CONTENTS. 
Page. 
Introduction 9 
Economic importance 9 
Life history 10 
Hibernation 10 
Aphides on hop roots 10 
Emergence from hibernation 12 
Method of reproduction 12 
Number of generations on alternate host 13 
Migrating forms 13 
Migratory activities 13 
Deposition of young 14 
Rate of growth 15 
Number of young deposited by viviparous females 16 
The fall migrants 17 
The winter egg 17 
The life cycle 18 
Theory regarding summer migrants 18 
Habits 19 
Habitation 19 
Protection 19 
Relation of ants to the hop aphis 19 
First appearance of the hop aphis in the season 20 
Favorable and unfavorable conditions for the aphis 20 
Effect of heat 20 
Food plants 21 
Nature of damage 21 
General effect of aphides upon hops 21 
Honeydew and its effect on the hops 22 
Blackening of hops 22 
Natural enemies 22 
Control of the hop aphis 23 
Axioms of successful control 23 
Insecticides used 23 
Time to begin spraying 23 
Number of applications 24 
Necessity for early spraying 24 
Necessity for thorough work 24 
Procrastination 24 
Spraying experiments 24 
Mixing nicotine solutions and whale-oil soap 27 
Preparation of the flour paste 27 
Advantages of flour paste over whale-oil soap as a spreader for contact insec- 
ticides 28 
5 
