The hobo spider (Eratigena agrestis) is a skilled web-builder that creates a distinctive silk structure to capture its prey. This European native was introduced to the United States and is now primarily established in the Pacific Northwest, spanning states like Washington, Oregon, and Idaho. The spider uses its web as a stationary hunting ground rather than actively pursuing insects. This funnel-web design is a defining feature of the species, which belongs to the family Agelenidae, known colloquially as funnel web spiders.
The Funnel Web Design
The hobo spider constructs a specific type of silk architecture called a funnel web. This web is composed of a non-sticky, horizontal sheet of silk that stretches out across a flat surface. The sheet-like portion functions as a trip line, connected to a narrow, tubular retreat where the spider waits.
The web’s structure is not designed to ensnare prey with adhesive silk, but rather to function as a pressure-sensitive platform. When an insect walks across the sheet, the vibrations immediately alert the hobo spider hiding in the retreat. The spider then rushes out with speed, ambushes the prey, and pulls it back into the safety of the funnel to feed.
These webs are typically built close to the ground, often found in undisturbed, sheltered locations. Outdoors, they are common under debris, in tall grass, or near wood piles and brick walls. Indoors, they may be found in basements, crawl spaces, or behind stored items, which offer the flat, stable surfaces necessary for the web’s function.
Identifying the Hobo Spider
Accurately identifying a hobo spider is difficult for non-experts because it closely resembles several other common funnel-weaving spiders, such as the Giant House Spider (Eratigena atrica). The hobo spider is a medium-sized brown arachnid, with a body length typically ranging from 7 to 14 millimeters. Its overall coloration is generally light to yellowish-brown, lacking the distinct color bands found on the legs of some related species.
A common visual indicator is the presence of a faint pattern of V-shaped markings, or chevrons, down the center of the abdomen, with the points directed toward the head. However, the most reliable characteristic to look for is the absence of distinct markings. Unlike other similar spiders, the hobo spider’s legs are uniformly colored, and its cephalothorax lacks the two prominent dark longitudinal stripes seen on competitors like the Barn Funnel Weaver.
Because external features can vary widely, positive identification often requires a trained arachnologist to examine the spider’s reproductive structures microscopically. For the average person, it is often easier to determine that a spider is not a hobo spider by looking for clear, contrasting characteristics, such as banded legs or distinct stripes.
Bite Risk and Current Scientific Consensus
The hobo spider gained a reputation in the United States for causing necrotic lesions, or dermonecrosis, which are tissue-destroying wounds. This historical association, known as arachnidism, led to the belief that the hobo spider was a medically significant threat similar to the Brown Recluse. However, this belief originated largely from circumstantial evidence and misdiagnosis in regions where the Brown Recluse is not present.
Current scientific consensus among entomologists has largely debunked the link between Eratigena agrestis venom and necrotic wounds in humans. Studies have shown no evidence that the spider’s venom has the hemolytic properties necessary to cause tissue destruction. Furthermore, the hobo spider is considered innocuous in its native Europe, and the venom of European and American populations is nearly identical.
Confirmed bites are rare, and when they do occur, they are generally minor, resulting in only localized pain, redness, or a slight prick sensation. The Centers for Disease Control and Prevention (CDC) no longer lists the hobo spider among venomous species of concern. For any suspected spider bite or unexplained skin lesion, seeking medical attention is always advisable to rule out other causes, such as bacterial infections, which are often the true source of necrotic wounds.