98 



Experiment No. 4- — Pyrethrum. — Two pounds per 1,000 cubic feet; 

 exposure, two hours; result, all mosquitoes killed. 



Mosquito cages were placed in several parts of the room. At the 

 end of the experiment some of the insects showed signs of life, but 

 none revived. 



Experiment No. 5 — Pyrethrum. — One pound per 1,000 cubic feet; 

 exposure, two hours ; result, all mosquitoes killed. 



The pyrethrum was burned in an open brazier upon the floor in 

 the same room used for the preceding experiments. The mosquitoes 

 were freely exposed to the effects of the fumes in appropriate cages, 

 which were placed upon the floor, near the ceiling, and one inside a 

 box laid upon a table. 



At the end of the experiment the cages were immediately taken to 

 the fresh air and many of the Stegomyia showed signs of life, but 

 none revived. 



Experiment No. ■ 6 — Sulphur. — Three and one- fourth pounds per 

 1,000 cubic feet; exposure,. two hours; result, all mosquitoes killed. 



In this experiment four large rooms and the hallway of our lab- 

 oratory building were fumigated to destroy some mosquitoes that had 

 escaped. The rooms communicated with each other and with the 

 hallway through large openings. No attempt was made to seal the 

 doors and windows or to paste cracks. 



Three pots of sulphur were distributed at points of vantage, each 

 pot containing 20 pounds, the total space to be fumigated being 

 12,280 cubic feet. 



Two hours after the sulphur was lighted the house was opened and 

 it was found that only about two-thirds of the sulphur had burned; 

 that is, about Z\ pounds per 1,000 cubic feet. In this experiment the 

 pots containing the sulphur were not placed in water, the object being 

 to obtain a dry gas and thereby minimize the destructive action of the 

 fumes upon the fabrics and pigments. 



Four cages containing mosquitoes were placed in different parts 

 of these rooms and all were killed. 



As a result of these disinfection experiments we conclude that: 

 While we found tobacco smoke efficacious in destroying the insects, 

 we also found that the method is exceedingly objectionable on account 

 of the persistent and disagreeable odor that it leaves, as well as on 

 account of the yellow stains which remain. Tobacco smoke in con- 

 centrated form stains fabrics, paint work, and other surfaces, but 

 the stains may be removed by washing; still, this forbids its use in 

 parlors and the rooms of fine houses. 



We found that the burning of 1 pound of tobacco per 1,000 cubic 

 feet, with an exposure of one hour, was only sufficient to stupefy the 

 insects. All Stegomyia fasciata were killed by an exposure of two 



