494 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



all the roots become affected the vine stops growing, the leaves 

 become sickly and yellowish, and the vine dies, and the phyl- 

 loxera disappears from the rotting roots, so that the cause of the 

 injury would be obscure were the nature of the injury not known. 

 Life History. The life history of the phylloxera is a com- 

 plicated one, involving four different forms of aphides; the leaf- 

 gall form, the root or destructive form, the winged or colonizing 

 form, and the sexual form. The winter eggs are deposited on the 

 rough bark of the old wood in the fall and hatch the following 



FIG. 355. The grapevine phylloxera: a, winged migrating female; b, last 

 stage of nymph of some; c, mouth-parts with thread-like sucking seta? 

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

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



spring. The young aphides settle on the leaves, where the irrita- 

 tion caused by their mouth-parts soon causes a depression around 

 each which forms a gall projecting on the lower side of the leaf. 

 " In about fifteen days the louse becomes a plump orange-yellow, 

 full-grown, wingless female, and fills its gall with small yellow 

 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, 



