THE GRAPE PHYLLOXERA IN CALIFORNIA. 105 
trunk is considered as the central point. On two occasions wan- 
derers were caught on paper placed equidistant (5 feet) from four 
trunks of infested vines. Examinations showed that between one 
vine and another, even of apparently equal phylloxeration, a great 
variation in the production of wanderers took place. It also ap- 
peared that there was a tendency to produce these forms all at one 
time as though they had collected in a mass and then issued all to- 
gether. As regards the time of day at which they were most abund- 
ant, it appeared that more might be observed between 10 a. m. 11 and 
1 p. m. than at other daylight hours. European observers found 
that in general the wandering larvae appeared in greatest abundance 
in the early afternoon, which is the hottest part of the day. 
Vineyard observations were continued in 1*915. The same vine- 
yard was used, but more attention was paid to phylloxerated vines 
on the parts in which the soil was a heavy black clay. On 
this heavy soil no wanderers appeared before July 24, and none 
was found after July 29. The larvae also were always very scarce, 
notwithstanding the fact that the soil contained numerous cracks 
which would enable the wanderers to reach the surface. On the 
lighter soil (clay loam), wandering larvae first appeared July 14, 
and they continued to issue until August 18. During this period 
of over a month about two -thirds of the phylloxerated vines exam- 
ined were producing wanderers. Between July 15 and 21 they 
were most abundant, as many as 20 or 30 living individuals being 
visible at one time beside the more heavily infested vines. In 
August hundreds of dead larvae could be seen on the surface of the 
soil around the bases of the vine trunks, and large numbers were 
caught in spider webs. As in the previous year, the vines bearing 
the largest numbers of wanderers were those of recent phylloxeration. 
In 1915, during the period of wanderer activities, the weather was 
for the most part quite hot and dry. Occasionally there were cool 
days, and on these the wanderers appeared to be as active as on the 
hot days. 
It appeared certain that the great majority of the wandering larvae 
ascended to the light by way of the main trunk of the vines, around 
w T hich there occurred almost always a wide crack. More issued from 
Zinfandel vines than from Carignan vines equally phylloxerated, 
perhaps because the Zinfandel had thrown out more fleshy rootlets in 
May and June, and these had decayed in July while heavily infested. 
It would thus appear that many of the wandering larvae are pro- 
duced on these surface fleshy rootlets and leave them because they 
have become overcrowded or have started to decay. 
In each of the years 1914 and 1915 wandering larvae appeared in 
the vineyard over the same period, i. e., from the middle of July to 
11 All references to clock time refer to " Standard time." 
