THE- RECORD FROM FOSSILS. 



true bugs, and dragon-flies being thus foreshadowed. With the 

 Mesozoic (5-8) the higher orders appeared, and by the end of the 

 Jurassic (7), the modern orders of insects were all in existence. Of 

 the various orders the higher ones appeared last. These orders, 

 since they feed upon flowers, could not be expected until flowers them- 

 selves appeared, and this was not until the middle of the Mesozoic 

 (5-8). [See Chap. VI.]. 



FIG. 13. Diagram of air-breathing Arthropoda. / Insecta. A Araneina. 

 Ar Arachnoida. M Myriopoda. 



The insects have thus developed within the period of fossil history. 

 In the Silurian they were represented by the lowest order and this 

 order, during the rest of the Paleozoic, gradually diverged in the sev- 

 eral directions which gave rise in the beginning of the Mesozoic (5-8) 

 to the beetles and bugs and dragon-flies. Later, when the flowering 

 plants made their appearance, there was a second divergence and a 

 production of new forms depending upon flowers for their existence. 



