94 BULLETIN" 903, U. S. DEPARTMENT OF AGRICULTURE. 



Table XXXIII.— Summary of Table XXXII. 



Days. 



Maximum developmental period 21 



Minimum developmental period 9 



Average developmental period 12.73 



Average developmental period, female 12.65 



Average developmental period, male 13.10 



During the developmental period preceding September the sexes 

 developed in an average of 11.1 days, and in the remaining period, 

 from September 1 to November 3, in 16.1 days. 



The males appeared to develop more slowly than the females, but 

 a larger series might not indicate such a difference. 



The sexes, as soon as mature, were confined in a microscope-slide 

 cell with a piece of vine bark and some filter paper. None lived more 

 than three days, and copulation was observed in several instances, 

 but on the whole the sexuals showed little activity and were not 

 much attracted to each other. Several of the females partly ex- 

 truded a winter egg, but chose no especial locality for oviposi- 

 tion, and their action was undoubtedly abnormal. 



Mating is said to occur normally on the bark of the vine, the 

 female depositing a single egg under and between the layers of 

 bark. The egg is attached by a curved peduncle generally to the 

 inner surface of the 2-year-old bark, but sometimes to older layers. 



The Italian investigators found that eggs were most abundant 

 about midway between the base and head of the vine trunk, but that 

 they might be deposited on any wood of 2 or more years of age as 

 well as on buds. The egg at first is greenish yellow, and later becomes 

 greenish brown, remaining so until the time for hatching in the 

 spring following. The phylloxera? issuing from the winter egg are 

 said always to become the gallicole (gall-inhabiting) stem mothers. 



At Walnut Creek all types of vines exposed to phylloxera infesta- 

 tion have been searched exhaustively without more than a single 

 winter egg being found. Among these vines were included viniferse 

 taken from phylloxerated vineyards, and vinifera? and American 

 experimental vines grown in pots and boxes. The single egg brought 

 to light was observed in December, 1912, located under the outside 

 layer of bark of a young potted vine (Champenal). This egg, after 

 having been kept under observation for three weeks, died. 



From all observations in California it appears that conditions are 

 unfavorable for the successful development of the sexual phylloxera? 

 and, therefore, for the " winter " egg and succeeding generations of 

 gallicoles. Since in some parts of France a similar condition in the 

 phylloxera cycle obtains, it was concluded that some factor was 

 lacking to insure successful development, and there was reason to 

 believe that humidity was one of the factors until the discovery of 



