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Spiders: Unappreciated Superpowers!

Monday, April 6, 2020

I recently put together a presentation about spiders for a training conference. Not being an arachnologist, I did a fair amount of research for this and realized I had a number of beliefs that weren’t quite accurate about spiders! Guess what? I know I’m not the only one! Spiders are a fascinating group, even if you have a spot of arachnophobia, which I do (but every day I’m getting better and better…). One thing I ran across changed my perspective on the terminology we use when talking about spider-human conflict. Hear me out.

I’ve known a lot of entomologists who would quickly correct anyone who carelessly used the term “bit” or “bite” when referring to a bee or wasp defense. The reprimand might sound something like this, “No, no. Wasps don’t bite you, it’s coming from the other end. They STING you!” Perhaps this common mix-up and our familiarity with insects that have mouthparts on one end and a sting on the other have derailed our chances of getting the terminology correct when it comes to spiders. Having recently been enlightened on this issue, I will explain why spiders can’t bite you — but they can sting you!

STING, NOT BITE. Let’s take a quick look at the anatomy on the front end of a spider. Recall, they don’t have a “head” per se, rather they have their eyes and other appendages stuck directly onto their body, which is called a cephalothorax. Notice how this word incorporates both the term “cephalo” for head, and “thorax” for body. (Incidentally, this is reminiscent of Mr. Potato Head’s anatomy, but you may get strange looks from any 5-year-olds within earshot if you refer to Mr. Potato Head’s “cephalothorax.”)

Directly below the spider’s eyes are the large chelicerae, tipped with the sharp, venom-delivering fangs that spiders use to defend themselves and to subdue prey. All arachnids (scorpions, mites, camel spiders, etc.) possess chelicerae, which generally take the form of a small pair of scissors that are used to grab prey and cut it up. Spiders as a group have simply lost one side of their “cheliceral scissors” so that they terminate in a single fang that is instead used to inject venom. I once believed that spiders sucked up the liquid contents of their prey through these same fangs, but that’s not correct. Newsflash — spiders actually have a separate opening, called a mouth (I know, the terminology is hard to follow here), which lies below their chelicerae. Unless you go looking for it, you will never see a spider’s mouth! It lies between the large chelicerae above and the labium and endites below. When combined, these parts form a perfect little package for bringing liquid nutrients directly into the mouth by cohesion.

I know I’m tossing out a lot of $10 words here, so to speak, so let’s bring this back into focus. Spiders deliver venom through fangs attached to specialized structures called chelicerae. They also possess a separate opening, called a mouth, which is used to slurp up the liquefied contents of their prey. By definition, when an animal bites a person, it uses its teeth or mouth to inflict damage; hence the entomologist’s revulsion when hearing this term incorrectly used to describe a sting. However, spiders do not use their mouth when defending themselves. If they did, it would be a laughable defense, and would at worst result in a very tiny hickey.

So, what to properly call a spider defense? In common usage, a sting is defined as “to prick or wound with a sharp-pointed, often venom-bearing organ” ( Wow! This is exactly what spiders do! They take their sharp cheliceral fangs and inject venom into you. Well, only if you deserve it.* It just so happens that a spider’s sharp-pointed organ is attached to their front side, instead of their posterior, thus rendering all of us otherwise well-informed entomologists clueless! You may protest that many snakes possess venom-delivering fangs and their defense is correctly called a bite. However, remember that a snake’s fangs are actually modified teeth that reside in the snake’s mouth, so the term “bite” applies nicely to them. Spiders’ fangs reside outside of their mouth and, by some genetic accounts, are homologous to insect antennae.

I know, evolution is messy — but interesting! So, unless we want to totally distort the definition of what we consider a bite…consider yourself warned, and beware of the sting of the spider!

*It is fairly difficult to be attacked by a spider; most species run when disturbed. Even the infamous brown recluse is fairly benign unless you inadvertently squeeze one against your body. (I’ve handled these spiders and they were not aggressive, though I don’t advise this practice.)

The author is the manager of education and training at Rose Pest Solutions, Troy, Mich. This article first appeared in the March issue of Pest Control Technology.

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