The sheer size of some spiders captures widespread human curiosity, prompting questions about the largest arachnids to ever exist. This fascination stems from the impressive scale these creatures can achieve, sparking intrigue about their presence in current ecosystems and the ancient past. Identifying the ultimate “biggest” spider involves understanding various measurements and examining the fossil record.
The Reigning Champion: Goliath Birdeater
The largest living spider by mass is the Goliath Birdeater, scientifically known as Theraphosa blondi. This imposing tarantula can reach a leg span of up to 30 centimeters (12 inches) and weigh as much as 175 grams (6.2 ounces). Its body alone can measure up to 13 centimeters (5.1 inches) in length.
These large spiders inhabit the rainforests of northern South America, including Suriname, Brazil, Guyana, Venezuela, and French Guiana. They are nocturnal, typically residing in burrows they dig or take over from other small animals, lining them with silk. Despite their intimidating name, birds are a rare part of their diet, which primarily consists of insects, small rodents, frogs, lizards, and occasionally small snakes and bats. Goliath Birdeaters possess poor eyesight, relying instead on sensitive hairs on their legs and abdomen to detect vibrations from nearby prey or threats. When threatened, they can rub bristles on their legs to produce a loud hissing sound, known as stridulation, or release irritating, barbed hairs from their abdomen.
Defining “Biggest”: Mass Versus Leg Span
The term “biggest” can be interpreted differently when discussing spiders, primarily focusing on either leg span or body mass. While the Goliath Birdeater holds the record for the heaviest spider, the Giant Huntsman Spider (Heteropoda maxima) often claims the title for the largest leg span. The Giant Huntsman, found in Laos, can boast a leg span of up to 30 centimeters (12 inches), matching or even slightly exceeding the Goliath Birdeater’s maximum spread.
However, the Giant Huntsman’s body is more slender, measuring around 4.6 centimeters (1.8 inches), making it significantly lighter than the robust Goliath Birdeater. While the Giant Huntsman appears larger due to its long, sprawling legs, the Goliath Birdeater is more substantial in terms of overall bulk. Other large spiders, like the Brazilian Salmon Pink Birdeater (Lasiodora parahybana), also exhibit impressive leg spans, reaching up to 28 centimeters (11 inches).
Giants of the Past: Dispelling Myths and Fossil Records
The question of the “biggest spider ever” often leads to discussions of extinct species, but some common misconceptions exist. For many years, Megarachne servinei, a fossil discovered in Argentina, was believed to be the largest spider to have ever lived, with initial estimates suggesting a leg span of 50 centimeters (20 inches) and a body length of 33.9 centimeters (13.3 inches).
However, in 2005, a re-examination of Megarachne servinei revealed it was not a spider, but rather a eurypterid, an extinct group of aquatic arthropods known as “sea scorpions.” This reclassification was based on features such as its carapace structure, large claws, and eye configuration. While some large fossil spiders exist, such as Mongolarachne jurassica from the Middle Jurassic period, with a body length of about 24.6 millimeters (0.97 inches) and front legs up to 56.5 millimeters (2.22 inches), none definitively surpass the Goliath Birdeater in terms of mass. The Goliath Birdeater remains the largest known spider by mass, whether living or from the fossil record.