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the following rule is to be observed: One portion of lettuce daily is given to the youngest; the double to those jn the second stage; bui, when they have arrived at their natural size or third stage, they will need more than triple of what they got at first, that is to" fay, five parts must be given them.
These insects eat indifferently fig and young elm leaves, but those of the white mulberry are their most favourite food. When these are given them, care must be taken, that they be neither moist, nor too succulent. The leaves of the young mulberries* or of those that grow in a moist soil, have this defect. Such an aliment does not suit their constitution. On the contrary, it is very hurtful to them, and almost always fatal. The best food for them is, the leaf of those white mulberries that grow in stony and dry places, on hills and mountains, which are op'en to the free air, beaten by the winds, and exposed to the violence of tempests. Such a tree has its juices purified, and fit for the nourishment of silkworms. Should the leaves happen to be surcharged with dew or rain, the situation of the tree soon shakes off the humidity, and the wind restores its former dryness.
I would not, however, advise any one to trust in this cafe, entirely to chance. I would rather chuse to delay gathering the leaves till the fun has succeeded the rain, or till mid-day, before making a provision of leaves, nor would I feed my silk-worms, before I had wiped off all the humidity which has escaped the winds, or the heat of the fun.
I cannot sufficiently recommend the keeping of the place where they are reared, neat and ciean.— Great care must be taken in the cleaning, which is done with a delicate rush or with a feather, not to
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come too near these delicate bodies, which can hardly be touched without hurting them. All places are not equally fit for them; they should neither be too dr). nor too moist, nor subject to be infested by such insects as they have an antipathy at, or which are restless and turbulent* Of all exposures the least favourable are those of the north and south. The winds from these tv/o quarters are exceedingly pernicious to them, the one by its coldness, the other by its humidity; for which reason, it is necessary, that the place be so disposed, as that its temperature may be regulated, by shutting the windows on one sidey and keeping them open on the other, according as the wind shall blow from the north or south. When the weather is moist, it is proper to keep the place quite close; but when it lightens, that is not sufficient; the silk worms must be covered up, otherwise they Contract a disease, which some curious persons have thought proper to term jaundice. They do indeed acquire a yellow colour, lose their appetite, and die insensibly. Those that die,' should be separated from the living, for fear of communicating infection t* them.
CHAP. I. How Insects Hurt The Produce Of The Earth.
Not only do insects pillage and ravage the fields, but they attack man in his domestic economy, and do him infinite mischief. Nothing can be protected against their ordure; we see, with regret, our most precious furniture tarnished and infected by flies. These restless insects enter our libraries, nestle in our cabinets, pass from one apartment to another, and leave every where behind them, the most conspicuous nmks of their having been present. There is not a man, from the king to the poorest of his subjects, who can defend himself against their attacks.
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Husbandmen perhaps are the most to be pitied. How often do they not find themselves disappointed of a plentiful crop by the depredations of locusts! These voracious animals often leave distant countries,, traverse oceans, pour in myriads upon sown fields, and deprive them in a few hours of every appearance of verdure. Are not caterpillars often as noxious to us i I know not a more cruel scourge for gardens than they are. . They eat into flowers, they gnaw the roots, and so destroy the plants they touch, that we are obliged to throw them away.' Some do not wait till a plant is able to furnish them food for weeks, they devour it the moment tt appears. Others on the contrary wait till the feed is produced ; they then devour it so greedily, that nothing is left but the empty skin to the owner. Weevils are not behind hand with these; they pierce the ripe grain, eat the pulp, and thus rob our granaries of that food which is of the greatest importance to the human race.
But it is not on herbaceous plants alone, that infects bring ruin ; their attacks are not less disastrous to fruit trees. If they deposit their eggs in autumn, the young caterpillars are hatched in the Spring when the trees are 'only beginning to shoot forth, and they commit such ravages on the buds and foliage, that wherever they are found in numbers, the fruits of the year entirely fail. The small Curculios, some beetles and several sorts of caterpillars conspire in producing this devastation, and sometimes reduce the trees to the fame state they were in during winter. This is. not all, for there are some forts of golden coloured beetles which produce two sorts of larvæ, red and . white. These larvæ penetrate the bark, and suck the juice till the tree becomes completely dried up. There are also some small beetles which, not content with eating .the bark, attack the wood, and contrive to desolate whole forests. This accident has but too oftenhappened with woods planted with pines. The wood of Schwartzenburg experienced this to such a degree in the year 1736, as cost its proprietor many thousand crowns. I lba.Il content myself with this one example; those whtch I could adduce of many other forts
which destroy wood are too common not to be known by every one.
Of The Eviu Which Insects Cause To Man.
We have spoken of the ravages which insects make both in the country and in towns; let us now take a view of ;he mischiefs they occasion to man himself personally. Some disturb his sleep, others oblige him to pass whole nights without sleeping at all. Indeed, what does he not sometimes suffer from the restless flea, and the loathsome bug? How can he take rest when unhappy enough to be exposed to the" sanguinary insults of such tormentors? But were he free from these, the gnats do not cease to persecute him. Their incessant buzzing disquiets him, and whether asleep or awake, while in darkness he is e>qually a prey to those stings which he dreads but which he cannot prevent. In the East Indies the inhabitants are exceedingly tormented by those insects which the Portuguese call Mosquitoes. These dangerous animals dart upon those whom they sur-> prize asleep, ancfin such prodigious numbers that it is no-easy matter to resist them. When one is stung in the face, or in any other part of the body, there ensues a considerable tumour, accompanied with itch* jng and intolerable pain,