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the following rule is to be observed: One portion of lettuce daily is given to the youngeft; the double to thofe in the fecond ftage; but, when they have arrived at their natural fize or third ftage, they will need more than triple of what they got at first, that is to fay, five parts must be given them.

Thefe infects eat indifferently fig and young elm leaves, but thofe of the white mulberry are their most favourite food. When these are given them, care must be taken, that they be neither moift, nor toc fucculent. The leaves of the young mulberries, or of thofe that grow in a moift foil, have this defect. Such an aliment does not fuit their conftitution. On the contrary, it is very hurtful to them, and almost always fatal. The best food for them is, the leaf of thofe white mulberries that grow in ftony and dry places, on hills and mountains, which are open to the free air, beaten by the winds, and exposed to the violence of tempefts. Such a tree has its juices purified, and fit for the nourishment of filkworms. Should the leaves happen to be furcharged with dew or rain, the fituation of the tree foon fhakes off the humidity, and the wind restores its former drynefs.

I would not, however, advise any one to truft in this cafe, entirely to chance. I would rather chufe to delay gathering the leaves till the fun has fucceeded the rain, or till mid-day, before making a provifion of leaves, nor would I feed my filk-worms, before I had wiped off all the humidity which has escaped the winds, or the heat of the fun.

I cannot fufficiently recommend the keeping of the place where they are reared, neat and clean.Great care must be taken in the cleaning, which is done with a delicate rufh or with a feather, not to

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come too near thefe delicate bodies, which can hard. ly be touched without hurting them. All places are not equally fit for them; they should neither be too dry, nor too moift, nor subject to be infested by such infects as they have an antipathy at, or which are restless and turbulent. Of all expofures the least savourable are those of the north and fouth. The winds from these two quarters are exceedingly pernicious to them, the one by its coldnefs, the other by its humidity; for which reason, it is neceffary, that the place be fo difpofed, as that its temperature may be regulated, by fhutting the windows on one fide, and keeping them open on the other, according as the wind fhall blow from the north or fouth. When the weather is moift, it is proper to keep the place quite clofe; but when it lightens, that is not fufficient; the filk worms must be covered up, otherwise they contract a difcafe, which fome curious perfons have thought proper to term jaundice. They do indeed acquire a yellow colour, lofe their appetite, and die infenfibly. Thofe that die, fhould be feparated from the living, for fear of communicating infection to them.

BOOK IL

BOOK II.

PART III.

CHAP. I.

How INSECTS HURT THE PRODUCE OF THE EARTH.

Not only do infects pillage and ravage the fields, but they attack man in his domeftic economy, and do him infinite mifchief. Nothing can be protected against their ordure; we fee, with regret, our most precious furniture tarnished and infected by flies. These restless infects enter our libraries, neftle in our cabinets, pafs from one apartment to another, and leave every where behind them, the most confpicuous marks of their having been prefent. There is not a man, from the king to the poorest of his fubjects, who can defend himself against their attacks.

Husbandmen perhaps are the most to be pitied. How often do they not find themselves disappointed of a plentiful crop by the depredations of locufts! These voracious animals often leave distant countries, traverse oceans, pour in myriads upon fown fields, and deprive them in a few hours of every appearance

of

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of verdure. Are not caterpillars often as noxious to us? I know not a more cruel fcourge 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 it appears. Others on the contrary wait till the feed is produced; they then devour it fo greedily, that nothing is left but the empty fkin to the owner. Weevils are not behind hand with thefe; 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 lefs difastrous to fruit trees. If they depofit their eggs in autumn, the young caterpillars are hatched in the Spring when the trees are only beginning to fhoot forth, and they commit fuch ravages on the buds and foliage, that wherever they are found in numbers, the fruits of the year entirely fail. The fmall Curculios, fome beetles and feveral forts of caterpillars confpire in producing this devaftation, and fometimes reduce the trees to the fame ftate they were in during winter. This is. not all, for there are fome forts of golden coloured. beetles which produce two forts of larvæ, red and white. These larvæ penetrate the bark, and fuck the juice till the tree becomes completely dried up. There are alfo fome fmall beetles which, not content with eating the bark, attack the wood, and contrive to defolate whole forefts. This accident has but too often happened with woods planted with pines. The wood of Schwartzenburg experienced this to fuch a degree in the year 1736, as coft its proprietor many thousand crowns. I thall content myfelf with this one example; thofe which I could adduce of many other forts

which deftroy wood are too common not to be known by every one.

CHA P. II.

OF THE EVILS WHICH INSECTS CAUSE TO MAN.

We have fpoken of the ravages which infects make both in the country and in towns; let us now take a view of the mischiefs they occafion to man himself perfonally. Some difturb his fleep, others oblige him to pass whole nights without fleeping at all. Indeed, what does he not fometimes fuffer from the restless flea, and the loathfome bug? How can he take reft when unhappy enough to be exposed to the fanguinary infults of fuch tormentors? But were he free from thefe, the gnats do not ceafe to perfecute him. Their inceffant buzzing difquiets him, and whether asleep or awake, while in darknefs he is equally a prey to thofe ftings which he dreads but which he cannot prevent. In the Eaft Indies the inhabitants are exceedingly tormented by those infects which the Portuguese call Mofquitoes. These dangerous animals dart upon thofe whom they furprize afleep, and in fuch prodigious numbers that it is no eafy matter to refift them. When one is ftung in the face, or in any other part of the body, there enfues a confiderable tumour, accompanied with itching and intolerable pain.

There

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