2 
Perfectly successful experiments were made, however, during the 
summer of 1901 by Mr. W. R. Beattie, of the Department of Agricul- 
ture, and by Mr. A. H. Kirkland, of Boston, Mass., formerly Secretary 
of the Association of Economic Entomologists. Mr. Beattie’s experi- 
ments were against cockroaches, and Mr. Kirkland’s in one case against 
fleas and in the other against clothes moths. 
Entomologists have long noticed that insects vary greatly in their 
susceptibility to cyanide fumes. The ordinary killing bottle used in 
making collections contains cyanide of potassium covered with plaster 
of Paris, which the fumes of the cyanide penetrate. Certain weevils, 
and especially such weevils as Lixus and Sphenophorus and other hard- 
bodied forms, will frequently be left overnight in a cyanide bottle and 
recover after being removed. It has been noticed, also, that in green- 
houses certain insects recover. The experience gained, however, indi- 
eates that the use of hydrocyanic-acid gas in houses is successful 
against cockroaches, bedbugs, clothes moths, ants, white ants, house 
flies, and other soft-bodied insects; and as these constitute the major- 
ity of the household pests, the use of the gas must now be consid- 
ered a standard remedy. Moreover, rats and mice are also killed by 
its use. 
Some entomologists recommend as a substitute for hydrocyanic-acid 
gas a substance which has been more or less effectively used, viz, 
carbon bisulphide. The great danger in the use of this latter substance, 
however, from its extreme inflammability and explosiveness of its 
vapor when confined, renders it, perhaps, less available and more than 
counteracts the danger to human beings from the use of the hydro- 
ecyanic-acid gas. 
Recent experience indicates that in order to destroy the household 
insects mentioned, one fluid ounce of commercial sulphuric acid, diluted 
with two fluid ounces of water, to increase the bulk of the liquid and 
insure complete chemical action, and one ounce of high-grade (98 per 
cent) cyanide of potassium must be used for every 100 cubic feet of 
space. 
Before performing the operation the house must be vacated, and it 
is well to do this just before nightfall. It 1s not necessary to remove 
any of the furniture or household belongings unless of polished nickel 
or brass, which may tarnish a little. Liquid or moist foods, as milk 
or other larder supplies that are not dry and might absorb the gas 
should be removed from the house. All fires should be put out, for 
while the gas will not burn under ordinary conditions, it is as well to 
take no risks. 
On the floor of each room should be placed a large porcelain wash 
basin, and into each wash basin should be poured the proportionate 
amount of water and sulphuric acid. It may be well to place under 
each wash basin a thick layer of newpapers, in order to avoid 
