GENERIC CLASSIFICATION OF APHIDIDAE. \) 
reaches maturity. The most primitive tribe on this line is the 
Eriosomatini. The forms of this tribe are not as a rule distinct gall 
formers. They possess rather prominent cornicles and have devel- 
oped special wax glands. They live as a rule upon deciduous trees, 
the summer forms of many species alternating upon the roots of 
plants. 
More specialized than the Eriosomatini are the Pemphigini, which, 
however, are very similar to the former in many respects. These are 
distinct and true gall formers on deciduous trees. For part of the 
year they are usually altogether closed within the gall. Wax secre- 
tion is common and the cornicles are present, but reduced to mere 
rings. 
The Melaphini are closely related to the Pemphigini and are gall 
formers like them. These forms, however, have lost entirely the 
cornicles which are usually still retained in the Pemphigini. 
A somewhat different specialization is met with in the Prociphilini. 
Here wax secretion has developed at the expense of the cornicles so 
that these organs are absent, at least in nearly all the forms of the 
species. Large wax plates have taken their places. The species are 
not true gall formers, but live upon foliage which they cause to roll or 
crumple into a pseudogall. Development along this line is also pres- 
ent in the next tribe, the Fordini. 
Here the cornicles are also absent, being replaced by large wax 
glands, but the species are nearly all root feeders and are usually 
associated with ants, often living with them in their nests. This tribe 
may be considered the most specialized of all the Eriosomatinae. 
The same specialization in the sexual forms has not occured in 
the Hormaphidinae. They are small and apterous, it is true, but 
they possess beaks, they feed, and the oviparous female lays more than 
one egg. In one regard, however, these insects are more specialized. 
Many of them have developed a pecular aleyrodiform stage, which is 
quite different from anything occuring elsewhere in the family. Along 
with this development peculiar wax glands have made their appear- 
ance so that some of these forms look very much like aleyrodids 
and are indeed often mistaken for them. < 
The most primitive tribe here is the Oregmini, which, although it 
possesses many of the other characters met with in these forms, lacks 
the aleyrodiform stage. These insects possess quite distinct cornicles. 
Closely related to the Oregmini is the Cerataphidini. These insects 
likewise possess cornicles and in several ways suggest the Oregmini, 
but they have developed a distinct aleyrodiform stage and in this 
regard are much more advanced than the members of that tribe. 
Lastly, and perhaps most specialized of all, are the Hormaphidini. 
These insects are curious gall formers, not only on their primary host, 
but often on their secondary one as well. They lack cornicles and 
