86 BULLETIN 826, U. S. DEPARTMENT OF AGRICULTURE. 



Drepanosiphina, this development varies to a great extent in the 

 different species. 



Only two genera occur in the tribe. They may be separated as 



follows : 



Key to the Genera of the Pterocommixa. 



Cornicles cylindrical PterocommOc 



Cornicles somewhat swollen Melanoxantheriunu 



Genus PTEROCOMMA Buckton. 



Plate IV, PP. 



1S57. Cladobius Koch, Die Pfianzenlause Aphiden, p. 251. 



I860. ApTiioidcs Passerinl, Gli Afidi, p. 28. 



1879. Pterocomma Buckton, Monog. Br. Aphides, v. 2, p. 142. 



1905. Arislaphis Kirkaldy, Can. Ent., v. 37, p. 416. 



In 1857 Koch erected the genus Cladobius with populeus Kalt. as 

 type. This name, however, had been used previously. So Passerini 

 in 1860 employed the name Aphioides. This name had also been 

 used. Kirkaldy, therefore, gave the new name Aristaphis in 1905. 

 In 1879, however, Buckton described the genus Pterocomma with a 

 very similar species as type. 



Characters. — Cornicles present, rather short and cylindrical. Antennae of six 

 segments armed with prominent hairs and sub circular sensoria. Fore wings with the 

 media twice branched; hind wings with both media and cubitus present. Cauda 

 and anal plate rounded. 



Type (monotypical), Pterocomma pilosa Buckt. 



Genus MELANOXANTHERIUM Schouteden. 



Plate IV, NN, 00. 



1879. Mclanoxanthus Buckton, Monog. Br. Aphides, v. 2, p. 21. 



1901. Melanoxantherium Schouteden, Ann. Ent. Soc. Belg., v. 45, p. 113. 



In 1879 Buckton described the genus Melanoxanthus with salicis 

 L. as type, but, as this name was preoccupied, Schouteden suggested 

 the name Melanoxantherium. 



Characters. — Cornicles present, variable in size, but usually more or less swollen. 

 Antennae of six segments armed thickly with hairs and possessing oval or sub circular 

 sensoria. Fore wings with the media twice branched, hind wing3 with both media 

 and cubitus present. Cauda and anal plate rounded. 



Forms living in colonies usually on the bark of trees, males usually winged. Ovi- 

 parous females laying several eggs. 



Type (monotypical), Aphis salicis L. 1 



Subtribe FULLAWAYINA. 



The subtribe Fullawayina is related somewhat closely to the 

 Chaitophorina from which it is a specialization, as is evidenced by the 

 reduction and total lack of the cornicles. It is very suggestive of 

 Monaphis, but evidently arose from quite a different line of develop- 

 ment, following Chaitophorns rather than the Callipterus group. 

 Only one genus is represented. 



1 The writer is forced to change his view that Pterocomma pilosa is closely related to populifoliae 

 Fitch. ' This was based on Pergande's published statement of his examination of the type. Later notes 

 on the type indicated that it resembles populea. 



