LECTURE XXXVII. 



APPLICATION: OF THEORY OF DESCENT TO TAXONOMY. 

 ILLUSTRATION OF THE APPLICATION OF THIS 

 METHOD. THE DESCENT OF THE LEPIDOPTERA. 



Prof. John H. Comstock. 



Selection of the organs of flight as the first organs 

 to be studied. 



Importance of wings to the lepidoptera. Chief or- 

 gans of locomotion of adult. Present in all known 

 species. Vary greatly in form ; hence they have been 

 the field of extensive action of natural selection. 



The results of this action are recorded in characters 

 which are easily read. These characters are varia- 

 tions in form, in the number and arrangement of the 

 supporting " veins," in the relation of the two pairs of 

 wings to each other, and in the nature of the clothing 

 of the wings. 



1. Variations in form and venation. Broad wings 

 with many veins, narrow wings with comparatively 

 few veins, and every gradation between these two ex- 

 ist. Which form probably represents most closely the 

 wings of the primitive lepidopterous insects ? 



The wings are organs of flight ; those members of 

 the order which fly best have narrow wings with com- 

 paratively few veins ; such are, therefore, probably 

 the more specialized. 



The wide-winged members of widely separated fami- 



