The members of this order, comprising the Harvest-spiders, the Book-scorpions, etc, are distinguished from the preceding by the possession of an abdomen, which is more or less distinctly segmented, but generally exhibits no line of separation from the cephalothorax, the two regions being of equal breadth and conjoined together. The mouth is furnished with masticatory appendages, and respiration is effected by tracheae, which open on the lower surface of the body by two or four stigmata.
The well-known "Harvest-men" belong to this family. They are characterised by the great length of the legs (fig. 166, B), and by the filiform maxillary palpi, terminated by simple hooks. The abdomen and cepha-lothorax are of about equal width, but clearly marked off from one another, and the former is segmented. There are two eyes, and the young pass through no metamorphosis. The Harvest-men are active in their habits and live upon animal food.
The members of this little group are readily recognised by the fact that the maxillary palpi (fig. 166, A) are of large size, and are converted into nipping-claws or chelae, thus giving the animal the appearance of a Scorpion in miniature. The abdomen is segmented, but there is no "post-abdomen," as in the true Scorpions. Eyes may be wanting, and the under surface of the abdomen carries a small spinning-organ. The "Book-scorpion" (Chelifer) is commonly found in old books and in dark places.
Fig. 166. - A, Chelifer cancroides, showing the chelate maxillary palpi, considerably enlarged. B, Phalangium copticum, of the natural size. C, Thelyphonus giganteus. D, Galeodes araneoides, of the natural size.
In this family (fig. 166, D) the abdomen is not only very distinctly segmented, but is also clearly separated from the cephalothorax, which is likewise segmented. The falces or mandibles are chelate, and of immense size; and the maxillary palpi constitute long feet. The front of the head carries two eyes, and respiration is by tracheae. Galeodes may be considered as the type of the group, all the members of which are tropical or subtropical in their range, and are nocturnal and carnivorous in habit.