KEY TO THE ORDERS 



295 



these insects is necessary. If the under side of the wing be 

 moistened with benzine or chloroform, by means of a small 

 camel's-hair brush, it will be noticed that the membranous 

 portion of the wing is supported by veins or nervures. The 

 relative positions of these veins remain fairly constant in the 

 various families, and thus these veins afford clear and ready 

 means of comparison. For these veins, various systems of 

 arrangement and nomenclature are extant. The one used here 

 was proposed by Redtenbacher, and has been modified and ex- 

 tended by Comstock. The principal trunks of the veins bear 

 the Roman numerals I, II, III, etc.; the branches of each of 



Ux.j 



FIG. 223. Wing of a Hepialid 

 moth, showing plan of vena- 

 . tion. (After Comstock.) 

 FIG. 222. Wings of a Noto- 

 dontid, showing venation. .F, 

 frenulum. (After Comstock.) 



these veins, where branches exist, are numbered III^ IIL, III 3 , 

 etc. The system considers I (the front margin of wing) simple, 

 II simple, III possessing five branches, IV with three branches, 

 and V with two branches. Those main veins which come after 

 V are called anal veins. They are generally simple. This ar- 

 rangement has reference to the early or primitive plan of the 

 wing. This condition is shown in Figure 222. This arrangement 

 is greatly modified in some of the higher types, by the elimination 

 of branches or even trunks and by the coalescence of veins for 

 part or for their entire length. 



AA. Antennae of various forms, frequently feather-like, rarely 

 knobbed at tip, but in such cases the hind wing bears a 

 frenulum. 



