Ctenizidae

Ctenizidae is a small family of medium-sized mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. They may be called trapdoor spiders, as are similar species, such as those of the families Liphistiidae, Barychelidae, Cyrtaucheniidae and some species in Idiopidae and Nemesiidae. In 2018, the family Halonoproctidae was split off from Ctenizidae, leaving only three genera. The name derives from Greek κτενὶζειν ktenizein, meaning 'combing' or 'cleaning', referring to their behaviour of cleaning continuously, and the suffix -idae, which designates belonging to a family. The family Ctenizidae was first described by Thorell in 1887, being based on the genus Cteniza. Since the advent of molecular phylogenetics and its application to spiders, the family has been progressively dismantled; the World Spider Catalog lists over 100 genera formerly placed in Ctenizidae but now transferred to other families. The Halonoproctidae were split off in 2018, leaving only three genera. Even so, the family is not monophyletic, since Stasimopus is not in the same clade as the other two genera, according to a 2018 study (the three genera left in Ctenizidae are shaded in yellow): The trapdoor is difficult to see when it is closed because the plant and soil materials effectively camouflage it. The trapdoor is hinged on one side with silk. The spiders, which are usually nocturnal, typically wait for prey while holding on to the underside of the door with the claws on their tarsi. Prey is captured when insects, other arthropods, or small vertebrates disturb the 'trip' lines the spider lays out around its trapdoor, alerting the spider to a meal within reach. The spider detects the prey by vibrations and, when it comes close enough, leaps out of its burrow to make the capture. A hungry individual will wait halfway outside its burrow for a meal. Male trapdoor spiders can overcome the female's aggressive reactions to their approach, but it is not known how. Females never travel far from their burrows, especially if they have an egg sac. During this time, the female will capture food and regurgitate it to feed her spiderlings. Enemies of the trapdoor spider include certain pompilids (spider wasps), which seek out the burrows and manage to gain entrance. They sting the owner and lay their eggs (usually one per spider) on its body. When the egg hatches, the larva devours the spider alive. Unlike other mygalomorph spiders, the Ctenizidae have a rastellum on the chelicera. Resembling 'teeth' or 'barbs' on each fang, this modification is used to dig and gather soil while constructing a burrow. They use their pedipalps and first legs to hold the trapdoor closed when disturbed.