Page. 
Embryology 94 
Methods and material 95 
General description of the egg 95 
Observations 97 
Summary of embryological development 102 
Natural enemies 103 
Internal or true parasites 104 
Aphidius testaceipes Cress 104 
Description and identity 104 
Life history 105 
Oviposition 105 
Length of period from egg to adult 106 
Effect of parasitism by Aphidius upon development of host. . 106 
Effect of parasitism by Aphidius upon fecundity of host 107 
Movement of larva within the host and manner of attaching it 
to the plant 109 
Fecundity 113 
Parthenogensis 114 
Hosts of Aphidius testaceipes 115 
Hibernation 117 
Influence of winds in the dispersion of Aphidius testaceipes 118 
Temperature influences of Aphidius 119 
Effects of wet weather on the diffusion of Aphidius 121 
Other species of Aphidius 122 
Aphelinus. 122 
Notes on life history and habits of Aphelinus 124 
Secondary parasites 125 
Megorismus sp 125 
Aphidencyrtus aphidiphagus Ashm 126 
Pachyneuron sp 127 
Allotria sp 128 
Predaceous enemies 128 
Lady-beetles 128 
Syrphid flies 129 
Lacewing flies 132 
Cecidomyiidae 133 
Birds 135 
Miscellaneous enemies of Toxoptera 135 
Ants and their relation to Toxoptera 136 
Remedial and preventive measures 136 
Field experiments 136 
Cultural methods 139 
Artificial introduction of parasites 142 
Literature consulted .' 144 
Index ? '145, 
