Currently, about 1,000 species of tarantulas have been identified. Some of the more common species have become popular in the exotic pet trade.

Roughly the size of a BB pellet, the spruce-fir moss spider (Microhexura montivaga) lives only beneath emerald green moss mats that cling to boulders at high elevations, typically above 5,300 feet.

Although a tarantula has eight eyes like most spiders, touch is its keenest sense, and in hunting, it primarily depends on vibrations given off by the movements of its prey.

Tarantulas primarily eat insects, though some species enjoy larger game like frogs, mice and small lizards. They also sometimes eat other varieties of spiders.

The Goliath birdeater is the size of a dinner plate. It can have a legspan up to 28 cm (11 in), a body length of up to 11.9 cm (4.7 in) and can weigh up to 175 g (6.2 oz). Native to the upland rain forest regions of northern South America, it is part of the local cuisine and is prepared by singeing off the urticating hairs and roasting it in banana leaves. The flavor has been described as "shrimplike".

Most tarantulas are burrowers that live in the ground and prefer dry, well-drained soils. However, some species live in trees, cliffs, caves, or in crops like bananas and pineapples.

The Texas brown tarantula, also known as Oklahoma brown tarantula or Missouri tarantula (Aphonopelma hentzi), is one of the most common species of tarantula living in the Southern United States today. While males rarely live more than a few years after reaching maturity, females have been known to live up to 40 years.

If a tarantula feels threatened, the first thing it will do is wave its abdomen as a warning. If this doesn't work, the tarantula will use its back feet to scrape barbed hairs off of its abdomen and kick them at a predator. Although the tarantula prefers not to waste its venom, which is designed to liquify body tissues so the tarantula can drink its victims, it will bite as a last resort.

Despite their relatively large size, tarantulas themselves are prey for many other animals. The most specialized of these predators are large members of the wasp family known as "tarantula hawks". The female tarantula hawk stings a tarantula between the legs, paralyzes it, then drags it to a specially prepared burrow, where a single egg is laid on the spider's abdomen, hatching to a larva which slowly eats the still-living tarantula.

Unlike many spider species, tarantulas do not use webs to catch their prey. They do, however, spin silk. If a tarantula lives in a place with dry soil, it will burrow into the ground and line the walls of the hole with silk to help keep sand and dirt out. Sometimes, tarantulas spin a line of silk near the entrance to a burrow, which acts as a trip wire, alerting the spider to prey that is nearing its home. Males also spin special webs which are used to transfer semen to females.