DISINFECTION AGAINST MOSQUITOES WITH FORMALDEHYD 
AND SULPHUR DIOXID. 
[By M. J. Rosenau, Passed Assistant Surgeon, Director of the Hygienic Laboratory, 
U. S. Marine-Hospital Service.] 
Until lately, mosquitoes and flies were looked upon merely as annoy- 
ances, but since it has been proved that they are able to transmit the 
infection of pestilential diseases, we must now regard them as danger- 
ous vermin. When the matter is generally understood, it will be a 
greater reproach to the housewife to have mosquitoes and flies in the 
home than bed bugs, and it is the duty of sanitarians to spread an abhor- 
rence for these most common and most dangerous of domestic pests. 
The mosquito is known to transmit the infection of malaria and filari- 
asis. The theory of Finlay, so brilliantly proven by Eeed and his col- 
leagues (Carroll, Lazear, and Agramonte) of the Army Medical Com- 
mission, that the mosquito transmits yellow fever must now be accepted 
as an established fact. One of the next problems is the destruction of 
the infected mosquitoes, and we have undertaken the following work 
to test the insecticidal value of formaldehyd gas and sulphur dioxid 
in the work of practical disinfection : 
METHODS. 
In our experiments we have endeavored to imitate the conditions 
found in actual practice in so far as they were compatible with accurate 
control of the results. 
The mosquitoes used were good specimens of the Cidex pungens raised 
in our laboratory. The insects were from one to seven days old and 
consisted of males and females in about equal proportions. They were 
exposed in battery jars covered with gauze, or in small pill boxes with 
gauze lids. The battery jars were used in order to allow the moscjui- 
toes to seek and choose their own iTrotection. To this end, crumpled 
crash toweling and paper, sometimes dry, sometimes moist, were placed 
loosely in the jars. It was always found that the insects would hide in 
the more remote folds and corners, thus often entirely escaping the 
stronger pei centages of the gas. 
After this self-protecting instinct was clearly demonstrated, mosquitoes 
were placed in pill boxes, as with tliese we were able to expose the insects 
Acknowledgment. — I am pleased to acknowledge the assistance rendered by Asst. 
Surg. S. B. Grubbs, U. S. Marine-Hospital Service, not only in conducting under my 
direction about half of the experiments, but for valuable sugge-stions throughout the . 
work. 
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