434 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



eggs, dying soon after. The eggs hatch in about eight days into 

 young females again, like the parent, and migrate to all parts of 

 the vine to form new galls. Six or seven generations of these 

 wingless females follow one another throughout the summer, 

 frequently completely studding the leaves with galls." In Cali- 

 fornia the young hatching from the winter eggs go directly to 

 the roots where they give rise to new colonies, there being no 

 gall forms, according to Quayle. Where the leaf-gall females 



FIG. 364. The grapevine phylloxera: a, winged migrating female; 6, last 

 stage of nymph of same; c, mouth-parts with thread-like sucking setae 

 removed from sheath; d, and e, eggs of male and female, showing sculp- 

 turing all enlarged. (After Marlatt, U. S. Dept. Agr.) 



occur many of them probably migrate to the roots during the 

 summer, and all do so with the approach of cold weather. In the 

 spring the roots are attacked and a series of generations of wingless 

 females multiply on them. As there are five to seven generations 

 in a season and each female lays from 30 (Quayle) to 100 (Marlatt) 

 eggs, it is evident that they will soon be numerous enough to 

 destroy the vine. The root-inhabiting females are very similar 

 to those in the leaf-galls, and are about one-twenty-fifth inch long 

 when mature and half as long when young and active. They are 

 light greenish-yellow in summer and darker in winter, and when 

 numerous the infested roots look as if dusted in spots with pow- 



