WHIP-SCORPIONS. 217 



ings, with the back on a level with the surface of the soil, and here concealed 

 from view they lurk on the look out for prey. Sound-producing organs have 

 been found in the large, black rock-scorpions of India and Africa; the organ, 

 which lies between the basal segment of the pincers and that of the first pair 

 of legs, consists of a set of tubercles and of a cluster of curved hair-tipped spines. 

 When the scorpions are excited, they wave their pincers up and down, and by thus 

 scraping the spinules against the tubercles emit a rustling sound, which has been 

 compared to that produced by rubbing a stiff tooth-brush with one's finger nails. 

 This organ is equally well developed in members of both sexes, and probably serves 

 as a warning to enemies to keep their distance. An analogous organ is found in 

 the South African Opisthophthalmus, but in this case it consists of leaf-like 

 hairs placed on the inner surface of the mandibles. 



THE WHIP-SCORPIONS AND THEIR ALLIES, Order PEDIPALPI. 



The members of the second order of the Arachnida resemble the scorpions in 

 having the abdomen composed of twelve segments, and the second pair of append- 

 ages transformed into huge seizing organs, but differ from them in a number of 

 important characters. The legs of the first pair, for instance, are not used for 

 locomotion, but only as organs of touch, and have their last segment devoid of 

 claws and divided into a series of secondary segments. Moreover, in the rest of 

 the legs the feet are three-jointed. The most marked distinctions are, however, 

 found in the abdomen. In the first place, this region is sharply marked off from 

 the cephalothorax by a deep constriction forming a narrow waist. There is no 

 trace of combs, and the first sternal plate is of large size, and entirely covers the 

 ventral region of the first and second segments ; so that, although there are twelve 

 dorsal plates on this region of the body, there are only eleven sternal plates. The 

 breathing-organs are of the same nature as those of the scorpions, namely, lung- 

 books ; but instead of forming four pairs, situated upon the third, fourth, fifth, and 

 sixth sterna, there are only two pairs, of which the apertures are placed behind 

 the sterna of the second and third segments. The order is divided into a tailed 

 group (Uropygi), and a tailless group (Amblypygi). In the former the body is 

 elongate, both cephalothorax and abdomen being much longer than wide ; and to 

 the last segment of the abdomen there is attached a movable tail corresponding to 

 the sting of the scorpions. On the lower side of the cephalothorax there are two 

 distinct sternal pieces, an anterior and a posterior, the latter being triangular and 

 lying between the coxas of the last pair of legs, while the anterior is longer and 

 placed between the coxae of the first pair of legs and behind those of the pincers, 

 which are united to form a kind of lower lip. The area between these sternal 

 plates is narrow, membranous, and largely encroached upon by the coxae of the 

 second and third legs, which nearly or quite meet in the middle line. The legs 

 of the first pair are also much shorter, and more typically leg-like than in the 

 Amblypygi, the tarsal segment alone being divided into a series of nine cylindrical 

 secondary segments. 



The tailed suborder may be further divided into the sections 

 Tartarides and Oxopcei. The former is a small group in which the 



