416 THE AMERICAN NATURALIST. [Vou. XXXII. 
cubitus coalesce with the first anal vein; and this coalescence 
has proceeded so far that both branches cross the anal furrow 
and end in the anal vein remote from the margin of the wing. 
It should be noted that vein Czz is rarely preserved in this 
order, even in the more generalized forms. We have found it 
=. SB Riss 
+Cu, M 
zst A Cu, M, 
Fic. 40. — Wing of Pantarbes. 
only in the genus Pamphilius. In Macroxyela! the position of 
the fork of the cubitus is indicated by a bend in this vein. 
If the branches of the media be now examined, it will be seen 
that vein Mı (Fig. 38) extends longitudinally near the center 
of the distal part of the wing, its primitive course being modi- 
fied slightly if at all. Vein M2 follows a course similar to the 
course of this vein in the dipterous genus Pantarbes (Fig. 40); 
so also does the medial cross-vein (Fig. 38, m). A comparison 
of the position of cells Mı, Zst Mz, and 2d Mz in these two 
genera (Figs. 39 and 40) is very instructive. 
Returning to Pamphilius (Fig. 38), we see that vein M3 
coalesces with the first anal vein, crossing the anal furrow near 
M+ Cu, 
Fic. 41, — Wing of Rhamphomyia. 
the margin of the wing. It is evident that the forces that are 
causing the branches of the cubitus to migrate along the first 
anal vein and towards the base of the wing are exerting a similar 
influence on this vein. It is also evident that vein M4 and Cu 
1 Comstock, /oc. cit, Fig. 735- 
