(see Plate B, Fig. 10). That part of the wing which is nearest to the thorax, is 

 called the base; the middle third of the wing is known as the median or discal area; 

 the outer third as the external or limbal area. The anterior margin of the wing is 

 called the costal margin; the outer edge is styled the external margin; the inner 

 edge is known as the inner margin. The tip of the front wing is called the apex, 

 which may be rounded, acute, falcate (sickle-shaped), or square (see Plate B, 

 Figs. 1-4). The angle formed by the outer margin of the front wing with the 

 inner margin is commonly known as the outer angle. The corresponding angle 

 on the hind wing is known as the anal angle, and the point of the hind wing, 

 which corresponds with the tip or apex of the fore wing, is designated as the external 

 angle. The margins of wings may have different styles of outline, and are spoken 

 of as entire, crenulate, scalloped, waved, lobed, or tailed (see Plate B, Figs. 5-8). 



A knowledge of the veins which form the framework of the wings is important, 

 because authors have frequently established genera upon the basis of the wing 

 structure. It is desirable on this account to understand the nomenclature which 

 has been applied to the veins. This nomenclature is somewhat variant, different 

 writers having employed different terms to designate the same vein. In what fol- 

 lows the writer has adopted the designations which are most current, and which are 

 generally accepted by authors. The best understanding of this matter is to be 

 derived from the attentive study of the diagrams given on Plate B, Figs, 9 and 10 



