A “funnel web” describes a specific type of spider web, characterized by its distinctive funnel-like shape. This web structure is created by various spider species across different families worldwide. These webs are a common sight, often found in gardens, fields, and around homes. The term refers to the architectural design of the silk trap rather than a biological classification of the spider that constructs it. Many spiders utilize this web design for both hunting and shelter.
Spiders Known for Funnel Webs
One notable group includes the Australian funnel-web spiders, belonging to the family Atracidae, with prominent genera like Atrax and Hadronyche. These spiders are robust, glossy black or dark brown. They primarily inhabit moist forest regions of eastern Australia, including the Sydney area, constructing silk-lined burrows under logs, rocks, or in tree hollows.
In North America, grass spiders of the family Agelenidae, specifically the genus Agelenopsis, are common builders of funnel webs. These spiders often appear brownish or grayish with distinctive markings on their abdomen and two dark bands on their cephalothorax. They build sheet-like webs with a funnel retreat in grassy areas, gardens, and low vegetation. Grass spiders are quick runners.
Another member of the Agelenidae family is the hobo spider, Eratigena agrestis, which constructs horizontal, trampoline-like webs near brick walls or wood piles. These medium-sized brown spiders may have chevron patterns on their abdomen. Hobo spiders are native to Europe and have established populations in western North America.
House funnel weavers, such as Tegenaria domestica, are also part of the Agelenidae family and are frequently found in human habitats. These spiders are brown or gray and build their funnel-shaped webs in undisturbed indoor areas like basements and closets. They are generally considered harmless to humans.
Characteristics of Funnel Webs
Funnel webs consist of a flat, sheet-like capture area that extends into a narrow, funnel-shaped tube. This tube serves as the spider’s retreat, where it waits for prey. The spider often positions itself at the narrow end of the funnel, ready to ambush.
Unlike the sticky orb webs of many garden spiders, funnel webs are non-sticky or only slightly adhesive. The silk strands are designed to entangle and trip prey. This non-adhesive quality necessitates the spider’s rapid movement once vibrations are detected on the web.
These webs are commonly found in various environments, including on the ground, in dense grass, or under rocks and logs. Indoors, they frequently appear in corners of basements, sheds, and around window frames. The web requires an anchor or recess for the funnel retreat, often against a surface or within a crevice.
The sheet portion of the web acts as a snare for prey, while the funnel provides a secure hiding spot and an ambush point. When an insect or other small arthropod lands on the sheet, vibrations alert the spider, which swiftly rushes out to capture its meal. The spider drags its prey back into the funnel to consume it, and the funnel also offers protection from predators and environmental elements.
Recognizing Dangerous Funnel Web Spiders
The most dangerously venomous funnel-web spiders belong to the family Atracidae, found almost exclusively in eastern Australia. Other funnel-web spiders encountered globally, such as those in the Agelenidae family, are not considered medically significant to humans.
Australian funnel-web spiders are robust, with a glossy black or dark brown coloration and a hairless, shiny carapace. They possess large, prominent fangs capable of penetrating skin or even soft shoes. Male Australian funnel-web spiders can be more slender than females but are often more venomous.
When threatened, these dangerous species may display aggressive behavior, rearing up on their hind legs and revealing their fangs. Male Sydney funnel-web spiders, Atrax robustus, are known to wander, particularly after rainfall, increasing the likelihood of encounters with humans. They can survive immersion in water for several hours, making them a concern if found in swimming pools.
If a bite from a suspected dangerous funnel-web spider occurs, especially in Australia, immediate medical attention is necessary. First aid involves applying a pressure immobilization bandage to the bitten limb and keeping the person still to slow venom spread. The introduction of antivenom in the 1980s has significantly reduced fatalities from these bites. Exercising caution around any large, dark spider is advisable.