136 MINUTE MARVELS OF NATURE 



successive generations of some species of insects 

 may make their appearance in the course of a 

 single year ; and some, like the aphides or " green- 

 flies," increase their kind by the production of 

 living young, although they commence primarily 

 at the beginning of the season from fertilised 

 eggs laid at the end of the previous autumn 

 between the winter scales of the leaf-buds. When 

 the warm sunshine of spring persuades the buds 

 to open, the young aphides or green-flies are there 

 to feed and multiply upon the young leaves. No 

 more eggs are laid until the autumn, for the 

 offsprings of these eggs are not male and female 

 insects, but all imperfect mothers which keep 

 feeding and budding out young just like them- 

 selves, which again go on budding, and so on, 

 until one aphis becomes the progenitor of billions 

 of descendants in the course of its life. 



Thus it might well have appeared to our fore- 

 fathers, who had no accurate knowledge of the 

 wonderful powers of increase of these tiny crea- 

 tures, that the atmosphere was " freighted with 

 insects' eggs that elude our senses," and that the 

 honey-dew which these aphides exude came as 

 " a peculiar haze or mist loaded with poisonous 

 miasm." 



Seeing in what abundance the green-flies are 

 produced, it naturally follows that, unless some 



