TR ACHE ATA 



367 



whicli are provided with the rudiments of wings ; before their 

 last change of skin they creep above ground, and then at the 



Fig. 207. — Phylloxera vastatrix, winged female 

 which lives on leaves and buds of vine, and 

 lays, parthenogenetically, eggs of two kinds, 

 one developing into a wingless female, the 

 other into a male. After Girard. 



final moult a winged female emerges and flies away. This 

 form serves to spread the vine disease from one district to 



Fig. 208. 



a. Phylloxera vastatrix, male 



produced from small egg 

 (c) laid by winged female 

 (Fig. 207). 



b. Large egg. 



c. Small egg. 



d. Wingless female from large 



egg (*) l^id by winged 

 female. 



After Girard. 



another. It is also parthenogenetic, but lays two kinds of 

 ecrgs. From the larger of these a complete female hatches out, 

 whilst the smaller produces in eight to ten days a male. This 



