THE GRAPE PHYLLOXERA IN CALIFORNIA. 99 
During the winter of 1913-14, two experiments were made on 
the resistance of hibernants to hot water. The temperatures used 
ranged from 116° to 137° F., and the duration of submergence 
ranged from one to four minutes. A temperature of 120° F. failed 
to destroy the aphids completely, while 125° F. with a submergence 
of one minute destroyed all the insects. Similar treatment of the 
roots of living vines resulted in no appreciable injury to dormant 
plants. 
The same winter, between December 3 and March 17, a series of 
nine experiments were carried out bearing upon the resistance of 
hibernant larvae to submersion in water of ordinary temperatures. 
Pieces of heavily infested grape roots were placed in petri dishes 
under about 1 inch of water. The periods of submersion ranged from 
48 hours (two days) to 1,512 hours (nine weeks). It was found that 
with the lengthening of the submersion period the percentage of 
aphids succumbing increased. A submersion of six weeks, however, 
resulted in the destruction of only 72 per cent of the aphids, one of 
five weeks in 64 per cent mortality, the final test (that of nine weeks) 
alone destroying all the aphids. In tests of from 48 to 168 hours' 
submergence the temperature of the water averaged 47° F., in the 
final test of nine weeks it averaged 55° F., and in four intermediate 
tests of from three to six weeks, 53° F. 
In the light of the results of this series of tests the fact that a 
practical vineyard submersion requires at least two months' flooding 
is not a cause for wonder. 
An observation made during the winter of 1913-14, from Decem- 
ber to February, showed that hibernant larva? can withstand short 
intermittent submersions in water interrupted by periods of low 
temperatures, even passing below 32° F. 
On June 9, 1914, two experiments were conducted, bearing on 
the resistance of eggs of the radicicole to heated water. In four of 
these tests the length of submersion was 90 seconds, and the tem- 
peratures ranged from 112.1° to 131° F. ; in the other seven, the eggs 
were submerged 60 seconds under temperatures varying from 108.5° 
to 132° F. Results showed that a temperature of 123° F., with an 
exposure of 60 seconds, destroyed all eggs. For practical use it is 
desirable to have a temperature of at least 125° F. 
In the experiments the eggs after treatment were placed on pieces 
of vine roots and observed for possible development. Temperatures 
of 123° F. or over killed the eggs immediately, but the lesser tem- 
peratures killed none or only a variable percentage. Those eggs 
not killed hatched normally. 
During June and July, 1914, a series of tests was made with 
radicicole eggs exposed, to atmospheric temperatures varying from 
76° to 90° F. for periods varying from 5 to 60 minutes. With a 
