Tree Frog, the name of the batrachian reptiles of the family hyladoe, distinguished from common frogs (ranidoe) by having the ends of the fingers and toes dilated into flattened disks or suckers, which enable them to lead an arboreal life. They are more elegant, smaller, brighter, and more active than the ranidoe, and are lively during the day; they feed on insects; they climb like the geckos among lizards, and by the same mechanism; the lower surface of the disks is endued with a viscid secretion, by means of which they can walk with the body suspended from the under parts of leaves and other smooth bodies; the skin is mostly smooth upon the back, but on the abdomen and inside of legs thickly studded with small warts or tubercles. They possess to a remarkable degree the faculty of changing color, which enables them to elude their numerous enemies. They are very clamorous, and particularly noisy at the approach of rain; in winter they bury themselves in the mud at the bottom of pools; they breed in the spring, depositing their eggs in the water. They are frequently called tree toads, and their French name is rainettes.
The species are numerous, especially in America; only one is found in Europe, and that also occurs in N. Africa and Asia. - The common tree frog of North America (hyla versicolor, Le Conte) resembles a toad in form, but is more flattened; body short and warty above, the color varying from pale ash to dark brown, with several large irregular blotches of greenish brown, white and granulated below, and abdomen yellowish near the thighs; the colors vary at the will of the animal. The head is short and rounded, the mouth largo, with teeth on upper jaw and vomer; eyes large and brilliant, the iris bright golden; there are four fingers and five toes, both ending in viscous pellets, the former distinct, but * the latter webbed for four fifths of their length. It is about 2 in. long, and is found abundantly in the northern and middle states, and as far west as the Mississippi; it is generally seen on decaying trees and about old fences of wood or stone, overgrown with mosses and lichens, the color of which it so nearly resembles that it is very difficult to detect; it is very noisy in spring and summer toward evening, especially in cloudy weather; the secretion of the skin is copious and very acrid.
This species is replaced in the southern states by the green tree frog (H. viridis, Laur.; calamita Carolinensis, Penn.), which is bright green above, yellowish white below, with a straw-colored lateral line extending from the upper jaw over the shoulder and along the side. The tree frog of Europe (H. arborea, Linn.) much resembles the green species of North America, and the latter was considered by Laurenti a variety of his H. viridis; it is spread throughout Europe, except in Great Britain. - In the genus acris ( Dum. and Bibr.) the locomotive disks are less developed and the limbs more slender than in hyla, and there are teeth on the palate instead of the vomer. The A. gryllus (Dum. and Bibr.), or Savannah cricket, occurring from New England to the gulf of Mexico, is about 1½ in- long, with an elongated pointed head, a triangular dusky spot between the orbits; body ashy above, with a green and sometimes reddish dorsal line, and three oblong black spots margined with white on the sides. It may easily be domesticated; it makes immense leaps; it is intermediate between the ranidoe and hyladoe, having the aquatic habits of the former and the method of watching for its prey of the latter; in consequence of the smallness of the disks it cannot adhere to the under surface of smooth bodies. - The flying tree frog of Borneo (rhacophorus), according to Mr. Wallace, has its very long toes fully webbed to their extremity, so that by expanding these webs and inflating its body, it is able to use them as a parachute or sailing membrane in its descent from high trees.
The frog is 4 in. long, deep green above, yellow below; the webs of all the feet cover a surface of 12 sq. in.; at the ends of the toes are the usual disks for adhesion. This is the only aerial batrachian known.
Common Tree Frog (Hyla versicolor).
Flying Tree Frog of Borneo (Rhacophorus).