182 INTERNATIONAL CONGRESS OF VITICULTURE 



appearance of a phylloxera spot in a vineyard generally means an infestation 

 of several years standing, perhaps as many as ten years or more. Through- 

 out the vineyard, on the roots of many apparently vigorous vines, inspection 

 will reveal the presence of the insect. Eventually other well denned spots 

 will be noticeable, but even in this advanced stage there are but compara- 

 tively few dead vines. This applies to vines eight to twelve years old before 

 being infested. Young vines, infested from the beginning, last a much 

 shorter time, and the injury of the insect produces a more pronounced effect. 



As a result of this investigation, both from a viticultural as well as an 

 entomological standpoint, a most important fact pertaining to this subject 

 has been placed on record. It is also of economic interest, because of its 

 bearing upon the mode of spread of the insect, and its consequent relation 

 to the severity of the damage to the viticultural industry. The leaf-gall 

 form of the phylloxera does not exist in California. This is true for the 

 American varieties of grapes, which are most susceptible to this form of the 

 insect, as well as for the varieties of the Vitis vinifera. To establish this 

 fact with certainty, a careful canvass has been made, and correspondence 

 exchanged with the entomologists of this State, and with persons profes- 

 sionally and commercially identified with California viticulture; with but one 

 exception all observations concur to prove the absence of the phylloxera 

 leaf-gall form in the California vineyards. This exception deserves special 

 mention, because of the authority of the statement and the peculiar circum- 

 stances pertaining to the production of the galls. 



Dr. F. W. Morse of Oakland, Cal., then Assistant in the General Agricul- 

 tural Laboratory of the University of California from 1881 to 1886, carried 

 on investigations of the phylloxera in said State. Late in August, 1884, he 

 found a few galls on the ends of three canes of a Canada vine growing in 

 the vineyard plot on the University grounds. Quoting him from Bulletin 

 No. 19 of the Agricultural Experiment Station of the University of California, 

 he found "few peculiarly formed galls, containing egg-laying mother-lice, 

 as well as eggs, and numerous larvae. A few isolated and abandoned ones 

 were found on the old leaves nearer the stock of the vine." Evidently these 

 were lice of a progeny of the ones which produced the galls on the older 

 leaves. They had increased but little, and struggled along for existence 

 since spring, contrary to their habit under Eastern condition, when they 

 are very prolific; they were never observed before that time, nor afterwards; 

 their presence on this occasion can, therefore, be considered as accidental. 



Life History. 



Space in this paper does not permit giving a detailed description of the 

 different forms of the grape phylloxera. It will suffice to point out in what 

 respect its life history differs under California conditions from that influenced 

 by existing conditions of its original habitat. 



In California the life cycle of the insect is restricted to parthenogenetic 

 reproduction, and to the radicicole or root form only. It comprises this form 

 in the two stages of Hibernant and Radicicole mother-louse. The Radicicole 

 of spring passes through the pupa or nymph stage to become the alate form, 

 also a root form, or Winged Migrant, which emerges from the ground only to 

 oviposit, and is also parthenogenetic. A great number of the Winged Migrants 



