GENERIC CLASSIFICATION OF APHIDIDAE. 35 



Characters. — Cornicles present, truncate in form, often sculptured. Antennae of 

 six segments (with the exception of the dimorph) armed with oval sensoria and promi- 

 nent hairs. Fore wings with the media twice branched; hind wings with both 

 media and cubitus present. Cauda and anal plate rounded. 



Forms living upon the foliage of trees. Sexes not strikingly different from the 

 other forms, possessing beaks and feeding. Males winged, oviparous females with 

 the ovaries normally developed, thus laying several eggs. Small lamellate or hairy 

 dimorphic forms produced in summer. 



Type (monotypical), Periphyllus testudo A'an der Hoeven (=testudinatus Thorn- 

 ton). 



Genus NEOTHOMASIA, n. n. 

 Plate IV, Y, Z. 

 1910. Thomasia Wilson, Can. Ent., v. 42, p. 336. 



Wilson erected the genus Thomasia with populicola Thos. as 

 type, and his description appeared in December, 1910. The same 

 name had, however, been used for a genus of Diptera, the description 

 of which appeared in September, 1910. A new name, Neothomasia, 

 therefore, is necessary for Wilson's genus. 



Characters. — Cornicles present; antennae of six segments aimed with subcircular 

 sensoria and prominent hairs. Fore wings with the media twice branched, hind wings 

 with both media and cubitus present. Cauda and anal plate both rounded. 



Forms living in colonies upon the leaves or bark of trees; no dimorphic forms pro- 

 duced; sexual forms not markedly different from the viviparous ones. Oviparous 

 females laying several eggs. 



Type (monotypical), Chaitophorus populicola Thos. 



Genus SIPHA Pass. 



1860. Sipha Passerinl, Gli Afidi, p. 29. 



This genus and Atheroides are distinct from the other genera in 

 the subtribe by possessing five-segmented antennae instead of six- 

 segmented ones. The genus has not been much confused excepting 

 by Thomas's placing of rubifolii. For a time some workers in this 

 country were led to conceive of the genus as indicated by that spe- 

 cies which in reality belongs in the Aphidini. 



Characters. — Cornicles present, truncate, short, almost mere, rings. Antennae of 

 five segments armed with large circular sensoria. Body form flat, entire insect cov- 

 ered with rather long stout hairs. Fore wings with the media twice branched, hind 

 wings with both media and cubitus present. Cauda knobbed, anal plate rounded. 

 Forms living upon the leaves of grasses usually in moist localities, sometimes even 

 submerged, the water appearing to affect them little. 



Type (fixed by Passerini, 1860), Aphis glyceriae Kalt. 



Subtribe PTERO COMMENT A. 



The subtribe Pterocommina is composed of bark-feeding insects, 

 some of which retain quite primitive characters. It is the writer's 

 opinion, however, that they are, as a group, more specialized than 

 the Chaitophorina, but closely related. This is indicated by the 

 development of the cornicles met with in the species. Like the 



