12 
contributed more or less to our knowledge of the pest and its natural 
enemies, and throughout the following pages credit has been given 
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Fig. 1. — The spring grain aphis ( Toxoptera graminum): Wheat plant showing winged and wingless 
viviparous females with their young clustered on the leaves, and a few parasitized individuals on lower 
leaves. About natural size. (Original.) 
each individual where possible to do so. For a critical, technical 
study of the parasites of the species, credit should be given Mr. J. C. 
Crawford, assistant curator, Division of Insects, U. S. National 
L 
