152 The Pedigree of Insects 



atmosphere, or as sails or parachutes (2), assisting their 

 possessors to take flying leaps through the air. 



Insects of Past Ages. — From our survey of the 

 lower orders of insects living around us to-day we 

 have tried to trace out the relationships which they 

 bear to each other. It will be well to test our results 

 by the facts available regarding the insects of past 

 ages of the earth's history, the insects whose fossil 

 remains are preserved for us in the rocks (203-5). 

 Fossil insects are somewhat rare ; as with other land 

 animals their preservation in sedimentary deposits is 

 less likely than in the case of inhabitants of the sea. 

 Still, enough insect remains have been preserved and 

 discovered to help us to trace in part the history 

 of the class through geological time.^ It is dis- 

 appointing to find that the oldest known fossil insects 

 do not bring us much nearer to a solution of the pro- 

 blem of wing-origin. They do however indicate 

 clearly that similarity between the fore and hind-wings 

 is an ancient character. A large number of remains 

 from the Carboniferous rocks of France and North 

 America prove that, in that remote period, lived a 



1 For readers unfamiliar with geological terminology the appended 

 table of the great periods and formations may be useful for reference. 

 The formations become more ancient from above downwards. 



'Pleistocene. 



Tertiary or Cainozoic. 



Secondary or Mesozoic. 



Primary or Palseozoic. 



Pliocene. 



Miocene. 



Oligocene. 



Eocene. 



Cretaceous. 



Jurassic. 



Triassic. 

 f Permian. 



Carboniferous. 

 I Devonian. 

 -J Silurian. 

 I Ordovician. 

 I Cambrian. 

 LArchsan. 



