236 EYE SPY 
for the present. Here, for instance, is the great 
sub-tribe of the aphis, to which our woolly spec- 
imen belongs. What is their life history ? The 
eggs of the mother aphis are laid in the autumn, 
giving birth to the baby swarm in the following 
spring. In an almost incredible time they have 
multiplied to such an extent that the twigs of our 
roses and many other plants are lost to view in 
the encircling swarm. The secret of this won- 
derful arithmetical progression may be seen in 
the following quotation, which applies to aphides 
in general : 
"The plant-louse of the apple-tree produces 
one hundred young ones in a single generation, 
these being born alive, and each of these brings 
forth others in equal number, until, at the end of 
the tenth generation, which is reached before the 
coming of frost, the original aphis has become the 
mother of one quintillion of her species." 
But up to this time nearly all the aphides have 
been females ; in the last generation the winged 
males appear, and are seen assembled among the 
swarm the last mother brood laying the eggs 
which are to start anew the cycle of life the fol- 
lowing season. 
So far as I have observed, however, the woolly 
species of aphis never acquires wings, nature hav- 
ing in a measure compensated for their absence 
in the growth of plumy down, which, according to 
