564 THE AMERICAN NATURALIST. [VOL XXXII. 
these figures will serve to show our conclusions regarding the 
homologies of the tracheæ. 
In the species represented by Fig. 50, the radial trachea is 
the most prominent one in both elytra and hind wings. On the 
other hand, in the species represented by Fig. 51, the radial 
trachea is reduced in both elytra and hind wings to a mere rudi- 
ment. If the elytra and hind wings were not homodynamous 
organs, it is not probable that the modifications of the two 
would be so closely correlated. We conclude, therefore, that 
the elytra are modified wings. 
In comparing the tracheation of the elytra with that of the 
hind wings, the most striking difference observed is the greater 
Fic. 52. — Hind wing of a pupa of a beetle. 
reduction of the anal area of the former. This is doubtless due 
to the fact that the meeting of the elytra when at rest in a 
straight line along the middle of the back does not admit of an 
expanded anal area. 
The extent of the correspondence between the venation and 
the tracheation of the hind wing of a full-grown pupa is shown 
by Fig. 52. The principal tracheze are within the veins, but 
the branches of. these trachez extend irregularly through 
the wing. In the region where the wing is to be folded the 
secondary vein-like thickenings are only partially supplied with 
trachez. 
Although the veins of elytra of adult beetles appear in many 
cases as well-marked ridges, when elytra of pupz are prepared, 
as we prepare wings for this purpose, and examined by trans- 
mitted light, we do not find any difference in color between the 
forming veins and the spaces between them. 
