21 
wu 
have been studied extensively so far can be reduced to a more 
or less uniform type for the family, in the Fulgoridae no such 
typical form can be given.” The same might be said of any 
group if some fourteen families were thrown into one, and is, 
in itself, a sufficient reason to indicate that we are dealing with 
a number of families. 
The classification of the Homoptera is founded upon other 
characters than wing venation, but a type of venation can be 
recognized as pertaining to most of the families. If we were to 
make a classification upon venation alone, without any knowl- 
edge of the rest of the insect, as we are forced to do with fossil 
Homoptera, it would be very different from our present one. 
The Sternorhynchi would have no connection with the Aucheno- 
rhynchi; the Psyllidae would be placed next the Psocidae 1f not 
with them; some of the Flatidae would be placed among the 
Cicadoidea because the claval veins do not form a Y; such 
forms as Tessitus insignis Walker would also be placed with 
them, perhaps to form a distinct family; the Tropiduchidae, as 
we know it now, would form several families not closely related ; 
the Derbidae would be considered as several families and some 
placed with the Cixiidae; the Delphacidae would be treated as 
Cixiidae, and most of the other families would be changed con- 
siderably. Pterologists might maintain that such a classification 
would represent the natural order of things better than the 
present one made by entomologists. It demonstrates the great 
care necessary when basing conclusions upon a few fossil wings, 
for similar deceptions as the Psyllidae and Psocidae may have 
existed in the past, and we have no means of recognizing their 
existence. 
But as fossils are the only direct evidence of the time sequence 
of evolution we must take every advantage of them, and for this 
reason a closer study of the venation in each family must be 
made. Except in three families of the Fulgoroidea, I have not 
sufficient knowledge to make a close comparative study of the 
venation, but there are several points which require discussing 
before such a task can be undertaken with any satisfaction. 
The two chief points are the status of the costa and the anal 
veins. Unfortunately, Metcalf‘ only traced the tracheae of the 
1 Ann. Ent. Soc. Amer., VI, 3 (1913), pp. 341-352. 
