97 



DISINFECTION EXPEEIMEUTS. 



A few tests were made to determine the relative efficiency of sul- 

 phur dioxid, tobacco smoke, and pyrethrum as insecticides with par- 

 ticular reference to the Stegomyia fasciata. 



A small room and hallway containing 1,200 cubic feet of air space 

 were used in these experiments. The room contained a large window 

 and one door, which were made reasonably tight to prevent the escape 

 of the fumes, and the mosquitoes were exposed in cages in various 

 parts of the room. 



Experiment No. 1 — Tobacco. — One pound of tobacco per 1,000 

 cubic feet; exposure, one hour; result, some mosquitoes survived. 



Six hundred and twenty-five grams of tobacco, which is about the 

 proportion of 1 pound.per 1,000 cubic feet, were burned in a pan in the 

 center of the room. The cages containing the mosquitoes were placed 

 on the floor, near the ceiling, and on a chair. 



The room was opened one hour after the tobacco was lighted, 

 which was done by means of alcohol. The mosquito cages were 

 immediately removed and placed in a current of fresh air in order to 

 give the mosquitoes a favorable opportunity to revive. 



All the mosquitoes in the cage which was near the ceiling were dead. 

 Of those in the cage on the chair, one female was flying actively 

 about; the other females and another male were all dead. Those in 

 the cage that stood on the floor were stupefied, but none was killed, 

 most of them flying actively about. 



The tobacco was completely consumed in this process, and the 

 fumes upon opening the door were very strong. The unpleasant odor 

 was very persistent and disagreeable. 



Experiment No. 2 — Tobacco. — Two pounds per 1,000 cubic feet; 

 exposure, two hours ; result, all mosquitoes killed. 



The mosquito cages were immediately removed after two hours had 

 elapsed, at which time none of the insects showed apparent signs of 

 life; but after remaining in the fresh air for three hours a few of 

 them moved their wings and tarsi. None, however, revived. 

 . Experiment No. S — Pyrethrum. — Two pounds per 1,000 cubic feet ; 

 exposure, 2 hours ; result, all mosquitoes killed. 



The pyrethrum was burned in a brazier placed upon some sand on 

 the floor. 



Three cages containing many mosquitoes were distributed, one on 

 the floor, one near the ceiling, and one in an open box on the table. 

 The cages had a piece of crumpled gauze upon the bottom ^and a 

 folded handkerchief hanging in the cage, in order to give the insects 

 retreats in which to hide from the effects of the fumes and to test 

 the penetrating action of the gas. 



All of the mosquitoes were killed. 



