The Tree-Frog, or Tree-Toad
SSOCIATED with the first songs of robin and bluebird, is the equally delightful chorus of the spring peepers, yet how infrequently do most of us see a member of this invisible choir! There are some creatures which are the quintessence of the slang word "cute" which, interpreted, means the perfection of Lilliputian proportions, permeated with undaunted spirit. The chickadee is one of these, and the tree-frog is another. I confess to a thrill of delight when the Pickering's hyla lifts itself on its tiny front feet, twists its head knowingly, and turns on me the full gaze of its bronze-rimmed eyes. This is the tiniest froglet of them all, being little more than an inch long when fully grown; it wears the Greek cross in darker color upon its back, with some stripes across its long hind legs which join the pattern on the back when the frog is "shut up," as the boys say.
The reason we see so little of tree-frogs, is because they are protected from discovery by their color. They have the chameleon power of changing color to match their background. The Pickering's hyla will effect this change in twenty minutes; in this species, the darker lines forming the cross change first, giving a mottled appearance which is at once protective. I have taken three of these peepers, all of them pale yellowish brown with gray markings, and have placed one upon a fern, one on dark soil and one on the purple bud of a flower. Within half an hour, each matched its surroundings so closely, that the casual eye would not detect them. The song of the Pickering's hyla is a resonant chirp, very stirring when heard nearby; it sounds somewhat like the note of a water bird. How such a small creature can make such a loud noise, is a mystery. The process, however, may be watched at night by the light of a lamp, as none of the tree-frogs seem to pay any attention to an artificial light; the thin membrane beneath the throat swells out until it seems almost large enough to balloon the little chap off his perch. No wonder that, with such a sounding-sac, the note is stirring. There are several species of tree-frogs that trill in the branches above our heads all summer, and their songs are sometimes mistaken for those of the cicada, which is far more shrill.
The tree-frogs have toes and fingers ending in little round discs which secrete at will a substance by means of which they can cling to vertical surfaces, even to glass. In fact, the way to study these wonderful feet is when the frog is climbing up the sides of the glass jar. The fingers are arranged, two short inside ones, a long one, and another short one outside. The hind feet have three shorter inside toes quite far apart, a long one at the tip of the foot and a shorter one outside. When climbing a smooth surface like glass, the toes are spread wide apart, and there are other little clinging discs on their lower sides, although not so large as those at the tips. It is by means of these sticky, disc-like toes that the tree-frogs hold themselves upon the tree trunks.
The whole body of the tree-frog is covered with little tubercles, which give it a roughened appearance. The eyes are black with the iris of reddish color. The tongue is like that of other frogs, hinged to the front of the lower jaw; it is sticky and can be thrust far out to capture insects, of which the tree-frogs eat vast numbers.
The hylas breathe by the rapid pulsation of the membrane of the throat, which makes the whole body tremble. The nostrils are two tiny holes on either side of the tip of the snout. The ears are a little below and just behind the eyes, and are in the form of a circular slit.
The eggs of the spring peepers are laid in ponds during April; each egg has a little globe of jelly about it and is fastened to a stone or a water plant. The tadpoles are small and delicate; the under side of the body is reddish and shines with metallic lustre. These tadpoles differ from those of other frogs in that they often leave the water while yet the tail is still quite long. In summer, they may be found among the leaves and moss around the banks of ponds. They are indefatigable in hunting for gnats, mosquitoes and ants; their destruction of mosquitoes, as pollywogs and as grown up frogs, renders them of great use to us. The voice of this peeper may be heard among the shrubs and vines or in trees during late summer and until November. The little creatures sleep beneath moss and leaves during the winter, waking to give us the earliest news of spring.
The Tree-Frog or Tree-Toad
Leading thought—The prettiest part of the spring chorus of the frog ponds is sung by the tree-frogs. These little frogs have the tips of their toes specially fitted for climbing up the sides of trees.
Method—Make a moss garden in an aquarium jar or a two-quart can. Place stones in the bottom and moss at one side, leaving a place on the other side for a tiny pond of water. In this garden place a tree-frog and cover the jar with mosquito netting and place in the shade. The frogs may be found by searching the banks of a pond at night with a lantern. However, this lesson is usually given when by accident the tree-frog is discovered. Any species of tree-frog will do; but the Pickering's hyla, known everywhere as the spring peeper, is the most interesting species to study.
1. How large is the tree-frog? What is its color? Describe the markings.
2. Place the tree-frog on some light-colored surface like a piece of white blotting paper. Note if it changes color after a half hour. Later place it upon some dark surface. Note if it changes color again. How does this power of changing color benefit the tree-frog? Place a tree-frog on a piece of bark. After a time is it noticeable?
3. Describe the eyes. Note how little the tree-frog turns its head to see anything behind it. Describe its actions if its attention is attracted to anything. What color is the pupil? The iris?
4. Note the movement of breathing. Where does this show the most? Examine the delicate membrane beneath the throat. What has this to do with the breathing?
5. What is the tree-frog's note? At what time of day does it peep? At what time of year? Describe how the frog looks when peeping.
6. How does the tree-frog climb? When it is climbing up a vertical surface study its toes. How many on the front foot? How are they arranged? How many toes on the hind foot? Sketch the front and hind feet. How do the toe-discs look when pressed against the glass? How does it manage to make the discs cling and then let go? Are there any more discs on the under side of the toes? Is there a web between the toes of the hind feet? Of the front feet?
7. Look at a tree-frog very closely and describe its nostrils and its ears.
8. Are the tree-frogs good jumpers? What is the size and length of the hind legs as compared with the body?
9. When and where are the eggs of the tree-frog laid? How do they look?
10. How do the tree-frog tadpoles differ from other tadpoles? Describe them if you have ever seen them. In what situations do they live?
11. Of what use are the tree-frogs to us?
References—"The Life History of the Toad," Cornell Nature Study Volume, S. H. Gage; The Frog Book, Dickerson; Familiar Life of Field and Forest, Mathews; American Natural History, Hornaday; Elementary Zoology, V. L. Kellogg; From River Ooze to Tree-top, Sharp.