112 



INSECTS AFFECTING THE GRAPE. 



i. e., the}' lay a few eggs which are of two sizes and 

 which produce males and females, organized and 

 constructed precisely as those born of the winged 

 females, and like them producing the solitary im- 

 pregnated egg. Thus, the interesting fact is estab- 

 lished that even the winged form is by no means 

 essential to the perpetuation of the species ; but that, 

 if all such winged individuals were destroyed as fast 

 as they issue from the ground, the species could go 

 on multiplying in a vineyard from year to year. 

 We have, therefore, the spectacle of an underground 

 insect possessing the power of continued existence, 

 even where confined to its subterranean retreats. It 



Fig. 51. Grape Phylloxera, root form : a, infested rootlets : b, hiber- 

 nating larva ; c, <l, antenna and leg of same ; e,f, g, more mature 

 forms : h, granulations of skin ; i, tubercle ; j, transverse folds at 

 border of joints ; /.-, simple eyes. 



spreads in the wingless state from vine to vine and 

 from vineyard to vineyard, when these are adjacent, 

 either through passages in the ground itself, or over 



