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Common Tree Frog — Part 3
In the different parts of its range, this Hyla shows considerable variation. The variation displays itself mainly in the changed shapes of the dark markings of head and back and in the varying amount of dark mottling on the undersides of the legs. Cope describes a brown spotted form from Mount Carmel, Illinois, giving it the rank of a variety (Hyla versicolor phaeocrypta Cope).
In May, when apple trees are loaded with flowers and give out their delicate fragrance, and the low hum of honey-bees, we may know that our tree frogs have put aside their sleepy tendencies for the time and are joyously paddling about in the water of some pond. The painted-cup and golden ragwort are giving colour to the marsh nearby. Probably the jack-in-the-pulpit means only convenient shade and a comfortable seat to the frogs. (Frontispiece.) Very likely they do not even notice at dusk the near voices of the redwings or the more remote one of the wood-thrush. However this may be, it is certain that they do hear the voices of their companion tree frogs, and that they feel the warmth of the spring air and of the shallow sun-warmed water.
The eggs are attached in small groups, and also singly, to grasses or plant stems at the surface of the water. They are not easily found unless the grasses are separated and examined minutely. The eggs are very light in colour, grey above, white below. They hatch on the second or third day, at a very early stage in the development. The tadpoles are then about one-fourth inch long and of a light yellow colour. After the hatching, the development proceeds very rapidly, so that in three weeks from the date of egg-laying, the tadpoles(The mouth structure of the tadpole of Hyla versicolor is as follows: The upper lip bears one row of teeth, the lower has three. The upper lip curves downward at each side of the beak. The border of the lower lip is not doubled in at the corners of the mouth.) not only are fully formed, but have the hind legs budded. They have much gold-colour in the skin, and the widely separated eyes are flame-colour. The whole surface of the tadpole shows a brilliant metallic sheen, and sometimes the tail is almost red in colour. The brightly coloured creatures are very timid indeed, and move with the rapidity of young fishes. This rapid movement saves them many a time from the clutches of a great diving-beetle or some other enemy. In early July, near the end of the seventh week after the eggs are laid, the tadpoles complete the metamorphosis and leave the water. It seems that the green dress is the one in which the young frogs begin their life on land, but they may very soon change to grey or some combination of the two colours. When they are green in colour, they can be recognized by the white spot under the eye. The yellow colouring of the body and legs does not appear until after they have left the water.(The most of the facts regarding the development are from M. H. Hinckley's account. Proc. Bos. Soc. Nat. Hist., XXI, 1883, p. 104.) The young frogs are over one-half inch long when they leave the water, and by October are one inch in length. They are known to feed upon spiders, flies, and plant-lice.
Hyla versicolor has a relatively keen sense of locality, sometimes remaining in one place for weeks or more at a time. It is said that these tree frogs may stay in one tree for weeks and months. In such a situation they would certainly find themselves surrounded by supplies for their every demand--food, shelter, and moisture. A tree frog is so small that a tree with its many branches and leaves is like a palace for him. There are sunny rooms which flies and beetles visit. There are darker ones where ants and plant-lice, beetles and tree crickets are to be found. There are rooms on the north side of the tree, where the large branches join the trunk. These are cool and moist on the hottest summer day.
The Common Tree Frog is most active at dusk and in the night. It is then that he wanders over his great palace. His bright eyes see every moving caterpillar and beetle, and his sticky tongue snaps them up greedily. He sees moving objects at two or more feet distance, and makes aerial leaps to get them. He is almost sure to catch the insect, and what becomes of himself does not trouble him, since he is certain to touch some leaf or twig with at least one of his four sets of sticky toes. A bit of frantic acrobat-work does the rest, and places him securely on some perch where he can enjoy his meal at leisure.