582 THE AMERICAN NATURALIST. 
reached the cubital trachea and usually coalesces to a greater 
or less extent with it. An extreme case of this migration is 
illustrated by Xiphidium (Fig. 81). And here there appears 
to be a reduction of the transverse basal trachea. It has served 
its purpose, and, like an abandoned road, is disappearing from 
view. It will not be surprising if Locustid nymphs are found 
Fic, 81.— Hind wing of a nymph of Xiphidium. 
in which this connection between the two groups is lost, but 
the presence of the medial trachea in the cubito-anal group will 
show it to have existed. 
In the Acridid, represented by Fig. 75, the radial trachea is 
following the medial in its migration; this is indicated well by 
the curve near the base of the radial trachea in the hind wing. 
VI. CONCLUSION OF CHAPTER IV. 
In this and the preceding chapter we have furnished data 
for determining the homologies of the veins in each of the 
orders of winged insects except the Euplexoptera, Mecaptera, 
Isoptera, and the Physopoda. Of the first two we have been 
unable to procure immature stages ; it is not probable, however, 
that they will present serious difficulties when they are studied. 
Of the Isoptera we have examined nymphs of two genera, Termes 
and Termopsis, but we wish to examine other forms before pub- 
lishing conclusions. In all of the Physopoda that we have seen, 
the tracheation of the wings is so reduced that we have been unable 
to determine definitely the homologies of the few remaining tra- 
chez. We therefore close at this pointour discussion of this phase 
of the subject and pass to a study of the beginning of wings. 
