Vol. 1.] Woodwortk. — ^¥ing Veins of Insects. 



89 



several of our existing orders were certainly very definitely 

 established. These lines of development lead to the present 

 orders Odonata, Ephemerida, Corrodentia, Orthoptera, and 

 Hemiptera. Those that prefer to consider these orders already 

 established will thus recognize six orders of winged insects as 

 existing at that period. 



We will now consider in order the ancient types of venation 

 that have been preserved to us, and the related modern 

 groups, where these can be recognized. From the nature of 

 the case one can not speak with as great contidence in regard 

 to fossil forms as in regard to living, but even fragmentary 

 data are of great value in tracing homologies. The classifica- 

 tions of fossil insects of the Paleozoic era given us by Scudder 

 and by Brongniart scarcely resemble each other in any par- 

 ticular, but figures of the fossils classified by these two 

 authors seem to indicate that, to a great extent, this difference 

 was justified and that we may almost add the two systems 

 together without doing violence to either. 



MEGASCOPTERID.I*:. 



This is the first of the ancient groups of insects in which 

 there appeared evidence of a tendency to suppress the cross 

 veins and still preserve a comparatively small number of lon- 

 gitudinal veins. The 

 group is quite sharply 

 defined from other 

 known insects, and is 

 supposed to represent an 

 extinct branch peculiar 

 to the Paleozoic era. 



As will be seen b}^ 

 the accompanying figure 

 (Fig. 26), the venation is distinctly of a neutral primitive type, 

 which it might be possible so to adjust as to rei^emble either one 

 of a number of venation types. In the shape of the wings, in 

 the number and arrangement of the veins, and in the peculiar- 

 ity exhibited by a number of the independents in changing their 

 attachments, this wing agrees with the Termitidaj; but the 

 really characteristic things about the venation of the Termi- 

 tidffi are not suggested in these wings, and there is little or 



FIG. 2G. Diagram illustrating the venation of 

 the MegascopteridiB. Dotted lines indicate veins 

 that may be present or not. Brackets imlicate 

 variableplace of attachment of veins. 



