72 John Henry Comstock 



farther specialization is to round off the angles in the path of 

 the tracheae, as the angles in our roads are rounded off by carts. 

 This process is continued until these cross veins become parts 

 of longitudinal veins, and their true nature as cross veins is 

 completely hidden. This is well shown by the connection ex- 

 isting between the third branch of media (vein V3) and cubitus. 

 A study of the venation of Castnia (Fig. 15) shows conclu- 

 sively that media is three-branched and cubitus only two- 

 branched. Here the connection between vein V3 and vein VII 

 is obviously a cro.ss vein. But in ever)' American moth and 

 butterfly known to me, except perhaps Hepialis and Micropte- 

 ryx, the union of these two veins is so complete that there is 

 no hint of the fact that vein V3 is not a branch of vein VII. 

 And in several families vein V2 has also become united with 

 vein VII in a similar manner. The result is that cubitus (the 

 median vein of many authors) is described as three-branched 

 in some families and four-branched in others. 



Two years after I had reached the conclusion that media is 

 three-branched and cubitus only two-branched in the Lepi- 

 doptera, Spuler published a paper* in which these facts are 

 demonstrated in an entirely different way. As I did not pub- 

 lish my conclusions, the credit of the discovery belongs of 

 course to Spuler. I wish merel}' to state that my conclusions 

 were reached independently of that author's work, and by an 

 entirely different method. I was led to the correct under- 

 standing of the relation of these veins by a study of existing 

 generalized forms (especially Hepialis and Castnia) ; while 

 vSpuler's conclusions were based on a study of the ontogeny of 

 certain butterflies. He found that in newly formed pupae the 

 trachea which later becomes enclosed by media is three- 

 branched, while that one which is the precursor of cubitus, is 

 only two-branched. This is an interesting instance of the 

 evidence of ontogeny confirming results obtained in an effort 

 to determine the phylogeny of a group by the study of gener- 

 alized forms. 



* A Spuler. — Zur Phylogenie luid Oiitogenie des Flugelgeaders der 

 .Schmetterlinge. Zeit. fur wissenschaftliche Zoologie, LIU. 



