INSECTS 



same primary veins; but, since the great specialty of in- 

 sects is flight, in their evolution they have concentrated 

 on the wings, and the different groups have tried out 

 different stvles of venation, with the result that now 

 each is distinguished by some particular pattern in the 

 arrangement of the veins and their branches. The 

 entomologist can thus not only distinguish by their wing 

 structure the various orders of insects, as the Orthoptera, 

 the dragonflies, the moths, the bees, and the flies, but in 



Kic. 5"). Wings of a cockroach, Periplamla, showing the vein 

 pattern characteristic of the roach family 



many cases he can identify families and even genera. 

 Particularly are the wings of value to the student of fossil 

 insects, for the bodies are so poorly preserved in most 

 cases that without the wings the paleontologist could 

 have made little headway in the study of insects of the 

 past. As it is, however, much is known of insects of 

 former times, and a study of their fossil remains has con- 

 tributed a great deal to our knowledge of this most 

 versatile and widespread group of animals. 



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