80 



exposed for three and a half hours to 1 in 90 gas, and two specimens 

 ont 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 3 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 lethal dose. 



Grain insects have been experimented with to determine if a mass 

 of grain was sufficientlj' penetrated b}' the gas to effect the destruc- 

 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 treatmc^nt of stored 

 grain. Strengths of gas up to 1 ounce to 12 cubic feet (10 grams to the 

 case) were found inefficient to destroy Calandra oryza, C. granariay 

 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 fortj^-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 awa}^ from the mass and those at or very close to the 

 surface were generallj^ destroyed. 



THE USE OF HYDROCYANIC ACID GAS FOR EXTERMINATING 

 HOUSEHOLD INSECTS. 



By W. R. Beattie, Washington, D. C. 



With the growth of our population and the consequent crowding- 

 together of residences, the problem of tlie 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 ]io 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 liydrocyanic-acid gas for the 

 extermination of insects infesting greenhouse plants have suggested 



