Funnel spiders often cause concern. While many spiders construct funnel-shaped webs, only a few species pose a significant threat to humans. This article clarifies the distinctions among “funnel spiders” and explains which are truly venomous.
Understanding Funnel Spiders and Their Venom
The term “funnel spider” refers to spiders that build webs with a flat sheet and a funnel-shaped retreat. These webs are non-sticky; the spider relies on vibrations to detect prey, then rapidly emerges from the funnel to capture it. These spiders often have brownish or grayish bodies, sometimes with stripes, and range from 0.2 to 2 inches, not including leg span. While many spiders possess venom, its potency and danger to humans vary depending on the species.
The most medically significant “funnel spiders” are the Australian funnel-web spiders, belonging to the family Atracidae, which includes genera like Atrax and Hadronyche. The Sydney funnel-web spider (Atrax robustus) is notorious, found within a 62-mile radius of Sydney, Australia. Its venom contains a potent neurotoxin, delta-atracotoxin, which is toxic to humans. Male Sydney funnel-web spiders are more dangerous than females due to their more potent venom and tendency to wander, increasing human encounters. Bites from other Hadronyche species, such as the northern tree-dwelling funnel-web (Hadronyche formidabilis) and the southern tree-dwelling funnel-web (Hadronyche cerberea), also produce medically significant envenomation.
In contrast, North American grass spiders (Agelenopsis species) are largely harmless to humans. They build funnel-shaped webs in grassy areas, gardens, or secluded corners of homes. While venomous to their insect prey, their fangs are small, and their venom typically causes only minor, localized reactions in humans, similar to a bee sting. They are not aggressive and usually retreat when disturbed.
Recognizing a Bite and Seeking Medical Attention
A bite from a non-dangerous funnel spider, such as grass spiders, typically results in mild symptoms. These include localized pain, redness, or swelling at the bite site. Reactions usually resolve within a day or two and do not produce systemic symptoms. Applying an ice pack to the affected area can help manage the discomfort.
However, a bite from a highly venomous Australian funnel-web spider presents a medical emergency. Symptoms can develop rapidly, often within minutes, and can be severe. Initial pain at the bite site is common, followed by profuse sweating, nausea, vomiting, and abdominal pain. Other signs include muscle twitching, salivation, difficulty breathing, and numbness or tingling around the mouth. Severe cases can include high blood pressure, confusion, and loss of consciousness.
Immediate first aid is crucial for suspected funnel-web spider bites. Call emergency services immediately. While awaiting medical help, apply a pressure immobilization bandage firmly to the bitten limb, wrapping from the bite site towards the extremities. Immobilize the limb with a splint to restrict movement, which helps slow venom spread. Keep the person calm and still; since antivenom development in 1980, no deaths have been recorded from Australian funnel-web spider bites when treated.
Living Safely Around Funnel Spiders
Minimizing encounters with funnel spiders, especially where dangerous species are prevalent, involves practical measures. Funnel spiders prefer moist, sheltered environments, building webs in woodpiles, rock crevices, dense vegetation, and dark corners of homes, basements, or sheds. Clearing clutter, debris, and leaf litter around the home reduces their preferred habitats.
Sealing cracks and gaps in foundations, doors, and windows prevents spiders from entering indoor spaces. When working outdoors, especially in gardens or areas with potential spider habitats, wearing gloves and closed-toe shoes protects against bites. Shaking out shoes or clothing left outside before wearing them can dislodge spiders seeking shelter. While most funnel spiders pose little threat, these precautions are relevant in regions with highly venomous species to ensure safety and prevent accidental contact.