The concept of “giant spiders” often conjures images from fiction, sparking both fascination and fear. While no spiders reach the monstrous sizes depicted in movies, some species are remarkably large, challenging common perceptions. This article explores what defines a “giant” spider and introduces some of the largest known species on Earth.
What “Giant” Means for Spiders
Defining a “giant” spider involves considering its overall dimensions, with leg span often being the most significant factor. While body length contributes to a spider’s perceived size, the distance covered by its outstretched legs usually makes the most striking impression. For context, common household spiders have a leg span ranging from 2 to 3 inches (5 to 7.5 cm). Some larger house spiders, such as the giant house spider, can reach a leg span of up to 4 inches (10 cm).
A spider is considered “giant” when its leg span extends significantly beyond these common measurements, often reaching several inches or more. This expanded reach allows them to cover more ground and can make them appear considerably larger than their body mass alone might suggest. Both body length and leg span are important, but the impressive leg extension frequently earns a spider the “giant” designation.
The World’s Largest Spiders
Among the myriad of spider species, two stand out for their impressive dimensions: the Goliath Birdeater and the Giant Huntsman Spider. The Goliath Birdeater (Theraphosa blondi) holds the record as the world’s largest spider by mass and body length. Found in the rainforests of northern South America, this tarantula can weigh up to 6.2 ounces (175 grams) and have a body length reaching 5.1 inches (13 cm). Its leg span can extend up to 12 inches (30 cm), a measurement comparable to a dinner plate. Its name derives from an 18th-century engraving depicting a similar tarantula consuming a hummingbird, though birds are rarely part of its diet.
The Giant Huntsman Spider (Heteropoda maxima), discovered in Laos in 2001, claims the title for the largest leg span of any known spider. Its legs can stretch an astonishing 12 inches (30 cm) across. Despite its expansive leg span, its body length is comparatively smaller, typically around 1.8 inches (4.6 cm). This species is known for its flattened body, which allows it to navigate narrow spaces.
Lifestyles of Large Spiders
These large spiders occupy specific ecological niches, their impressive size influencing their habits and behaviors. The Goliath Birdeater inhabits the deep rainforests of northern South America, in countries like Venezuela, Guyana, and northern Brazil. It is a terrestrial species, living in deep burrows in marshy or swampy areas. This spider is primarily nocturnal, emerging from its burrow at night.
The diet of the Goliath Birdeater consists mainly of large arthropods, worms, and amphibians. It also preys opportunistically on small vertebrates such as rodents, frogs, lizards, and occasionally snakes. They are ambush predators, lying in wait for prey to pass by, then injecting venom into their prey. The Giant Huntsman Spider, found in Laos, resides in caves, under loose tree bark, rocks, and in crevices within warm climates. These spiders are also nocturnal, actively hunting their prey using their speed and agility. They do not construct webs for hunting but rather chase down insects, small rodents, and reptiles.
Assessing the Threat to Humans
Despite their size, most large spiders pose minimal danger to humans. Most large spider species are not aggressive toward people and tend to bite only when they feel threatened or provoked. Bites are typically a defensive response rather than an act of aggression.
The Goliath Birdeater’s venom is not considered medically significant to humans. While its fangs are large enough to break human skin, a bite is commonly compared to a wasp or bee sting, causing pain and swelling. A more common defense mechanism involves flicking urticating hairs from its abdomen, which can cause irritation, itching, rashes, or respiratory issues upon contact or inhalation. Similarly, the Giant Huntsman Spider’s bite is mild. Its venom is not considered dangerous to humans and primarily causes localized pain, swelling, and minor skin irritation. Serious allergic reactions are rare, and these spiders prefer to flee rather than confront humans.