386 BEDBUGS AND THEIR ALLIES 



every case every bedbug was killed and none of the eggs showed 

 signs of hatching in 12 days. According to experiments made by 

 the U. S. Public Health Service five ounces of powdered potas- 

 sium cyanide per 1000 cubic feet is sufficient for the destruction 

 of bedbugs, four ounces for mosquitoes, two and one-half ounces 

 for fleas and ten ounces for lice. 



Sulphur. — The fumes of burning sulphur, sulphur dioxide, 

 rank next to hydrocyanic acid gas as both a disinfectant and an 

 insecticide, but they have a serious disadvantage in their tendency 

 to bleach fabrics and to tarnish metals, especially in a humid 

 atmosphere. Sulphur dioxide is considered the most effective 

 remedy for mosquitoes in cellars, barns, etc., since it kills these 

 insects even when very dilute, and it has remarkable penetrating 

 power. The methods of sealing rooms or buildings are similar 

 to those described for hydrocyanic acid fumigation. All dyed 

 goods and metallic articles, however, must be removed or covered 

 with vaseline. Two pounds of sulphur is used to 1000 cu. ft., 

 more if the building cannot be tightly sealed. The sulphur is 

 placed in some suitable dish with a little wood alcohol poured on 

 it to make it burn more readily. In order to avoid danger of fire, 

 the dish of sulphur should be placed on bricks or in a tub of shal- 

 low water before igniting. After two hours the place may be 

 opened and ventilated. 



Other Fumigants. — Another effective insecticide is the vapor 

 of carbon bisulphide, a poisonous gas which is not nearly so 

 virulent as hydrocyanic acid gas. As its vapor is heavy it 

 settles rapidly. Its effect on many insects is less certain than in 

 the case of the hydrocyanic acid gas and it has the additional 

 disadvantage of being both inflammable and explosive. Re- 

 cently cresyl or creolin, a very volatile substance, has come into 

 favor as a fumigating medium, especially for destro3dng mos- 

 quitoes. It is not injurious to higher animals in the strength 

 used (125 cc. to 1000 cubic feet), does not injure household goods 

 and is destructive to all exposed insects. It is volatilized by 

 means of an alcohol lamp. Cresyl does not, however, have the 

 penetrating power of hydrocyanic acid gas or sulphur, and is 

 therefore of less value for such secretive insects as bedbugs, 

 though highly valuable for exposed insects, such as mosquitoes, 

 since they may be destroyed without having the rooms vacated. 

 Formaldehyde, though a valuable disinfectant, i.e., active in 

 the destruction of microorganisms, is not an effective insecticide. 



