INSECTS, Insecta, in Natural History. See Entomology. Noxious Insects; Means of destroying them, or preventing their increase. Of those substances which have been generally observed to be efficacious in driving away or in destroying insects, mercury, and its various preparations, may be reckoned the most generally effectual. Sulphur is also useful. Oils of all kinds have often been deservedly recommended; and tobacco is not less remarkable for its utility.

Mercury is known to kill or drive away lice from the human body; and it may probably be of equal efficacy in ridding other animals of insects. For instance, a small quantity of mercurial ointment rubbed upon the skins of sheep, on the sides, between the fore-legs and the body, may kill or drive away the insect peculiar to these animals. Sulphur is recommended to be added to the mercurial ointment. Thus not only the insect peculiar to them, but also the scab, may be cured.^[1. Transactions of the Society for the Encouragement of Arts, London, vol. víL viii. p. 90. ] Ailway^[2. Ibid. vol. V. vi. p. 59. ] directed that, in the winter, the walls, frames, and other parts of his green and hot houses should be well washed with corrosive sublimate mercury, dissolved in water. These houses had been greatly in fested with red spiders and ants. After having been washed • with this solution, neither of these were to be seen next summer. This wash, if made weaker, may be used on old garden-walls, and the roots of fruit-trees infested with in- • sects. It may destroy the tender leaves of plants, though not the roots. The same wash will effectually destroy that dis- • agreeable insect the bug, and all other insects of a tender cuticle; and it will not in the least hurt the colour of bedfurniture or hangings. Care must be taken that the wash be applied into every crevice or folding of the furniture with a painter’s brush. It will sometimes be necessary to repeat the wash, as the ova of bugs may remain concealed, notwithstanding the utmost care.

Some of the West India islands were much infested with large ants, which greatly injured the sugar-canes. The remedy was, to dissolve corrosive sublimate mercury in rum, in the proportion of two drams to a pint of spirits. This solution was poured upon dry powdered sugar; and when the sugar was dried, it was laid in the paths of the ants. They ate it, and were destroyed. Might not this practice be imitated, by laying sugar thus prepared on paper or pieces of thin boards near the roots of fruit-trees infested by insects, especially when the fruit is ripening? The papers or boards might be taken in during the night, or when it rained. The sugar should be coloured with indigo, or other substance, thereby to mark it as a substance to be avoided by curious idlers.

We are informed that a person in Philadelphia employed brimstone in the following manner. Having cleared all round the roots of trees infested with caterpillars or other insects, he strewed some flowers of brimstone round the roots, and covered it with a thin sprinkling of fine mould, that it might not be blown away by the wind, yet so that the sun might operate through the mould, and cause the brimstone to fumigate. In this manner he destroyed the caterpillars. One pound he found sufficient for two∙hundred trees. In that hot climate the sun may perhaps have that effect; but it scarcely will in this. To drive insects from small trees, he also employed sulphur in the following manner. He split the end of a pole, and put in the slit some matches, set them on fire, and held them under the parts of the trees chiefly affected. A pole thus armed, he found, would answer for three or four trees. Brimstone mixed with damp straw, and set on fire, in hop-ground infested with the fly, for instance, might be of use in driving away that insect.

The itch is supposed to originate from a very small insect which nestles under the skin, and proceeds no farther; and it is, therefore, attended with no dangerous consequences. Brimstone made into an ointment with hogs-lard is a sure remedy.

Sheep are liable to an eruption on the skin, known by the name of the scab. Brimstone, when added to the mercurial ointment recommended for that disorder,^[3. Ibid. vol. vii. p. 90. ] might perhaps render the application more efficacious and less dangerous.

The natives of hot countries are taught by experience, that an unctuous covering of their bodies prevents the bites of musquitos and all gnats. The white inhabitants in such countries are not sufficiently careful in preventing the least stagnant water near their dwellings, in which the musquitos are bred; they are produced even in the waste water thrown out. Dr Franklin, by a careful attention to this circumstance, guarded his family in Philadelphia from such insects. One day seeing a number of musquitos in his library, he found on inquiry, that one of his servants had taken off the cover of a tub placed near his window for receiving rain-water. On such an occasion the remedy is [7:12:294] easy, namely, shutting up the room for the day, so that the musquitos cannot come at any water, in which time they die. Though this caution may seem trifling to us who live in a mild climate, it is far otherwise in hot countries.

Oil being known to be most efficacious in destroying insects, may not the use of it be extended to the destruction of worms in the bowels of horses, where they probably occasion the violent pain which these animals seem sometimes to suffer? If the horse were for some time kept fasting, and a large quantity of oil, say a pint, were given, supposing worms were the cause, the oil might in that case destroy them.

Flowers, leaves, and fruits, are known to be devoured by caterpillars. But these are destroyed by oils, which close the lateral pores by which they breathe. For this purpose it is advised that, on the approach of spring, a cloth dipped in train oil be laid on those parts of the tree in which there is any appearance of them.

We are informed in the Memoirs of the Society of Agriculture at Paris, that oil of turpentine, when applied to animals covered with insects, destroyed the insects without hurting the animal. The author tried it on several trees, mixed with fine earth so as to incorporate therewith, adding water, till the whole was brought to some degree of fluidity. In this mixture he dipped branches of fruit-trees on which there were insects, and thereby destroyed not only the eggs but also the insects, without hurting the leaves. This composition may be got off by washing, or the first heavy shower. From these experiments the author thinks, that oil of turpentine may with equal efficacy be employed for killing various kinds of lice on domestic animals.

We are informed that Mr Winter, amongst other experiments on turnip-seed, steeped the seed twenty-four hours in a sufficient quantity of train-oil. He then drained the oil from the seed, which he mixed with a quantity of fine sifted earth, and immediately sowed it in drills. When the plants began to appear on the surface, the ground was sown with soot. He found that seed steeped in linseed oil answered equally well.^[4. Transactions of the Society for the Encouragement of Arts, vol. v. p. 45. ] The turnips least injured by the fly, were those which grew from seed steeped in this way; they grew so luxuriantly as to produce rough leaves several days prior to the most flourishing of any of his other experiments, and were the better enabled to withstand the attack of the fly. The leaves of these turnips were of a darker green, and appeared twice as thick in bulk and luxuriancy as the other turnips, and were considerably larger. The seed was drilled an inch and a half deep, and a foot distant in the rows. Train oil is apt to kill the Ieaves of plants which have been injured by insects, but linseed oil has not that effect, though equally destructive to the insects. The train oil seems to act as an oil, and by its disagreeable smell to prevent insects approaching it. In this respect it may be successfully used to prevent field mice or other vermin preying on acorns, chestnuts, or other seeds steeped in it before they are sown.

When thus giving directions for preventing the fly on turnips, an experiment may be mentioned, by the disclosure of which a person gained a considerable reward. His se- ' cret was, running a roller over the ground early in the morning, whilst the dew remained on the ground, on the first appearance of the fly. The dew entangled the flies so much, that they could not make their escape, and were therefore crushed to death. But as the roller may leave the surface of the earth too hard, it was recommended to fix some boughs of elder in a gate or hurdle, to be drawn over the field; and if the boughs had before been fumigated with the smoke of tobacco, or tincture of assafoetida, the success would be the surer. The most certain method of preventing the injury done by the fly is to raise the plants in a nursery, and at a proper age to transplant them, being carried to the ground in a wheel-barrow filled with manure softened with water so as to admit the plants. This method will secure their more speedy growth. In the nursery the attack of the fly may be prevented by sprinkling soot or quicklime on the ground. The utility of transplanting turnips is evident by the practice of transplanting the turnip-rooted cabbage. They who are discouraged from having recourse to this practice by the expense attending it, do not reflect that the hoeing is prevented, and the plants grow the better, being set in fresh earth.

Before proceeding to direct the use of the last means mentioned, viz. tobacco, for destroying insects in turnips, it may be proper to mention an experiment made by Mr Green, of the flower-garden at Kew. He contrived a pair of bellows similar to that employed in recovering people apparently drowned. It had a cavity in the nozzle, in which some tobacco was put, with a live coal over it. The bellows being then worked, the tobacco was set on fire, and the smoke directed to any particular spot. A lady was fond of having the mosk-rose in her dressing-room, but was prevented having it on account of the green insects which constantly adhere to that plant. To remedy this inconvenience, Mr Green had a box made large enough to contain a pot in which a plant of the mosk-rose grew. In one end of the box was a hole, to admit the nozzle of the bellows; the bellows was worked, and the smoke was received into the box. When the tobacco was consumed, the nozzle was withdrawn, and a cork being put into the hole, the box thus remained till morning, when the insects were all laid dead on the earth. Being swept off, the plant was in a state fit for a dressing-room. Many plants thus infested with insects may be too large, or otherwise so placed as not to be put into a box. In this case it occurred to the writer of these observations, that sprinkling the plants with an infusion of tobacco in water might in some degree answer the same purpose. On trial he found it answer, and he thus freed other plants from their insects. He also used it on trees of easy access with advantage. Train oil is so inimical to tender plants or leaves, that it destroys them if insects have in the least hurt them; whereas the infusion, instead of killing the leaves, promoted a fresh vegetation.

Fruit-trees often become the prey of insects. Those trained against a wall, or as espaliers, being easily come at, much of the mischief may be prevented by cutting off the leaves as soon as they are observed to be curled; for then fresh eggs are laid on them, probably by butterflies. If sprinkled with the infusion of tobacco, it will prevent their coming to life. After the fruit is formed, the infusion must not be used, lest the taste and smell should remain. The scissors are then the proper remedies, which ladies may employ as amusement, and may thereby present fruit to their friends of their own preserving. A lye of the ash of plants sprinkled on the leaves may have a good effect, as also on other pot-herbs, which are often the prey of caterpillars. As many insects, besides those bred on the leaves or in the walls, may destroy the fruit, the sugar with the corrosive sublimate, as already described, may be laid in the way of other insects, to all which it will prove a speedy death. Diligent inspection of their retreats is the most certain means of preventing the loss sustained by snails. Ants are prevented rising up the trees by laying round the roots powdered chalk, or any other substance which, by entangling their feet, prevents their crossing it. Care should be taken to destroy their nests everywhere near the garden.

Hops have now become an article of so great consequence, that it deserves our particular attention. Early in its growth when the vines begin to ascend the poles, a black fly preys [7:12:295]on its leaves, frequently in such numbers as, by destroying the leaves, to interrupt the vegetation, much of the food of plants being absorbed by the leaves. The infusion of tobacco destroys them, or at least drives them away so effectually, that a plant almost totally stripped of its leaves has pũt out fresh leaves after the use of the infusion. If care be not taken, the insects will again fall on the fresh leaves. As the flics lodge on the lower side of the leaves, they are protected from storms of rain, and therefore the infusion must be driven upwards by a forcing-pump. It is said that the expense of tobacco is too great, but perhaps lime-water, or even water by itself, driven strongly against the leaves, might drive them away. The labour attending such experiments in a large plantation discourages persons, who do not reflect, that, if such means are used early, the flies may more easily be got rid of. Free ventilation is undoubtedly beneficial to all plants; and hence perhaps the particular advantages of drilling corns in rows a little distant. If alleys somewhat larger than common were made in the plantations of hops, there might be sufficient spaces left, where the alleys cross one another, to admit of setting damp straw or other materials mixed with brimstone, soot, or the like, on fire. Smoke itself is said to prevent the fly; and if so, it still will act more powerfully when mixed with such materials. It has been observed in Sweden, that the hops grow naturally amongst heaps of stones or fragments of rocks. They therefore advise to cover the ground round their roots with stones, which will prevent the insects laying their eggs near the roots in the ground, where they lay them to be protected during the winter. The stones will also preserve moisture at the roots during the summer. A rope cannot be drawn across a plantation of hops, as it can across a field of corn, in case of mildew. Here water to wash off the clammy juice, which entices and feeds insects, seems to be the only remedy. The plantation being well ventilated, may at least prevent the frequency of it. The forcing-pump will most effectually wash off this exudation.