86 INSECTS AND MAN 



death ensues. Before the death of the host plant takes 

 place, however, considerable progress has been made in the 

 life-cycle of Phylloxera. During the late summer and 

 early autumn of the second year, some of the eggs, laid by 

 the root insects, give rise to winged females (fig. 20), in 

 place of the wingless forms that had been thus far produced. 

 These winged females find their way to the surface of the 

 ground and then fly to neighbouring vines that they are 

 carried by the wind would be a more correct statement, 

 perhaps, for they are frail creatures, and their powers of 

 flight are feeble in the extreme. They are short-lived : in 

 two or three days their mission in life is accomplished, and 

 they die. Their one object is to lay eggs, and this they 

 do like their mother, parthenogenetically ; there the re- 

 semblance ends, for, instead of depositing a large number 

 of eggs, they lay at the most two to four beneath the 

 loose bark on the old vine wood. Now we arrive at one 

 of the most curious phases in this wonderful life -history. 

 The eggs laid by the winged females are of two sizes ; the 

 smaller ones, which, by the way, are in the minority, give 

 rise to males, whilst the larger and more numerous pro- 

 duce females, and this stage, which is sometimes termed the 

 stage of regeneration, is the only one in which males are 

 produced. In about ten days the two sexes emerge. Both 

 have rudimentary mouth parts and take no food ; their sole 

 mission in life is, probably, to imbue their progeny with 

 renewed vigour. How far this stage is necessary to the 

 continuance of the race is a debated point, for all the Avhile 

 the root forms continue to exist and carry out their de- 

 structive work ; and that they can do without help from 

 their sexually produced relatives for at least four years 

 has been proved. But to return to the sexual forms ; after 

 mating, the body of the female is rapidly occupied with a 

 single egg of relatively enormous size, and this winter egg, 

 which is laid within three or four days, completes the life- 

 cycle. These changes, as described, extend over a period of 



