GENERIC CLASSIFICATION OF APHIDIDAE. 9 



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 



