DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., February 21, 1916 No. 21 
MORPHOLOGY AND BIOLOGY OF THE GREEN APPLE 
APHIS 
By A. C. Baker and W. F. Turner, 
Entomological Assistants, Deciduous Fruit Insect Investigations, Bureau of Entomology 
CONTENTS 
Page 
Introduction. 955 
Name of the species. 956 
History and distribution. 957 
Methods of study. 958 
The egg. 960 
Plan of descriptions. 967 
Stem mother. 968 
Summer forms. 970 
Wingless viviparous female. 971 
Winged viviparous female. 974 
Intermediate form. 978 
Comparison of the three forms. 980 
Dimorphic reproduction. 981 
Overlapping generations. 981 
Page 
Feeding habits. 982 
Sexes. 984 
Oviparous female. 984 
Male. 985 
First appearance of sexes. 986 
Percentage of males to females. 988 
Length of Nymphal life. 988 
Longevity. 989 
Hardiness. 989 
Mating. 989 
Oviposition. 990 
Summary of life history. 991 
Genealogical diagram. 991 
Literature cited. 992 
INTRODUCTION 
Owing to the abundance of the green apple aphis {Aphis pomi De Geer) 
at all times in most apple-growing regions and to the serious outbreaks 
of the species at different places and in different seasons, the writers 
were instructed to make a careful study of its life ‘history. It was 
thought best to study the embryology of the insect in order, if possible, 
to explain the high mortality of the eggs in certain cases, their wintering 
condition, and, among other things, the most suitable time to attempt 
their destruction. Eggs were therefore taken during the winter of 
1913-14 and again during that of 1914-15. With the opening of the 
season of 1914 generation experiments were begun at the deciduous fruit 
insect laboratory at Vienna, Va., and carried throughout the summer, 
fall, and early winter until the last sexes and eggs of the year were 
obtained. The material obtained from these experiments and the eggs 
in hand were studied and the manuscript prepared for publication during 
the winter of 1914-15. 
Journal of Agricultural Research, 
Department of Agriculture, Washington, D. C. 
Vol. V, No. ax 
Feb. 21, 1916 
