THE GRAPE PHYLLOXERA IIST CALIFORNIA. 53 



and those in the saucers above were also plugged with cotton. This 

 procedure tended to prevent the phylloxera 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, h, 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 larvae 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 ©rowded, 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 phylloxeras, and 

 sometimes they settle and mature on the root without causing any 

 perceptible lesion. When no lesion is formed, the insects develop 



