104 
BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 
Wanderers were first caught on sticky papers July 21 and first ob- 
served alive in the vineyard August 11. After August 18, no more 
were caught on the sticky papers, and after August 25, no more were 
observed alive. The weather during July and August was for the 
most part bright and warm. In the vineyard the wanderers were 
observed in by far the greatest abundance near the trunks of the 
vines, and it appeared that they had reached the soil surface by fol- 
lowing up the roots. No wanderers were observed on the aerial 
portions of the vines themselves. They showed much activity, wan- 
dering aimlessly around over the soil. They seemed to prefer the 
shaded parts, but appeared also on ground surface exposed to the sun. 
Large numbers were found dead close to the vine trunks, and these 
occurred in places where the soil was very fine, indicating that the 
phylloxeras were unable to progress in fine soil. Laboratory ex- 
periments bore out this supposition. Many others became caught 
in spider webs stretched over the soil surface. The character of the 
soil in the vineyard in August, 1914, was such as to enable phylloxera^ 
to pass from one vine to another without necessarily encountering 
very fine soil, as no cultivation had been practiced since May, 1914, 
and the vineyard had been cultivated previously only in one direction. 
As regards the capture of wandering larvae upon sticky papers, 
the data given in Table XXXIV are of interest : 
Table XXXIV. — ~\Yandering larvw of the grape phylloxera ; diffusion in vine- 
yard; Walnut Creek, Calif., 191'}. 
Date caught on paper. 
Number of 
Distance 
wandering 
from nearest 
larvae caught. 
vine trunk. 
Fee'. 
3 
o 
1 
2 
20 
2 
1 
5 

2 
1 
h 
1 
2 
Area of 
sticky paper 
on which 
phylloxera 
were caught. 
July 21-24.... 
July 24-28 
July 31- Aug. 3 
Do 
Aug. 7-11 
Aug. 11-15.... 
Aug. 14-18 
Square incites. 
135 
135 
135 
135 
135 
135 
135 
During the period from July 21 to August 18 many sheets of 
sticky paper 135 square inches in area (9 by 15) were placed on the 
surface of the ground, and wanderers were caught on 7 (see above) out 
of 32 papers. In the majority of instances the individuals were caught 
on the side of the paper toward the nearest vines, which would indi- 
cate that they arrived there straight from the trunk of the vine. On 
sides of the paper facing vines farther away it would be natural 
to expect fewer wanderers when one considers how the circum- 
ference of a circle increases in proportion to its radius, and also the 
comparatively equal diffusion of wanderers in all radii, if the vine 
