CHAPTER XI 



PHYLUM ARTHROPODA, CLASS ARACHNIDA 



The arachnids differ from all other arthropods in having 

 the following combination of characters: (1) no antennae; 

 (2) no true jaws, but only a pair of claw-like appendages 

 on either side of the mouth; (3) the head and thorax are 

 combined to form a cephalothorax, which bears the four 

 walking legs and is usually distinct from the abdomen. 

 There are twelve orders in the Class Arachnida but only 

 four will be considered. The other eight contain animals 

 which are rare, minute in size, or confined to tropical 

 countries. 



ORDER 1. ARANEIDA, SPIDERS 



The true spiders (Fig. 59) have two body regions the 

 cephalothorax and abdomen. The cephalothorax is rec- 

 tangular and flattened; the abdomen is unsegmented, soft, 

 and rounded. The spiders are, therefore, readily distin- 

 guished from the other common arachnids. The ticks and 

 mites have no division of the body into regions; in the 

 scorpions the body is flattened and the abdomen is very 

 slender; and in the phalangids, or "daddy-long-legs," the 

 appendages are slender and the body small. 



The class Arachnida received its name on account of the 

 spinning ability of the spiders. It is related in ancient 

 mythology that Arachne was a mighty spinner; so good, in 

 fact, that she became conceited and boasted that she could 

 beat Minerva herself. That great goddess, after spinning 

 and winning a match with the foolish Arachne, turned her 

 into a spider. And thus, says the legend, spiders had their 

 beginning. Modern zoology has kept Arachne's memory 

 green by naming spiders and related arthropods for her, 



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