bw 
SB 
818 
10.46, SECOND SERIES, REVISED EDITION.! Issued February 20, 1907. 
a ee en Or 
ited States Department of Agriculture, 
BUREAU OF ENTOMOLOGY, 
L. O. HOWARD, Entomologist and Chief of Bureau. 
HYDROCYANIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 
e By L. O. Howarp. 
Hydrocyanic-acid gas is one of the most effective remedies known 
against various classes of insects. For more than twenty years it has 
been the principal means of controlling scale insects on citrus trees in 
California and is now in general use for the disinfection of all deciduous 
nursery stock and other plant material for shipment, and is also one of 
the most effective methods of ridding greenhouses and cold frames of 
plant-lice, thrips, white fly, and various scale pests which infest plants 
grown under glass.” 
It has been fully demonstrated that this gas, which is very deadly to 
all forms of animal life, is, under proper precautions, 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 book-lice in 
the residence of an employee of the Department of Agriculture, using 
the cyanide first at the ordinary strength employed on fruit trees, then 
double, and finally quadruple the strength. The book-lice 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 household insects was in 1899 in 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 24 
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. 
Perfectly successful experiments were made during the summer of 
1901 by Mr. W. R. Beattie, of the Department of Agriculture, and by 
Mr. A. H. Kirkland, of Boston, Mass., formerly Secretary of the Asso- 
ciation of Economic Entomologists. Mr. Beattie’s experiments were 
against cockroaches and Mr. Kirkland’s in one case inst fleas~and 
in the other against clothes moths. A\\s snian Institute, s 
ief ieee of CHIer, 
fin! 172: 
1 Revised by C. L. Marlatt, Entomologist and Acting 
?Refer to Circulars 37, 42, and 57, and Farmers’ Bul 
