OF THE FAEM AHD GARDEN. 



251 



five generations during the year, and taking the lowest 

 of the above figures,, the immense prolificacy of the spe- 

 cies becomes manifest. As summer advances, they fre- 

 quently become prodigiously multiplied, completely cov- 

 ering the leaves with their galls, when they appear as 

 in figure 153. The lice also settle on the tendrils, 

 leaf -stalks, and tender branches, where they also form 

 knots and rounded excrescences (figure 152, e), much 

 resembling those made on the roots. In such a case, the 

 vine loses its leaves prematurely. Usually, however, the 



Fig. 153. LEAF OF THE GKAPE-VINE WITH PHYLLOXERA GALL. 



natural enemies of the louse seriously reduce its numbers 

 by the time the vine ceases its growth in the fall, and 

 the few remaining lice, finding no more succulent and 

 suitable leaves, seek the roots. Thus, by the end of 

 September, the galls are mostly deserted, and those which 

 are left are almost always infested with mildew, and 

 eventually turn brown and decay. On the roots, the 

 young lice attach themselves singly or in little groups, 

 and thus hibernate. The male gall-louse has never been 



