The Bug Lady

Let’s talk poison

This is the mighty Phoneutria nigriventer. If you have never heard of it, I am going to explain why, when my brother saw it on our lawn, he came running to me.

We know that all spiders are poisonous, since all but one recently discovered species, are predators. Most spiders don’t pose any risks to us humans, though. Here is why:

- Toxicity: for a poison to be dangerous, it needs to do the most damage with the smallest amounts. Most spiders don’t have very toxic poisons.

- Injected volume: the more poison that gets injected in a bite, the stronger the effects. Poisons are very expensive for spiders, so they tend to save up on it.

- Aggressiveness: If you have played with a spider before, thrown something at their webs, or poked one with a stick, you’ll notice that they don’t want any trouble. Almost all spiders run away when provoked.

- Size of fang: Many spiders have such tiny fangs that they can’t even cut our skin. Some manage to give us a little scratch and cause some soreness. But to really do damage, they have to inject the poison deeply, and few spiders can do that.

And that is why most spiders are harmless to us.

Now, the P.nigriventer is a case apart.

Its poison is one of the most toxic among spiders. A tiny 0.006 mg of this poison kills a rat, and inject way more than that with each bite. Not to mention that they bite repeatedly when they are upset, jumping at whatever is attacking them over and over. And the fangs, well, just take a look at the picture!

Adding to that the fact that these spiders don’t form webs, and they just wander around looking for a warm and dry place to stay, like say, your shoe, that explains why the Brazilian wandering spiders are responsible for 42.2% of all spider bites with medical significance in Brazil.

The bites are painful and cause a lot of discomfort, but they don’t pose life risks to adults. They cause redness, swelling, local pain that can irradiate and comes with the feeling of “pins and needles”. Depending on the person, if it’s a child or an elder or a debilitated person, it can cause tachycardia, high blood pressure, intense sweating, blurry vision, vomiting. It can later evolve to pulmonary edema and chock, and that’s when people die… Pretty nasty.

Apparently, they kill a lot of dogs in Brazil. It must be because dogs thinks they’re playing when the spider is standing on its back legs and biting it on the nose over and over. Silly dogs.

Another curious thing about this poison that I have to mention, is that it contains a toxin Tx2-6, which causes men that have been bit to experience long lasting and painful erections. So researchers have been studying this poison to find a way to make money out of this. Now this poor spider won’t get a second of peace!

Let’s talk poison by The Bug Lady, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

Tags: arachnid, armadeira, Arthropod, banana spider, brazilian armed spider, brazilian wandering spider, poisonous