No. 374] THE WINGS OF INSECTS. 85 
There can be no doubt that the veins of the fore wings and 
of the hind wings are homodynamous. Any one that studies the 
subject much is impressed by this fact. A single diagram will 
be sufficient, therefore, to represent the venation of both pairs 
of wings of this type. Fig. 4 is such a diagram. 
te Se, Se, 
Fic. 4. — Hypothetical tracheation of a wing of the primitive nymph. 
As the wing of a nymph is much more instructive than a 
wing of an adult for the purpose of determining homologies, we 
represent this ideal wing in that stage of development in which 
the forming veins appear as light-colored bands and the trachez 
as dark lines. This stage in the wings of an actual nymph 
is well shown by the half-tone reproductions of photographs of 
the wings of a nymph of Nemoura, given in Chapter I (Figs. 
2, 3).!_ In our hypothetical type we have represented only the 
trachez, which precede the forming veins. 
By representing the wing of a nymph we are able to repre- 
sent the basal connections of the trachez that precede the 
veins, and thus show which are principal veins and which are 
branches of them. This point has received very careful attention, 
a large number of nymphs and pup, representing nearly all of 
the orders of insects, having been examined especially for this 
purpose. Fortunately, this evidence confirms the conclusions 
reached by various writers who have studied only the wing- 
veins of the adult, and merely serves to remove any doubt there 
might have been regarding these conclusions. 
Another point which can be brought out in this way is the 
1 American Naturalist, January, 1898, vol. xxxii, pp. 46, 47- 
