54 CALIFORNIA STATE COMMISSION OF HORTICULTURE. 



Another underground form is the dreaded Phylloxera vastatrix. This 

 pest is known all over the world and has caused millions upon millions 

 of dollars' loss by its depredations in the vineyards of Europe and 

 America. The life history of this pest is given by Professor Marlatt, as 

 follows: 



"The life cycle of the phylloxera is a complicated one. It occurs in 

 four forms in the following order: The leaf-gall form (gallicola), the 

 root or destructive form (radicicola), the winged or colonizing form, 

 and the sexual form. The leaf-gall insect produces from 500 to 600 

 eggs for each individual, the root-inhabiting insect not much above 100 

 eggs, the winged insect from 3 to 8, and the last sexed insect but one 

 egg. This last is the winter egg, and may be taken as a starting point 

 of the life cycle. It is laid in the fall on the old wood, and hatches, 

 the spring following, into a louse, which goes at once to a young leaf, 

 in the upper surface of which it inserts its beak. The sucking and 

 irritation soon cause a depression to form about the young louse, which 

 grows into 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, frequently completely studding the leaves 

 with galls. With the approach of cold weather the young pass down 

 the vines to the roots, where they remain dormant until spring. The 

 root is then attacked, and a series of subterranean generations of wing- 

 less females is developed. The root form differs but slightly from the 

 inhabitant of the leaf galls, and the swellings or excrescences on the 

 roots are analogous to those on the leaves. 



" During late summer and fall of the second year some of the root 

 lice give rise to winged females, which escape through cracks in the soil, 

 on warm, bright days and fly to neighboring vines. These winged lice 

 lay their eggs within a day or two in groups of two or four in cracks in 

 the bark or beneath loose bark on the old wood of the vine, and die 

 soon after. The eggs are of two sizes, the smaller and fewer in number 

 yielding males in nine or ten days, and the larger the females of the 

 only sexed generation developed in the whole life round of the insect. 

 In this last and sexed stage, the mouth parts of both sexes are rudi- 

 mentary, and no food at all is taken. The insect is very minute, and 

 resembles the newly hatched louse of either the gall or the root form. 

 The single egg of the larva-like female after fertilization rapidly 

 increases in size until it fills the entire body of the mother, and is laid 

 within three or four days, bringing us back to the winter egg, or start- 

 ing point. 



