FROG

any of various tailless amphibians belonging to the order Anura. Used strictly, the term may be limited to any member of the family Ranidae (true frogs), but more broadly the name frog is often used to distinguish smooth-skinned, leaping anurans from squat, warty, hopping ones, which are called toads. A brief treatment of frogs follows. For full treatment, see Anura (frogs and toads). In general, frogs have protruding eyes, no tail, strong, webbed hind feet that are adapted for leaping and swimming, and smooth, moist skins. Many are predominantly aquatic, but some live on land, in burrows, or in trees. A number depart from the typical form. Sedge frogs (Hyperolius), for example, are climbing African frogs with adhesive toe disks. The dagger frog (Babina holsti) of Okinawa has thumbs developed into sharp, daggerlike spines. The flying frogs (Rhacophorus) are tree-dwelling, Oriental ranids; they can glide 12 to 15 m (40 to 50 feet) by means of expanded webbing between the fingers and toes (see tree frog). Frogs range in snout-vent length from 9.8 mm (0.4 inch) in the Brazilian Psyllophryne didactyla to 30 cm (12 inches) in the West African Conraua goliath. The male anuran is generally smaller than the female. Although frogs have poisonous skin glands, these toxins do not usually provide protection from predatory mammals, birds, and snakes. Edible anurans rely on camouflage; some blend with their backgrounds, while others change colours. Several species have bright colours on their underparts that flash when the frog moves, possibly confusing enemies. Most frogs eat insects, other small arthropods, or worms, but a number of them also eat other frogs, rodents, and reptiles. The annual breeding of frogs usually takes place in freshwater. In the sexual embrace (amplexus) the male clasps the female from behind and extrudes sperm over the eggs as they are ejected by the female. The eggs, laid in numbers varying from a few hundred to several thousand (depending on the species), then float off in clusters or sheets and may become attached to the stems of water plants; the eggs of some species sink. The tadpole hatches in a few days to a week or more and metamorphoses into a frog within two months to three years. During metamorphosis the lungs develop, limbs appear, the tail is absorbed, and the mouth becomes typically froglike. In some Oriental species the eggs are deposited on land and the young hatch as froglets, not tadpoles.