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. Unfortimately, 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 simrise, 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 

 adtdt, even when starved, would not 

 bite when the temperature was below 

 23° 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° and 25° and that the optimum 

 temperature was between 27" and 30° C, but their experiments led 

 them to believe that it would bite in nature at a temperature as 

 low as 17° 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- 

 groimd cisterns which are in general use. Often the larvae (fig. 1356) 

 are foimd 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 chtirches. 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. 



