GENERIC CLASSIFICATION OF APHIDIDAE. 47 



cylindrical but extremely short, not as long as wide. Cauda very short and rounded, 

 not Aphis-like; anal plate rounded. 



Type (monotypical), Cryptosiphum artemisiae Buck! 



Genus HYSTERONEURA Davis. 



1919. Heteroneura Davis, Can. Ent., v. 51, p. 228. 

 1919. Hysteroneura Davis, Can. Ent., v. 51, p. 263. 



Characters. — Head without prominent antennal tubercles. Antennae of six seg- 

 ments armed with subcircular sensoria. Fore wings with the media twice branched. 

 Hind wings with the cubitus absent. Cornicles somewhat tapering or subcylindric, 

 Cauda Aphis-like; anal plate rounded. 



Type (monotypical), Aphis setariae Thos. 



Genus HYADAPHIS Kirk. 



Plate VI, AA, BB. 



1904. Hyadaphis Kirkaldy, The Entomologist, v. 37, p. 279. 



1863. Siphocoryne Passerini, Aphididfe Italic®, p. 8 (not Siphocoryne , 1860). 



As indicated under the discussion of Siphocoryne, Passerini set 

 xylostei as type of his genus in 1863. NympJiaeae had, however, 

 been set in I860, so Kirkaldy gave Hyadaphis to Passerini's 1863 

 conception, of which genus xylostei becomes the type. Xylostei has no 

 caudal horn and is quite similar in general appearance to a Rhopalo- 

 siphum. We may separate the two genera, however, on the cauda, 

 which in xylostei, particularly in the apterous form, is very large, fully 

 as long as the cornicles, and broad, quite unlike that of nymphaeae- 

 Several other species which have generally been considered in the 

 same genus with xylostei possess a distinct caudal projection on the 

 abdomen. One of these has been made the type of Cavariella so that 

 such species will be removed from our conception of Hyadaphis. 



Characters. — Head without prominent antennal tubercles; antennae of six segments 

 which are rather abundantly armed with tubereulate sensoria. Wing venation normal. 

 Cornicles somewhat swollen but not prominently so. Cauda, particularly in the 

 apterous form, large, as long as the cornicles, and broad. Males usually winged; 

 oviparous females apterous; summer forms usually feeding on the Umbelliferae. 



Type (fixed by Kirkaldy, 1904), Aphis xylostei Schrk. 



Genus HYALOPTERUS Koch. 



Plate VI, ER-WW. 



1854. Hyalopterus Koch, Die Pflanz. Aphiden, p. 16. 

 1917. Hayhurstia Del Guercio, B.edia, v. 12, p. 208. 



Aphis pruni Fab. was set as the type of this genus in 1860 by 

 Passerini. In 1917 Del Guercio erected the genus Hayhurstia. 

 There is little difference between the two as will be seen by examining 

 the drawings given herewith. The cauda in Hayhurstia is slightly 

 narrower than that in Hyalopterus. It is the writer's opinion that 

 the two represent only one genus. 



Two other genera may be mentioned here. They are Brachycolus 

 Buckt. and Pergandeidia Schout. Specimens of the type species of 

 Brachycolus show that this genus is quite similar to Hyalopterus, 

 but it differs in the cornicles. In Brachycolus the cornicles are very 

 small, almost mere rounded swellings in the apterous form, whereas 



