The terminal phalanges are generally bifurcated, rarely obtuse, and support well-developed adhesive discs. The fingers and toes are webbed to a variable extent. The two outer metatarsals are likewise connected by a web. The tympanum is distinct. The general appearance is that of tree-frogs, and many of them are green. The males have one or two internal vocal sacs. Not all the species have dermal appendages. Rh. maximus, for instance, the largest of all, living in the Himalayan forests, has none. A heel-flap occurs in some half-dozen Indian species; and Rh. madagascariensis has these flaps on the heels and on the elbows. Some have queer little lappets above the vent, or on the edges of the arms and legs; in others the bend of the arm is fringed. The small size of these appendages, in comparison with the webs and discs, makes them practically useless so far as increase of surface is concerned, and they have most likely some other, although unknown meaning, especially the flaps over the vent. Lastly, in the majority of species the fingers are not more than half-webbed, or even less, and in a few only, the webs reach down to the discs.
Several species of this genus are remarkable for two reasons. First, the great enlargement of the fully-webbed hands and feet, which are then used as parachutes; secondly, the mode of propagation.
Greatly exaggerated notions are, however, entertained about the parachutes, ever since Wallace's description[[110]] of the first "flying frog." The creature was brought to him in Borneo by a Chinese workman. "He assured me that he had seen it come down, in a slanting direction, from a high tree, as if it flew.... The body was about four inches long, while the webs of each hind-foot, when fully expanded, covered a surface of four square inches, and the webs of all the feet together about twelve square inches."
Fig. 48.–Rhacophorus pardalis, × about 1. (From Wallace, Malay Archipelago.)
The species in question is Rh. pardalis, an inhabitant of Borneo and of the Philippine Islands. Specimens from Wallace's Collection are in the National Collection and the largest specimen shows the following measurements. Total length 6.5 cm. or 2½ inches, not 4 inches.
| Area covered by one fully-expanded hand | 3.4 square cm. |
| Area"covered by"one fully-e"panded foot | 6.0 sq"are c" |
| --- | |
| 9.4 square cm. |
i.e. for the four limbs 18.8 square cm. = about 3 square inches, and not 78 square cm. or 12 square inches. By some unfortunate oversight Wallace must have mixed up the total expanded area with that of the four hands and feet! In Brehm's Thierleben the 78 square cm. have increased to 81 cm., and the artist has in the somewhat larger species Rh. reinwardti improved upon this, and has produced a truly startling picture by a further exaggeration based upon the figure given by Wallace.
Rh. reinwardti lives in the forests of the mountains of Java and Sumatra. It reaches 3 inches in length, and is grass-green above, yellow below. Younger specimens are further adorned with large blue patches on the webs of the hands and feet and behind the armpits. Besides the flap on the heel and the curious cutaneous fringe on the forearm, suggestive of an incipient flying-membrane, the skin forms a projecting fringe on the inner side of the fifth toe and a transverse flap above the vent.
Of Rh. leucomystax, Annandale, who accompanied the Skeat Expedition to Malacca, gives the following account:–"This frog, which is called by the Malays of Lower Siam either 'Berkata Pisang' (banana-frog) or 'Berkata Rhumah' (house-frog), lays its eggs either on leaves of branches overhanging the water, or on the mud surrounding buffalo-wallows. The ova are enclosed in a round mass of yellow froth, which afterwards becomes steel-grey, about as large as a cricket-ball. Should they be placed judiciously in a position sheltered from the sun, the tadpoles may either hatch, and reach a considerable degree of development, before the mass is washed into the water, or the froth may be melted almost as soon as it is formed and the eggs be carried into a pool by a shower of rain. Very often, however, the whole mass is dried up by the heat of the sun before the rain comes. During the breeding season, which seems to occur as often as the land is flooded under the trees, for I have never seen the eggs of this frog on the bank of a river, the males croak loudly, producing a sound which can hardly be distinguished from the chattering of the large black and yellow squirrel, Sciurus bicolor."