EXPERIMENTS WITH FUMIGATION. 37 
The fig moths, as has been stated in other portions of this bulletin, 
usually soon die out in America and are replaced in this country in 
the same material by the Indian-meal moth, which is more hardy and 
more nearly omnivorous. 
HYDROCYANIC-ACID GAS. 
Experiment No. 1.—June 23, at 4.05 p m., in a recorded tempera- 
ture of 94° an experiment was made in the hope that the temperature 
would continue or increase, as frequently happens in the District of 
Columbia. In this experiment, which was conducted under the 
writers’ personal supervision, Messrs. Duckett and O’Neill assisted. 
June 24, Mr. O’Neill made count of the insects after removal from 
the fumigator at 4.05 p.m. It will be seen that this was the usual 
94-hour exposure. The proportions used were 6 ounces of sodium 
eyanid and 6 ounces of sulphuric acid to 1,000 cubic feet of air space. 
Owing to atmospheric conditions probably the exact temperatures and 
other conditions were not recorded, but the minimum was not lower 
than 80°, which would give a mean temperature of about 85°F. 
This experiment was conducted chiefly for the purpose of testing the 
results on the Indian-meal moth (Plodia interpunctella). Large 
“numbers of these were in dried figs, packed as closely as possible. 
The result was that only 60 per cent were killed, showing that a 
relatively heavier dosage is necessary to kill this insect than is the 
case with bisulphid of carbon.¢ 
EHxperiment No, 2—Owing to the failure of the first hydrocyanic- 
acid gas fumigation experiment, undertaken June 23, a second ex- 
periment was found necessary. This was started at 3.45 p. m., June 27, 
and the same formula, 10 ounces of potassium cyanid and 10 ounces 
of sulphuric acid to 1,000 cubic feet, was used. The temperature 
during this period was 92° at the beginning, the lowest temperature 
recorded, between 6 and 8, being 80°, when the fumigation was com- 
pleted. The mean temperature was about 85° F. Exposure was as 
before, exactly 24 hours being the time. The Indian-meal moth larve 
and adults in figs were all killed. The*same was true of their occur- 
rence in meal. The granary weevil was completely destroyed, and the 
same is also true of the lesser grain borer and the saw-toothed grain 
beetle. Only one species of insect survived: Four living adults of 
the Zribolium confusum, the confused flour beetle, in meal were not 
killed. It would be difficult to determine the percentage in this case.? 
« Of other insects treated at this time, specimens of the lesser grain borer (Rhizopertha 
dominica Fab.) were all destroyed, furnishing additional testimony of the weak resistant 
power of this species to both gases. 
»The larve and moths of the Mediterranean flour moth (Ephestia kuehniclla Zell.) 
were also all killed, and the same was the case with the Indian-meal moth in meal. The 
saw-toothed grain beetles (Silvanus surinamensis L.) were all destroyed, but of the 
granary weevil (Calandra granaria L.) only 82.5 per cent were destroyed. In the case 
of the rust-red flour beetle (Vribolium navale Fab.) three larye were living. The 
four-spotted bean weevil (Bruchus [Pachymerus] quadrimaculatus Fab.) was destroyed. 
