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Among their enemies, one of the principal is a small black species of Ichneumon fly*, which darts its pointed tail into the bodies of the Aphides, and at the same time deposits in each an egg. This egg afterwards produces a grub, which feeds on the body of the insect till it has acquired its full growth, when it undergoes its change, and entirely destroys its living nidus.
After a mild spring, most of the species of Aphis become so numerous as to do considerable injury to the plants on which they are found. The best mode of remedying this evil, is to lop off the infected shoots before the insects are greatly multiplied, repeating the same operation before the time that the eggs are deposited. By the first pruning, a very numerous present increase will be prevented; and by the second, the following year's supply may, in a great measure, be cut off.
THE APHIS OF THE BEANT.
Among the Garden Beans, a small black Aphis may frequently be observed, adhering to the tops in immense numbers, and afterwards gradually spreading over the whole plants. They are principally to be observed in the months of June and July; and so small and light are they, as often to be carried from one plant to another by the wind. They seldom appear until after the beans are in blossom; and, if carefully watched, it will be found that they are confined to a small extent. Dr. Anderson says, that he has seen a row of beans greatly tainted, whilst another, at the distance only of six or eight feet, had none. At the beginning, the upper
leaves and the blossom are alone infected. These now appear crumpled together, and full of blackish specks.
* The Ichneumon aphidum, of Linnæus.
In such case, the tops should all be cut off. By this means the danger of their increase, especially in gardens, may be averted without any extraordinary degree of exertion. In fields, however, this is not so easy: in a field where they are observed, it would, perhaps, on some occasions, be found economical for the farmers of a district to contribute among themselves, so as to pay the damage that would arise to any particular person for having the whole crop of the field, in which they first began, destroyed at once, in order to prevent the insects from spreading further, and thus injuring the adjacent crops.
OF THE COCCUS, OR COCHINEAL
These are an extremely fertile race, and many of them are very troublesome in stoves and green-houses. The females fix themselves, and adhere almost immovably, to the roots, and sometimes to the branches, of plants. Some of them, having thus fixed themselves, lose entirely the form and appearance of insects: their bodies swell, their skin stretches and becomes smooth, and they so much resemble some of the galls or excrescences, found on plants, as by inexperienced persons to be mistaken for such. After this change, the abdomen serves only as a kind of shell or covering, under which the eggs are concealed. Others, though they are likewise thus fixed, preserve the form of insects, till they have laid their eggs and perish. A kind of down or cotton grows on their belly, which serves for the formation of the nest, in which they deposit their eggs.
*In the Cochineal insects the beak is situated on the breast; and the antennæ are thread-shaped, or of equal thickness throughout. The abdomen is terminated by four or six light-coloured bristles. The male has two erect wings, but the females have none.
The males are from the females.
very different in their appearance They are furnished with wings, and
are small but active insects.
Most of the species of Coccus, which infest our greenhouses and conservatories, have been brought over, with exotic plants, from other climates.
THE LAC COCHINEAL*.
Mr. Kerr, who, in the Philosophical Transactions, had given a minute account of these insects, says, that he has often observed their birth, but could never see any of them with wings; nor was he ever able to remark any distinction in the sexes; owing, most probably, to the minuteness of the objects, and the want of proper glasses.
They are produced from the parents in the months of November and December. For some time they traverse the branches of the trees upon which they are produced, and then fix themselves on the succulent extremities of the young shoots. By the middle of January they are all fixed in their proper situations, and, though they now exhibit no marks of life, they appear as plump as before. The limbs, antennæ, and bristles of the tail, are no longer to be seen. Around the edges of their body they are environed with a sub-pellucid gelatinous liquid, which seems to glue them to the branch. The gradual accumulation of this liquid at length forms a complete cell for the
* DESCRIPTION. The head and trunk seem to form one uniform, oval, compressed, red body, consisting of twelve transverse rings, and somewhat of the shape and size of a very small louse. The back is keel-shaped, and the belly flat. The antennæ are half the length of the body, filiform, and diverging, sending off two and sometimes three diverging hairs. The tail is a little white point, from which proceed two horizontal hairs as long as the body.
SYNONYMS. Coccus ficus. Linn.-Gum Lac, in the East Indies.
insect. The insect is now, in appearance, an oval, smooth, red bag, without life, about the size of a small American Cochineal insect, emarginated at the obtuse end, and full of a beautifully red liquid.
In October and November, twenty or thirty small oval eggs, or rather young grubs, are to be found within the red fluid of the mother. When this fluid is all consumed, the young insects pierce a hole through the external covering, and walk off one by one, leaving their nidus behind. This nidus is that white membranaceous substance found in the empty shells of the Stick Lac.
These insects are found on only four different kinds of trees, the principal of which are the Ficus religiosa and Ficus Indica, of Linnæus.
They generally fix themselves in such numbers, and so close to each other, that scarcely more than one female in six has room to complete her cell: the others die, and become the food of various insects. The extreme branches of the above trees appear as if they were covered with a red dust, and their sap is frequently so much exhausted, that the adjoining parts wither away. The sap of the trees seems much allied to the cell of the Coccus, so that it appears to have undergone very little change by its formation into these cells.
These insects, which in the East Indies have the name of Gum Lac, are principally found on the trees of the uncultivated mountains on both sides of the Ganges, where nature has been so bountiful, that, were the consumption many times greater than it now is, the markets would be fully supplied. The only trouble is in breaking down the branches and carrying them to market.
In the year 1781, the price of Gum Lac, in Dacca, was only twelve shillings for the hundred pounds weight, notwithstanding its being brought from so great a distance as Assam. The best Lac is of a deep red colour. If it be pale, and pierced at the top, the value diminishes, because the insects have left their cell, and con
sequently it can be of no use as a dye; though probably it may be of more value as a varnish.
Stick Lac is the natural state of this production. When the cells are separated from the sticks, broken into small pieces, and appear in a granulated form, they are called Seed Lac. This, liquified by fire and formed into cakes, is Lump Lac. When the cells are liquified, strained, and formed into thin, transparent laminæ, the substance has the name of Shell Lac.
Of Shell Lac the natives of Eastern countries make ornamental rings, to decorate the arms of females. They also form it into beads, necklaces, and other female ornaments. This substance was formerly used in medicine, but it is now confined principally to the making of sealing-wax, and to japanning, painting, and dyeing.
THE AMERICAN COCHINEAL*.
This Cochineal, so useful to painters and dyers, is a native of South America, where it is found on several
DESCRIPTION. The Cochineal Insect of the Brasils is convex, with legs of a clear bright red in both male and female, and the antennæ moniliform or bead-like. The male is a delicate and beautiful insect: the colour of its whole body is bright red, nearly resembling the pigment usually called red lake; the breast is elliptical, and slightly attached to the head. The antennæ are more than half the length of the body. The legs are of a more brilliant red than the other parts. Two fine white filaments, about three times the length of the insect, project from its belly or abdomen. The wings are two, erect, of a faint straw-colour, and of a very delicate texture. female has no wings, is elliptic in its form, and convex on both sides; but chiefly so on the back, which is covered with a white downy substance resembling the finest cotton. The abdomen is marked with transverse rugæ or furrows. The mouth is situated in the breast, having a brown beak, inclining to a purple tint, that penetrates the plant on which the insect feeds. Its six legs are of a clear bright red. Barrow's Travels.
SYNONYMS. Coccus cacti. Linn.-La Cochenille du Nopal, by the French.