Sometimes the term toad is restricted to the so-called true toads, members of the family Bufonidae. These are characterized by warty skins and prominent parotid glands behind the eyes and as a group are the most terrestrial of the order. In most the feet are only slightly webbed. They range in length from about 1 to 7 in. (2.5-18 cm). Most species belong to the genus Bufo; members of these species spend much of the time on land, generally near water. They generally live in cool, moist places and absorb moisture through the skin. The white fluid that they exude through the skin, as well as from the parotid glands, is very poisonous and causes intense burning if it comes in contact with the eyes or mouth; however, contrary to an old belief, it does not cause warts. Toads, like frogs, move on land by jumping and feed on insects and grubs. Also like frogs, they usually lay their eggs in water in strands of jelly. Fertilization is external. The egg hatches into a tadpole, a gilled, aquatic, larval toad that undergoes metamorphosis into the adult.
There are about a dozen Bufo species in the United States, among them the common American toad (Bufo americanus), Fowlers toad (B. fowleri), of the E United States, and the red-spotted toad (B. punctatus), of the Southwest. The cane, marine, or giant toad (B. marinus), a large toad native to Central and N South America, was widely introduced in warm regions (Caribbean, Pacific, Australia, and Florida) to control agricultural pests but is now regarded as an invasive species; they compete with and prey on native species, and their toxic secretions can kill predators.
The spadefoot toads, burrowing toads of the family Pelobatidae, are represented in the United States by several species of the genus Scaphiopus. Toads are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Anura.
A toad can refer to a number of species of amphibians in the order Anura. A distinction is often made between frogs and toads by their appearance, prompted by the convergent adaptation among so-called "toads" to dry habitats. Many "toads" often have leathery skin for better water retention, and a brown coloration for camouflage. They also tend to burrow. However, these adaptations are not reliable indicators of its ancestry. Because taxonomy reflects only evolutionary relationships, any distinction between frogs and toads is irrelevant to their classification.
For instance, many members of the frog families Bombinatoridae, Discoglossidae, Pelobatidae, Rhinophrynidae, Scaphiopodidae, and some species from the Microhylidae family are commonly called "toads". However, the only family exclusively given the common name "toad" is Bufonidae, or the "true toads". Some "true frogs" of the genus Rana have also adapted to burrowing habits, while a bufonid species in the genus Atelopus are conversely known by the common name "harlequin frogs".
The Moche people of ancient Peru worshipped animals and often depicted toads in their art. To Vietnamese people, toad is the uncle of the Sky. According to a Vietnamese ancient story, whenever toads grind their teeth, it is going to rain.
It is commonly believed that physical contact with a toad can cause warts on humans. Warts are, in actuality, caused by an internal viral infection; thus, a toad could not possibly cause a wart. The paratoidal glands, which toads use to secrete poison for protection, are often mistaken for warts. This misconception could very conceivably have brought about such a superstition.