FAMILY APHIDAE 5 
secondary or summer hosts, usually annuals or herbaceous plants. 
On the primary host the winter is passed in the egg, consequently 
here also occur the fundatrix and one or more ensuing generations 
until the population consists of only alate viviparae which act as 
spring migrants and fly away to the summer or secondary hosts. 
Here successive generations are produced till the sexuparae, fall 
migrants, appear and, in many cases, alate males, both of which fly 
back to the primary. hosts. The oviparous females are deposited 
here, mature and, after mating, lay the over-wintering eggs and die. 
However, many variations and exceptions occur. Scattered in- 
dividuals may remain on the primary host all summer and the same 
may occur on the secondary host over the winter if the plant con- 
cerned is a perennial or is protected, as in a greenhouse. Indeed in 
the latter situation and in warm climates the sexual part of the cycle 
may be entirely omitted. 
ECONOMIC IMPORTANCE 
The economic importance of aphids is a matter of major con- 
cern. Aphids constitute one of the most injurious insect groups. 
Their attacks on plants cause serious damage in three ways: (1) By 
robbing the plant of sap, (2) by toxic action of their salivary secre- 
tions, injected during feeding, thus causing stunting of growth, 
deformation of leaves and even of fruit or causing galls on leaves, 
stems or roots, and (3) by acting as vectors of viruses which cause 
many diseases of plants. Since aphids are usually specific both as to 
plants attacked and as to plant viruses carried in the capacity of 
vectors their taxonomy is highly important. 
COLLECTING AND SHIPPING 
Adult aphids, especially winged ones, are essential for identifi- 
cation and since the colonies usually consist predominately of imma- 
ture individuals, the mature ones often leaving soon after the last 
molt to establish other colonies, it is highly desirable to preserve the 
aphids alive and in confinement for a day or two after capture in 
order to allow more individuals to mature. The aphid colony, to- 
gether with the part of the plant to which they are attached, may be 
enclosed in a vial or a tight tin box, without holes, so as to prevent 
drying of the plant. The end of the stem should be caught with the 
cork or lid. The box or vial should be lined with paper to absorb 
moisture thus preventing formation of droplets which would en- 
tangle and damage the aphids. First of all, examination must be 
made to eliminate any enemies, which would destroy the aphids. 
They may be kept thus for several days or even a week in a cool 
