The Giant House Spider (Eratigena atrica) is a large, swift-moving arachnid commonly encountered within human dwellings, especially as the seasons change. Its size and speed often lead to public apprehension regarding its potential to bite. While this species possesses venom and is capable of biting, such events are exceedingly rare and occur only under specific circumstances. The Giant House Spider is not aggressive, and its venom is not considered medically significant to humans, posing little health threat.
Identifying the Giant House Spider
This species is one of the largest spiders found in homes, with a body length up to 0.7 inches and a leg span extending up to 4 inches. They are characterized by a robust, hairy body and long, thick legs, typically colored brown or dark reddish-brown. The abdomen and carapace often feature indistinct dark markings. A notable feature is their extraordinary speed, as they have been documented running up to half a meter per second.
Giant House Spiders construct a distinctive sheet-like web that incorporates a funnel-shaped retreat. They wait within this funnel for prey to become entangled in the flat, messy silk structure. These webs are typically found in dark, undisturbed, and damp locations, such as basements, garages, and sheds. They are nocturnal hunters, most often observed when they leave their webs to search for mates or water, sometimes becoming trapped in sinks or bathtubs.
When and Why Bites Occur
Biting is a defensive action of last resort for the Giant House Spider, not a form of aggression. When encountering a human, the spider’s natural inclination is to retreat quickly to escape the perceived threat. Unprovoked bites are virtually nonexistent because the spider actively avoids human contact. A bite will only happen when the spider feels threatened or its escape route is blocked.
The vast majority of bites occur when the spider is accidentally trapped or crushed against the skin. This might happen if a person rolls over on one in bed, pins it while moving items, or unknowingly puts on clothing containing a spider. The spider interprets this pressure as a life-threatening attack and responds by biting defensively. Furthermore, the fangs are often not long or strong enough to penetrate thick human skin effectively, meaning penetration typically only occurs on thinner skin or when the spider is pressed firmly against the skin.
What Happens After a Bite
The venom of the Giant House Spider is mild and not considered dangerous to people. Because the bite is rare and the venom is weak, the health risks are minimal. A bite from this species is often compared to a bee sting or a mosquito bite in terms of severity and discomfort. The typical reaction is localized, involving minor redness, slight swelling, and a degree of pain or itchiness at the site of the bite.
If a bite occurs, the area should be immediately cleaned thoroughly with soap and water to prevent secondary infection. Applying a cold compress or an ice pack can help reduce any swelling and localized discomfort. Over-the-counter pain relievers or antihistamines may be used to manage pain and itching if symptoms are bothersome. Severe symptoms are extremely uncommon and are almost always the result of a pre-existing allergic reaction to the venom, rather than the venom’s inherent toxicity.