FARMERS’ 
BULLETIN 
Wasuineron, D. C. 699 Aprit 5,. 1916 
Contribution from the Bureau of Entomology, L. O. Howard, Chief. 
HYDROCYANIC-ACID GAS AGAINST HOUSEHOLD 
INSECTS.’ 
By L. O. Howarp, Hntomologist and Chief of Bureau, and C. H. PorEnon, 
Entomological Assistant. 
INTRODUCTION. 
The purpose of this bulletin is to enable the reader to use hydro- 
cyanic-acid gas safely and effectively as a means of destroying the 
various insect pests of the household, such as bedbugs, fleas, cock- 
roaches, ants, clothes moths, and carpet beetles. 
By way of caution it should be stated at the outset that hydro- 
cyanic-acid gas is extremely poisonous and is fatal to human beings 
if breathed in any quantity, while the chemicals used in generating 
the gas—sodium cyanid or potassium cyanid and sulphuric acid— 
are also very poisonous, the cyanid being necessarily fatal if only a 
small piece be eaten and the sulphuric acid burning badly when com- 
ing in contact with the skin. Special attention is called to the full 
discussion of this subject on pages 6 to 8, under the heading “ The 
cyanid and gas a deadly poison.” Zhe chemicals must be handled 
with the greatest care and the fumigation process must not be under- 
taken until it is thoroughly understood in every particular. 
Hydrocyanic-acid gas has been for more than 20 years one of the 
most effective known fumigants in use against noxious insects. It 
has a wide range of applicability, including the control of scale in- 
sects on citrus and nursery stock and the fumigation of greenhouses 
and cold frames, and it is a standard remedy against insects in mills 
and warehouses.2. As a fumigant against household insects it has 
1A revision of Circular No. 163 of the Bureau of Entomology. 
2Bntomologists have long noticed that insects vary greatly in their susceptibility to 
eyanid fumes. The ordinary killing bottle used in making collections contains cyanid of 
potassium, or cyanid of sodium, covered with plaster of Paris, which the fumes of the 
ecyanid penetrate. Certain weevils, especially hard-bodied forms, will frequently be left 
overnight in a cyanid bottle and recover after being removed. It has been noticed also 
that in greenhouses certain insects recover after fumigation with hydrocyanic-acid gas. 
10614°—16 
