The response of the malaria mosquito, Anopheles gambiae, to two componentsof human sweat, ammonia and L-lactic acid, in an olfactometer

In an olfactometer study on the response of the anthropophilic malaria mosq uito Anopheles gambiae s.s. (Diptera, Culicidae) to human sweat it was foun d that freshly collected sweat, mostly of eccrine origin, was attractive, b ut that incubated sweat was significantly more attractive than fresh sweat. The behavioural response to L-lactic acid and ammonia, the main constituen ts of sweat, was investigated. L-lactic acid was attractive at one concentr ation only (11.11 mM) and removal of the L-lactic acid from the sweat by en zymatic decomposition did not affect the attractiveness of sweat. Ammonia c aused attraction over a range of 0.1-3.4 M on glass slides and at 0.84-8.40 mu mol/min in an air stream. It is concluded that: human sweat contains ka iromones for host-seeking An. gambiae; ammonia is an important kairomone fo r this mosquito, and that L-lactic acid is not a prerequisite in the attrac tion of An. gambiae to sweat.