MITES AND SCOMPIOm. 



113 



Orders of Abachnida. 



1. Body small, rounded ; no distinct abdomen. ^c«n«a, Mites. 



3. Body with a jointed abdomen Arthrogastra, Scorpion. 



3. Body with a thick unjointed abdomen Araneina, Spiders. 



Order 1. Acarina. — The mites (Fig. 135) are the sim- 

 plest Arachnida, the body being oval in form, the head 

 usually small, more or less merged with the thorax, while 

 the latter is not separate from the abdomen. The tick 



Fig. 135. — Sugar-mite. 

 Much enlarged. 



1.36.— Cattle-tick (Ixodes hovis). 

 Natural size and enlarged. 



(Fig. 136) is a large mite. It infests cattle, sometimes 

 burying itself in the skin of human beings. 



Order 2. Arthrogastra. — This group embraces the scor- 

 pion (Fig. 137), the false-scorpions, the whip-scorpions, and 

 the harvest-men {Phalanginm). In all these forms the ab- 

 domen is plainly segmented, the segments not being visible 

 in the mites or spiders. Usually the maxillary palpi are 

 much enlarged, and end in claws. The scorj^ion is vivij)a- 

 rous, the young being brought forth alive. The young scor- 

 pions cling to the back of the mother. The sting of the 

 scorpion is lodged in the tail, which is perforated, and con- 

 tains in the bulbous enlargement an active poison. Though 



