80 
exposed for three and a half hours to 1 in 90 gas, and two specimens 
out of seven, placed between box covers screwed together so that the 
insects were held but not crushed, survived two hours of treatment 
with 1 to 125 gas. A beam of light was visible between the boards, 
and the survivors were found within 5 inches of the edge. <A thin 
covering of dry dust or earth seems a great protection. Living sow — 
bugs and earwigs were found along with numerous dead ones on the 
surface dirt of the plague room mentioned above as having been 
treated for two hours with 1 to 125 gas. None of the creatures were 
in sight when the room was closed, and the presumption is that those 
that escaped destruction were disturbed from the rubbish on the 
earthen floor too late to get a lethai dose. 
Grain insects have been experimented with to determine if a mass 
of grain was sufficiently penetrated by the gas to effect the destrue- 
tion of those contained therein. <A series of tests with this object in 
view was made in a tight glass-sided case inclosing 4.16 cubic feet of 
space. To insure accuracy the cyanide employed was weighed out 
on delicate balances. The results of the tests were most disappoint- 
ing and have led to our abandonment of hopes that the gas would 
serve as a substitute for carbon bisulphid in the treatment of stored 
grain. Strengths of gas up to 1 ounce to 12 cubic feet (10 grams to the 
ease) were found inefficient to destroy Calandra oryza, C. granaria, 
and other common grain insects in an exposure of forty-two hours. 
In the test with the strongest gas a grain bag containing about a half- 
bushel of refuse corn mixed with coarse mill screenings alive with 
the insects was exposed. The case was tight, the chemical reaction 
perfect, and the gas still strong at the end of the forty-two hours; yet 
scores of the insects escaped death. Throughout the series it was 
evident that the air within even small bulks of material remained 
harmless to the insects a short distance from the surface.. The insects 
which crawled away from the mass and those at or very close to the 
surface were generally destroyed. 
THE USE OF HYDROCYANIC ACID GAS FOR EXTERMINATING 
HOUSEHOLD INSECTS. 
By W. R. BEatTTIE, Washington, D. C. 
With the growth of our population and the consequent crowding 
together of residences, the problem of the prevention and control of 
household insects is deserving of careful consideration from a sanitary: 
standpoint, but one that is usually overlooked. These pests are to be 
found in fewer or greater numbers, both of species and individuals, 
in every dwelling, office, or storehouse, and no_ perfectly efficient 
means, either to prevent their gaining an entrance or to exterminate 
them when they are once established, has as yet been devised. 
Recent successful applications of hydroeyanic-acid gas for the 
extermination of insects infesting greenhouse plants have suggested 
