Studies on the Responses of the FemaleAëdesMosquito. Part I.—The Search for Attractant Vapours

Abstract

The question of the attractancy of water-vapour, carbon dioxide and candidate attractant compounds was investigated by the use of an olfactometer emitting freely into a 360-cu. ft. cage filled with female adultAëdes aegypti. Moist air (85 per cent. R.H.) was found to attract 3–5 times as many mosquitos as dry air (15 per cent. R.H.). A moistened billiard-ball was found to attract about seven times as many mosquitos as a dry one, the result being similar whether black or white balls were used. The attractancy was reduced and even reversed at very high room humidities.The addition of 10 per cent. CO2to a dry air stream approximately doubled its ability to bring mosquitos within 0·5 inches of the olfactometer port. Its addition to a moist air-stream did not significantly increase its attractancy. Pure CO2vapour proved to be no more attractive than dry air, and several times less attractive than moist air.A number of chemical compounds found in body exudations, and some housefly attractants, were tested in the olfactometer for their effect onAëdesadults. None were consistently attractive, and many were significantly repellent. However, sweat itself proved significantly attractive at a low vapour concentration, while significantly repellent at a high concentration.