THE GRAPE PHYLLOXERA IN CALIFORNIA. 103 
the rootlets growing in contact with the pot. Experiments showed 
that when sand was dry it obstructed the wanderings of the phyl- 
loxerae, but when moistened the phylloxerae might be drawn through it 
with the water. It was also found that in sandy soils water might 
occupy all the interstices between the grains of sand, repelling the 
phylloxera?, whereas in soils of other types air cavities existed suf- 
ficient to enable the phylloxeras to live. 
In California the wandering larvae were first observed in glass 
jars in which were kept phylloxerated roots in the summer of 1913. 
When such jars were removed from the darkness of the cellar to a 
light room, young larvae were observed wandering up the sides of 
the jars. In the dark cellar such wandering took place, but after 
light was admitted to the jar the wandering became much accentu- 
ated. Similar wandering of larvae was observed in the cages used 
for observations on living roots (Pis. V, VI, fig. 1; VII). 
Until 1914 no vineyard observations in this direction had been 
made, but in that year wanderers were observed in their normal 
state. For these observations, vines in a phylloxera " spot " in a 
Zinfandel vineyard 10 years old were selected. This "spot" was 
situated on light clay loam upon sloping ground, and within its 
confines wandering larvae were observed during July and August. 
These were found in greatest numbers coming from vines near the 
outer edge or periphery of the "spot." Such vines had little ex- 
ternal evidence of phylloxeration, but upon examination it de- 
veloped that the roots were heavily infested and produced many 
migrants as well as wanderers. From vines obviously moribund a 
smaller number of wanderers appeared. Wanderers also were ob- 
tained on the same horizontal boards with sticky papers on which 
migrants were caught. These were captured close to the edge of 
the sticky substance and never farther from it than 6 mm., and it 
appeared that all those taken had crawled to the papers and that 
none had been borne on the wind. On vertical papers, not even 
when placed within 2 feet of the wanderers, and to the leeward of 
them, were any phylloxerae captured. It was observed, however, 
that on favorable occasions wanderers are easily borne off by gusts 
of wind. The part of the vineyard in which wanderer activity oc- 
curred was moderately well cracked through drying. On the hori- 
zontal sticky papers wanderers were caught at points from a few 
inches from the vine trunk to 5 feet from the nearest vine and 
directly in the center of a square described with a vine at each angle. 
In this latter case either the phylloxerae had ascended by the trunk 
of the vines, and then walked 5 feet, or else they had ascended by 
means of cracks nearer the paper. In either case it is obvious that 
the spread of a given phylloxera " spot " may result from the activi- 
ties of these wanderers without the agency of wind. 
