INJURING THE EOOT. 



Ill 



for no other purpose than the reproduction of their 

 kind, and are without means of flight, or of taking 

 food, or excreting. 



" They are quite active and couple readily, one male 

 being capable, no doubt, of serving several females : 



Fig. 50. Grape Phylloxera, leaf form : a, b, newly hatched nymphs, 

 dorsal and ventral view ; c, egg ; d, section of gall ; e, swelling of 

 tendril ; /, g, h, mother of gall-louse, lateral, dorsal and ventral 

 views ; i, her antenna ;j, two-jointed tarsus. Natural sizes indi- 

 cated by small dots or figures. 



the abdomen of the female, after impregnation, en- 

 larges somewhat, and she is soon delivered of a soli- 

 tary egg, which differs from the egg of the partheno- 

 genetic mother only in becoming somewhat darker. 

 This impregnated egg gives birth to a young louse 

 which becomes a virginal, egg-bearing, wingless 

 mother, and thus recommences the cycle of the spe- 

 cies' evolution. But one of the most important dis- 

 coveries of Bolbiana is that, during the latter part of 

 the season, many of the wingless, hypogean mothers 

 perform the very same function as the winged ones ; 



