2 HYDEOCYANIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 



Perfects 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, at Boston, Mass. Mr. Beattie's experiments 

 were against cockroaches and Mr. Kirkland's in one case against 

 fleas and in other against clothes moths. 



During the j)eriocl between 1901 and 1907 hydrocyanic-acid gas 

 was used in practical work by several members of the Bureau of 

 Entomology, under the direction of Mr. Marlatt, many residences 

 and public buildings, schools, churches, and stores being fumigated 

 with practicall}' uniform success. Indeed the efficiency shown by 

 this gas in the control of household insects has led to its adoption as 

 a standard remedy for these j^ests, and it has since been adopted for 

 the destruction of insects affecting stored products, especially for the 

 control of the ]\Iediterranean flour moth {Ephestia kuehniella Zell.) 

 in mills and warehouses. For this purpose it has proven extremely 

 effective, having been used under the direction of agents of this 

 bureau for the destruction of the flour moth in over 100 mills with 

 excellent results. 



Some entomologists recommend as a substitute for hydrocyanic- 

 acid gas a substance Avhich has been more or less effectively used, viz, 

 carbon bisulphid. The great danger in the use of this latter sub- 

 stance, however, from its extreme inflammability and the explosive- 

 ness of its vapor when confined, renders it perhaps less available and 

 more than counteracts the danger to human beings from the use of 

 the hydroc3^anic-acid gas. It has, moreover, been found that the 

 hydrocyanic-acid gas is much more effective for the control of all 

 groups of household insects, Avith the exception of the beetles, than 

 is the other fumigant. 



Entomologists have long noticed that insects vary greatly in their 

 susceptibility to cyanid fumes. The ordinary killing bottle used in 

 making collections contains cyanid of potassium covered with plaster 

 of Paris, which the fumes of tlie cyanid penetrate. Certain weevils, 

 and especiall}^ such weevils as Lixus and Sphenophorus and other 

 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. The experience gained, 

 howeA^er, indicates that the use of hydrocyanic-acid gas in houses is 

 successful against cockroaches, bedbugSj fleas, clothes moths, ants, 

 white ants, house flies, and other soft-bodied insects; and as these 

 constitute the majority of the household pests, the use of the gas 

 must now be considered a standard remedy. Moreover, rats and mice 

 are also killed by its use, and it fortunately has the effect of first 

 causing these animals to rush out from their holes into the open, so 

 that the subsequent annoyance of dead mice in walls and under floor- 

 ings is not experienced. 



