The hobo spider (Eratigena agrestis) originated in Europe but is now widely established throughout the Pacific Northwest of the United States. This arachnid belongs to the funnel-web family, known for their long legs and swift movements. Hobo spiders are relatively quick runners, especially when fleeing or capturing prey. Their speed results directly from their body structure and a hunting method that relies on rapid, short-distance acceleration.
Quantifying Hobo Spider Locomotion
The hobo spider is classified as a cursorial spider, meaning it is adapted for running, a fact evident in its elongated leg structure. In controlled environments, the spider exhibits a considerable top speed relative to its size. Its average running speed is approximately 0.45 meters per second, or about 17 inches every second.
When startled or hunting, this speed can increase dramatically. The maximum recorded speed is around 1.1 meters per second, translating to a burst of speed up to 2.23 miles per hour. This rapid velocity is primarily used for short, powerful dashes rather than long-distance travel.
The spider’s specialization as a ground-level runner is highlighted by its inability to climb smooth surfaces. Unlike spiders that scale glass, the hobo spider’s “feet” are designed for traction on uneven terrain, such as soil or wood. This reliance on running capability explains why they are most often encountered near ground level.
The Funnel Web and Ambush Hunting Strategy
The hobo spider’s speed is intricately tied to its unique method of predation, which centers around its distinctive funnel-shaped web. This web is not sticky like classic orb webs. Instead, it functions as a sheet-like surface with a retreat tunnel built into a protected space, such as a rock crevice or hole. The web acts as a sophisticated tripwire, alerting the spider to the presence of prey.
The spider positions itself inside the narrow end of the silk funnel, waiting patiently for a small insect to wander onto the sheet. When prey makes contact, the resulting vibrations are immediately detected, triggering the spider’s rapid response. Its speed is maximized for a very short, explosive sprint.
It darts out of the funnel retreat, quickly subdues the prey with venom, and then immediately drags the meal back into the safety of the funnel. This ambush hunting style requires rapid acceleration and maneuverability over a matter of inches. The entire process must be executed quickly to prevent the prey from escaping the web’s confines.
Identifying the Hobo Spider and Debunking Danger Myths
Correctly identifying the hobo spider, Eratigena agrestis, can be difficult for the average person, as it closely resembles several other common funnel-web spiders. They are typically brown, with a body length ranging from 7 to 14 millimeters, and they possess long legs. One distinguishing, though often faint, feature is a pattern of V-shaped markings, known as chevrons, down the center of the abdomen, with the points facing toward the head.
A more reliable visual cue is the absence of dark bands on the legs; a spider with noticeable dark rings on its leg joints is not a hobo spider. However, positive identification often requires a microscopic examination of the spider’s anatomy, typically performed only by an arachnologist. Many reported sightings turn out to be the Giant House Spider, a harmless relative.
Historically, the hobo spider was incorrectly accused of causing necrotic, or flesh-eating, wounds in humans. This claim has been largely refuted by current scientific consensus and research. The Centers for Disease Control and Prevention (CDC) does not include the hobo spider among the venomous species that pose a threat to human health. Studies attempting to replicate the necrotic effects have failed to do so, confirming that the hobo spider’s venom is not considered medically significant to humans.