THEIR RELATION TO PLANTS 



47 



for the purpose of renewing the vitahty 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; i, 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. 



