570 THE PANORPOID COMPLEX, ill., 



Section iv. The Structure op the Cubitus. 



(Plate xxxii., fig. 17, Plate xxxiii., figs. 19-20, Plate xxxiv., 



figs. 21-22, Plate xxxv., fig. 23, and Text-figs. 46-50). 



Before we can arrive at a correct conclusion with respect to ' 

 the archetypic venation of any of the Panorpoid Orders, it is 

 very necessary that we should study the cubital vein with spe- 

 cial care, seeing that, on this point more than anywhere else, 

 errors have been allowed to creep in, in the work of the Com- 

 stock-Needham school. 



Comstock has assumed (15) for the Lepidoptera and Trichop- 

 tera, that the cubitus is two-branched, thus making this vein 

 conform, in these two Orders, with his theoretical type. The 

 fact that three branches can be clearly seen in the tracheation 

 of the pupal wing, in all archaic Lepidoptera, is then explained 

 by saying that the first anal trachea has migrated over to the 

 cubitus, and fused with it entirely for its basal portion. The 

 same explanation is given for an exactly similar occurrence in 

 the Homoptera. But it does not seem to have occurred to the 

 author of this extraordinary statement, that a careful com- 

 parative study of the veins in question, with the same veins in 

 other Orders closely allied to them, might have offered a much 

 more simple and obvious explanation, viz. that the cubitus is 

 really three-branched, and the first analis remains in its usual 

 position. Yet such is, as a matter of fact, the case, and the 

 proof thereof is a very simple one. 



Text-fig. 46a shows the form of Cu in the Orders Mecoptera, 

 Paratrichoptera and Diptera. The cubital fork lies close to the 



Text-Fig. 46. 

 Structure of the cubitus in the Panorpoid Complex, a, the two-branched 

 type found in Mecoptera, Paratrichoptera and Diptera; /;, the 

 original three-branched type found in the other Orders of the Com- 

 plex. Lettering as on p. 535. 



