IDENTITY OF ERIOSOMA PYRI 
By A. C. Baker, 
Entomological Assistant, Deciduous Fruit Insect Investigations , Bureau of Entomology 
This paper has been written in order to reinstate the woolly aphis 
described by Fitch from apple (Malus spp.) roots, to point out its dis¬ 
tinctness from the woolly apple aphis ( Eriosoma lanigerum Hausmann), 
with which it has been confused, and to place it among the species of the 
genus to which it properly belongs. 
In 1851 Fitch 1 described a woolly aphis under the name “ Eriosoma 
pyri .” At the same time he described the work of what seems to be 
E. lanigerum Hausmann on apple. At the time of his original description 
Fitch evidently did not know of the genus Pemphigus. This is indicated 
from his remarks in his first report, 2 for in the description in this publi¬ 
cation he is quite positive in placing his species in that genus. The 
description of the wingless forms agrees well, however, with lanigerum . 
The identity of pyri has for many years been in doubt, and the name 
has been referred to different species as a synonym. The writer, 3 in his 
recent work on the woolly aphis, considered it to be lanigerum. This was 
based on two things: The description of the wingless forms, with the pos¬ 
sibility of abnormality in the winged form, and Gillette’s 4 statement in 
regard to the type. One fact, however, seems evident. The descrip¬ 
tions given by Fitch for his winged forms could not have been made from 
normal migrants of lanigerum . In fact, they could not have been made 
from winged forms of lanigerum at all. This is particularly true of the 
description in the first report. 
Fitch’s original notes on the species are now in the writer’s hands, and 
they throw some interesting light on the question. After describing the 
wings minutely, Fitch says: “The wings serve best to distinguish this 
species, and an exact figure of one or both of them will be the best illus¬ 
tration of it that can be given,” and again, “Neuration of the wings 
identical with that of Myzoxylus imbricator .” By 1871 Fitch had some 
feeling that his pyri might be a synonym of lanigerum , for in his notebook, 
under October 11 of that year, he suggests such a possibility. He adds, 
“My winged lanigera from Dr. Signoret is a Pemphigus, the 3rd vein 
being simple, but not so abortive at its base, and has all the veins 
slender.” 
1 Fitch, Asa. Catalogue with references and descriptions of the insects collected and arranged for the 
State Cabinet of Natural History. In 4th Ann. Rpt. [N. Y.] State Cab. Nat. Hist,, p. 68. 1851. 
3 -[Report on the Noxious and Other Insects of the State of New York.] p, 7. In Trans. N. Y. 
State Agr. Soc., v. 14, 1854, p. 711. 1855. Reprint, p. 7, Albany, N. Y., 1856. 
8 Baker, A. C. The woolly apple aphis. U. S. Dept. Agr. Office Sec. Rept. 101, p. 13. 1915. 
4 Gillette, C. P. Plant louse notes, family Aphididae. In Jour. Econ. Ent., v. 2, no. 5, p. 352. 1909. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
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Vol. V, No. 23 
Mar. 6,1916 
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