Aquatic insects must regulate the ion concentrations of their haemolymph, and freshwater insects tend to loose ions to their aquatic environment. The osmoregulatory organs of larvae and pupae of C. sonorensis have not been previously reported. Silver nitrate was used to detect tissues in immature stages of C. sonorensis with active chloride exchange. Larvae of C. sonorensis actively exchanged ions with their anal papillae, cutaneous chloride cells, and to a lesser extent the hindgut. Only the cutaneous chloride cells were stained in their pupae.