by Rex Trulove

Created on: December 21, 2009

It may come as a shock or a surprise to many people, but all the spiders in the US are poisonous. In fact, all spiders are poisonous, regardless of where they live. Such a blanket statement does require some clarification.

All spiders are carnivorous predators. Most eat insects, however some also eat small reptiles, fish, small rodents, and even birds. To facilitate taking prey, they have piercing mouthparts connected to venom sacks. It is the venom that is most often referred to as poison, and they all have them. It is therefore proper to say that all the spiders in the US are poisonous.

It should be noted, though, that most either are incapable of biting people because of the size of the mouthparts, or only produce a mild reaction when they do. There is an important exception to this. As with bee stings, some individuals can be extremely sensitive to spider venom or they may have an allergic reaction to it. In this case, a spider bite can very well be life threatening.

Of more danger to people is the potential for secondary infections brought on by the necrosis, or death of flesh, around the spider bite. For instance, if the amount of venom is great, flesh can quickly die, making gangrene a real concern.

In the US, when people think of poisonous spiders, they probably most often think of those that cause the biggest problem, either from the amount of venom injected, or because of the potency of the venom. Two of the spiders most often considered because of potency of venom are the black widow and the brown recluse.

Both of these spiders have quite potent poison, causing rapid necrosis and often such symptoms as shortness of breath, rapid heartbeat, profuse sweating, vomiting, and fever. However, neither of these spiders is particularly aggressive. They will use their venom for self-protection, but its main purpose is to subdue prey. It is a waste for them to use it to bite when they don't need to.

Black widows have poor eyesight; as well, and seldom venture far from their web. In fact, the author had a black widow (or a succession of them) that nested at the corner of a 55-gallon fish tank. It or they never ventured from that corner. However, the quantity of insects, including bees and wasps, which were caught in the web and devoured was enormous.

When thinking of quantity of venom they inject, it is normal to think of the tarantula. These large spiders have substantial fangs and are capable of injecting a large amount of poison in a single bite. Again, though, they are non-aggressive, despite their size. It takes quite a bit to rile one up enough that it will bite, and since the venom isn't especially more toxic than with most common spiders, such a bite is rarely dangerous.

Of more concern are imports. Spiders have been brought in from other areas, such as on shipments of bananas. One such is a type of wolf spider. It is large and highly aggressive, plus it is capable of injecting a large amount of poison. These bites aren't usually thought of as life threatening, however they can be very painful.

Identifying which spiders are poisonous in the US is easy. All spiders are. Pointing out which are dangerous or deadly takes a little bit more effort and knowledge. Just a little tidbit, though; it is likely that most people will have numerous spider bites in their life time, and most will never even know it. Take care around spiders, but don't let the fear of them control you.

Learn more about this author, Rex Trulove.
Click here to send this author comments or questions.