While “big” in reference to spiders can be subjective, it generally refers to species with significant leg spans or considerable body mass. These larger arachnids populate a variety of environments across the globe.
Geographic Distribution of Large Spiders
The largest spider species are predominantly found across the tropical and subtropical regions of the world, with some notable exceptions. South America is home to some of the most massive spiders, including the Goliath Birdeater (Theraphosa blondi), which is the largest by mass, weighing up to 175 grams with a leg span of up to 30 cm. This tarantula inhabits the rainforests of northern South America, spanning countries like Suriname, Guyana, French Guiana, and Brazil. Another South American giant is the highly venomous Brazilian Wandering Spider (Phoneutria species), found throughout dense forests in Central and South America, including Costa Rica, Peru, and Brazil.
Australia hosts a diverse range of large spiders, particularly various species of Huntsman spiders and Trapdoor spiders. Huntsman spiders, some reaching over 15 cm leg spans, are widespread across Australia, inhabiting deserts, rainforests, and even cooler sub-alpine zones. Trapdoor spiders, common in eastern and southern Australia, are known for their burrowing habits. Africa is home to large tarantulas like the Baboon spiders (Harpactirinae subfamily), with the King Baboon spider (Pelinobius muticus) found in the grasslands of Kenya and Tanzania, reaching leg spans of up to 20 cm. Camel spiders (Solifugae order), though not true spiders, are also large arachnids found in arid regions across Africa, Asia, and the Middle East.
Asia contributes to the distribution of large spiders with species like the Giant Huntsman spider (Heteropoda maxima), with the largest leg span, up to 30 cm, found primarily in Laos. While generally smaller than their tropical counterparts, North America has its own share of larger spiders, predominantly tarantulas of the Aphonopelma genus. These include species like the Texas Tan Tarantula and Arizona Blond Tarantula, found in the southwestern United States and Mexico, with leg spans up to 15 cm.
Preferred Habitats of Giant Spiders
Large spiders have adapted to a wide array of environments, with tropical rainforests a primary habitat for many imposing species. The consistent warmth and high humidity in these dense ecosystems, such as the Amazon, provide abundant prey and stable conditions. Species like the Goliath Birdeater and many Brazilian Wandering Spiders thrive on the forest floor, often utilizing deep burrows, natural crevices, or even fallen logs for shelter during the day.
Arid and semi-arid regions also support large spider populations, particularly those with burrowing adaptations. Desert tarantulas, found in the southwestern United States and parts of Africa and Asia, construct burrows to escape extreme daytime temperatures and conserve moisture. Camel spiders, for instance, are well-suited to desert environments, hiding in burrows or under rocks during the day and emerging at night to hunt. Their ability to dig and seek subterranean refuge helps them survive in these harsh climates.
While less common for truly giant species, some large spiders inhabit temperate climates, typically dwelling on the ground in forests or grasslands. Trapdoor spiders, for example, create silk-lined burrows in the soil, often near embankments, across eastern and southern Australia. Certain species, like Huntsman spiders, are known to venture into human habitations, seeking shelter in homes and other buildings, especially during warm or wet weather. Caves and other subterranean environments also serve as specialized habitats for some large spiders, offering stable temperatures and high humidity.
Environmental Factors and Spider Size
The size attained by spider species is influenced by a combination of environmental and biological factors. Consistent warmth and high humidity, typical of tropical rainforests, allow spiders to maintain higher metabolic rates and grow over longer periods, contributing to their large size. In contrast, spiders in colder regions might have shorter active periods, limiting their potential for growth.
An abundant and readily available food supply is another factor supporting the development of large spiders. Ecosystems rich in insects, small rodents, amphibians, and reptiles provide the necessary energy and nutrients for spiders to reach impressive dimensions. The Goliath Birdeater, for instance, primarily feeds on large arthropods, worms, and amphibians, contributing to its substantial mass.
Predation pressure also plays a role; fewer natural enemies or effective defensive behaviors allow individuals to survive long enough to grow larger. Evolutionary adaptations, such as burrowing, enable spiders to regulate their body temperature and escape harsh conditions, thereby extending their lifespan and growth potential.