Mosquitoes and Yellow Fever 
207 
in dark comers, under picture moldings and behind the heads of 
old-fashioned bedsteads. It will enter closets and hide in the folds 
of garments.”—Howard. 
It was claimed by the French Commission, and subsequently 
often stated in discussions of the relation of the mosquito to yellow 
fever that the mature Aedes calopus will bite only at night. If this 
were true it would be of the greatest importance in measures to 
avoid the disease. Unfortunately, the claim was illy founded and 
numerous workers have clearly established that the exact converse 
is more nearly true, this mosquito being pre-eminently a day species, 
feeding most actively in early morning, 
about sunrise, and late in the afternoon. 
On cloudy days it attacks at any time 
during the day. Thus there is peril in 
the doctrine that infected regions may 
be visited with perfect safety during 
the daytime and that measures to 
avoid the mosquito attack need be 
taken only at night. 
Dr. Finlay maintained that the 
adult, even when stamed, would not 
bite when the temperature was below 
23 0 C, but subsequent studies have 
shown that this statement needs modi¬ 
fication. The French Commission, 
working at Rio de Janeiro, found that Aedes calopus would bite 
regularly at temperatures between 22 0 and 25 0 and that the optimum 
temperature was between 27 0 and 30° C, but their experiments led 
them to believe that it would bite in nature at a temperature as 
low as 17 0 C. 
The yellow fever mosquito breeds in cisterns, water barrels, 
pitchers and in the various water receptacles about the house. In 
our own Southern States it very commonly breeds in the above¬ 
ground cisterns which are in general use. Often the larvae (fig. 135 b) 
are found in flower vases, or even in the little cups of water which 
are placed under the legs of tables to prevent their being overrun by 
ants. They have been repeatedly found breeding in the holy water 
font in churches. In short, they breed in any collection of water in 
close proximity to the dwellings or gathering places of man. 
135a. Aedes calopus. Pupa. 
After Howard. 
