XXXVI 

 THE DEADLY PHYLLOXERA 



IT was only after long and patient investigation that, 

 the various broods of the terrible Phylloxera which 

 between 1868 and 1888, destroyed half the vineyards of 

 France, became known, their relations to one another 

 determined, and the final cure for the devastation caused 

 by them decided upon and put into practice. 



In all ordinary plant-lice or green-fly (aphides) at the 

 end of the summer, the last parthenogenetic brood pro- 

 duces a generation of distinct males and females, which 

 differ a good deal in appearance from the virginal broods 

 of the spring and summer. Each female, after receiving 

 sperm-cells from a male, lays a single egg, which consists 

 of a fertilised egg-cell enclosed in an egg-shell. It is 

 deposited in a safe place in a crack of the bark of a tree, 

 or on the rootlets of some plant, and remains unchanged 

 through the winter. In the spring from every such egg 

 hatches a single female aphis, which feeds and increases 

 in size. In a very short time (a week or so) this solitary 

 female (Fig. 58) proceeds to produce, without male inter- 

 vention, young which grow from true egg-cells which are 

 not laid but remain inside her. The young are born or 

 pass out of her as small six-legged insects. They feed and 

 grow up, and in turn produce " parthenogenetically " and 

 viviparously broods of young like themselves. The first 



