The hairs are usually more noticeable than with most other spiders. First the hairs: in the Americas most tarantulas have urticating hairs, though some, such as the Hemirrhagus genus, lack these. There are multiple ways to identify a tarantula. Tarantulas are usually confused for those in the Mygalomorphae, such as trapdoor spiders, funnel-web spiders and purseweb spiders, and sometimes even those in the Lycosidae family. Tarantulas are becoming increasingly popular as pets and some species are readily available in captivity. They are burrowers that live in the ground. They are generally classed among the terrestrial types. Their natural habitats include savanna, grassland such as in the pampas, rainforest, desert, scrubland, mountains, and cloud forest. Elsewhere, species have been found that variously display cobalt blue ( Cyriopagopus lividus), black with white stripes ( Aphonopelma seemanni), yellow leg markings ( Eupalaestrus campestratus), metallic blue legs with vibrant orange abdomen and green prosoma ( Chromatopelma cyaneopubescens). Most species of North American tarantulas are brown. The fang size of this tarantula reaches a maximum of 4 cm ( 1 + 1⁄ 2 in). Some of the largest species of tarantula may weigh over 85 g (3 oz) the largest of all, the goliath birdeater ( Theraphosa blondi) from Venezuela and Brazil, has been reported to attain a weight of 170 g (6 oz) and a leg-span up to 30 cm (12 in), males being longer and females greater in girth. Leg span is determined by measuring from the tip of the back leg to the tip of the front leg on the opposite side. Depending on the species, the body length of tarantulas ranges from about 5 to 11 cm (2 to 4 + 1⁄ 2 in), with leg spans of 8–30 cm (3–12 in). Tarantula sizes can range from as small as the size of a BB pellet to as large as a dinner plate when the legs are fully extended. This waist-like connecting piece is actually part of the prosoma and gives the opisthosoma a wide range of motion relative to the prosoma. The prosoma and opisthosoma are connected by the pedicel, or pregenital somite. Like other Arachnida, a tarantula's body comprises two main parts, the prosoma (or cephalothorax) and the opisthosoma (or abdomen). Like all arthropods, the tarantula is an invertebrate that relies on an exoskeleton for muscular support.

Smashing four orb cycle