Tarantula is the common name for a group of "hairy" and often very large spiders belonging to the family Theraphosidae, of which approximately 900 species have been identified. Tarantulas hunt prey in both trees and on the ground. All tarantulas can emit silk, whether they be arboreal or terrestrial species. Arboreal species will typically reside in a silken "tube web", and terrestrial species will line their burrows or lairs with web to catch wandering prey. They mainly eat insects and other arthropods, using ambush as their primary method. The biggest tarantulas can kill animals as large as lizards, mice, or birds. Most tarantulas are harmless to humans, and some species are popular in the exotic pet trade while others are eaten as food. These spiders are found in tropical and desert regions around the world.
The name tarantula comes from the town of Taranto in Italy and was originally used for an unrelated species of European spider. In Africa, Theraphosids are frequently referred to as "baboon spiders". Asian forms are known as "earth tigers" or "bird spiders". Australians refer to their species as "barking spiders", "whistling spiders," or "bird spiders". People in other parts of the world also apply the general name "mygales" to Theraphosid spiders.
Despite their often scary appearance and reputation, none of the true tarantulas are known to have a bite which is deadly to humans. In general the effects of the bites of all kinds of tarantulas are not well known. While the bites of many species are known to be no worse than a wasp sting, accounts of bites by some species are reported to be very painful.
Before biting, tarantulas may signal their intention to attack by rearing up into a "threat posture", which may involve raising their prosoma and lifting their front legs into the air, spreading and extending their fangs, and (in certain species) making a loud hissing noise called Stridulating. Their next step, short of biting, may be to slap down on the intruder with their raised front legs.