238 OUR INSECT FRIENDS AND FOES 



The life-history of the Aphis is an extra- 

 ordinarily interesting one, and has attracted 

 the close attention of many of the most dis- 

 tinguished scientific men. Reaumur and Bonnet 

 being the first to accurately investigate its life- 

 history, while their researches have been con- 

 firmed and further enlarged by the investigations 

 of Owen, Huxley, and Buckton. The perfect- 

 winged male Aphides make their appearance 

 in large numbers in the autumn, and mate with 

 the oviparous or egg-laying females. These 

 females then deposit their minute eggs upon the 

 plants, frequently covering them with a natural 

 protective secretion; and with the advance of 

 autumnal cold weather, the males and oviparous 

 females soon die. From these autumn-deposited 

 eggs are hatched in the following spring im- 

 perfect wingless Aphides which are all females, 

 no males being present amongst them. These 

 wingless females very soon commence to produce, 

 not eggs, but living young, and are therefore 

 called viviparous females. Their offspring in turn 

 give birth to other living young exactly like them- 

 selves in appearance, and so on throughout the 

 summer there is a constant succession of these 

 viviparous females, all producing young without 

 the presence of the male ; this non-sexual method 

 of reproduction being known as parthenogenetic 

 reproduction. Reaumur, in the course of his 

 experiments with Aphides, succeeded in rearing 

 about fifty parthenogenetic generations, all des- 

 cended from one mother, by keeping up for 

 several years a constant summer temperature 

 and abundance of food ; thus demonstrating 



