Magst du auf Regen harren.
When the tree-frogs croak, you may wait for rain. Sometimes it does come true.
Tree-frogs are not very intelligent, although they have a keen sense of locality; but they are nice pets, being easily kept, and have a pretty appearance. There is a record of one which lived for twenty-two years in confinement.
The pairing begins soon after the frogs reappear from their hibernation in the ground; in Germany in the month of May. The congregating males make a great noise and take to the water before the females, which join them when ready to spawn. The male grasps his mate near the shoulders, and the pair swim about together, sometimes for days, until the eggs are expelled. These are laid in small clumps of 800 to 1000, which soon swell up and remain at the bottom of the pond. The larvae are hatched in ten days; two days later the adhesive sucker below the throat appears, and after another two days a pair of thread-like external gills are developed. The tadpoles, which reach a length of 2 inches, owing to the long tail, which is nearly three times as long as the body, metamorphose in about twelve weeks, and the baby tree-frogs, scarcely half an inch in length, hide in the grass for the next two years, until they are about half grown, not reaching maturity until the fourth year.
Since many pairs congregate in the same pool, and each produces up to one thousand eggs, most of which are hatched, the neighbouring meadows sometimes literally swarm with tiny tree-frogs. Nevertheless the adults are comparatively rare and are very local.
H. carolinensis s. lateralis of the South-Eastern States of North America greatly resembles H. arborea in general appearance, size, and habits. But the head is more pointed, and the vivid green of the upper parts is separated from the yellowish white under surface by a conspicuous, pure white line, giving the little creature a very smart and neat appearance. According to Holbrook, it ascends trees, but most commonly lies upon broad-leaved water-plants, like Nymphaea, and in fields of Indian corn. Motionless during the daytime, they emerge in the morning and evening from their hiding-places, and become very brisk and noisy, often repeating their single note, which is not unlike that of a small bell. When one begins, hundreds take it up from all parts of the corn-field.
Among other tree-frogs of the South-Eastern States may be mentioned H. squirella, 1½ inch in length, which is very changeable in colour, generally olive above with darker spots and bars on the limbs, and with a white upper lip. It lives in trees, sheltering in the bark. H. femoralis of the same size, without the white lip, lives high up in the trees of the dense forests of Georgia and Carolina.
H. versicolor is one of the most delicately coloured species of Eastern North America, extending northwards into Canada. It is about 2 inches long. Its colour passes within a short time from dark brown or olive grey to pale delicate grey, almost white, occasionally retaining a few large darker patches on the back, and delicate cross-bars on the limbs. A small portion of the sides and the posterior part of the belly are bright yellow. The skin is granular, owing to the presence of small warts which produce an acrid secretion. It is said to be found in trees, or about old stone fences overgrown with lichens, the colour of which it resembles to perfection. It becomes very noisy towards the evening, in cloudy weather or before rain, the voice consisting of a liquid note, terminating abruptly, like "l-l-l-l-luk." My own captives fully bear out this statement of Holbrook's. Settled motionless during the day upon a piece of bark in a shady corner, but occasionally uttering the quaint and rather faint note, they become very lively in the evening, catching insects by long jumps, or investigating the hollows of decaying mossy stumps. Their general colour is then spotless, almost silvery grey. In the day-time they are sometimes suffused with delicate green.
The propagation has been studied by Miss M. H. Hinckley.[[85]] They pair in shallow pools, in Massachusetts, in May. On the 10th of that month eggs were attached singly, and in groups, on the grasses resting upon the surface of the water; first drab-coloured, they became lighter in a few hours. Some larvae escaped from the gelatinous envelopes on the following day, the others on the third day; they clung to the grasses by means of their prominent suckers. The head and body were cream-coloured, with olive dots, and averaged ¼ inch in length. Gills appeared on the fourth day, to disappear again during the four following days, first those of the right, then those of the left, side; the suckers became less conspicuous, and the general colour turned into deep olive-green, with fine golden dots on the upper and lower surfaces. The eyes were of a brilliant flame-colour. On the eleventh day the suckers or "holders" had disappeared, and the hind-limbs were indicated by small white buds. By June 5th, i.e. the twenty-seventh day, the toes developed the terminal discs; the mottling of gold had given way to a uniform olive or pea-green. Movements of the future arms beneath the skin appeared on the 28th of June, at the age of seven weeks. The arms, mostly the right one first, were thrust out on the 2nd of July; the fins of the tail were absorbed rapidly, and towards the end of the seventh week the nearly transformed creatures began to leave the water. The young frogs changed colour rapidly, in adaptation to their surroundings, but the four specimens which survived were never all found to be of the same colour during the next three months. They first lived upon Aphides, later upon flies, and they were alert nocturnally. About the beginning of October they left the fronds of their fernery and nestled away in the damp earth, which they left only when the temperature rose above 60° F.
H. vasta of Hayti is the giant of the tree-frogs, reaching a length of 5 inches. In order to support its great weight the adhesive discs of the fingers and toes are of a surprising size, about as large as a threepenny piece. The skin is covered with small warts, and forms a peculiar fold on the hinder surface of the fore-arm and on the tarsus, and small flaps near the vent. The colour is grey above, blackish on the head, with a brown band between the eyes; the under parts are flesh-coloured, the throat with black spots.