210 
ized type from which both suborders evolved, the Heteroptera 
retaining certain of the more primitive characters. 
The distinction between the two suborders generally given in 
text-books, of the “beak” arising from the front or back of the 
head, is incorrect. The “beak” arises from the same place in 
both suborders, but in one the gula is large and the head straight 
out, while in the other the gula is small or absent and the head 
turned under. 
My objection’ to considering these two suborders as distinct 
orders is that, by so doing, we divide a monophyletic group and 
make the same distinction between them as we do between them 
and Coleoptera and other orders. The characters of the teg- 
mina, upon which the two suborders are generally based, and 
upon which they are named, do not hold good, for some of the 
Homoptera are heteropterous and some of the Heteroptera are 
homopterous. If we use the venation to separate the two sub- 
orders, then we must be logical and divide the Homoptera into 
several orders." 
THE Two Groups OF THE HOMOPTERA. 
The line of evolution of the head that has divided the Homop- 
tera from the Heteroptera has continued within the Homoptera 
and divided them into two groups, the Auchenorhynchi and the 
Sternorhynchi. In the former, the labium, while being intimately 
related to the prosternum, is still in close relationship with the 
head capsule. In the latter, a portion of the head capsule, along 
with the clypeus, labium and tentorial structure, is more or less 
detached from the head capsule; the labium is in more intimate 
contact with the prosternum, and an invagination at the base 
of the labium penetrates the thorax and forms a setal chamber 
or crumena, wherein the setae lie coiled when at rest. In the 
Aphiidae and Psyllidae the relationship of these parts can be 
plainly seen, but in the Coccidae and some Aleurodidae the head 
is greatly reduced and the true relationship is lost or very 
obscure. 

1 Dr. E. Bergroth informs me that the Heteropterous family Pelori- 
diidae has no gular region, and that the labium is not bent at the base. 
This is a very interesting fact and I would like to examine one of these 
rare insects. 
