FUMIGATION METHODS 
CEA Pia 
ECONOMIC USE OF HYDROCYANIC ACID GAS 
HE discovery of the value of hydrocyanic acid 
gas as an insecticide was due to the presence 
of the cottony cushion scale in the citrous 
orchards of California. This insect was un- 
wittingly introduced into California from Australia. 
For a time it seemed certain that the pest would ruin 
the orange and lemon industry in spite of the con- 
certed efforts of the most intelligent horticulturists to 
combat it. Despairingly, the growers appealed, as a 
last resort, to the United States Department of Agri- 
culture for aid. The matter was taken up by the 
Division of Entomology, and two assistants were 
detailed by Dr. C. V. Riley, then Entomologist, to 
undertake the study of methods for the control of the 
insect. These assistants were D. W. Coquillett and 
A. Koebele. To Mr. Coquillett belongs the credit of 
first discovering the value of hydrocyanic acid gas, 
now so extensively used, for the destruction of insects 
and other animal pests. 
In addition to the detailed account of the gas treat- 
ment given by Mr. Coquillett, in the report of the 
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