Book-scorpion (Chelifer cancrroides), a small Arachnid, in appearance between scorpion and mite. It is like a small flattened scorpion without a tail. The front of the body is scorpion-like, and bears a transverse dorsal groove; the posterior body is flat, with 10 or 11 rings. There are two eyes; the respiration is by means of air-tubes; the eggs are carried about on the abdomen of the female. Spinning-glands are present, and the body is sometimes covered by the secretion. The size is about one-eighth of an inch, the colour brownish. The book-scorpion lurks among old books and papers, and probably helps their preservation by killing off and eating book-lice, mites, and other small insects. Upon the whole it likely does more good than harm. Other related forms are common under bark, moss, &c. Some species are found attached to the legs of house-flies, which not improbably indicates a partial parasitism. See ARACHNIDA, BOOK-LICE, SCORPION, SPIDER.