THE GENEALOGY OF ANIMALS 79 



insects came into existence toward the latter part 

 of the Silurian period,* probably contemporaneous, 

 or nearly so, with the appearance of land vegeta- 

 tion. The spiders and insects were the aborigines 

 of the land and air. They are the only races of 

 living beings, except the original inhabitants of 

 the sea, who ever invaded and settled an unoccu- 

 pied world. The earliest land fossils so far found 

 are the fossils of scorpions. But the existence of 

 a sting among the structural possessions of these 

 animals indicates that there were already others 

 who contended with them for supremacy in the 

 new world. The first insects were the masticating 

 insects, insects such as cockroaches, crickets, grass- 

 hoppers, dragon-flies, and beetles. They are found 

 abundantly in the Devonian and Carboniferous 

 rocks. The licking insects (bees) and the pricking 

 insects (flies and bugs) appeared first in the 



* The following are the divisions and subdivisions of 

 geological history : 



'Pleistocene period. 

 Pliocene 



5. Cenozoic Era (Tertiary) 



Miocene 



Oligocene 

 V-Eocene 



I" Cretaceous period. 



4. Mesozoic Era (Secondary) j Jurassic 



ITriassic 



Permian period. 



Carboniferous period. 



Devonian 



3. Paleozoic Era (Primary) 



Silurian 



Ordovician 



Cambrian 



2. Proterozoic Era ... Algonkian period. 



I. Archeozoic Era. 



