-78- 



of vein III in Rhyphus, is really the fourth and fifth coalesced, and is 

 numbered vein III4 + 5. The tracing out of the homologies of the 

 branches of veins, or veinlets as they are sometimes termed, is often 

 very difficult, but it is of the greatest importance in determining the 

 relationships of different genera or of families. 



Names.of wing- veins. — There have been many differ- 

 ent sets of names applied to the veins of wings. Not only 

 have the students of each order of insects had a peculiar 

 nomenclature, but in many cases different writers on the 

 same order have used different sets of terms. This condi- 

 tion of affairs was incident to the beginning of the science, 

 the period before the correspondence of the veins in the dif- 

 ferent orders had been worked out. But now the time has 

 come when it seems practicable to apply a uniform nomen- 

 clature to the 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 simple in flies ; this is the 

 stibcosta (Fig. 2, II). 



Radius. — Immediately caudad of the subcosta there is a 

 vein which in generalized insects is always branched ; this 

 is the radius. In Rhyphus, radius is three-branched (Fig. 2, 

 IIIi, III2+3, and III4+5). 



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 media is three- 

 branched (Fig. 2, Vi, V2, and V3, ). 



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

 is the cubitus. This vein is two-branched in Rhyphus (Fig. 

 2, VII 1, and VH 2) ). 



Anal furrow or first anal vein. — Immediately caudad of 

 the cubitus and closely parallel with it, there is in most flies 

 a prominent furrow in the wing ; this is the anal furrow or 



