Evolution and Taxoyiomy 49 



PART II. 

 THE EVOLUTION OF THE WINGS OF INSECTS. 



This essay is an outgrowth of an effort to determine the 

 phylogeny of the families of the Lepidoptera, in order to de- 

 cide upon a classification to be used in a general text book of 

 Entomology. More than three years were devoted to the prob- 

 lem before a systematic method of procedure was adopted. 

 This time was largely spent in a comparative study of pub- 

 lished classifications and in an effort to determine which of 

 these represented most accurately the facts of nature. A large 

 part of the work yielded poor returns for the labor expended ; 

 for it was carried on with no definite plan ; it was a blind 

 groping in the dark. 



Suddenly one day a flood of light was thrown upon the 

 work by the recognition of the fact that a moth which I was 

 studying {Hepialis, Plate I, Fig. 2) was a generalized type. 

 I found that a knowledge of the structure of this insect gave 

 a clue to the probable structure of the primitive Lepidoptera. 

 And that with this knowledge it was not too much to expect 

 to be able to trace out the various lines of descent represented 

 by existing forms. Then began a systematic study which 

 has resulted in the development of the method outlined in 

 Part I of this essay. 



I regret that I have been unable to apply the method as 

 fully as I should like to before publishing it. But the results 

 which I have been able to obtain by it lead me to hope that 

 the publication is not premature. And as the leisure which 

 a teacher can get for study is limited, I could not hope to 

 make a complete application of it, even to the families of a 

 single order, for many years. 



A complete application of the method to the Lepidoptera 

 alone will involve a study of the segments of the body a sa 

 whole, the peculiarities of development of particular segments, 

 the structure of internal organs, the structure of organs of 

 special sense, the various appendages of the body as antennae, 

 mouth-parts, legs, wings, and the external appendages of the 

 reproductive organs, the clothing ofthebody,in a word the 



