376 MOSQUITOES OF NORTH AMERICA 
clusions 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 réle of carriers of disease was ascertained, 
so that exact experimentation was necessary. Rosenau’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 are 
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. 
“Tt 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 New 
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- 
