No. 391.] THE WINGS OF INSECTS. 579 
are no indications that the primitive branching has been retained 
in the Orthoptera; here, when the two-branched condition ex- 
ists, it is a secondary development; it would be misleading, 
therefore, to designate these branches as Scı and Sc2, for they 
do not correspond to the branches so designated in other orders. 
In this case the branch, or branches, of the subcostal trachea 
are merely accessory branches, like the accessory branches 
developed on other principal trachez. 
Although the costal trachea has been lost, the thickening of 
the costal margin of the wing should be called the costal vein ; 
for it is still the vein that was formed about the costal trachea 
in the beginning. 
The few illustrations given here will show how easily the 
homologies of the trachez of the wings of orthopterous nymphs, 
and consequently of the veins that are formed about them, 
can be determined. But if one studies only the wings of adults, 
where many cross-veins have been developed, and where the 
basal connections of the principal veins are obscured, it is ex- 
tremely difficult to determine these homologies. It is also evi- 
dent that the wings of these insects present many characters 
which are easily available for taxonomic purposes. 
The Position of the Orthoptera in the Class Insecta as indicated 
by the Tracheation of the Wings. — The making of genealogical 
trees does not fall within the scope of the present series of 
_ papers. Our object has been to learn in what ways wings have 
been modified in order to determine the homologies of the wing- 
veins. It is obvious that this had to be done before the char- 
acters presented by the wings could be used intelligently in 
working out the phylogeny of the orders. Now that this has 
been accomplished, it would be possible to propose a provi- 
sional classification of insects based on the characters of the 
wings ; but we feel that it is much better to wait till the results 
we have attained can be correlated with similar studies of other 
organs. There is, however, one character in the tracheation 
of the wings to which it seems worth while to call attention 
now. 
In most insects the principal tracheze of the wings form two 
quite distinct groups. These we have already designated as the 
