We present the results of a field study led in 2009 and aiming at a better understanding of the activity of the mosquito control workers of the EID Atlantique in the wetlands of the French Atlantic seaboard (from Morbihan to Gironde). First, we endeavor to characterize their context of work, in ecological terms as well as in social ones. Then, we propose a modelling of their activity, which brings to light in an original way its important social component: their work (...) consists in maintaining, in the areas they take care of, an ecological equilibrium minimizing the proliferation of mosquitos; but it also consists in maintaining a social equilibrium, which aims at the satisfaction of all the users they are dealing with (salt workers, oyster farmers, cattle breeders, members of hunting associations and naturalist associations, hikers, and walkers). (shrink)