ARETHUSA, in botany: A genus of the gynandria diandria class; and in the natural method ranking under the 7th order, Orchidæa. The generic character is taken from the nectarium, which is tubular, situated at the bottom of the corolla, and the inferior labium fixed to the stylus. There are four species; all natives of America, except the capensis, which is only found at the Cape of Good Hope.