376 MOSQUITOES OF NORTH AMERICA 



elusions with regard to the latter substance in a previous paragraph. Formal- 

 dehyde gas, on account of its germicidal use, was early suggested against mos- 

 quitoes when their importance in the role of carriers of disease was ascertained, 

 so that exact experimentation was necessary. Eosenau's results were as follows : 



"Formaldehyd gas is a feeble insecticide. Mosquitoes may live in a very 

 weak atmosphere of the gas overnight. It will kill them, however, if it is 

 brought in direct contact in the strength and time prescribed for bacterial dis- 

 infection. For this purpose any of the accepted methods for evolving the gas 

 is applicable, but the methods which liberate a large volume in a short time aru 

 more certain than the slower ones. 



" Direct contact between the insects and the gas is much more difficult to 

 obtain in ordinary room disinfection against mosquitoes than against germs, 

 because the sense of self-protection helps the former to escape from the effects 

 of the irritating gas. They hide in the folds of towels, bedding, clothing, hang- 

 ings, fabrics, and out-of-the-way places where the formaldehyd gas does not 

 penetrate in sufficient strength to kill them. The gas is polymerized and de- 

 posited as paraform in the meshes of fabrics, which prevents its penetration, and 

 large quantities are lost by being absorbed by the organic matter of fabrics, 

 especially woolens. In our tests, whenever the insects were given favorable 

 hiding places, such as in crumpled paper or in toweling, they quickly took ad- 

 vantage of the best place for themselves and thus escaped destruction. 



" There is a striking analogy between the strength of the gas and the time of 

 exposure necessary to penetrate the fabrics in order to kill mosquitoes, and the 

 strength and time necessary to penetrate in order to kill the spores of bacteria. 



" Mosquitoes have a lively instinct in finding cracks or chinks where fresh 

 air may be entering the room, or where the gas is so diluted that they escape 

 destruction. They are able to escape through incredibly small openings. Some 

 of the smaller varieties, such as the stegomyia fasciata can get through a wire 

 screen having 12 meshes to the inch. Therefore, formaldehyd gas can not be 

 trusted to kill all the mosquitoes in a room which can not be tightly sealed. 



" It is concluded, that to succeed in killing all the mosquitoes in a closed 

 space with formaldehyd gas, the following definite requirements are essential : 

 A very large volume of the gas must be liberated quickly, so that it may diffuse 

 to all portions of the space in sufficient concentration. The room must have 

 all the cracks and chinks where the insects may breathe the fresh air carefully 

 sealed by pasting strips of paper over them. The room must not contain heavy 

 folds of drapery, clothing, bedding, or fabrics in heaps, or so disposed that the 

 insects may hide away from the full effects of the gas." 



REMEDIES FOR MOSQUITO BITES. 



It must have been the experience of most people that ordinarily little swell- 

 ing and irritation results from the puncture of a mosquito where there has been 

 no scratching or rubbing of the part. But individuals vary greatly in this 

 respect and it is undoubtedly true that not only do different species of mos- 

 quitoes vary in their effect but that different individuals of the same species may 

 also vary. The application of household ammonia has been found by many to 

 give relief and alcohol is also said to stop the irritation. Dr. E. 0. Peck, of 

 Morristown, N". J., finds glycerine a sovereign remedy. Touch the bite with 

 glycerine and in a few minutes the pain is gone. Dr. Charles A. Nash, of Kew 

 York City, marks the punctures with a lump of indigo and states that this 

 instantly stops the irritation, no matter whether the application is made im- 



