight eyes, the brown recluse is unique in that it has only six. Also, the abdomen of the recluse spider is devoid of markings, and their legs are smooth with no thick hairs.

Brown recluses have a smaller range than most people think, not straying further west than the Rocky Mountains and rarely venturing north of Nebraska. They prefer quieter, darker, and warmer places to raise their families, so they don’t travel with humans to new places as often as black widows do.

Because the brown recluse is so excellent at hiding, there have not been many studies on them outside of research on the effects of their bites. So, the statement that the brown recluse has no natural enemy should be taken with a grain of salt. People who have watched and collected data from the brown recluses in their homes have noted seeing other spiders (particularly the jumping spider) attack and kill them with relative ease.

Brown Recluse Bites

Red itching skin is the first symptom of the bite of a brown recluse spider. The area then develops into a blister, followed by an open sore, which in turn is accompanied by a rash of tiny red dots. Fever and nausea can also occur. If you are bitten by a brown recluse, see a doctor immediately. Stay calm and apply concentrated heat to the bite to minimize the spread of the venom and alleviate pain. The venom of a brown recluse causes necrosis, or the death of tissue, which can take a long time to heal.

Hobo Spider

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Hobo spiders are often confused with giant house spiders or brown recluses.Hobo spiders have 8 eyes, like most spiders, whereas brown recluses have 6.Hobo spiders may not be as dangerous as people once thought.
Hobo spiders are often confused with giant house spiders or brown recluses.
Hobo spiders are often confused with giant house spiders or brown recluses.

The hobo spider is one that more people need to be aware of. They are the real cause of countless so-called “brown recluse bites.” The brown recluse is often wrongfully blamed because both species look related at a glance, and their bite patterns and symptoms are similar. But a second look at these critters can identify them in minute’s time. Hobo spiders, unlike brown recluses, have a mottled coloration and distinctive ‘herringbone’ patterns on their abdomen. Their legs are also hairier than those of the brown recluse.

The easiest way to differentiate brown recluses from hobo spiders is by geographic location. The hobo spider was introduced to the Port of Seattle from Europe in the late 1920s, and they have since spread throughout the Northwestern United States and Western Canada. Brown recluses do not live in the Northwest or Canada.

Fortunately for us Northwesterners, the hobo spider has a nice list of natural predators, particularly the crab spider, Pardosa wolf spider, and again our friend the jumping spider.

Hobo Spider Bites

Purported hobo spider bites have had symptoms similar to the bites of brown recluse spiders, though no fatalities have been reported. In fact, scientists debate whether this spider’s venom can cause the necrosis of human tissue at all. The research is murky because most people who report bites do not capture the spider, so experts have not been able to identify whether the hobo spider is actually associated with dangerous bites. If bitten, it is imperative that the spider be captured or preserved as entirely as possible, and then sent to a lab (many state universities have labs that are appropriate for this) to aid in identification and future research.

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