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well, is lasting, and resists the wind, while kerosene alone is easily blown 
aside. Oiling should be done every twelve days during the heat of the 
summer, but less frequently in spring and fall, according to temperature, 
which determines the rate of mosquito development. However, if it is 
desired to control other mosquitoes than the malaria carriers, an applica- 
tion once a week is necessary. Vegetation should first be removed, if pos- 
sible, from the edges of the breeding-places, because it prevents the main- 
tenance of a perfect film. Especially when a wind blows the plants back 
and forth, the surface film can not be kept unbroken. 
4. The Use of Larvicides—A larvicide as used in mosquito control 
is a chemical put into the water and which mixes thoroughly with it to 
kill the larvae. It has been found satisfactory in some situations, espe- 
cially in yellow-fever control work in the Canal Zone. The larvicide most 
commonly recommended is one tested out by the Ancon Hospital Board 
of Health Laboratory in 1911. The stock solution is made as follows :* 
150 gallons of carbolic acid is heated in a tank to 212° F. Then 150 
pounds of powdered or finely broken resin is poured in. Thirty pounds 
of caustic soda are then added, and the solution is kept at the same tem- 
perature until a perfectly dark emulsion without sediment is formed, con- 
stantly stirring after the resin is put in. One part of the emulsion to ten 
thousand of water is said to kill the larvae in less than one half hour, and 
one part to five thousand in five to ten minutes.” 
5. Screening—Screening houses to keep out mosquitoes is very com- 
mon, yet there are many houses, especially in the country, which are not 
protected by screens, and too frequently those used are torn, or do not fit 
tightly, really acting as traps, allowing the mosquitoes to get into the 
house but providing no exit which can be readily found. The malarial 
mosquitoes begin to bite at dusk, and if one keeps inside of a properly 
screened house in the evening, he is quite safe. 
6. Fumigation—Fumigation is of some value when mosquitoes get 
into a house or tent. In such cases burning powdered sulphur or a heap 
of pyrethrum powder should clear them out. Cresol, about four ounces 
to a thousand cubic feet of space, heated in a shallow vessel until vapor- 
ized, is often recommended. 
%. Use of Palliatives on Mosquito Bites—Those who are especially 
sensitive to mosquito bites will profit by recent experiments of Dr. H. E. 
_Ewing.* He found rubbing helpful in diffusing the poison. Although 
it increased the itching at first it presently caused it to cease. Strong 
alcohol and strong ammonia were more useful than dilute alcohol, dilute 
ammonia, soap, or bay rum. 
SUMMARY 
1. Malarial disease is common in southern Illinois, causing some 
loss of life and a large loss of time and money. 
* Farmers’ Bull. 444, U. S. Dept. Agr. 
*“The Use of Palliatives for Mosquito Bites,” Journ. Econ. Ent., Vol. XI, 
pp. 401-404. 
