Cognitive Mileage

Brown Recluse Spiders (BRS)

Posted on: October 5, 2007

My girlfriend, her daughter, and I had to deal with an infestation of brown recluse spiders about a couple months ago. There was a sparsity of information available about them so I thought I would share what I learned through research (about half from several websites that shared personal BRS experiences and half from Bruce Cutler, an Arachnologist at KU).

How do I know if I have brown recluse?

Here is the one easily recognizable unique feature of brown recluse spiders: they have three pairs of eyes. No other spiders (at least not any I’m familiar with) have this. Almost all other spiders have 8 or more eyes. Brown recluse are the only ones I’m aware of that look like they only have 3.

They also typically have a light brown body. You’ll find more information about what they look like here (the source of the images).


The Wound

First: the bites aren’t deadly. They are just extremely (temporarily) damaging and painful. What will happen: you will experience necrosis, meaning anywhere from a centimeter to a few inches of your skin will just die over the course of a couple weeks. It will produce a big dip in your flesh and, again, the process is very painful. However, people only die from it when the open necrosis wound gets infected. If you keep the wound clean with disinfectant, you should probably be okay.


Many sites I’ve been to say something to the effect of “if you get bit by brown recluse, seek medical attention immediately”. This is a very common sense reaction and in most medical situations would be helpful. However, you may be surprised to learn that there is absolutely no effective treatment for brown recluse bites. If you get bit, you will experience necrosis. There is no getting around it. The only thing doctors can help you do is treat the wound for infections. But your skin is going to die.

On the bright side, you will also heal from necrosis if you tough it out and let the skin heal naturally. About the worse thing you could do is let a physician debride the infected skin. People who do this get permanent dips in their skin. Without that (temporarily) infected skin, you won’t be able to grow back healthy skin later. So don’t cut it off.

But if you get bit or aren’t sure if you got bit, my advice is: don’t sweat it. You probably don’t need to go to the hospital or even a doctor (and if you did, there is nothing they can do anyways). You should just keep an eye on the wound and see how it develops. If it becomes throbbing, sharply painful, and pusy, there is a chance it is a brown recluse spider (BRS) bite.


Shake out your clothes before putting them on. BRS only bite defensively and this is how the vast majority of bites occur. A BRS (or any spider) is never going to like chase after you trying to bite you. The only time they are going to bite is when they feel like their death (by squishing) is imminent. This happens most often in bed sheets, clothes, and towels.


So fine, the bite isn’t that bad for an adult. But what if you have children? And what if you just don’t like the idea of having a huge open-wound hole in your skin for a few months or otherwise suffering the pain of a bite? That is understandable. My girlfriend and I were worried about her daughter and we really didn’t want to get bit ourselves. So how do you get rid of these damn things?

Pesticides Don’t Work

First, let me tell you up front that an exterminator is a waste of your money. Like doctors, when it comes to BRS, there is nothing they can do. In fact, it has been theorized that pesticides will actually increase the amount of BRS you have. This is because, unlike other spiders, BRS aren’t picky: they will eat dead bugs. And they (and other spiders) are immune to pesticide because their long legs keep them up off the ground away from the chemicals. So if you use pesticides, you are at best doing nothing and at worst giving the BRS a free lunch.

Fancy Gadgets Don’t Work

We tried sonic devices. I had one of the BRS we captured in a jar and held it next to the device. It did not respond. I also killed two BRS within inches of sonic devices. I wrote a full review about how ineffective these devices are against BRS here.

Manual Extermination

What does work? Good old-fashioned squishing them with a paper towel. After discovering we had an infestation, I went on a hunt every night to kill them. They were mainly right out in the open but I checked every room. Some nights I killed as many as 3. Some nights I didn’t find any. But after a few weeks of this, their numbers rapidly dissipated.

Spider Traps

What is a spider trap? Basically a piece of duct tape turned upside-down. The spider steps on it, can’t get off, and starves to death (or you come by and expedite the process by squishing it since they can survive for weeks without eating). Some upside down duct tape caught a couple spiders for us. Place these near dark, structurally crowded places like utility closets.

Encourage the Presence of Other Spiders

You may be surprised to learn that other spiders actually kill BRS. That’s right: spiders eat each other. How do you know which ones to encourage? Well for one, BRS don’t have webs; they are walking hunters. So if you see any webs in your basement and don’t mind the aesthetic blemish, don’t tear them down. Those spiders will eat your BRS. Basically almost any spider but BRS in the United States (other than black widows) are not a serious threat to anyone in your house and they will eat pesky bugs as well as the painful, semi-dangerous brown recluse.


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