The Insect World: Being a Popular Account of the Orders of Insects

Another species of cochineal is the Coccus polonicus, which is met with in Poland and Russia, more rarely in France, on the roots of a small plant, the Sclcranthus pcrennis. This cochineal is gathered in the Ukraine towards the end of June, when the abdomen of the female is swollen, and filled with a purple and sanguineous juice.

The Polish kermes (Coccus polonicus) was formerly used very much in Europe. This product has not indeed lost all its importance in those countries where it is met with in abundance.

We have now only to point out among the insects of this group the Coccus lacca, which lives in India on many trees, among others on the Indian fig-tree, the Pagoda fig-tree, the Jujube tree, on the Croton, &c. These last-mentioned insects produce a colouring matter known under the name of Lac Dye. They fix themselves on the little branches, getting together in great numbers, forming nearly straight

HemipterA. 137

lines. The bodies of many fecundated females, united together by a resinous exudation which is caused by the piercing of the bark, constitutes the matter called in commerce and by dyers by the name of Lac Dye, Shell-lac, Gum-lac, &c.

Resinous lac is found in commerce under four forms:— First, the stick-lac, such as it is found concreted at the extremity of the branches whence it exudes — it is an irregular brownish crust; secondly, the seed-lac, picked off the branches and pounded; thirdly, shell-lac in scales melted down and run into thin plates, which vary in quality according to the proportion of colouring matter they contain; fourthly, thread-lac, which resembles reddish threads, and is prepared thus in India.

One more word about the cochineal. The Coccus mamiiparus^ which lives on the shrubs {Tamarix mannifera) on Mount Sinai, causes to exude from the branches it has pierced a sort of manna. The Coccus sinensis produces a kind of wax which is employed in China in the manufacture of candles.

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IV.

LEPIDOPTERA.

This order of insects is known popularly by the names of Butterflies and Moths. Linnaeus gave them the name of Lepidoptera, meaning insects with scaly wings {xiiris, a scale; and irT(p6v, a wing). They are to be found in great numbers in all parts of the world. All the insects contained in the order are, in their perfect state, remarkable for the elegance of their shape, the rapidity and airiness of their flight, and the multiplicity and beauty of their colours. Before they arrive at this perfect state, the Lepidoptera have to undergo three complete transformations. They leave the egg in the larva or caterpillar state; they pass next to the state of pupa, or chrysalis: they then assume, after a variable time, their final or perfect form. We will study them in their three difterent states in succession.

The Larva, or Caterpillar.

When the winter has stripped the leaves ofl" the trees, the Lepidoptera are seen no more; but as soon as the leaves begin to show themselves on the trees and shrubs, this tribe of the insect race again makes its appearance. Caterpillars of all kinds are gnawing at the leaves, even before they are fully developed. Many of them have just emerged from the eggs which the perfect insects had laid at an earlier period; others have passed the winter in this state.

When they come out of the egg the young caterpillars are in shape more or less elongated and cylindrical. Their body is composed of twelve segments, or rings. In front is the head; then come three segments, on which are the front legs, and which constitute the thorax; the other segments constitute the abdomen. The head is formed of two scaly parts. It is often very deeply hollowed out on its upper side, and divided into two lobes, which contain in the angle formed by their separation the different parts of the mouth. The head is uniform, rarely having, so far as our cater-

pillars are concerned, any protuberance; but in the tropical species it is often armed with prickles, spikes, and extraordinary appendages. They are provided with six small simple eyes, isolated from each other. The mouth is armed laterally with a pair of very solid horny mandibles, articulated by means of vigorous muscles, and moving horizontally. It is the function of the mandibles, as with the jaws, to divide the creature's food. On the middle of a broad under-lip one may perceive a little elongated tubular organ, pierced with a microscopic orifice. This organ is the spinning apparatus, which the animal uses in fabricating the threads which it will one day require. It is a tube composed of longitudinal fibres. It presents only one orifice, cut obliquely, and capable of applying itself exactly to the body on which the larva is placed. From the contractile nature of

Fig. 94.— Scaly legs of the Caterpillar of the Gipsy Moth {Liparis dispar).

this organ and the form of its orifice, combined with the faculty the insect possesses of moving it in all directions, result the great differences we observe in the diameter and form of the threads.

The external organs of the trunk and abdomen are the legs, the spiracles, and various occasional appendages. The legs are of two different kinds. One set, to the number of six, attached by pairs to the trunk, are covered with a shiny cartilage, and armed with hooks.

These are the true legs. Fig. 94 represents, after Reaumur's "Memoire sur les Differentes Parties des Chenilles,"* the scaly legs of the caterpillar of the Gipsy Moth. The others are membranous, fleshy,

■generally conical or cylindrical, contractile, and taking, according to the will of the animal, very different forms. Fig. 95 represents, after the same Memoir of Reaumur's, the different forms of the membranous legs of the silkworm caterpillar. This plate gives a sufficiently good

• Tome i., p. 164; Plate III., Figs, i, 2.

idea of the shape of these organs, and of the hooks, circular or semicircular, with which they are furnished. In Fig. 96 are represented, after the same author, two mem-

Fig- 95- — Membranous legs of the Silkworm {Bombyx mart).

branous legs of a large caterpillar, of which the hooks of the feet are fastened into a branch of a shrub. Caterpillars have from two to ten false legs, the scaly legs being always six in number. The pro-legs, as the fleshy ones are called, are divided into hinder and intermediate. The former are two in number; the intermediate are rarely more than eight in number. In the caterpillars which have the full number of legs — that is to say, sixteen — there are two empty spaces, where the body has no support: the one between the legs and the pro-legs, formed by the fourth and fifth segment; the other, between the intermediate pro-legs and the anal legs, formed by the tenth and eleventh ring. The variations which caterpillars present, so far as the number and

Fig. 96.— Membranous legs of a large

Caterpillar embracing a twig. situations of their pro-legs are concerned, are the following;— The greatest number among them have ten pro-legs; others have only eight; others only six — these may be called semi-loopers; others

only four, one pair being situated on the last ring, and the other on the ninth, as in the case of looper caterpillars. And, lastly, there are others which have only two pro-legs.

The various forms, numbers, and positions of these organs, produce great differences in the mode of locomotion of caterpillars. Those provided with ten or eight membranous legs have in walking only a very slight undulating motion. Their bodies are parallel to the plane which supports them. They can walk very quickly; but their steps are short and quickly repeated. Others, on the contrary, in proportion as the number of their false legs diminishes, and the spaces between the legs increase, walk in a more irregular and quaint manner.

If the reader will glance at Fig. 97, taken from Re'aumur's " Memoire sur les Chenilles en ge'neral,"* which represents a looper caterpillar, with four membranous legs, he will see that there is a considerable space between the posterior legs and the first pair of pro-legs, along which the body has Fig. 97. — Looper Caterpillar. no points of support. If one of these caterpillars, lying quiet and at full length, determines to walk, in order to take its first step (Fig. 98) it begins by humping its back, curving into an arch that part which has no legs, and finishes by assuming the position seen in Fig. 99. In the former position it has

Fig. 98.— Caterpillar curved into an arch. Fig. 99. Caterpillar at full length.

its two intermediate legs against the posterior legs, and, in consequence, ithas brought forward the hinder part of its body, a distance equal to the interval of the five segments which separate them. There it hooks on by its intermediate and hind legs. Then it has only to raise and straighten the five rings which had formed the loop, ' and to advance its head to a distance equal to the length of five

• Tome i., p. 49, Plate I., Fig. 6.

segments. The step is thus made, the caterpillar making the same movements in taking the second and following steps.

This sort of gait has gained for them the name of Geometers, because they seem to measure the road over which they travel. When they make a step, they apply the part of their body which they have just curved up to the ground, in exactly the same way as a land surveyor applies his chain to it.

These looper caterpillars cannot shorten or lengthen their segments at will, as other caterpillars, but only bend their bodies.

Fig. TOO. — Caterpillar of the Canary-shouldered Thorn {Eugonia alniaria).

There are many species whose bodies are cylindrical, stiff, and of the same colour as bark. Their attitudes deceive even the close observer. They embrace the stem of a leaf or twig with their hinder and

intermediate legs, whilst the rest of their body, vertically elevated, " remains stiff and immovable for hours together. Fig. loo shows the caterpillar of the Canary-shouldered Thorn {Eugo?iia alniaria) in this strange position. Now, this is a feat of strength which the most skilful of our acrobats, ordinary and extraordinary, which all the Leotards of the present day, and those who are to succeed them, can never accomplish. With such a persistency, this caterpillar can

LEPIDOPTERA,

sustain its body in the air for a considerable time, in all the positions imaginable, between the vertical and the horizontal, and downwards again in any incline from the horizontal to the vertical. '' If one considers," says Reaumur, " how far we are from having in the muscles of our arms a force capable of supporting us in such attitudes as these, we must own that the power of the muscles in