GENERATION OP INSECTS. i9 



^olia, WiLLD,), the young shoots of which have 

 swarmed with aphides all the winter, and the leaves 

 below are covered with honey-dew. We tried the 

 experiment of wiping it off from a leaf, but no more 

 was formed when it was protected by a piece of 

 writing-paper from the aphides above ; while the 

 writing-paper became sprinkled all over with it in a 

 few hours. By means of a lens, also, we have ac- 

 tually seen the aphides ejecting the honey-dew*. 



The almost instantaneous appearance of these 

 destructive insects in great numbers at the same 

 time, is taken notice of with wonder by almost every 

 writer. This circumstance, it must be confessed, 

 gives considerable plausibility to the notion of their 

 being brought by winds, — for whence, we may be 

 asked, could they otherwise come? Simply, we 

 reply, from the eggs deposited the preceding autumn, 

 which, having all been laid at the same time, and ex- 

 posed to the same degrees of temperature, are of 

 course all simultaneously hatched. In the case of 

 the aphides, also, the fecundity is almost incalculable. 

 Reaumur proved by experiment, that one aphis may 

 be the progenitor of 5,904,900,000 descendants dur- 

 ing its life ; and Latreille says, a female during 

 the summer months usually produces about twenty- 

 five a day. Reaumur further supposes, that in 

 one year there may be twenty generations. We 

 ourselves have counted more than a thousand 

 aphides on a single leaf of the hop; and in sea- 

 sons when they are abundant — when every hop-leaf 

 is peopled with a similar swarm — the number of 

 eggs laid in autumn must be, to use the words of 

 Good, " myriads of myriads." The preservation 

 and hatching of these eggs in the ensuing spring 

 must, it is obvious, depend on the weather and other 

 * J. R. 



