THE PALEONTOLOGICAL DATA 



89 



links that we should be glad to see have not been found, certain others that 

 throw much light on the origin of wings are known. 



It is now believed that the oldest known insect remains are from the 

 lower part of the Upper Carboniferous ; for it has been concluded that the 

 two supposed insect remams from the Silurian are not of insect origin; and 

 that the supposed Devonian insects described by Scudder belong to the 

 Upper Carboniferous. No insect remains have been found in the Sub- 

 carboniferous.* 



In the classification of geological formations adopted by Handlirsch, 

 the Upper Carboniferous, in which most of the insect remains that are 

 referred to in this Chapter were found, is divided into the Lower Upper 

 Carboniferous, the Middle 

 Upper Carboniferous, and the 

 Upper Upper Carboniferous. 

 For convenience of reference 

 to his work I have followed 

 him in the use of this some- 

 what cumbersome nomen- 

 clature. 



Among the Paleozoic in- 

 sects there are certain very 

 generalized forms that differ so 

 markedly from all of the living 

 orders of insects that they have 

 been placed in a separate order 

 to which the name Palteodic- 

 tyoptera has been applied, 

 been found. 



Fig, 76. — Ruble plus danielsi (After Handlirsch). 



Many representatives of this order have 

 Handlirsch describes and figures 115 of them. 



The Palasodictyoptcra is believed to include the stem forms from which 

 all other orders of insects, both fossil and recent, have been evolved. It is 

 obvious, therefore, that the search for paleontological data bearing on the 

 origin of wings should be made among the remains of this order. . These are 

 found in each of the divisions of the Upper Carboniferous mentioned above. 



From the Lower Upper Carboniferous only eight insect remains are 

 known; these are all wings or fragments of mngs. To test either of the 

 theories regarding the origin of wings it is necessary to study the remains 

 of the body of a palaodictyopteron. 



In the Middle Upper Carboniferous, there has been found a member of 

 this order in which the body is well-preserv^ed. This is Eiibleptus danielsi 

 (Fig. 76), from Mazon Creek, Illinois. While this insect furnishes import- 

 ant data regarding the venation of the wings of primitive insects, it throws 

 but little if any light on the origin of wings. 



*The reader is referred to page 84 for a chart of geologic time and formations. 



