GENERIC CLASSIFICATION OF APHIDIDAE. 17 



Genus UNILACHNUS Wilson. 



Plate II, E-G. 

 1919. Unilachnus "Wilson, -Ent. Xews, v. 30, p. 5. 



The genus Uriilaclinus Wilson appears to be a connecting link 

 between this subtribe and the Eulachnina. In some respects the 

 genus is very suggestive of that subtribe. The form is elongate and 

 the cornicles are reduced. They are armed, however, with hairs and 

 are not so reduced as in the Eulachnina. The ocular tubercles here 

 are very rudimentary, almost absent, and in this regard, too, the genus 

 suggests the Eulachnina, but it seems to belong in this subtribe. 



Characters. — Form elongate; cornicles somewhat reduced; ocular tubercles small; 

 media of fore wings simple. Antennse of six segments moderately armed. 



Type, Lachnus parvus Wilson. 



Subtribe PTEROCHLORINA. 



The genera belonging in the subtribe Pterochlorina are in some ways 

 more primitive than those of the Lachnina, but in other respects some 

 of them are more specialized. The radial sector of the fore wings is still 

 curved and in some genera cprite elongate. This is much nearer the 

 early type of wing than is the wing of the Lachnina where the radial 

 sector is short and has migrated almost to the tip of the wing. Of 

 course, the distinct curving of this vein found in some of the genera 

 is an advance on the slightly curved elongate vein usually met with 

 in the fossils, but to our mind the location and character of this vein 

 are much more primitive than in the Lachnina. The stigmal area and 

 the sexual forms appear considerably more primitive than in the 

 Anoecina, the specialization of which has been in a different direction 

 from that of the Lachnina. The male of Stomaphis is, however, an 

 exception. 



Characters. — Head often divided; antennse of six segments, armed with hairs and 

 sub circular sensor ia. Fore wings with radial sector somewhat curved and not close 

 to the tip of the wing. Cornicles on broad hairy cones. Males usually winged. 



Key to the Genera of the Pterochlorina. 



1. Stigma extending along costal margin almost to the tip of the wing..Longistigma. 

 Stigma not so extending 2. 



2. Beak extremely long, very much longer than body; antennse covered 



with very fine, short hairs Stomaphis. 



Beak normal in length; antennse with rather stout hairs, often quite 



long Pterochlorus. 



Genus LONGISTIGMA Wilson. 

 Plate II, H-L. 

 1909. Longistigraa Wilson, Can. Ent., v. 41, p. 385. 

 1909. Davisia Del Guorcio, Redia, v. 5, p. 185. 



The genus Longistigma Wilson can be distinguished at once by the 

 shape of the stigma which is drawn out at the tip to an acute point 

 which extends almost to the tip of the wing. The type species is 

 141613°— 20— Bull. 826 2 



