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. Xone 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 esjDecial 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 viniferaa 
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 discovers of 
