1911 Encyclopædia Britannica/Pedipalpi
PEDIPALPI, Arachnida (q.v.) related to the spiders, and serving in a measure to bridge over the structural interval between the latter and the scorpions. The appendages of the second pair are large and prehensile, as in scorpions, but are armed with spines, to impale and hold prey. The appendages of the third pair, representing the first pair of walking legs in spiders and scorpions, are, on the contrary, long, attenuated and many-jointed at the end. Like the antennae of insects, they act as feelers. It is from this structural feature that the term “pedipalpi” has been derived. In the tailless division of the Pedipalpi, namely the Amblypygi of which Phrynus is a commonly cited type, these tactile appendages are exceedingly long and lashlike, whereas in the tailed division, the Uropygi, of which Thelyphonus is best known, the limb is much shorter and less modified. Thelyphonus and its allies, however, have a long tactile caudal flagellum, the homologue of the scorpion’s sting; but its exact use is unknown. 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. Apart from the Tartarides, the Pedipalpi
Mexican tailed Pedipalp (Mastigoproetus giganteus).
are large or medium-sized Arachnida, nocturnal in habits and spending the day under stones, logs of wood or loosened bark. 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. Specimens of another species have been found under stones between tide marks in the Andaman Islands. The Pedipalpi feed upon insects, and like spiders, are oviparous. The eggs after being laid are carried about by the mother, adhering in a glutinous mass to the underside of the abdomen.
Pedipalpi date back to the Carboniferous Period, occurring in deposits of that age both in Europe and North America. Moreover, the two main divisions of the order, which were as sharply differentiated then as they are now, have existed practically unchanged from that remote epoch.
In spite of the untold ages they have been in existence, the Pedipalpi are more restricted in range than the scorpions. 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 absence of the entire order from Africa is an interesting fact. 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. Both groups are unknown in Madagascar, in Australia, with the exception possibly of the extreme north, and in New Zealand. Very little can be said with certainty about the distribution of the Tartarides. They have been recorded from the Indian Region, West Africa and sub-tropical America. (R. I. P.)
Mexican tailed Pedipalp (Mastigoproetus giganteus).