ir] WHAT IS A SPIDER? 7 



and having said this we may dismiss them, for insects 

 and arachnids are strictly limited as to legs ; and no 

 myriapod can ever be mistaken for a spider. 



The Arachnida are so varied in structure that it 

 is not easy to give characteristics common to them 

 all, and to any general statement there are bound to 

 be exceptions, but for practical purposes it may be 

 said that while an insect, when mature, has only six 

 legs, and a pair of feelers or antennae of quite 

 different structure, Arachnids have normally eight 

 legs, and their feeling organs are not antennae but 

 leg-like " pedipalps." 



Most insects are distinguishable at once by the 

 possession of wings, which are never found among 

 the Arachnida, and they generally undergo a marked 

 transformation or metamorphosis in their progress 

 from the egg to maturity, taking on at first the form 

 of a caterpillar or grub and then that of a chrysalis ; 

 but as there are many wingless insects and many in 

 which the metamorphosis is very slight, the test 

 supplied by these characteristics is only of partial 

 application, and we shall do better to rely on the 

 number of legs, and the nature of the feeling organs. 

 If, therefore, we find a small wingless animal with 

 eight legs and a pair of feelers which are not thread- 

 like but much of the same character as the legs, 

 though not used for locomotion, we may be sure that 

 we are concerned with an Arachnid. 



