H. maxima, of the forests of British Guiana, is scarcely less gigantic, and is distinguished by a projecting rudiment of the pollex, while the adhesive discs are smaller than the tympanum. The skin forms folds on the arms and tarsus, like those of H. vasta, in addition to a triangular flap at the heel. The general colour is reddish-brown above, sometimes with a dark vertebral line, the under parts are whitish and covered with large granules; the throat of the male, which has an inner vocal sac, is brown.
H. faber of Brazil is closely allied to the last species, but the skin of its upper parts is quite smooth. There is a small tarsal fold, and one extending from the upper eyelid to the shoulder. It is light brown above, with darker marks which form a conspicuous vertebral line, transverse bars on the hind-limbs, and a few irregular, scattered, vermicular or linear marks on the head and body. The adult, when put into a strong light, will rapidly turn pale; at night the longitudinal stripe on the back and the bars on the hind-limbs become very distinct; the under parts are white, and exhibit a beautiful orange tinge. This is the famous "Ferreiro" or "smith." As will be seen from the following graphic account by Dr. Goeldi[[86]] of Para, this species doubly deserves its name of faber, not only in virtue of its voice, but also because of the marvellous nest-building habits recently discovered.
"The Ferreiro is common in the Province Rio de Janeiro, more frequently still in the mountain regions of the Serra dos Orgãos than in the hot lowland. Its voice is one of the most characteristic sounds to be heard in tropical South America. Fancy the noise of a mallet, slowly and regularly beaten upon a copper plate, and you will have a pretty good idea of the concert, given generally by several individuals at the same time and with slight variations in tone and intensity. When you approach the spot where the Tree-frog sits, the sound ceases. But keep quiet, and it will be resumed after a few moments. You will discover the frog on a grass-stem, on a leaf of a low branch, or in the mud. Seize it quickly, for it is a most wonderful jumper, and it will utter a loud and shrill, most startling cry, somewhat similar to that of a wounded cat."
The "Smith" makes very regular pools, in the shallow water of ponds, or nurseries for the tadpoles surrounded by a circular wall of mud. Dr. Goeldi has watched the building process during a moonlit night: "We soon saw a mass of mud rising to the surface carried by a Tree-frog, of which no more than the two hands emerged. Diving again, after a moment's time, the frog brought up a second mass of mud, near the first. This was repeated many times, the result being the gradual erection of a circular wall. From time to time the builder's head and front part of body appeared suddenly with a load of mud on some opposite point. But what astonished us in the highest degree was the manner in which it used its hands for smoothing the inside of the mud wall, as would a mason with his trowel. When the height of the wall reached about 4 inches, the frog was obliged to get out of the water. The parapet of the wall receives the same careful smoothing, but the outside is neglected. The levelling of the bottom is obtained by the action of the lower surface (belly and throat principally) together with that of the hands."
The male takes no active share in the construction of the nest, but will suddenly climb up the wall of his home, and then upon the back of his busy mate. The building operation may take one or two nights, and is performed in the most absolute silence; the croakers around are all males clamouring for a mate.
The eggs are laid during one of the following nights, and are hatched some four or five days later, the parents keeping hidden in the neighbourhood of the nursery. Heavy rains may destroy the walls, and thus prematurely release the tadpoles.
It is only owing to such keen observers and lovers of nature's fascinating ways that the breeding habits of some Brazilian Hylidae have become known.
H. nebulosa s. luteola also living in Brazil, is yellow above, with brown dots; the sides of the belly and thighs have transverse bluish bars, the under parts are whitish. Its size is under 2 inches. Goeldi has often found it in the sheaths of decaying banana-leaves. It glues the lumps of eggs on to the edges and to the inside of the withered leaves, where even during the hot hours of the day sufficient coolness and moisture are preserved. These lumps are enveloped in a frothy substance, in which the nearly metamorphosed tadpoles can be watched wriggling. If these are put into water, all will die in a few hours.
H. polytaenia deposits its eggs in free lumpy masses on water-plants. It is a small creature, little more than 1 inch in length, light olive above, with numerous brown parallel longitudinal bands on the body and limbs. A dark, white-edged band extends from the nose along the side of the body. The heel has a short flap of skin. The male has an internal vocal sac.
H. goeldii is a most interesting form, leading to the allied genus Nototrema. Boulenger[[87]] has described a female which was captured by Goeldi in January on the Serra dos Orgãos. It is about 1½ inch long. The whole surface of the back is occupied by a layer of twenty-six pale yellow eggs which are 4 mm. in diameter. The skin of the back is expanded into a feebly reverted fold, which borders and supports the mass of eggs on the sides, thus suggesting an incipient stage of a dorsal brood-pouch. Owing to the great amount of yolk, the young are probably able to remain upon the mother until they are nearly metamorphosed.