THE GRAPE PHYLLOXERA IN CALIFORNIA. 117 
practice to use the same boxes many times in the picking season, 
and the same boxes may be used in more than one vineyard or dis- 
trict. In California, wine grapes are rarely picked before the middle 
of September, and raisin grapes are picked toward the end of August. 
In the experimental wine-grape vineyard, wandering larvae were not 
found issuing after August 25, but in young vines in pots they were 
collected well into September. The fact that the wanderers were 
not found issuing in the wine grape vineyard at the time when picking 
boxes were distributed to a certain extent invalidates the theory of 
spread by these boxes. It is within the realm of possibility, however, 
that the latest issuing wanderers remained active and alive until the 
boxes were distributed some two weeks later. Observations on wan- 
derers issuing from potted vines lead to the conclusion that the natural 
period of wanderer issuance may be considerably lengthened beyond 
that which was found to obtain in the experimental vineyard during 
the years 1914 and 1915. This longer period would include the time 
of picking wine as well as raisin grapes. 
PLANTS BETWEEN THE VINES. 
Walnut trees planted in vineyards indicate the possibility of 
diffusion through the agency of plants. The long roots of the 
walnut offer facilities for phylloxeras to spread whenever vine 
roots come in contact with them or are very close to them. That 
phylloxeras have been found moving on these roots would indicate 
that the latter often provide an underground channel of diffusion. 
MAN AND DOMESTIC ANIMALS. 
The possibility of the portage of phylloxeras by man and do- 
mestic animals should not be overlooked. The winged forms and 
aerial wanderers may be blown on clothes or animals, and thereby 
spread, or they may be picked up with wet earth. This latter chance 
is greatly lessened under California conditions, because during the 
months in which wanderers and winged migrants are produced, 
the surface soil is dry, and the winged migrant is not a" factor in 
diffusion. 
Recognizing the possibility of the spread of phylloxeras through the 
agency of flowing water, the writers conducted the following experi- 
ments in 1914: From May 5, 11 a. m., to May 6, 11 a. m., a piece of 
severed root, infested by six adult overwintered phylloxeras and about 
100 eggs and larvas, was subjected to a stream of water for the most 
part playing directly upon the insects and flowing 6 feet to an unin- 
fested vine (Catawba) so as to effect contact with some of its roots and 
