turret spider

turret spider, (Atypoides riversi), species of small burrowing spider endemic to California, one of the best-known folding-door spiders. The turret spider inhabits shady slopes and banks in forests of northern and central California west of the Sierra Nevada mountains. It is reclusive, rarely leaving its burrow, and its bite is not considered dangerous to humans. As with the majority of the world’s invertebrate animals, the conservation status of the turret spider has not been assessed because of a lack of research, but it is fairly common in suitable habitats.

Physical description

Turret spiders grow to a body length of 1.8 cm (0.71 inch), and females are larger than males. The cephalothorax (fused head and thorax) and stout legs are chestnut brown. The abdomen is purplish brown and characterized by the presence of sclerites (hard plates) on the upper surface; males have three sclerites and females have one. The male’s chelicerae (jawlike mouthparts) have large hornlike projections ending in a tuft of bristles. As members of the infraorder Mygalomorphae, which also contains tarantulas and trapdoor spiders, turret spiders have long fangs that strike downward and impale their victims rather than clasp them like pincers.

Burrow and natural history

The turret spider digs a long, slanting burrow in the soil and lines it with silk. The silk lining extends about 2.5 cm (1 inch) or more above the burrow to form a collapsible rim—the “turret” from which the spider gets its name. The spider camouflages the outside of the turret by attaching bits of debris to the silk. Some turrets are camouflaged simply with soil or moss, whereas others are neatly arranged with spiraling leaves or tiny twigs. It is thought that the turret may help keep rain out of the burrow or may reduce moisture loss from the burrow itself.

The burrow entrance is typically open during the day when the spider is in its den. A nocturnal ambush predator, the spider surfaces at night to perch in its turret, waiting for a small insect or other invertebrate to pass within reach. It impales the prey with its large, venomous fangs and drags it inside to consume.

Mature males leave their burrows to wander in search of a mate. They probably locate a receptive female by her scent, but little is known of their mating behavior. The male dies shortly after mating, and the female lays her eggs and wraps them in a silken sac, which she positions halfway down her burrow. The spiderlings overwinter inside the burrow with their mother until the following year, when they emerge to build their own burrows nearby. The spiders are susceptible to dehydration and have a limited dispersal range, thus making entire populations vulnerable to habitat loss or other disturbances. Females may live more than 15 years, while males typically live less than 10 years.