INSECTS AUACUNID A DIAGBAM 6. 147 



CLASS ARACHNIDA. 



The class Arachnida, which at first sight seems greatly to resem- 

 ble that of insects, is nevertheless very easily distinguished from it. 

 While insects have six legs, the spiders 

 and all the animals included with them 

 in this class have eight legs. There 

 are also other differences. The head and 

 thorax are united, in such a manner 

 that there is no neck. The abdomen 

 itself is sometimes joined to the head and 

 thorax, as in the mites ; and the body 

 then forms only a single ovoid mass 

 Spider, back riew. with eight legs. The eyes are conse- 



quently placed on the corslet ; there are often 6 or 8 or even 



12, separated from 

 each other, instead of 

 being united in a 

 cluster like those of 

 insects. The remain- 

 Side view of Spider. der of> their structure 

 much resembles that of insects ; but they have not metamorphoses 

 but only moults. 



Many people are often much terrified at spiders, without 



