REPORT OF COMMITTEE ON PUBLICATION 183 



are sterile, in the meaning that these do not deposit eggs. However, when 

 mounted for microscopic examination, generally two large eggs are discern- 

 ible in the bodies of these sterile migrants. This sterility may be ascribed 

 to incomplete parthenogenesis. A relatively small number only of the winged 

 migrants oviposite one to five eggs being the number; two, a fair average. 

 The eggs lack vitality; they fail to give issue to healthy active sexed forms. 

 Most of the eggs do not hatch, and when they do, the young die in the act 

 of molting. Hence, in California the winged migrant stage is the end of 

 the progress in the insect's life cycle towards the production of the gallicole 

 or leaf-gall form. This corroborates field observations and explains why 

 grape phylloxera leaf-galls are never found in California vineyards, not even 

 when composed of varieties of American grape. 



Hibernants differ in no respect of structural form from the radicicole 

 young larvae. The latter attain maturity the same season, on an average 

 from eighteen to twenty-one days after hatching, while the former make 

 their way up along the roots in search of a place to settle down on, and 

 pass the winter in a dormant state. They neither molt, nor increase in size 

 before they settle down. They awaken about the middle of March, and after 

 four molts attain maturity, in five weeks' time on an average. These adults 

 are the first radicicole mother-lice of the year. Hibernation begins in Sep- 

 tember; by December there are no more active young larvae, all are hiber- 

 nants; adults are very scarce and no longer oviposit. From March to 

 December there are from four to five generations of the radicicole apterous 

 form. From late June to October a small proportion of the young larvae, 

 the number depending upon the nature of the roots and on their more or less 

 healthy condition, differentiate after the second molt, and become pupae 

 or nymphs; these after two more molts attain the adult stage of winged 

 migrants, which live from one to four days, rarely more. The nymph works 

 its way up toward the surface of the ground; after transformation, the 

 winged migrant emerges from the ground. 



In late June or July a very marked migratory movement of the recently 

 hatched larvae takes place from the roots in the deeper soil towards the 

 surface of the ground, some traveling on the roots, but many more abandon- 

 ing them for cracks and crevices in the soil by which they gain egress to 

 the surface. This is in fact a true migration, and these young active apterous 

 radicicole larvae furnish the only means by which the phylloxera spreads in 

 California. The term "wanderer" is a suitable designation for these wingless 

 migrants, and avoids confusion with the winged form to which the term 

 migrant is usually applied. 



The wanderers, if not exposed to the direct heat of the sun, can live for 

 several days upon the surface of the ground. They can reach neighboring 

 vines, as yet not infested, by crawling to them, or by the aid of the wind, 

 be carried to different parts of a vineyard. Infestation from vineyard to 

 vineyard, or from one viticultural district to another, can possibly happen 

 by the exchange of grape-picking boxes, into the cracks or joints of which 

 wanderers have crept, they thus being transported from one place to another. 



