102 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 
August 3, 7, 11, 14, 17, 20, 21, 31. Horizontal boards were placed 
July 10, 13, 21, 24, 31 ; August 7, 11, 14, 17, 21, 25, 31 ; September 
5, 11, 26. 
On the vertical boards eight migrants were captured between July 
13 and August 21, and on the horizontal boards, between July 10 and 
August 17, 51 were taken. The area of paper exposed on the vertical 
boards was 63,725 square inches, almost 50 square yards, while that 
of the horizontal boards was 7,625 square inches, not quite 6 square 
yards. The papers kept sticky for about four days on the average. 
Considering the comparatively large number of migrants captured 
on the limited areas of sticky paper, there must have been a 
heavy infestation throughout the vineyard. Winged phylloxerse were 
observed on and about the bases of vine trunks, and many were 
caught in spider webs and died. Whether the migrants deposit the 
sexual eggs in the vineyard or not, the total absence of galls on 
the vines (viniferse and resistants) surely indicates that such eggs 
come to nought. 
From rather meager observations it appears that the sexuals require 
a high temperature, coupled with considerable humidity, for their 
successful development, and that the climatic conditions of Califor- 
nia lack the requisite combination. 
DIFFUSION BY NEWLY HATCHED RADICICOLES ISSUING FROM THE SOIL. 
In the summer of 1868, Faucon, in France, observed young radici- 
coles wandering over the surface of the soil following a heavy rain, 
which had caused the soil to crack open in drying. He also observed 
the phylloxerse to enter cracks and disappear. In 1872, he again 
observed these phenomena between August 4 and September 30. The 
year following, his observations were made from June 14 to Septem- 
ber 13, so that he was able to see wandering larvae during a period of 
three months. In 1876, Boiteau, in France, confirmed the observa- 
tions of Faucon, adding that he found that the greatest number of 
wanderers issued from vines at. the periphery of the phylloxera 
" spot." Since then other observers have discussed the phenomenon 
of "wanderer" diffusion. Grassi (11, p. 351, 138, 148) and his col- 
leagues, working from 1907 to 1911, conducted a series of experiments 
with the wandering larvae. They found that these were strongly 
attracted to light and that in walking over the soil surface they did 
not go in a straight line, but deviated according to the variations of 
the surface. On a piece of glass they proceeded in a straight line and 
covered a distance of about 2 cm. the first minute. 
As regards inoculation of vines by these wandering young, suc- 
cessful experiments were carried out in Europe on vines in pots, it 
being found that the wanderers penetrated the cracks formed be- 
tween the inside periphery of the pot and the drying soil and infested 
