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round their bodies, which completely disguise the animal form. Others leave the plants upon which they formerly fed, and hide themselves in little cells which they make in the earth. The rat-tailed worm abandons the water upon the approach of its metamorphosis, retires under the earth, where it is changed into a chrysalis, and, after a certain time, bursts from its seemingly inanimate condition, and appears in the form of a winged insect. Thus the same animals pass the first and longest period of their existence in the water, another under the earth, and the third and last in the air. Some caterpillars, when about to change into a chrysalis state, cover their bodies with a mixture of earth and of silk, and conceal themselves in the loose soil. Others incrust themselves with a silky or glutinous matter, which they push out from their mouths, without spinning it into threads. Others retire into the holes of walls or decayed trees. Others suspend themselves to the twigs of trees, or to other elevated bodies, with their heads undermost. Some attach themselves to walls, with their heads higher than their bodies, but in various inclinations: and others choose a horizontal position. Some fix themselves by a gluten, and spin a rope round their middle to prevent them from falling. Those which feed upon trees attach themselves to the branches, instead of the leaves, which are less durable, and subject to a greater variety of accidents. The colours of the caterpillars give no idea of those of the future flies.

In general, the figure of chrysales approaches to that of a cone, especially in their posterior part. When under this form, the insect seems to have neither legs nor wings. It is incapable either of walking or of crawling, It takes no nourishment, because it has no organs suited to that purpose; yet, in some species, life is continued for several

months before their last metamorphosis takes place. In a word, it seems to be a lifeless mass. But, upon a more attentive observation, it possesses the power of bending upward and downward the posterior part of its body. The skin, or exterior covering, of those which do not spin cods, seems to be of a cartilaginous nature. It is commonly smooth and shining; but in some species it is more or less covered with hair and other rugosities. Though chrysales differ both in figure and colour, their appearances are by no means so various as those of the caterpillars from which they are produced. The colour of some chrysales is that of pure gold, from which circumstance the whole have received their denomination. For the same reason they are called aurelia in Latin. Some are brown, others green; and, indeed, they are to be found of almost every colour and shade.

The life of winged insects consists of three principal periods, which present very different scenes to the student of Nature. In the first period, the insect appears under the form of a worm or caterpillar. Its body is long, cylindrical, and consists of a succession of rings, which are generally membraneous, and encased within each other. By the aid of its rings, or of crotchets, or of several pair of legs, it crawls about in quest of food; and its movements are, in some species, remarkably quick. Its head is armed with teeth, or pincers, by which it eats the leaves of plants or other kinds of food. In this state, it is absolutely deprived of sex, and, consequently, of the power of multiplication. Its blood moves from the tail toward the head. It respires either by small apertures placed on each side of its body, or by one or several tubes situate on its posterior part, which have the resemblance of so many tails. In the second period, the insect appears under the form of a nymph, or that of a chrysalis. When an insect, after throwing off the skin of the caterpillar, exhibits

all its external parts, only covered with soft and transparent membranes, it is called a nymph: but, when to these membranes is added a common and crustaceous covering, it receives the name of a chrysalis. While in a state of a nymph, or of a chrysalis, insects, in general, are totally inactive, and seem not to possess any powers of life. They can make no use of their eyes, their mouth, or any of their members; for they are all imprisoned by coverings more or less strong. Deprived of the faculty of motion, they remain fixed in those situations which they have chosen for their temporary abode, or where chance has placed them, till their final metamorphosis into flies. Some of them, however, are capable of changing place; but their movements are slow and painful. Their blood circulates, but in a contrary direction from what takes place in the caterpillar state; for it proceeds from the head toward the tail. Respiration continues to go on, but the organs are differently situated. In the caterpillar, the principal organs of respiration were placed at the posterior part of the body; but now these same organs are to be found at the anterior part of the animal. In the third period, the insect has acquired that perfect organization which corresponds to the rank it is to hold in the scale of animation. The bonds of the nymph, or the chrysalis, are now burst asunder, and the insect commences a new mode of existence. All its members, formerly soft, inactive, and folded up in an envelope, are expanded, strengthened, and exposed to observation. Under the form of a worm or caterpillar, it crawled; under that of a nymph, or chrysalis, its power of motion was almost annihilated; under the last form, it is furnished with six springy legs, and two or four wings with which it is enabled to fly through the air. Instead of teeth or pincers, with which it divided a gross aliment, it has now a trunk by which it extracts the refined

juices of the most delicate flowers. Instead of a few smooth eyes which it possessed in the worm or caterpillar state, the new insect is furnished with both smooth and convex eyes, to the number of several thousands.

The internal parts of the insect have likewise undergone as many changes as the external. The texture, the proportions, and the number of the viscera, are greatly altered. Some have acquired an additional degree of consistence; others, on the contrary, are rendered finer and more delicate. Some receive a new form, others are entirely annihilated. Lastly, some organs in the perfect insect, which seemed formerly to have no existence, are unfolded, and become visible. The most important of this last kind are the organs of generation. The caterpillar, the nymph, and the chrysalis, were of no sex; but, after transformation, both sexes are distinguishable, and the animals are capable of multiplying their species.

But there are some examples of transformations which deviate from the common mode. Some insects hold a middle rank between those which preserve their original figure during life, and those that suffer transformations. Their existence is divided into two periods only: they walk in the first, and fly in the second. Thus their only metamorphosis consists of the addition of wings, the growth and expansion of which are performed without any considerable alteration in the figure of their bodies.

There is not a law established among organized bodies which seems to be so universal, as that all of them grow, or augment in size, after birth till they arrive at maturity. If a hen were to bring forth an egg as large as her own body, and if this egg, when hatched, were to produce a bird of equal dimensions with either of the parents, it would be considered as

a miracle. But the spider-fly, so denominated from its figure, affords an example of a similar prodigy. This fly actually lays an egg, from which a new fly is hatched that is as large and as perfect as its mother. This egg is roundish, is at first white, and afterward assumes a shining black colour. Upon a more accurate examination, however, this production was found to be an egg only in appearance. When the envelope is removed, instead of a gelatinous substance, the new insect, furnished with all its members, is discovered. But this discovery does not render the fact the less wonderful. All winged insects undergo their different transformations after being expelled from the bodies of their mothers, and receive great augmentations of size before their metamorphosis into the nymph or chrysalis state, after which their growth stops. But the spider-fly affords an instance of an insect transformed in the belly of its mother, and which grows no more after it escapes from its envelope. The fact is fully authenticated by Reaumur, Bonnet, and other naturalists.

The worm from which the tipula, or crane-fly, is produced, is perfectly smooth. Immediately before its transformation it retires under ground. After this metamorphosis, the surface of the nymph is furnished with a number of prickles. By means of these prickles, the nymph, when about to be transformed into a fly, raises itself in its hole till the chest of the insect is above ground. The fly then bursts its prison, mounts into the air, and leaves its former covering behind in the earth.

Many species of flies deposit their eggs in the leaves and different parts of plants. Soon after the egg is inserted into the leaf, a small tubercle begins to appear, which gradually increases in magnitude till the animal is hatched, and has passed through

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