Spiders, with their diverse forms and behaviors, often spark curiosity, especially regarding their size. Many wonder which of these fascinating arachnids holds the title for the largest in America. The answer depends on how “biggest” is defined, whether by leg span, body length, or body mass.
North America’s Largest Spiders
When considering the largest spiders in North America, tarantulas frequently come to mind. Two prominent species, the Texas Brown Tarantula (Aphonopelma hentzi) and the Desert Blonde Tarantula (Aphonopelma chalcodes), are found predominantly in the southwestern United States and northern Mexico.
The Texas Brown Tarantula can achieve leg spans exceeding 4 inches (10 cm) and weigh over 3 ounces (85 g). These terrestrial burrowers have dark brown bodies, a bronze carapace, and a burgundy abdomen. They inhabit grasslands, scrublands, and prairies, residing in silk-lined burrows or abandoned dens.
The Desert Blonde Tarantula is a burrowing spider found in southwestern deserts. Females can reach a leg span of 3.5 to 4 inches (9 to 10 cm), with a body length of 2.75 inches (7 cm). Females are a uniform tan, while males exhibit black legs, a copper-colored cephalothorax, and a reddish abdomen. They construct burrows in arid, sandy soil to escape extreme temperatures and predators.
Other Notable Big Spiders
A common misconception involves the Goliath Birdeater (Theraphosa blondi), which is often believed to be found in the United States. It is the largest spider in the world by mass and body length, with a leg span that can reach 11 inches (28 cm), but it is native to the rainforest regions of northern South America. Despite its name, this spider rarely preys on birds, primarily consuming other arthropods and small vertebrates.
Other large spiders found in North America include the Carolina Wolf Spider (Hogna carolinensis) and various Fishing Spiders (Dolomedes spp.). The Carolina Wolf Spider is the largest wolf spider in North America, with females measuring 0.87 to 1.4 inches (22 to 35 mm) in body length. These mottled brown spiders are found across the United States in open areas like fields, grasslands, and deserts, hunting by ambushing prey from their burrows rather than using webs.
Fishing Spiders (Dolomedes spp.) are also large, with some species having leg spans that can exceed 3 inches (75 mm). These semi-aquatic spiders are found near bodies of water. They are known for their ability to walk on water and even submerge themselves to catch small fish and aquatic insects. Several species exist in North America, inhabiting wetlands.
Behavior and Safety Concerns
Despite their intimidating size, most large spiders in North America, including tarantulas, are docile and non-aggressive towards humans. They prefer to retreat or hide when threatened, and a bite is a last resort. Tarantulas may flick irritating urticating hairs from their abdomen as a defense mechanism, which can cause skin irritation or rashes.
If a bite occurs, the venom of North American tarantulas is mild and not dangerous to humans. Symptoms are limited to localized pain, redness, and swelling at the bite site, which resolve within a few hours to a few days. In rare cases, more severe allergic reactions can occur, necessitating medical attention. Observing these spiders from a distance and avoiding provocation are recommended for safe encounters.