88 TAXONOMY. 



lies agree in the possession of wing veins, which are 

 lacking in the narrow-winged members of the same 

 families. The media, and the third anal vein. If the 

 narrow-winged forms are considered the more general- 

 ized, we are forced to conclude that the media and the 

 third anal vein have been independently developed 

 in each family where they exist, which is very im- 

 probable. 



Conclusion that the primitive lepidopterous insect 

 possessed broad wings, furnished with at least eight 

 principal veins, including the media and three anal 

 veins. 



Conclusion strengthened by a study of wings of in- 

 sects of other orders ; also by a study of fossil insects. 



The chief method of specialization of the wings of 

 insects as regards their area and their venation has 

 been by reduction. This specialization has changed 

 the wing from an organ which acted as a kite, or a 

 parachute, to one fitted for vigorous flight. 



Origin of wings not yet satisfactorily explained. 

 Theory of origin from tracheal gills. Theory of origin 

 from keel-like expansions of the sides of the body seg- 

 ments. 



Different lines of descent from the primitive lepid- 

 optera indicated by different methods of reduction. 

 In hepialis and micropteryx the anal area of the hind 

 wings is greatly reduced, while the radius retains the 

 maximum number of branches. In all other lepid- 

 optera all of the branches of the radius disappear 

 before the anal area is reduced. Subdivision of the 

 groups thus formed. 



2. Relation of the two pairs of wings to each other. 



