No. 378.] THE WINGS OF INSECTS. 419 
vein Mı. Inthe Hymenoptera a cross-vein has been developed 
between veins RX; and R, But this is not a peculiarity of this 
order ; a similar cross-vein exists in many insects, and has been 
represented in our figures of the wings of a nymph of Nemoura.! 
From the foregoing account it will be seen that even in the 
most generalized of living Hymenoptera there exists a highly 
Fic. 44.— The typical radius. 
modified wing venation. The indication of the details of the 
further modifications exhibited by the more specialized members 
of this order has already been done by one of us in another 
place. We will, therefore, merely refer to a single illustration. 
When the fore wing of a honey-bee (Fig. 43) is examined it 
is found that, although this insect exhibits a wonderfully high 
development of instinctive powers, it retains a comparatively 
generalized wing venation. This wing, however, is much more 
modified than the fore wing of Pamphilius; and hence a com- 
parison of the two is instructive. 
In the honey-bee the subcosta is lost; so, too, is the second 
branch of the radius. Veins Ry and R; retain a more general- 
R, R, R, 
Fic. 45. — The radius in Hymenoptera. 
ized condition than do these veins in the sawflies. The coales- 
cence of the radius and the media extends farther than in 
Pamphilius, the’ base of the free portion of the media being 
carried farther from the base of the wing than the medio- 
cubital cross-vein (m-cu). This results in the base of the free 
1 American Naturalist, vol. xxxii, January, 1898, pp. 46, 47. 
