The invention is a method for attracting mosquitoes by producing a volatilized acid by combining an acid precursor with water to produce the humidified vapor acid attractant, preferably hydrogen chloride. The humidified volatilized acid can be further combined with carbon dioxide, or carbon dioxide can be simultaneously produced to attract mosquitoes. The acid precursor can be a hydrate of ferric chloride, such as ferric chloride hexahydrate. The acid precursor can be impregnated in a carrier, and can be combined with water through exposure to water vapor in the atmosphere, the intentional addition of water, or water produced by a chemical reaction.
