The Hobo Spider, scientifically known as Eratigena agrestis, is a common funnel-web spider found throughout the Pacific Northwest and parts of the western United States. For many years, this species was widely feared due to reports suggesting its venom could cause serious, flesh-rotting wounds in humans. The definitive answer is no: the hobo spider is not considered dangerous to human health, and its venom is not lethal.
The Truth About Hobo Spider Lethality
The fear surrounding the hobo spider originated from its introduction to the United States and subsequent misinterpretation of its impact. Early reports and a 1980s study suggested the venom could cause dermonecrotic lesions (dead skin tissue), leading to the species being labeled medically significant. This designation has since been largely discredited by arachnologists and medical professionals.
Extensive research since the early 2000s has found no consistent evidence that the hobo spider’s venom causes necrosis in humans. The venom has negligible cytotoxicity, meaning it is not destructive to human cells. In 2017, the Centers for Disease Control and Prevention (CDC) removed the hobo spider from its list of venomous species considered toxic to humans, reflecting the updated scientific consensus.
The severe necrotic arachnidism once attributed to this spider is now understood to be caused almost exclusively by the Brown Recluse spider (Loxosceles reclusa) or, more often, by bacterial infections like Methicillin-resistant Staphylococcus aureus (MRSA). Confirmed hobo spider bites result in mild and temporary symptoms, showing none of the severe tissue damage that fueled the initial panic.
Identifying the Hobo Spider
Accurate identification of the hobo spider is difficult, even for experts, but a few general characteristics can help distinguish it from other species. The hobo spider is a brownish spider with a body length ranging from 7 to 14 millimeters, with females being slightly larger than males. Its abdomen often displays a pattern of chevron-like (V-shaped) markings running down the middle, with the points of the ‘V’ facing toward the head.
Unlike many other common spiders, the hobo spider does not have dark bands or rings on its legs. The front body section, or cephalothorax, is usually a uniform brown color with indistinct, diffused darker markings. These spiders are part of the funnel-web family and construct a distinctive web structure.
The web is a flat, sheet-like surface that narrows into a funnel-shaped retreat where the spider waits for prey. These webs are often found in dry, undisturbed areas, such as under rocks, woodpiles, tall grass, window wells, and in dark corners of basements or crawl spaces. Hobo spiders are poor climbers and prefer to stay close to the ground.
Symptoms and Necessary Treatment of a Bite
A bite from a hobo spider is a rare event, as the spider is not aggressive and only bites defensively if it feels threatened or is accidentally pressed against the skin. Many suspected spider bites are not actually from a spider, and even when a hobo spider does bite, it is estimated that over half of these instances are “dry bites” where no venom is injected.
When venom is injected, the initial reaction is a slight prickling sensation or a mild sting, often compared to a mosquito bite. Symptoms are localized to the bite site and include minor pain, slight redness, and mild swelling. In verified cases, these minimal symptoms subside within 12 hours with no lasting effects or complications.
If you suspect any spider bite, clean the area thoroughly with soap and water to minimize the risk of secondary infection. Applying a cold compress or an ice pack can help reduce mild swelling or localized discomfort. Keeping the bite area elevated can also assist in reducing minor swelling.
It is important to seek professional medical attention if the wound shows signs of worsening, which may indicate a secondary bacterial infection. Symptoms that require a doctor’s visit include significantly spreading redness, increasing pain that persists after 24 hours, the presence of pus, or an elevated temperature. Immediate emergency care is necessary if systemic symptoms occur, such as difficulty breathing, hives, or swelling of the face or throat, as this could indicate a severe allergic reaction.