As of 2015, there are about 40,000 known species of spiders worldwide, and they live in almost every habitat in every continent except Antarctica. Despite this diversity, all spiders share some of the same common traits, such as having eight legs and two body parts (the cephalothorax and the abdomen).
Almost all spiders have venom, although only a small number can harm humans. Spiders use their venom to paralyze or kill their prey by pressing their fangs into the victims to make the venom glands contract and release their poison. Spiders eat a wide variety of creatures, including small insects, other spiders and, in the case of large tarantulas, lizards, birds and mice. Some spiders eat enough insects each year to equal the population of the United Kingdom. They cannot digest solids, so they use enzymes to transform the food into a liquidized state.
Spiders catch their prey in many ways. Many species build webs from silk present in their bodies. These webs can be stronger than steel of equal size and weight. The wolf spider hunts its prey on the ground, while the jumping spider hides and pounces on unsuspecting food items.
Some male spiders perform rituals in front of females to signal that they are suitors and not food. Despite this, some species have females that eat the males after mating, as in the case of the black widow.