THE GKAPE PHYLLOXERA IN CALIFORNIA. 9 



with entomologists and prominent viticulturists in California elicited 

 the same information. 



Laboratory experiments, conducted under favorable conditions to 

 obtain winter eggs with the existing strain of phylloxera in Cali- 

 fornia, have failed to go beyond the production of the winged form 

 in specially devised cages, although in other laboratory experiments 

 the sexed forms were produced and the discovery in the natural state 

 of a single winter egg must be mentioned. 



A study of the life history has corroborated the observations of 

 Dr. Morse relating to the sterility of a portion of the winged migrants 

 and to the sterility of some and the debility of the remainder of their 

 progeny. The writers' observations demonstrate that the normal life 

 cycle of the insect in California is wholly parthenogenetic and that 

 the natural spread, or diffusion, is due entirely to young radicicole 

 larvae possessing migratory instincts, at least during July, August, 

 and September, and to which has been given the name of "wan- 

 derers" to distinguish them from "migrants," a term which com- 

 monly is applied to winged forms of the Aphididae. 



The conclusions of the investigations of Dr. Morse point to the 

 possibility of such a condition, though not affirming that the winged 

 migrant is not responsible for the diffusion of the species in Cali- 

 fornia. The late Prof. E. W. Hilgard (14) shared this view, which 

 he expounded in his report, in which he indicates the discovery by 

 him of one of the first phylloxera spots in Napa Valley, as follows : 



The first phylloxerated " spot " within the Napa Valley was observed by me 

 in 1877, close to the stage road and public highway leading directly fronr the 

 worst-infested portion of Sonoma, and on which vineyard material was, and 

 is, constantly being hauled back and forth. It is plainly from this highway 

 and its infested wagonloads that the insect has spread in the Napa Valley. 



The " spot " alluded to is believed by the writers to have been 

 either in the old Squibb vineyard (10 acres), in the old McClure 

 vineyard adjoining, or in the Callan vineyard (50 acres). All these 

 were located close together. They have long since been pulled up, 

 the land is now pasture, and only a very few of the old original 

 vines still exist, although browsed down by the stock. These vines 

 date back to 1866. 



From present knowledge of the biology of the phylloxera, it is be- 

 lieved by the writers that the vineyard material referred to by Prof. 

 Hilgard was responsible for the spread of the pest to this location, 

 but the inoculation was due to the wandering young radicicole 

 larvae rather than to the winged form. 



PHYLLOXERA SPREAD BY PICKING BOXES. 



" Vineyard material " may imply many sources of infestation. 

 Besides rooted vines, grape-picking boxes are very likely to trans- 



