Liphistiidae
The spider family Liphistiidae, recognized by Tamerlan Thorell in 1869, comprises 8 genera and about 100 species of medium-sized spiders from Southeast Asia, China, and Japan.[1] They are among the most basal living spiders, belonging to the suborder Mesothelae. In Japan, the Kimura spider (Heptathela kimurai) is well known.
Liphistiidae are tube-dwelling spiders that construct rudimentary trap-doors. They spend most of their time here and are rarely seen above ground. The medium to large spiders range from 8 to 23 millimetres (0.31 to 0.91 in) long. They are characterized by their downward pointing, daggerlike chelicerae,[2] and the segmented series of plates on the upper surface of the abdomen. The carapace is mostly flat, though it can be slightly elevated near the head. The eyes are distinctly clustered together on a single nodule. Anterior median eyes are small, but posterior median eyes are large and round. The lateral eyes are long and kidney-shaped. The distal leg segments have strong spines and three claws. Chelicerae are vertically attached to the cephalothorax.[3] In the past, they were frequently believed to lack venom, but in 2010 it was shown that at least Liphistius species have venom glands.[4]
They are active at night and live for many years. Although most species live in burrows, cave-dwelling species also fasten their retreats to the cave walls. Both burrows and retreats are sealed with woven doors.[5] Trapdoor nests are generally built in shady areas with moss or sparse vegetation. Some make silk trip-lines radiating away from the burrow entrance. Adult males sometimes wander in search for females, but females rarely leave their burrows. The respiratory system consists only of book lungs, which could help explain why they are relatively inactive.[6]
Although they have downward pointing chelicerae like the Mygalomorphae, there is no close relationship between the two. It is thought that the common ancestor of all spiders was orthognath and that in the Opisthothelae, comprising Mygalomorphae (mostly tarantulas) and Araneomorphae (all other spiders), only the Araneomorphae changed their alignment of chelicerae, while the mygalomorphs retained this symplesiomorphic feature.[6]
Molecular phylogenetic studies have repeatedly shown that the family is monophyletic, at least as regards extant (living) species. The relationship between the genera is shown in the following cladogram:[7]
In 1923, Kyukichi Kishida suggested dividing the family into two subfamilies, Liphistiinae and Heptathelinae, corresponding to the genera Liphistius and Heptathela.[8] More genera have since been added to the family, but the subfamily division has been upheld by modern phylogenetic studies. Liphistius, the sole genus in the subfamily Liphistiinae, is found only in Southeast Asia (Laos, Myanmar, Thailand, Malaysia and Sumatra). The Heptathelinae are found further north: five genera in northern Vietnam and China and two genera in Japan and offshore islands (Okinawa, Ryukyu Islands).[7]
