24 BULLETIN 842, U. S. DEPAETMENT OF AGRICULTURE. 
all larvae in these experiments at 50° and 52° C, namely, 15 and 
10 minutes, respectively, is exactly half that consumed in accom- 
plishing an identical result with the nematodes inclosed in galls 
which were soaked in water previous to treatment. Thus, the data 
as a whole in Table III show conclusively that the active parasites 
are much more sensitive to high temperatures outside of the pro- 
tective galls than inside of them. 
EFFECT OF CHEMICALS ON THE LARViE. 
As adequate and dependable data regarding the response of larvae 
Jlo some of the chemicals more commonly used as sterilizing and dis- 
infecting agents were not available, the writer has carried out a large 
number of experiments which were planned to obtain such data. 
In these experiments, as in those with hot water, both the free larvae 
removed from galls and the protected larvae inclosed in galls were 
treated. Experiments with the protected larvae will be discussed 
first. 
LARV^ IN GALLS. 
The method of procedure followed in subjecting the nematode 
galls to the chemicals and in determining the effect of the latter 
on the larvae was essentially the same as that used in the hot-water 
investigations; that is, water-soaked galls were submerged in the 
solution for the desired length of time, then washed in water sev- 
eral times, and each opened in distilled water in a Syracuse watch 
glass. The larval contents were subsequently examined microscop- 
ically daily for several days to determine the effect of the treatment. 
The average number of larvae from each lot of galls surviving the 
treatment, as well as other data, is recorded in Table IV. 
By a study of Table IV it will be seen that unheated formalde- 
hyde at strengths of 1 : 640, 1 : 320, 1 : 160, 1 : 100, and 1 : SO produced no 
marked effect on the larvae within two or four hours. Submerged 
in a 1 : 50 solution, however, for two hours only 2 per cent of the 
larvae in the galls remained alive, and when kept in this same 
strength of the chemical for four hours none survived. Likewise, 
all larvae were killed when the galls were treated in 4 per cent for- 
maldehyde for two and four hours, respectively. A 1 : 320 strength 
of the chemical at a temperature of 50° and 52° C. killed less than 
half the larvae when the galls were treated for one, two. and four 
minutes. It was thought that these hot solutions might be effective 
in eliminating the nematode, since Melhus (23) controlled oat smut 
by applying a 1:320 strength at temperatures of 15°, 50°, and 55° 
C. for one minute. In the galls kept in tap water for four days 
and used as a check on those treated with formaldehyde, 95 per cent 
of the nematodes were alive. 
