While the colossal arachnids of cinema are biologically impossible, nature hosts several species massive enough to dwarf common house spiders. These eight-legged giants push the physical boundaries for terrestrial invertebrates. The largest among them possess either the bulk or the reach to claim world records, offering a fascinating look into how size constraints affect the arachnid body plan.
How Large is “Giant”
Defining the “largest” spider requires understanding the two different metrics used by scientists, as a single species does not hold both records. One method measures the spider’s overall mass and body length, focusing on the size of the cephalothorax and abdomen to determine the animal’s true bulk. The other metric is leg span, which measures the maximum distance from the tip of the longest front leg to the tip of the longest hind leg on the opposite side.
Spiders with heavy, dense bodies, like many tarantulas, typically win the competition for overall mass. Conversely, species with slender, elongated legs excel in the leg span category. This distinction is important because a spider can appear enormous due to its long legs, even if its actual body is comparatively small. The physical limits of the arthropod exoskeleton prevent any spider from becoming truly gargantuan, but the largest species manage to maximize one of these two dimensions.
The World’s Record Holders
The title of the world’s largest spider is split between two arachnids, each dominating one size metric. The Goliath Birdeater, Theraphosa blondi, holds the record for body mass and overall bulk. Adult females can weigh up to 175 grams, and their bodies alone can reach 13 centimeters in length. This tarantula possesses robust fangs that can grow up to 4 centimeters long.
While the Goliath Birdeater has an impressive leg span of up to 30 centimeters (12 inches), it is outmatched in reach by the Giant Huntsman Spider, Heteropoda maxima. The Huntsman holds the record for the world’s largest leg span, also reaching approximately 30 centimeters. However, its body is far less bulky, measuring only about 4.6 centimeters in length. This difference highlights the two body plans: the Giant Huntsman is a long-legged runner built for speed, while the Goliath Birdeater is a heavy, powerful burrower.
Geographic Range and Human Impact
These record-holding spiders live in remote habitats far from most human population centers, which limits the frequency of human encounters.
Goliath Birdeater
The Goliath Birdeater is native to the deep, humid rainforests of northern South America, specifically in countries like Guyana, Suriname, and Venezuela. This spider is a nocturnal, deep-burrowing species, spending most of its life hidden in silk-lined tunnels on the forest floor. When disturbed, its primary defense is to rub its abdomen to fling irritating urticating hairs that can cause severe skin and mucous membrane reactions in predators.
Giant Huntsman Spider
The Giant Huntsman Spider has a restricted and specialized distribution, having been discovered only in caves in Laos in Southeast Asia. Its pale coloration and exceptionally long legs are adaptations for a life spent in dark, secluded cave systems.
Venom and Behavior
While both species possess venom, it is generally considered mild and not medically significant to healthy humans. A bite from either spider is often compared to a wasp sting, producing localized pain and swelling. The large fangs can pierce skin, but these spiders are not aggressive and will typically only bite defensively as a last resort.