There are more than 34,000 different species of spiders worldwide. However, there are only a few dozen spiders that cause fairly pronounced envenomations in human beings. All spiders are poisonous. However, all cannot pierce the skin, and all do not have significant amounts of venom that cause skin lesions or systemic illness in humans. Spiders have long been a major cause of fears and phobias. The media has not done the spider population any favors, and have always portrayed them as evil creatures, dating back to the early days of film. It is somewhat surprising that something so small can cause such great fear. However, when one looks at an arthropod with eight eyes and eight legs that can also run very fast, one can easily understand how fears and phobias can develop.

Many spiders are capable of wind-blown disbursal. This is called ballooning. It gives us some understand how spiders have been found on even isolated islands.

The anatomy of an arthropod is segmented into two body parts, the cephalothorax, which is the head and the upper torso, and the abdomen. They have eight legs and the pedipalp, frequently mistaken for fangs, is actually used to hold prey. Fangs are usually tucked in, and therefore difficult to see.