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 



