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= Antrodiaetus riversi =

Description
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Range
This spider is endemic to California, along the Monterey coast and stretching up north almost to the Oregon border. There are populations are in the central Sierra Nevada range, from Mariposa County to El Dorado County. Also, a small population is located in Sutter Buttes, which is a Central Valley mountain range, but there are no other known populations residing in the dry climate of the Central Valley.

Habitat
The ideal habitats for turret spiders are moist and cool to avoid drying out. These include shaded forests among tree roots on north facing slopes or in ravines. Due to their various habitat requirements and inability to disperse readily, many A. riversi burrows are grouped in dense clusters, including burrows of many adult females and their offspring.

Ecology
Turret spiders are rarely active during the daytime and males can be seen leaving their burrows during mating season. In late summer or fall, sexually mature male spiders pursue a female. In accordance with the rainy season, adult males leave their burrows to seek female mates at night, hiding during the day. When mating, male spiders will position females with their cheliceral apophyses, and males die shortly after attempting to or successfully mating. Female spiders can live up to 16 years and have multiple batches of eggs every year. They produce lens-shaped eggs and secure them to the internal walls of their burrows.

The turrets constructed by A. riversi are small, hollow cylindrical structures that stand upright. They have flexible rims that form a folding door. It can an be a maximum of three inches tall, and the width of a turret corresponds to the size of the spider living inside it. To camouflage the burrow’s opening, the spider weaves in dirt, moss, pine needles and other pieces of plants. This makes the turret look like a natural part of the forest floor to unsuspecting prey. When prey walk on the soil near their burrow, A. riversi can detect vibrations while waiting at the internal edge of their turret. When close enough, they grab their prey and drag it into their tunnels to feast. California turret spiders hunt at night and are sedentary during the day.

Etymology/Taxonomy
This spider belongs to the Antrodiaetus genus and its species is riversi. A. riversi is called the turret spider for the entrance to its burrow, which has a similar shape to a castle´s turret. It is in the mygalomorphae infraorder, which consists of tarantulas and trapdoor spiders. It is also included in the Antrodiaetidae family of folding-door spiders.

The name California Turret Spider has been found to be the overarching name of five genetically different species that have morphological similarities. Earlier the riversi species was in a different genus Atypoides and was moved to the Antrodiaetus group upon further analysis by scientists. The genus Antrodiaetus differs from Atypoides since the latter consists of trapdoor spiders, spiders with different morphological structures, and those that live in a more varied habitat range.

Antrodiaetidae spiders have diverged into different species after being separated loctionally. Geographic changes caused by glaciers and other geological events prevent them from sharing genetic material. Also, to prevent inbreeding, Antrodiaetus riversi males will leave their home burrows and travel far to find a mate.