64 THE STUDY OF INSECTS. 



and thus afford excellent distinctions for the purposes of 

 classification. The various parts of the wing have, there- 

 fore, received special names. There is considerable lack of 

 uniformity among entomologists as to the names applied to 

 these parts ; but we have adopted the set of terms defined 

 below as representing the best usage. 



An insect's wing is more or less triangular in outline ; it 

 therefore presents three margins : the costal margin, or costa 

 (Fig. 78, a, b) ; the outer margin (Fig. 78, b, c) ; and the inner 

 margin (Fig. 78, c, d). 



The angle at the base of the costal margin (Fig. 78, a) is 

 the humeral angle (hu'me-ral) ; that between the costal mar- 

 gin and the outer margin (Fig. 78, b) is the apex of the wing ; 

 and the angle between the outer margin and the inner mar- 

 gin (Fig. 78, c) is the anal angle (a'nal). 



There have been many different sets of names applied to 

 the veins of the wings. Not only have the students of each 

 order of insects had a peculiar nomenclature, but in many 

 cases different students of the same order of insects have 

 used different sets of terms. This condition of affairs was 

 incident to the beginning of the science, the period before 

 the correspondence of the veins in the different orders had 

 been worked out. But now the time has come when it 

 seems practicable to apply a uniform nomenclature to the 

 wing veins of all orders ; and the following set of terms is 

 proposed for that purpose. 



The principal veins of the wing, those that arise at or 

 near the base of the wing, are termed, beginning with the 

 one lying on the costal margin, the costa (cos'ta), the subcosta, 

 the radius (ra'di-us), the media (me'di-a), the cubitus (cubi- 

 tus), and the anal veins. The radius, media, and cubitus 

 are usually branched, and there may be several anal veins. 



In certain orders of insects two other veins arising near 

 the base ot the wing have been developed : one lying between 

 the media and the radius, the premedia ; and one lying be- 

 tween the media and the cubitus, the postmedia. 



