THE GRAPE PHYLLOXERA IN CALIFORNIA. 31 
RESUME OF LIFE HISTORY IN CALIFORNIA. 
A resume of the life history will be presented before all the dif- 
ferent stages and habits of the phylloxera in California are discussed 
in detail. This resume is confined to the biology of the insect on 
viniferas and does not consider the life history on resistant roots. 
Over 99 per cent of the phylloxerse pass the winter as small brown- 
ish unmolted larvae, the remainder hibernating after having passed 
one or two molts. All parts of the root system are used for hibernat- 
ing quarters, but the majority cluster on the larger roots, following 
an upward migration in the fall. 
Coincident with the first sap flow in early spring is the growth of 
the hibernants, but in a given vineyard the earliest individuals com- 
mence to grow fully six weeks before the most tardy ones, so that 
after the foliage has opened, hibernating larvae are still to be found 
on the roots. The development of the hibernants is considerably 
slower than that of the summer broods, and the former mature on 
the average about five and one-half weeks after they commence their 
spring growth. The development of the larvae is at all times influ- 
enced by the quality of food and by conditions of humidity and 
temperature. 
Upon casting its fourth skin, the hibernant is mature and com- 
mences egg deposition. Its progeny are the first-generation phyl- 
loxeras, and these on hatching from the eggs either settle beside the 
eggshell or go in search of new food. Many aphids settle on young 
growing rootlets and produce the fleshy swellings, termed " nodo- 
sities. " Others settle upon older roots and produce swellings, termed 
" tuberosities." Still others develop on roots without causing the 
development of either perceptible swellings or lesions. Individuals 
feeding upon nodosities develop more rapidly than do those on the 
unswollen surface of the root. The nodosities usually decay within 
a few weeks after their formation, and in most cases the destruction 
of the rootlets follows. The tuberosities also usually decay in time. 
The rotting of the nodosities is not very serious, as the vine can 
supply new apical growth, but the decay of the tuberosities leads to 
the decay of the larger roots either wholly or in part, and as a result 
the vitality of the vine is greatly impaired, or the vine is killed 
outright. 
The first-generation individuals are mature in from four to seven 
Aveeks after the eggs have been deposited, and they in their turn 
deposit eggs, which produce further generations throughout the 
summer and autumn. 
Owing to the fact that, under favorable conditions, the adults 
deposit eggs during an average period of 45 days, an overlapping of 
generations ensues during the summer and fall. In order to avoid 
