40 BULLETIN 903, IT. S. DEPARTMENT OF AGRICULTURE. 
is curtailed and commences late. On nodosities and tuberosities 
which have remained fresh during winter, the succulent condition of 
the food induces early growth on the part of the phylloxera?. 
Hibernation under cellar conditions. — During the period 1911-1915 
hibernation was observed on severed roots in the laboratory cellar. 
These roots were kept in glass battery jars and in petri dishes and 
remained in a fresh condition when systematically moistened. Good 
callus growth and sometimes fleshy offshoots were obtained, es- 
pecially when a layer of moist sand was placed in the bottom of the 
dishes. The phylloxera? caused the formation of lesions in similar 
manner as on roots of living vines. 
Under cellar conditions hibernation was often prolonged beyond 
the period found to occur in the vineyards, and this prolongation re- 
sulted in a small number of phylloxeras maturing very late. The 
" awakening " period in spring was not different from that found 
in the vineyards under equalized temperatures. Under cellar con- 
ditions a greater mortality existed among hibernants than in the 
vineyards. This was supposedly due to the greater range of daily 
temperatures, to the abnormal condition of the roots severed from 
the vine, and to the apparent lack of sap flow. In the cellar hiber- 
nants a greater variation in size and color existed, even in unmolted 
phylloxeras, than in the vineyard on living vines. A very small per- 
centage of hibernants were observed to pass the winter in the second 
and third instars. Eggs were never observed to pass the winter, 
since all eggs laid late in the year hatched in due course according to 
temperatures. No mature or fourth-instar phylloxera? were observed 
to hibernate. Adult radicicoles in late autumn, as at other times, 
lived for some days or even weeks after they deposited their last egg, 
but none was found that survived until spring. 
Observations on the hibernation of phylloxera? reared on sev- 
ered roots under cellar conditions may be summed up as follows: 
The first phylloxera? entered hibernation as early as August, in ex- 
treme cases in July, and the percentage of hibernating individuals 
from that time gradually increased. By October 1, it was found 
that on the average about 30 per cent of the individuals were hiber- 
nants. By the last of October from 85 to 90 per cent were hibernants. 
All the living phylloxera?, however, were not hibernants until the end 
of December, and during November and December a dwindling num- 
ber of adults and unhatched eggs were observed. All larva? hatching 
after November 1 settled down to hibernate, and about three- fourths 
of those which hatched in October did likewise, the individuals com- 
prising the other fourth maturing toward the end of October and 
in November and continuing to deposit eggs up to December. 
