HOW TO KNOW THE BUTTERFLIES 



traverse the middle portion of the wing are 

 branched; the subcosta divides into two branches, 

 the radius into five, the media into four, and 

 the cubitus into two. In this primitive type 

 the costa and the three anal veins are not 

 branched. 



In designating the branches of a forked vein 

 they are numbered, beginning with the one near- 

 est the costal margin of the wing. Thus, the first 

 branch of radius is designated as radius-one ; and 

 for this term the abbreviation Rj is used. 



In some insects there are very many cross- 

 veins, but it is believed that the greater number 

 of these have been developed secondarily. There 

 are, however, a few cross-veins that are so con- 

 stantly present among generalized insects that we 

 feel warranted in believing that they were pres- 

 ent in the wings of the primitive winged insect. 

 These are represented in Figure 5, and are desig- 

 nated as the humeral cross-vein (Fig. 5, Ji) ; the 

 radio-medial cross-vein (Fig. 5, r~m) ; the medial 

 cross-vein (Fig. 5, m); and the medio-cubital cross- 

 vein (Fig. 5, m-cti). 



In Figure 6 is represented the venation of the 

 wings of Stkenopis, a moth, which is one of the 

 most generalized of the living Lepidoptera. Here 

 is found quite a close agreement in venation with 



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