THE GRASSHOPPER'S COUSINS 



"jointed-legs"; but, since many other animals have jointed 

 legs, the name is not distinctive, except in that the legs of 

 the arthropods are particularly jointed, each being com- 

 posed of a series of pieces that bend upon each other in 

 different directions. A name, however, as everybody 

 knows, does not have to mean anything, for Mr. Smith 



l'li.. 14. Kxamples of four common classes of the Arthropoda 



A, a crab (Crustacea). B, a spider (Arachnida). C, a centipede (Chilopoda). 



D, a fly (Insecta, or Hexapoda) 



may be a carpenter, and Mr. Carpenter a smith. A phylum 

 is divided into classes, a class into orders, an order into 

 families, a family \nto genera (singular, genus), and a genus 

 is composed of species (the singular of which is also species). 

 Species are hard to define, but they are what we ordinarily 

 regard as the individual kinds of animals. Species are 

 given double names, first the genus name, and second a 

 specific name. For example, species of a common grass- 

 hopper genus named Melanoplus are distinguished as 

 Melanoplus atlanus, Melanoplus femur-rubrum, Melanoplus 

 differentia/is, etc. 



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