SCHOOL IN THE OPEN

Star (Christchurch), Issue 18467, 19 May 1928, Page 20 (Supplement)

SCHOOL IN THE OPEN

STUDIES IN THE GREAT OUT-OF-DOORS (By J. J. S. Cornes, 8.A., B.Sc.) The "Star” has arranged with Mr J. J. S. Cornes, 8.A., B.Sc., to write a series of illustrated articles which will give teachers and others a fuller appreciation of the Great Out-of-doors. They will deal with various aspects of plant and animal life, as well as with inanimate nature. Questions and material for identification will be welcomed.

THE FROG. CCXII. The frog has to live in or near water, because its skin must be kept moist, in order that breathing may take place through it. The frog, unless it is among wet grass or weeds, must remain where it can moisten the skin by an occasional plunge into the water Moreover, the water is a convenient means of escape from enemies. Anyone who has walked along the margin oi a pond or stream must have observer that a startled frog makes a jump fo the water. Frequently it will swim * few strokes away from the bank, an then turn back and come quietly b the surface among the vegetation. During the breeding season, in th

spring, frogs are still more closely cor fined to water, for their tadpole of.i spring can live there only. Pood. This consists of earthworms, insect; spiders; in fact, of almost any anima small enough to be seized and swal lowed. Large frogs have no sentiment al scruples against devouring thei smaller relatives. They will eat cock chafe, beetles, employing both foreleg: to push the rough legs of the insectinto the mouth. Bees and wasps are eaten greedily, for their strings apparently affect the frog but little. While the frog is a gourmand, he is no epicure. Almost any living creature, and even decayed meat, if once taken into the mouth, continues on its downward course—in short, the sense k of taste and the sense of smell are apparently very dull. In seizing food, the frog usually makes use of its extensile tongue, which can be thrown out of the mouth with surprising rapidity. The tongue is attached by its front end to the tip of the lower jaw, while the forked hind end lies free. In the capture of prey the forked posterior end is thrown forward, when the sticky secretion with which the tongue is covered adheres to the object it strikes against, so that they may be drawn to the mouth. The frog has an instinct to snap at small moving objects—and unless a thing is moving, a frog pays little attention. Frogs may even be caught by dangling small pieces of red yarn before them on a hook. Locomotion. This is effected by leaping and by swimming, and in both of these operations the long hind legs play the chief part. In the ordinary resting position the body slopes upward in front, sup ported on the front legs, which are held in a peculiar twist, so that the large thumb points nearly backward The hind limbs are folded, ready for a spring, and il one causes the frog to leap in various directions, it will be observed that the body is adjusted before each leap in a new direction by the movements of the foie limbs. The movements of the hind legs in swimming are much the same as in leaping. In both cases the legs are drawn up into a Z, and quickly extended. As they are pushed back, the toes are spread apart, and the web between them offer considerable resistance to passing through the water (which is when the frog scores over us, when we try the similar “ breast stroke”). The fore limbs are held stiff against the body, after the stroke, and if the frog does not make several strokes in quick succession the hind limbs are held extended, to offer as little resistance as possible to a glide. As on land, the fore limbs guide. To swim down, the hand is twisted so as to press its broad surface against the water. This pushes the front of the body down. In starting to swim upward, the hand beats downward. Every boy knows how similarly to vary the depth of his dive by the same devices. The hind legs usually make a stroke at the same moment, but sometimes, especially when struggling near some object, the frog uses them alternately. Attitude when Floating at the Surface. —When frogs are kept in water beyond their depth, they spend a considerable portion of the time at the surface with just the tip of the nose exposed, for breathing. The more the lungs are inflated, the higher the body floats. It lies quiet, hanging obliquely, the hind legs fairly extended, the fore legs spread. This sprawled out attitude enables the animal to draw itself suddenly downward when dangej

threatens from above. The action is performed so quickly that it is not easy to see at first how it is done. To swim downward the frog has to reverse its position, so it suddenly brings the hind legs forward (which gives the body a backward impulse). As the body withdraws from the surface, the front legs make a sudden stroke backward and upward, throwing the head down. Then the hind legs extend and shoot the animal further down through the water. Th* Voice. The croaking may be represented rnghly by the syllables “ Au-eu-au-au-uk.” The voice of the male is the :uder and deeper. These notes are nore often he.ard in the breeding seaon, when they are supposed to serve s a Sex call. A damp atmosphere .is >0 conducive to their song, and the popular reputation that they enjoy as

•veather prophets is not altogether unmerited. Instincts for Protection.—When a frog is seized in the hands, it usually makes violent efforts to escape, and at he same time inflates the body with iir. which enables it to slip the more . eadily from one’s grasp.

Hibernation.—ln late autumn frogs betake themselves to water and bury themselves in the mud, out of the reach of frost—or they hide in the wet soil under logs or grass. Here they lie in a dormant condition until the next ! spring. The general vital activities of the animal run down so low that little expenditure of energy is required to maintain life. There is need then for only a small amount of oxygen, and skin respiration suffices. During the whole winter the frog breathes without its lungs. The temperature of the bodysinks until it is only a few degrees above that of the surrounding medium. The frog takes no food; vital activity is kept going at the expense of fuel stored in its tissues; and these stored reserves which keep the heart beating and the temperature above zero must also afford the substance for the growth of the sexual products, which increase during the winter at the expense of the other parts, in preparation for the mating in spring. To keep alive its stock, a process which requires, of course, the preservation of its own body (and equally implies its immortality), is the great end of the frog’s existence. (To be continued next Saturday.)