THEIR RELATION TO PLANTS 



47 



for the purpose of renewing the vitality of the species 

 for they are without wings, incapable of flight and with- 

 out mouth parts, incapable of feeding. They are 



FIG. 14. Phylloxera vastatrix a, sound grape rootlets; b, rootlets with newly 

 formed galls; c, same with old, dried up tissue; dd, groups of lice on roots and 

 rootlets; e, f, female pupa, above and beneath; g, h, winged females; , antenna; 

 j, oviparous wingless female and her eggs; k~, root showing location of the eggs. 



sexually mature when born, copulate soon afterward, 

 and each female produces one egg which hatches into 

 a form similar to that which started the cycle in spring. 

 But the winged form is not essential for this renewal, 



