46 THE AMERICAN NATURALIST. [VoL. XXXII. 
It is obvious that one who has learned the homologies of the 
principal trachez of wings can easily determine the homologies 
of the wing-veins of the adult by the study of wings taken in 
the stage of development shown by Figs. 2 and 3. It should- 
be remembered, however, that the determining of the homolo- 
gies of these trachez necessitates the study of a large series 
of well-selected types. One is not warranted in arriving at 
conclusions in this matter from the study of a few representa- 
tives of a single order of insects. 
During the past year we have studied in the manner indi- 
cated the wings of representatives of nearly all of the more 
important groups of winged insects, and have made several 
et 
Fic, 2.— Fore wing of a nymph of Nemoura. 
hundred photo-micrographs of them. We feel, therefore, that 
we have at hand sufficient data to warrant the conclusions 
regarding the homologies of the wing-veins that we purpose 
to offer.? 
Although Figs. 2 and 3 will be discussed in detail in a sub- 
sequent chapter, we will give a few words of explanation here. 
These figures represent the wings of one side of a nearly 
mature nymph of a Nemoura, one of the genera of stone flies 
(Plecoptera). In making the preparations it was impracticable 
to remove all of the dirt adhering to the wings without danger 
of injuring them; this is often the case in preparing mounts of 
1 The most important gap in our series of observations is due to the fact that 
as yet we have been unable to procure pupz of any of the Mecoptera. We would, 
therefore, be under great i fri to any one who would send us living pup® 
of either Panorpa or Bittacu 
