Loh Chee Hee: Ravine Trapdoor Spider

RAVINE TRAPDOOR SPIDER

Ravine Trapdoor Spider is the common name of a rare, oddly shaped North American spider, Cyclocosmia truncata, belonging to the trapdoor spider family Ctenizidae. The Ravine Trapdoor Spider is a burrowing spider, inhabiting sloping riverbanks and ravines in Georgia, Alabama, and Tennessee. The abdomen of spiders in this genus is abruptly truncated and ends in a hardened disc which is strengthened by a system of ribs and grooves. They use this to clog the entrance of their 7 to 15 cm deep vertical burrows when threatened, a phenomenon called phragmosis. The tough, flattened abdomen is this species' defining characteristic and serves as their primary method of defence against intruders. When threatened, it faces head-down in its burrow, locks itself in place, and uses its abdomen as a plug to deter attackers. This is a defence tactic that prevents predatory wasps from stinging or pulling the spider out of its burrow. The female reaches a body length of 1.2 inches (3 centimetres) while the male grows to 0.75 inch (1.9 centimetres). This species can be incredibly difficult to find due to the superb camouflage of their burrows. This species tends to be found within certain micro-habitats. They are primarily found in hilly, undisturbed woods that are far from any flood-prone bodies of water, such as rivers. They are frequently found near stream banks, however. The burrow is a vertical tube that narrows toward the bottom. Only the bottom portion of the burrow is silk lined. Click here to see this spider in video.