400 



THE WINGS OF INSECTS 



from that of the hypothetical primitive type. The most striking modifica- 

 tion of the primitive type is the fact that in both fore and hind wings there 

 are only three separate branches of media. Vein M4 coalesces either with 

 vein M3 or with vein Cui. As there is doubt regarding the fate of vein M4 

 the student in lettering his drawings of lepidopterous wings may omit any 

 reference to this vein. 



Wings of Prionoxystus. — Make a drawing of each wing. 



Note that the fore and hind wings differ greatly in venation. This is 



Fig. 416. — Wings of Pielus labyrinthecus. 



true of the wings of all Lepidoptera except one small family, the Hepialidae, 

 of which Peilus labyrinthecus, the wings of which are represented in Figure 

 416, is a member. 



Letter the veins of the fore wing. Note the anastomosis of veins R3 

 and R4+5. 



In the hind wing veins vSc and Ri coalesce in the outer half of the wing 

 and the radial sector is not branched ; these facts have been determined by 

 studies of the tracheation of pupal wings. With this information before 

 you, letter the veins of the hind wing. 



