Pemphigus tartareus

Pemphigus nortonii

Pemphigus monophagus

Pachypappa rosettei

Pemphigus juncti-sensoriatus n. sp.

Host, Populus deltoides. 

The Gall. A more or less globular gall located at the base of the leaf composed of leaf blade and petiole. That part consisting of leaf blade is somewhat oval, very much thickened, and more or less convex. The leaf margins can be traced along the edges of this thickened portion for some distance. The greater part of the gall is composed of a very much widened, thickened and twisted portion of the petiole. The opening is long, passing more than half way around the gall. The mouth is loosely closed and lacks the small, round orifice found in the galls of Pemphigus populi-caulis. 

Taxonomy.-This species is close to populi-caulis but differs from it in having the greater part of the gall composed of petiole instead of leaf blade as in the latter and in having many of the secondary antennal sensoria of the fundatrigenia coalescent. 

Pemphigus nortonii, n. sp.

Described from holotype and 18 paratypes from galls taken on Populus deltoides at Wheatland, Wyoming, August 2, 1924, and July 2, 1929.

Galls: The galls are similar to those of Pemphigus populi-caulis. 

Taxonomy.-This species is most closely related to Pemphigus populi-caulis, differing from it mainly in having the antennae longer in proportion to the hind tibiae and a greater number of secondary sensoria on joints III to VI of the fundatrigenia.

Pemphigus monophagus, n. sp.

Described from holotype and 16 paratypes from gall on Populus balsamiferae at 8,200 feet elevation, August 17, 1924, in Rocky Mountain National Park, Colorado.

The Gall. A more or less globular gall composed of leaf blade located at the base of the leaf with nearly circular opening on the under side closed by a thickened portion of the petiole that lays in a plane almost parallel to the blade of the leaf. The opening may be at the right or left of midrib. In a gall open on the right side of the midrib the thickened part of the petiole bends sharply to the left; then from a point near where the petiole passes into the midrib there is an abrupt bend to the right. Thus the thickened parts form a letter S. When the gall opens on the left of the midrib the S is backwards. There is usually a shallow furrow passing over the gall near its middle suggesting a double gall. 

Taxonomy.-This species is placed in the genus Pemphigus because of the great structural similarity. In the number of generations and the sequence of forms it differs from the typical Pemphigus. There are but four generations, three of which, the fundatrix, fundatrigenia and sexupara, all develop in the same gall. Observations lead to the conclusion that all of the young of the fundatrix develop into apterous viviparae, these in turn producing the sexuparae. Further study may place this species in a new genus since it resembles Pemphigus much as Cornaphis does Asiphum. What appears to be this species was taken by J. J. Davis on August 5, 1913. near Flat Head Lake in Montana. Material received from R. Glendenning collected at Lillooet and Merrit, B. C., on Populus trichocarpa also appears to be this species.

Asiphum rosettei n. sp.

Described from holotype and 9 paratypes taken on Populus tremuloides, 7,000 feet elevation in canyon of South St. Vrain Creek, Boulder Co., Colo., July, 1915. 

The fundatrix appears to feed on the petioles of the newly opening leaves, causing them to become curved more or less backward. This forms a rosette of leaves by stunting the growth of the internodes of the young branch. 

The fundatrigenia feed on the unexposed surfaces of the leaves forming the rosette. After the migration the young wood elongates somewhat so that the rosette gradually disappears except for a slight deformity of the branch and leaves. 

Taxonomy: This species is very near Asiphum tremulae De Geer as described by Tullgren, but differs from it in having wax pores on lobes of metathorax and fewer secondary sensoria on III and IV of the antennae of the fundatrigenia. 

Four new pemphigids from Colorado (Aphidae: Homoptera)