Michigan is home to many spider species, but one consistently stands out as the largest. This article identifies Michigan’s biggest spider and discusses other commonly encountered large spiders that are often mistaken for it.
Identifying Michigan’s Largest Spider
The Dark Fishing Spider, Dolomedes tenebrosus, is Michigan’s largest spider. Females can reach a leg span of 3 to 4 inches, roughly the size of a human palm, with body lengths from 15 to 26 millimeters. These spiders typically display a pale to dark brown coloration, often featuring distinctive chevron or “W”-shaped markings across their abdomen. Their legs are characteristically banded with alternating dark and light stripes.
Dark Fishing Spiders inhabit various Michigan environments. While often found near water sources like ponds, lakes, and streams, they also thrive in wooded areas, forests, and under rocks, sometimes venturing into homes. These spiders are active ambush predators that do not rely on webs to capture their prey. They can walk effortlessly across the water’s surface and dive beneath it for safety if threatened. Their diet primarily consists of insects, but they are opportunistic hunters and will also prey on small fish, tadpoles, and slugs. Despite their size, Dark Fishing Spiders are not aggressive towards humans. Bites are rare, occurring only if provoked, and their effects are comparable to a bee sting, not medically significant.
Common Large Spiders in Michigan
Several other large spider species are common in Michigan and are sometimes mistaken for the Dark Fishing Spider. Among these are various species of Wolf Spiders (family Lycosidae). Wolf Spiders can have a leg span up to 2 inches, with body lengths reaching about 1.5 inches. These spiders are often dark, gray, or brown, and possess a hairy body.
Wolf Spiders are active ground hunters, frequently found in leaf litter, grassy areas, and sometimes indoors in basements or garages. Unlike the Dark Fishing Spider, they do not build webs for catching prey, instead relying on their speed and keen eyesight to pursue and ambush insects. Female Wolf Spiders carry their young spiderlings on their backs for several weeks after hatching.
Another large species sometimes encountered is the Nursery Web Spider, Pisaurina mira. While some individuals can have a leg spread up to 3 inches, their body length is generally smaller than the Dark Fishing Spider, typically ranging from 12 to 15 millimeters for females. These spiders are often yellowish-brown and may have a darker band running down their back. Nursery Web Spiders are wandering hunters, commonly found on vegetation in fields, forests, and tall grasses, distinguishing them from the more ground-dwelling Wolf Spiders. Females construct a silken “nursery web” to protect their egg sacs and young, a behavior from which they derive their common name.