818 
c578 10. 46, SECOND SERIES. 
ale ited States Department of Agriculture, 
DIVISION OF ENTOMOLOGY, 
L. O. HOWARD, Entomologist. 
HYDROCYANIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 
The use of hydrocyanic-acid gas for nursery stock affected by 
insects is described in Circular No. 42 (second series), of this Office. 
Its use on trees in orchards is described in the Yearbook of the 
U.S. Department of Agriculture for 1900 (pp. 257-260). 
Recently it has been fully demonstrated that this gas is an excellent 
remedy for household insects. Probably its first use for this purpose 
was in June of 1898 by Mr. Marlatt, of this Office, against Psocids 
in the residence of Mr. G. K. Holmes, of the Division of Statistics 
of the Department of Agriculture, using the cyanide first at the ordi- 
nary strength employed on fruit trees, then double, and finally quad- 
ruple the strength. The Psocids came from recently introduced 
leather-covered furniture, the covering of which was so tightly fastened 
as to be almost, if not quite, impervious to the gas; and the treatment 
was only partially successful. Another early use of this gas for house- 
hold insects was in 1899in San Francisco by Mr. Alexander Craw, Chief 
Quarantine Officer of the Board of Horticulture. In this case it was 
used against bedbugs, and in very small proportions. Two and one- 
half fluid ounces of commercial sulphuric acid and 25 ounces 98 per 
cent cyanide of potassium were used in a house of several rooms, each 
containing about 2,250 cubic feet of space; the rooms were closed 
for two hours, then entirely aired. The operation was apparently 
successful. 
To determine its availability against the insect enemies of stored 
products or in granaries, some experiments were made during 1898 and 
the spring of 1899 by Messrs. Marlatt and Chittenden, of this Office, in 
the presence of D. G. Fairchild and others, against certain grain weevils 
and the Angoumois grain moth, but with imperfect success, although 
the proportions used were much greater than in Mr. Craw’s experiment. 
In his recent book on fumigation methods, Prof. W. G. Johnson states 
that he used the hydrocyanic-acid gas in a granary and storehouse in June, 
1899, using -it at the rate of 0.1 gram of cyanide per cubic foot of space. 
The granary was affected by weevils. and, from the report of the owner, 
it appears that most of them were destroyed, though many escaped. 
During the same month in an Ohio mill another experiment of this 
kind was carried on under Professor Johnson’s instructions. The 
owner considered the experiment to be a most grand success. The 
Mediterranean flour moth and certain granary beetles were destroyed. 
