loS 



student should take up the work indicated below before 

 everything in this discussion is clear to him. 



Study the fore wings of the insects named below. It is 

 not best to attempt to determine the homologies of the veins 

 of the hind wings at first, owing to the great reduction of 

 wing-veins that has taken place in these wings. The direc- 

 tions for the study of wings given on page 97 will apply here 

 except that Figures 6 and 7 instead of Figure 2 will be used 

 for comparison. Indicate the media with red ink. 



The fore wings of Tenthredinids. The wings of two 

 saw flies will be used as examples of different degrees of 

 specialization : 



(a.) Macroxyela. 



(b.) Pteronus. The currant sawfly. 



The fore wing of a Siricid. The best genus of the 

 Siricidae for this study is Sirex. The more common, Tremex, 

 is more difficult. 



The fore wing of a Sphecid. Use for this purpose a 

 wing of the common mud-dauber, Pdopceus. 



The fore wing of an Ichneumon-fly. A species of 

 Ichneumon will furnish an example. 



The fore wing of a Braconid. Compare with the wing 

 of an Ichneumon-fly. Color vein J/ 3 red and the medial 

 cross vein black. 



The fore wing of the Honey-bee. 



THE WINGS OF NEUROPTERA. 



The foregoing studies of the wings of Diptera, Lepidop- 

 tera, and Hymenoptera have shown that in none of the 

 genera studied has the number of the branches of any vein 

 exceeded that of our hypothetical type (Fig. 5), and that in 

 none of them have all of the branches of all of the veins re- 



