154 



IXVERTEBRATE ANIMALS. 



interest as attacking man. One of these causes the skin -disease 

 which is known as the "itch," and tlie other is found inhabiting 



Fig. 102. — Acarina. A, Tegeocranus elongatus, one of the Mites, enlarged 65 times. B, 

 Ixodes rlcinus, one nf the Ticks, greatly enlarged. C, Mouth-organs of a Tick 

 (Ixodes albipictus), enlarged : I La'biuni ; m Mandibles ; mp Maxillary palpi. 

 (After Michael, Packard, and Cuvier.) 



certain glandular follicles of the skin, probably without an excep- 

 tion even in favour of the most cleanly people. 



Order III. Pedipalpi. 



In this family are the most formidable of all the Araehnida — 

 namely, the Scorpions (fig. 101). They are all distinguished by the 

 fact that the abdomen is divided into distinct segments, and is con- 

 tinued into the cephalothorax without any well-marked boundary 

 or constriction. In the tiue Scorpions the end of the abdomen (fig. 

 101, t) is composed of a hooked telson, which is perforated for the 

 duct of a poison-gland, situated at its base. It is by means of this 

 that the Scorpions sting ; and the poisonous fluid which they secrete 

 is sufficiently powerful to render their wounds painful or even 

 dangerous. Tlie mandibles in the Scorpions, as already said, are 

 developed into pincers, and the so-called "maxillary palpi" con- 

 stitute powerful nipj)ing-claw.s. The respiratory organs are in the 

 form of pulmonary sacs, four on each side, opening on the under 



