336 SCHOOL ENTOMOLOGY 



much less effective at low temperatures and that the dosage 

 must be greatly increased at temperatures below 60 F. 

 For fumigating buildings " there should be about one square 

 foot of evaporating surface to every twenty-five square feet 

 of floor area, and each square foot of evaporating surface 

 should receive from one-half to one pound of liquid." For 

 fumigating clothing or household goods, place them in a tight 

 trunk and place an ounce of liquid in a saucer just under the 

 cover. The gas is exceedingly explosive; allow no fire or light 

 of any kind around the building or enclosure until it has been 

 well aired. The fumes should not be inhaled, for though not 

 seriously poisonous, they have a suffocating effect and will 

 soon produce dizziness and a consequent headache. Carbon 

 tetrachloride is now used for some purposes in much the 

 same manner as carbon bisulphide, and is not so explosive. 



Hydrocyanic Acid Gas is used for the fumigation of nur- 

 sery trees and plants, certain greenhouse insects, pests of 

 dwelling houses, storehouses, mills, etc., and in California 

 for scale insects on fruit trees. It is made by combining 

 cyanide of potassium, sulphuric acid and water. The gas is 

 slightly lighter than air and is a most deadly poison. It 

 should be used only by thoroughly competent and careful 

 persons who are fully advised as to the method of use for 

 the particular purpose desired. Concerning its use advice 

 should be sought from the State Agricultural Experi- 

 ment Station, or from the State Entomologist, or from the 

 Bureau of Entomology of the U. S. Department of Agricul- 

 ture.* 



Sulphur Dioxid. The fumes of burning sulphur, mostly 



sulphur dioxid, have long been recognized as a standard 



remedy for the fumigation of dwellings and barracks for 



insect pests. Successful fumigation for the bedbug has been 



*See Appendix A, No. 40. 



