Pemphigus populicaulis

Pemphigus obesinymphae

Pemphigus populivenae

Pemphigus tartareus

Pemphigus populicaulis

This plant louse has been previously recorded from Illinois by Walsh (1862), LeBaron (1873), Thomas (1879). and Davis (1910d). It causes a gall at the base of the leaves of poplar somewhat similar to P. populi-transversus except that opening is a semi-circular curved slit. Under a discussion of P. brevicornis Hart we have already advanced our supposition that populicaulis is the aerial and gall-making form of the root-feeding plant louse described as brevicornis Hart. and the nomenclatorial changes that must result if this theory is substantiated. Data associated with our specimens collected in galls on species of Populus are as follows: Champaign (July 16). 18S5; Albion (May 26). Cave-in-Rock (May 30). Oakwood (July IS). Shawueetown (May 27). I'r-bana (July 10). 192S; Eldorado (June 19). Elizabethtowu (June 20), Kansas (June 17), Oakwood (June 1), Rock Island (July 7), Starved Rock State Park (July 5). 1929: Seymour (June 20), 1930. 

PEMPHIGUS POPULI-TRANSVERSUS Riley [photos show the morphotype now known as P obesinymphae]

The details of the life history of this species are very well known because of the studies of Jones and Gillette (1918), who have shown that it alternates between poplars and the roots of various cruciferous plants. The winged migrants (fundatrigeniae) leave the galls (Fig. 48) on poplars in spring or summer and fly to cruciferous plants, where the sexuparae are eventually produced. The latter return to the trunks and branches of poplars in spring and produce the sexual forms which produce eggs from which the stem mothers hatch. The stem mothers start tile galls, each of which produces a large number of winged females or migrants. 

We have been unable to separate the cotypic specimens of P. rubi Thomas (1879), which are sexuparae, from sexuparae of P. populi-transversus Riley. The similarity in their antennae, which are quite different from the antennae of other sexuparae taken in Illinois, seems to us quite indicative that they are the same species. 

Data associated with our Illinois material on Populus are as follows: Danville (Sept. 18), Elizabethtown (October 12), Golconda (October 13), Havana (.June 21), Mahomet (October 2), Mt. Carmel (May 26). Pekin ( July 22), 1928; Parmer City (September 22), Herod (Sept. 27), Oakwood (October 13), Starved Rock State Park (July 5), 1929; Fairmount (September 28), Watson (Nov. 13), 1930. 

In addition, the sexuparae have been taken on roots of Lepidium virginicum at Mt. Carmel on May 26, 1928. Previously recorded from Illinois by Davis (1910) and Gronemann (1930).

PEMPHIGUS POPULI-VENAE Fitch

Thomas (1879), in the "Eighth Report of the State Entomologist of Illinois," lists a species of Pemphigus under this name but without definitely recording it from Illinois. This species has been rarely recorded in literature, and the only detailed description of its forms is that by Maxson and Knowlton (1929). 

Our record establishing the occurrence of this species in Illinois is based upon the finding of the characteristic cockscomb-like galls upon the upper surfaces of leaves of Populus deltoides at Watson, Illinois, on November 13, 1930 (Frison and Ross). 

PEMPHIGUS TARTAREUS new species

[Described from sexupara collected from roots of Bidens sp.]

The plant lice, or Aphiidae, of Illinois