Frogs and toads occur wherever insect food is procurable, and their distribution is a world-wide one, with the exception of many islands.
The former type is exemplified by the toads and the lower Ecaudata, whilst the latter is characteristic of the true frogs (Ranidae), although when quite young these batrachians present a condition similar to that which persists throughout life in their lower relatives.
Some of the poison-secreting glands attain a greater complication of structure and are remarkable for their large size, such as the so called "parotoid" glands on the back of the head in toads and salamanders.
Of which (toads, for instance) are entirely Ivc, Inferior vena edentulous.
The larynx, which is rudimentary in most of the Caudata and in the Apoda, is highly developed in the Ecaudata, and becomes the instrument of the powerful voice with which many of the frogs and toads are provided.