Estlund, in describing the characters and work of Aphis crataegifolia Fitch, says: "Found on leaves of Crataegus corrugating them. Specimens taken during May on Crataegus tomentosa Linn, were found to curl the leaves very much, and as they turned dark brown or red they became very conspicuous.''
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
Sirrine, F. Atwood
"A New Species of Pemphigus Occuring on Thorn,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 129-131.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/44