390 THE WINGS OF INSECTS 



Names of the longitudinal wing-veins. — There have been many different 

 sets of names appHed to the veins of wings. Not only have the students of 

 each order of insects had a peculiar terminology, but in many cases 

 different writers on the same order 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 is practicable to apply a 

 uniform terminology to the longitudinal wing-veins of all orders ; and the 

 following set of terms has been proposed for that purpose : 



Costa. — The vein extending along the cephalic or costal margin of the 

 wing is the costa. 



Subcosta. — Immediately caudad of the costa and extending parallel with 

 it, is a vein, which is usually simple in flies; this is the subcosta (Fig. 

 410, Sc). 



Radius. — Immediately caudad of the subcosta there is a vein which in 

 generalized insects is always branched; this is the radius. In Rhyphus, the 

 radius is three-branched (Fig. 410, R\, R0+3, and Ri+h-) 



The radial sector. — When the radius preserves its primitive mode of 

 branching, it separates at its first fork into two unequal parts; the first of 

 these is vein Ri ; the other gives rise to the remaining four branches of the 

 radius (Fig. 408). This second part of the radius, including its branches, 

 is termed the radial sector or vein R^. 



Media. — Traversing the middle of the wing there is a longitudinal vein 

 which is always branched in generalized insects; this is the media. In 

 Rhyphus the media is only three-branched (Fig. 410, Mi, Mi, and M3) and a 

 part of its stem is atrophied. 



Cubitus. — The third and last of the branched veins in flies is the cubitus. 

 This vein is two branched in Rhyphus (Fig. 410, Cui and Cuo^. 



Anal veins. — Caudad of the cubitus there is in Rhyphus a single well- 

 developed vein ; this is termed an anal vein . As in more generalized insects 

 there are three anal veins, and as this is the second of the series, it is desig- 

 nated the second anal vein (Fig. 410, 2d A). Vestiges of the first and third 

 anal veins persist in Rhyphus; these are indicated in the figure by dotted 

 lines. 



Designation of the longitudinal wing-veins by numbers. — Several writers have 

 designated the longitudinal wing-veins by numbers. In Comstock's Manual for the 

 Study 0} Insects both the names given above and numbers are used. The following 

 table indicates the correspondence of the names and numbers. 



Costa = vein I. Cubitus = vein VII. 



Subcosta = vein II. ist anal vein = vein VIII. 



Radius = vein III. 2d anal vein = vein IX. 



Media = vein V. 3d anal vein = vein X. 



It will be observed that in the above table the numbers IV and VI are omitted. 

 At the time the Manual for the Study of Insects was published, it was believed that 



