76 BULLETIN 826, U. S. DEPAKTMBNT OF AGRICULTURE. 
in the genus by Lichtenstein (1885) and this species has been indicated 
as type of the genus by Kirkaldy (1905). Tremulue De Geer is a well- 
known species but the writer has been unable to obtain ligustrineUum 
and, in fact, has been unable to learn anything definite in regard to 
the species. The following conception of the genus, therefore, is 
based upon tremulae De Geer in view of the fact that ligustrindlum 
appears to be unknown, and since ApMs populi Fab. was indicated 
by Gerstaecker in 1859. 
Characters. — Cornicles absent; wax plates present in the alate forms; stem mother 
with five-segmented antennae. Ablate form with six-segmented antennae which are 
armed with rather narrow transverse sensoria. Fore wings with the media once forked, 
hind wings with both media and cubitus present. Forms living in the somewhat 
crumpled leaves of their host. 
Type (fixed by Gerstaecker. 1859), Aphis populi Fab. 
Genus NEOPROCIPRTLUS Patch. 
Plate XIII, A-F. 
1912. XeoprocipTiilus Patch, Bui. Me. Agr. Expt. Sta., no. 202, p. 174. 
The genus Xeoprociphilus Patch is very close indeed to Prociphilus, 
the characters which separate it being the somewhat more oval or 
rounded sensoria and the fact that the sensoria are not ciliate. How- 
ever, in some of the species of ProcipTtilus, particularly in the fall 
forms, somewhat oval sensoria are met with. It is retained doubt- 
fully. ' 
Characters. — Stem mother with five-segmented antennae. Cornicles absent, large 
wax plates similar to those of Prociphilus present. Alate form with six-segmented 
antenna? which are armed with oval or subcircular nonciliate sensoria. Fore wings 
with the media simple, hind wings with both media and cubitus present. Sexes small, 
apterous, and beakless. Oviparous female developing only one egg. 
Forms living free upon their host, the stem mother and following generations in 
company. 
Type (monotypical , Pemphigus attenuatus O. S. 
Genus PROCIPHILUS Koch. 
Plate XIII, G-N. 
1857. Prociphilus Xoch, Die Pflanzenlause, p. 279. 
1857. Stagonia Koch, Die Pflanzenlause, p. 284. 
1S75. Holzneria Lichtenstein, Bui. Soc. Ent. Pr. (5) v. 5, p. lxxyi. 
1917. Nishiyana ilatsumura, Synopsis of the Pemphigidae of Japan, p. 90. 
In 1857 Koch erected his genus Prociphilus with three species: 
bumeliae Schrank, erraticus Koch, and gna phalli Kalt. Later in 
the work (p. 2S4) he used xylostei De Geer as the type of the genus 
Stagonia. This species, xylostei } is in all respects similar to bumeliae 
and therefore Stagonia becomes a synonym of Prociphilus. In 37 : 
Lichtenstein erected the genus Holzneria with poschingeri Holzner 
as type. Poscliingeri has been considered by many authors as the 
alternate form of bumeliae. In such case Holzneria must necessarily 
