Appendages of 2nd pair very large and completely chelate, their basal segments meeting in the middle line, as in the Uropygi, and provided in front with membranous lip-like processes underlying the proboscis.
A third division, the Tartarides, a subordinate group of the Uropygi, contains minute Arachnida differing principally from the typical Uropygi in having the caudal process unjointed and short.
Some species of the Uropygi (Thelyphonidae) dig burrows; and in the east there is a family of Amblypygi, the Charontidae, of which many of the species live in the recesses of deep caves.
The Uropygi are found only in Central and South America and in south and eastern Asia, from India and south China to the Solomon Islands.
The distribution of the Amblypygi practically covers that of the Uropygi, but in addition they extend from India through Arabia into tropical and southern Africa.