6 
It should not be imagined that because this method is of value 
against the Mediterranean fiour moth and related insects, and soft- 
bodied species like psocids or book-lice, which also occur in mills, 
that it is a sovereign remedy for other insects in mills and other 
inclosures. Quite the contrary; it has been found only partially 
effective and therefore unsatisfactory when used against grain 
weevils, flour beetles, and other hard-bodied insects, and the pre- 
paratory stages of the Angoumois grain moth, although effective 
in. killing the adults of the latter. Indeed, not until very recent 
years has its use become generally recommended for the flour moth. 
Mr. C. H. Popenoe, working under the writer’s direction, in fumi- 
gating primarily for the flour moth, succeeded in killing many of the 
confused flour beetle (Triboliwm confusum Duv.) in two applications 
at 4 ounces to 1,000 cubic feet. A larger percentage was destroyed 
by one application at the rate of 8 ounces, and so on up. Mr, D. K. 
MeMillan had similar good success with 10 ounces. 
In pamphlets published in 1904 Prof. F. L. Washburn has rec- 
ommended hydrocyanic-acid gas for the treatment of the flour 
moth, stating the advantages of this treatment and giving details 
as to the penetrating power of the gas and other matters.¢ 
As an instance of the successful use of hydrocyanic-acid gas, the 
experience of a Kentucky milling firm that was advised to use this 
method of fumigation may be briefly narrated. 
In the city where this firm is located the species had been present 
in their mill four years, yet a few months prior to hearing from them 
the writer did not know of the insects’ occurrence in that State. It 
had been introduced in second-hand machinery. Bisulphid of carbon 
had been used by them previous to their correspondence with the 
writer and was described as ‘“‘no good except for weevils in stored 
grain.” It had been employed at the rate of 300 pounds to 62,400 
cubic feet of air space, or about 5 pounds to 1,000 cubic feet—fully 
twice as strong as necessary in an ordinary mill. Afterwards, by the 
writer’s advice, hydrocyanic-acid gas was employed and the follow- 
ing report was made, August 24, 1909: 
Saturday, July 24, 1909, our mill was fumigated with hydrocyanic-acid gas, using 
18 4-gallon jars, each charged with 3 pounds of cyanid of potassium, 44 pounds of 
sulphuric acid, and 7 pounds of water. We killed moths and their eggs, worms and 
bugs of all kinds, wasps, mud-daubers, spiders, bats, rats, and mice, and also English 
sparrows perched outside on the roof. It has just been one month since we fumigated, 
and we see no more as yet. There is no sense in a miller being pestered with the 
flour moth. Hydrocyanic-acid gas will kill the moth and the eggs. 
Our correspondents also wrote that in their opinion it would be 
difficult to operate any mill infestéd with the flour moth without 
a Ninth Annual Report State Entomologist of Minnesota, pp. 31-36, 1904; Special 
Report State Entomologist of Minnesota, February 29, 1904. 
(Cir. 112] 
