TREE-FROG. Many groups of tailless Amphibia (see FROG) are adapted to arboreal life, which is indicated by adhesive discs on the tips of the fingers and toes. These discs adhere by rapid and intense pressure of the distal phalanx and special muscles upon the lower surface, which is also provided with glands pro ducing a sticky secretion.
The best-known European tree-frog is the little Hyla arborea, often kept in glass cylinders, with a ladder which it is supposed to ascend or descend according to the coming weather. This frog rarely reaches gin. in length; its upper parts are smooth and shiny, normally of a bright grass-green, which may change rapidly to yellow, brown, olive, or black; some specimens lack the yellow pigment which contributes to form the green colour, and are sky blue or turquoise blue ; the lower parts are white. The commonest American species is H. versicolor, green, grey, or brown, with a loud piping voice. Tree-frogs in U.S.A. are often called tree-toads.
The family Hylidae is related to the Bufonidae or toads, being distinguished by the presence of teeth in the upper jaw and by the claw-like shape of the terminal phalanx of the digits. It is a large family, with about 30o species, 25o of which belong to the genus Hyla, distributed over Europe, temperate Asia, North Africa, North and South America, Papua, and Australia. Nototrema of Central and South America, in the female, develops a broad dorsal pouch in which the young undergo their metamorphoses. Phyl lomedusa, also from Central and South America, is quadrumanous, the inner finger and the toe being opposable to the others, and the foot being very similar to the hand. These frogs deposit their spawn between the leaves of branches overhanging water, into which the tadpoles drop and spend their larval life.