5 



exoskeleton of chitin 

 quantities of lime. 



Fig. i. Crustacean 

 A Wood-louse. 

 Enlarged. (From U. 

 De}it. A<jric.) 



S. 



is often impregnated with large 



The Class Arachnida includes 

 the spiders, mites, ticks and scor- 

 pions. These animals breathe by 

 means of air-tubes (tracheae), or 

 air-sacs. Certain species, mites, 

 especially, have the entire surface 

 of the body adapted for respira- 

 tion. In the case of most mem- 

 bers of this group, the head and 

 thorax are fused to form a cepha- 

 lothorax, and the eyes are simple. 



The scorpions (Fig. 2) are well- 

 known in tropical countries, on 

 account of the painful sting they 

 are able to inflict. They are 

 mostly predaceous and nocturnal 

 in habit, living in damp situations. 



Fig. 2. Arachnid. A scorpion. 

 Slightly reduced. (Original.) 



The whip scorpions (Fig. 3) receive their name from the 

 long lash-like development of the first pair of legs. In the 

 illustration these are the slender appendages which are 



