THE WINGS OF INSECTS. 
J. H. COMSTOCK anp J. G. NEEDHAM. 
CHAPTER IV (continued). 
The Specialization of Wings by Addition. 
IV. THE VENATION OF THE WINGS OF EPHEMERIDA. 
Tue determination of the homologies of the wing-veins of 
May-flies appears, at first sight, to be an extremely difficult 
problem; for the wings of these insects are very different 
from those of any other order. But, as soon as one under- 
stands the ways in which the wings have been modified, it is 
easy to identify the principal veins. 
In this order a marked cephalization of the flight function 
has taken place, which has resulted in a great reduction of the 
hind wings of all living forms. In some cases (Cenis et al.) 
this has gone so far that the hind wings are wanting. 
In a few genera (Oligoneura et al.) both pairs of wings are 
furnished with but few veins. It requires only a little study, 
however, to convince one that these genera with few-veined 
wings are degraded and not generalized. It is in the fore 
wings of those forms in which many wing-veins have been 
retained that the homologies of the wing-veins are most easily 
determined. 
Fig. 69 represents the venation of a species which will serve 
well as a type of the recent May-flies; and the lettering of 
the figure indicates our conclusions regarding the homologies 
of the veins. But the most characteristic feature of the wings 
is not shown in the figure. If the reader will examine one of 
the larger May-flies, he will see that the corrugation of the 
wings is much more perfect than in any other order of insects, 
extending to all parts of the wings. 
This fan-like structure of the ephemerid wings has been 
referred to by many writers. But it is worth while to point 
: 117 a 
