The only living members of the primitive Mesothelae are the family Liphistiidae, found only in Southeast Asia, China, and Japan.
Most of the Liphistiidae construct silk-lined burrows with thin trapdoors, although some species of the genus Liphistius build camouflaged silk tubes with a second trapdoor as an emergency exit.
Members of the genus Liphistius run silk "tripwires" outwards from their tunnels to help them detect approaching prey, while those of the genus Heptathela do not and instead rely on their built-in vibration sensors.
Spiders of the genus Heptathela have no venom glands, although they do have venom gland outlets on the fang tip.

The extinct families Arthrolycosidae, found in Carboniferous and Permian rocks, and Arthromygalidae, so far found only in Carboniferous rocks, have been classified as members of the Mesothelae.
The only living members of the primitive Mesothelae are the family Liphistiidae, found only in Southeast Asia, China, and Japan. Most of the Liphistiidae construct silk-lined burrows with thin trapdoors, although some species of the genus Liphistius build camouflaged silk tubes with a second trapdoor as an emergency exit. Members of the genus Liphistius run silk "tripwires" outwards from their tunnels to help them detect approaching prey, while those of the genus Heptathela do not and instead rely on their built-in vibration sensors. Spiders of the genus Heptathela have no venom glands, although they do have venom gland outlets on the fang tip.
The extinct families Arthrolycosidae, found in Carboniferous and Permian rocks, and Arthromygalidae, so far found only in Carboniferous rocks, have been classified as members of the Mesothelae.
Spider