The hobo spider is a common arachnid in North America, often feared due to a reputation for danger that outweighs its actual threat. This misunderstanding stems from historical misidentification and early, inconclusive studies about its venom. This article explores the identity of the hobo spider, its presence, and the current scientific understanding of its medical significance.
Defining the Hobo Spider
The hobo spider is a member of the funnel-web spider family, Agelenidae, characterized by long legs and swift movements. Its current scientific name is Eratigena agrestis, though it was previously Tegenaria agrestis until a 2013 taxonomic revision. The species is not native to North America; it was introduced from Europe, with the first documented detection occurring in the Pacific Northwest in 1936.
The common name, “hobo spider,” is linked to the theory that the species spread across the continent by traveling along major transportation routes, such as railways. Its former name, “aggressive house spider,” was a misinterpretation of its species name, agrestis, which translates to “of the field” or “rural” in Latin.
Identifying Features and Geographic Range
The hobo spider is a medium-sized arachnid; mature females measure about 3/8 to 5/8 inches in body length, while males are slightly smaller. The spider is typically light to medium brown or yellowish-brown, often displaying a distinctive pattern of light, yellowish chevron or herringbone markings on its abdomen. Unlike many similar-looking spiders, its legs lack dark bands or stripes, appearing uniformly colored.
Definitive identification of the hobo spider often requires microscopic examination of its reproductive structures, even for experts, due to its resemblance to many other funnel-web spiders. Its established geographic range in North America is concentrated in the Pacific Northwest, extending from British Columbia through Washington, Oregon, and Idaho. The range also stretches eastward into parts of Montana, Wyoming, Colorado, and northern Utah.
Assessing the Bite and Medical Significance
The hobo spider historically had a reputation for possessing venom capable of causing necrotic lesions, or tissue death. This reputation stemmed largely from early, circumstantial studies and unverified reports in the 1980s that implicated the species. Current scientific understanding has largely debunked these claims, concluding that the hobo spider is not a spider of medical concern.
The Centers for Disease Control and Prevention (CDC) does not list the hobo spider among species toxic to humans, and multiple studies have found no evidence that its venom causes necrosis. When a bite occurs, the effects are generally minor, often resulting in slight local pain, redness, or swelling that resolves quickly, similar to a bee sting. Basic first aid involves cleaning the area with soap and water and applying a cold compress to manage localized swelling.
Behavior and Web Structure
The hobo spider is a ground-dwelling hunter that relies on speed rather than climbing ability, which is why it is often found trapped in sinks or bathtubs. They are not aggressive and will only bite if they feel threatened or are accidentally pressed against human skin.
The species is a funnel weaver, constructing a non-sticky, horizontal sheet web that features a tubular retreat at one end. The spider waits inside this retreat and rushes out to ambush prey that falls onto the sheet. These webs are commonly found low to the ground in dark, moist, and undisturbed locations, such as under rocks, in woodpiles, beneath debris, or in foundation cracks. Males are most active during late summer and early fall as they wander in search of females, which is often when they are encountered indoors.