INSECTS 



insects known are roaches, or insects closely related to 

 roaches, there were many other forms besides. Some of 

 these are of particular interest to entomologists because, 

 in some ways, they are more simple in structure than are 



B 



Fig. 5 c. Fossil cockroaches from Upper Carboniferous rocks 



A, A ' semoblatta mazorta, found in Illinois, length of wing one inch. 



(From Handlirsch after Scudder.) B, Phyloblalta carbonaria, 



found in Germany. (From Handlirsch) 



any of the modern insects, and in this respect they ap- 

 parently stand closer to the hypothetical primitive insects 

 than do any others that we know. And yet, the charac- 

 ters by which these oldest known insects, called the 

 Paleodictvoptera, differ from modern forms are so slight 

 that they would scarcely be noticed by anyone except 

 an entomologist; to the casual observer, the Paleodic- 

 tyoptera would be just insects. Their chief distinguish- 

 ing marks are in the pattern of the wing venation, which 

 is more symmetrical than in other winged insects, and, 

 therefore, probably closer to that of the primitive ances- 

 tors of all the winged insects. These ancient insects 

 probably did not fold the wings over the back, as do most 

 present-day insects, showing thus another primitive 



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