THE GRAPE PHYLLOXERA IN CALIFORNIA. 53 
and those in the saucers above were also plugged with cotton. This 
procedure tended to prevent the phylloxerae from leaving the exposed 
portion of the root between the saucer of the upper pot and the 
surface of the lower. This exposed portion of living root averaged 
about 4 inches in length. 
Scaffolding was built above the trench and a rope and pulleys pro- 
vided in order that the cages might be raised and set in place on the 
stand for examination of roots. Electric connections were also pro- 
vided so as to enable the cages to be examined after dark. 
The cages above described were designed by R. L. Nougaret. 
DEVELOPMENT OF THE RADICICOLE LARVA. 
The young radicicole larva (PL IX, g, 7i, p. 64), upon hatching 
from the egg, seeks a place on the root where it may implant its beak 
and settle down to feed. During the summer some of the newly 
hatched larvae desert the vine and go in search of other vines, travel- 
ing either through cracks in the soil or over its surface. Newly hatched 
larvae are very active at all times and, being flat, can go through 
very small passages. Considering only those that remain on the 
vine on which they were born, it is found that the length of time 
elapsing between the hatching and settling on the root surface varies 
according to conditions of food at hand. On a decaying root the 
insect may not find a location for several hours, but if the root is 
sound the larvae mostly settle down immediately close by the egg- 
shells. 
A certain percentage of larvse always wanders about on the roots 
before finally settling. Many of these make their way outward and 
downward to the smaller rootlets, while others (mostly of the hiber- 
nant generation) in the fall make their way up to the bases of the 
larger roots and even to the main trunk. Larvae hatching on a 
decayed root usually leave it, but occasionally they remain and die 
of starvation. Observations on pieces of severed roots kept under 
cellar conditions indicated very little movement of the young larvae, 
provided their food was in good condition and they were not too 
much crowded. In the summer, however, large numbers deserted 
the roots in a manner similar to that observed in the vineyards, and 
these were apparently imbued with a wandering instinct. 
On vinifera vines young larvae prefer to settle on succulent parts 
of roots or rootlets. When they settle on growing rootlets, they 
generally cause the formation of nodosities, and on the roots of one 
or more year's growth the formation of tuberosities. They fre- 
quently settle on lesions already formed by older phylloxerae, and 
sometimes they settle and mature on the root without causing any 
perceptible lesion. When no lesion is formed, the insects develop 
