Seeing a large arachnid in Ohio can be alarming, but the state’s biggest spiders are generally harmless. Despite popular culture promoting the idea of dangerous species, the reality is that these large examples of local wildlife pose little threat to humans. This article identifies the largest species and details why it is the biggest spider one might encounter in Ohio.
Identifying Ohio’s Largest Spider
The title of Ohio’s largest spider belongs to the Dark Fishing Spider, scientifically known as Dolomedes tenebrosus. This species is a member of the nursery web spider family. A large female Dark Fishing Spider can measure up to an inch in body length, but their long, sprawling legs are what truly make them stand out.
The leg span of these arachnids commonly ranges between 3.5 and 4.5 inches, giving them an overall diameter that can approach the size of a human palm. They are typically a mottled mix of pale to dark brown or gray, which allows them to blend into the bark and leaf litter of their environment. The legs are marked with distinctive bands of darker brown or black, and the abdomen may feature subtle dark, W-shaped patterns.
Habitat and Hunting Behavior
The Dark Fishing Spider is commonly found across Ohio, particularly in wooded areas, despite its name suggesting a strict association with water. While it does frequent habitats near streams, ponds, and marshes to hunt aquatic prey, it is also highly adaptable to drier, terrestrial environments. This flexibility means they are often encountered on tree trunks, under logs, or in woodpiles.
The spider is an active hunter rather than a trapper. They possess excellent eyesight and instead chase down or ambush their prey. In aquatic settings, they use specialized hairs on their legs to detect vibrations on the water’s surface, allowing them to snatch insects, small fish, or tadpoles. When they wander into human structures, they frequently seek the shelter of dark, undisturbed spots like basements or garages, where they hunt house-dwelling insects.
Addressing Safety Concerns
Despite its size, the Dark Fishing Spider is a non-aggressive animal that prefers to flee from a perceived threat. These spiders are quite skittish and will generally run and hide at the slightest disturbance. They are fast runners and rarely stand their ground when confronted by a human.
A bite is extremely unlikely unless the spider is handled roughly or accidentally trapped against the skin. Should a bite occur, the venom is not considered medically significant to a healthy person. The sensation is comparable to a bee or wasp sting, resulting in only mild, localized pain and swelling. The best course of action upon finding one indoors is to leave it alone or gently relocate it outside with a cup and a piece of paper.