68 BULLETIN B26, U. S, DEPARTMENT OF AGRICULTURE. 
Genus TETRAJSTEURA Haitig. 
Plate X.. H-M. 
184L. Trtraneura Hartig, Germar's Zeitschriit fur die Entomologie, v. 3, p. 366. 
In 1841 Hartig erected the genus Tetraneura under which he gave 
Tetraneura ulmi Lin. ? questioned thus and described. He also 
listed T. rugicornis Hartig. One of these species was questioned 
and the other merely listed. Ulmi L.. however, was questioned only 
in the sense of the determination, and a good description was given 
so that it is known what insect Hartig had. 
In 1843 Kaltenbach gave a description of the genus Tetraneura 
crediting it to Hartig and described thereunder one species, Aphis ulmi 
De Geer. Aphis ulmi De Geer (1773) is the same species as Aphis 
ulmi GeofTroy (1764) but this name can not be used, since Linnaeus 
used Aphis ulmi for a different insect. This is the same insect de- 
scribed by Hartig as T. ulmi L. ? and it is evident that it requires a 
new name, to which ulmifoliae is given. 
_ traders. — Cornicles very slightly elevated rings, not at all prominent. Stem 
mother with four-segmented antennae; apterous form "Frith five-segmented antennae. 
Wax glands present. Alate form with six-segmented antennas which are armed with 
narrow annular sensoria almost completely encircling the segment. Fore wings with 
the media simple; hin d wings with only the media present. 
Forms living in galls and migrating in spring to other plants. Sexes small, apterous 
and beafcless. Oviparous female developing only one egg. 
Type. Tetraneura ulmifoliae Baker {Aph L. of Karrig'i. 
Tribe PEMPHIGINI. 
The tribe Pemphigini is composed of forms which are highly spe- 
cialized and most of which have developed the habit of true gall 
formation. The secretion of wax also occurs but wax secreting plates 
are not developed to the extent met with in some of the other tribes 
of the subfamily. Alternation of hosts is found to occur, migrants 
leaving the galls in early spring or summer and returning in autumn. 
In some species. however, the insects do not leave the galls until the 
mothers of the sexual forms are produced. Distinct cornicles are 
present and by this character forms in some of the other tribes which 
are suggestive of the Pemphigini may be distinguished. The typical 
group is Populus and the galls are normally spring galls. 
Characters. — Forms usually inhabiting true galls and often migrating to other plants 
during the summer. Antennae of six segments in the ala.te form and in nearly all 
genera armed with linear, oval, or somewhat irregularly shaped sensoria. Small 
secreting areas present. Sexual forms small, apterous, and beakless, parous 
le developing only one egg. 
Six genera may be included in the tribe and these genera may be 
ated by the following key: 
