Natures' night serenade

Frogs, and toads offer some interesting sexual difference namely, in musical powers possessed by the males; but to speak of music, which applied to the discordant and overwhelming sounds emitted by male bull-frogs and some other species, seems, according to our taste, a singularly inappropriate expression. Nevertheless, certain frogs sing in a decidedly pleasing manner. Near Rio Janerio I used often to sit in the evening to listen to a number of little Hylae, perched on blades of grass close to the water, which sent forth sweet chirping notes in harmony. The various sounds are emitted chiefly by the males during the breeding-season, as in the case of the croaking of our common frog. In accordance with this fact the vocal organs of the males are more highly-developed than those of the female. In some genera the males alone are provided with sacs which open into the larynx. . . . Page 362 ~ Excerpt: "The Descent of Man" Charles Darwin