Ravine trapdoor spiders(Cyclocosmia truncata) are a species of Cyclocosmia with truncated opisthosomas that end in a heavily sclerotized round plate or disc similar to a manhole cover.
This “manhole” allows the Ravine trapdoor spider to seal off the open end of their burrow when attacked.
Ravine trapdoor spiders.
The female ravine trapdoor spiders measure 1.2 inches in length, while the males clock in at a mere 0.75 inches long, sporting brown bodies – similar to many other Cyclocosmia species.
Trapdoor spiders, such as tarantulas and their ilk, live in tunnels they burrow beneath the earth and cover with a trapdoor. Generally, these creatures do not leave their abode but rather wait behind closed doors at night for unsuspecting prey to pass by – then they leap out and seize them.
Trapdoor spiders lead stationary lifestyles, making them especially susceptible to predators and parasites that can quickly locate their burrows. However, species of the Cyclocosma have developed a remarkable physiological adaptation due to this evolutionary pressure.
The spider’s abdomen appears to be cut off abruptly as if it were truncated. A heavily sclerotized disc covers this region and creates a false bottom when the spider is inactive in its burrow. This impenetrable surface fits perfectly with the tunnel walls, ensuring their safety even when not active.
Further recommended reading about spiders.
Spider pages: Learn how to identify and avoid these spiders.