Chapter X: Letter VI: Injuries Caused by Insects (1)

INDIRECT INJURIES CONTINUED.

Having endeavoured to give you some idea of the mode in which insects establish and maintain their empire over man and his train of dependent animals, I shall next call your attention to his _living vegetable_ possessions, whether the produce of the forest, the field, or the garden; whether necessary to him for his support, convenient for his use, or ministering to his comfort, pleasure and delight:--and here you will find these little creatures as busily engaged in the work of mischief as ever, destroying what is necessary, deranging what is convenient, marring what is beautiful, and turning what should give us pleasure into an object of disgust.

Let us begin with the produce of our _fields_.--Bread is called "the staff of life:" yet should divine Providence in anger be pleased to give the rein to the various insects which, in the different stages of its growth, attack the plant producing it, how quickly would this staff be broken! From the moment that _wheat_ begins to emerge from the soil, to the time when it is carried into the barn, it is exposed to their ravages. One of its earliest assailants in this country is that of which Mr. Walford has given an account in the _Linnean Transactions_, taking it for the wire-worm; but, as Mr. Marsham observed, not correctly; it being probably the larva of some coleopterous insect, perhaps of one of the numerous tribe of _Brachyptera_ or rove-beetles which are not universally carnivorous. This animal was discovered to infest the wheat in its earliest stage of growth after vegetation had commenced; and there was reason to believe that it began even with the grain itself. It eats into the young plant about an inch below the surface, devouring the central part; and thus, vegetation being stopped, it dies. Out of fifty acres sown with this grain in 1802, ten had been destroyed by the grub in question so early as October[270].--Other predaceous _Coleoptera_ will also attack young corn. This is done by the larva of _Zabrus gibbus_, particularly with respect to wheat. In the spring of 1813 not less than twelve German hides (_Hufen_), equal to two hundred and thirty English acres, were destroyed by it in the canton of Seeburg, near Halle in Germany; and Germar (who with other members of the Society of Natural History, at that place, ascertained the fact,) suspects that it was the same insect, described by Cooti, an Italian author, which caused great destruction in Upper Italy in 1776.--Not only is the larva, which probably lives in that state three years, thus injurious; but, what one would not have expected, the perfect beetle itself attacks the grain when in the ear, clambering up the stems at night in vast numbers to get at it.--Along with the larvæ of this insect were found, in the proportion of about one fourth, those of another beetle (_Melolontha ruficornis_), which seemed to contribute to the mischief[271].

Mr. Markwick has given us the history of a fly that attacks wheat in a later period of its growth, which, if it be not indeed the same, appears to be nearly related to the _Musca Pumilionis_ of Bierkander[272], (_Oscinis_ F.) accused by him of being extremely injurious to rye in the spring. Our insect was discovered on the first sown wheats early in that season, making its lodgement in the very heart of the principal stem just above the root, which stem it invariably destroyed, giving the crop at first a most unpromising appearance, so that there seemed scarcely a hope of any produce. But it proved in this and other instances that year (1791) that the plant, instead of being injured, derived great benefit from this circumstance; for, the main stem perishing, the root (which was not hurt) threw out fresh shoots on every side, so as to yield a more abundant crop than in other fields where the insect had not been busy. These flies therefore seem to belong to our insect benefactors; and I should not have introduced them here, had it not been probable that in some instances later in the spring they may attack the lateral shoots of the wheat, and so be injurious. It is also not unlikely that the new progeny, which is disclosed in May, may oviposit in barley or some other spring corn, which would bring the next generation out in time for the wheat sown in the autumn.--These flies are amongst the last, and, in some seasons, the most numerous, that take shelter in the windows of our apartments when the first frosts indicate the approach of winter, previous to their becoming torpid during that season. When this little animal was first observed in England, it created no small alarm amongst agriculturists lest it should prove to be the _Hessian fly_, so notorious for its depredations in North America; but Mr. Marsham, by tracing out the species, proved the alarm to be unfounded[273]. That there was sufficient cause for apprehension should it have so turned out, what I have formerly stated concerning the latter insect, and the additional facts which I shall now adduce, will amply show.

The ravages of the animal just alluded to, which was first noticed in 1776, and received its name from an erroneous idea that it was carried by the Hessian troops in their straw from Germany, were at one time so universal as to threaten, where it appeared, the total abolition of the culture of wheat; though, by recent accounts, the injury which it now occasions is much less than at first. It commences its depredations in autumn, as soon as the plant begins to appear above ground, when it devours the leaf and stem with equal voracity until stopped by the frost. When the return of spring brings a milder temperature the fly appears again, and deposits its eggs in the heart of the main stems, which it perforates and so weakens, that when the ear begins to grow heavy, and is about to go into the milky state, they break down and perish. All the crops, as far as it extended its flight, fell before this ravager. It first showed itself in Long Island, from whence it proceeded inland at about the rate of fifteen or twenty miles annually, and by the year 1789 had reached 200 miles from its original station. I must observe, however, that some accounts state its progress at first to have been very slow, at the rate only of seven miles per annum, and the damage inconsiderable; and that the wheat crops were not materially injured by it before the year 1788. Though these insect hordes traverse such a tract of country in the course of the year, their flights are not more than five or six feet at a time. Nothing intercepts them in their destructive career, neither mountains nor the broadest rivers. They were seen to cross the Delaware like a cloud. The numbers of this fly were so great, that in wheat-harvest the houses swarmed with them to the extreme annoyance of the inhabitants. They filled every plate or vessel that was in use; and five hundred were counted in a single glass tumbler exposed to them a few minutes with a little beer in it[274].

America suffers also in its wheat and maize from the attack of an insect of a different order; which, for what reason I know not, is called the chintz-bug-fly. It appears to be apterous, and is said in scent and colour to resemble the bed-bug. They travel in immense columns from field to field, like locusts destroying every thing as they proceed: but their injuries are confined to the states south of the 40th degree of north latitude[275]. From this account the depredator here noticed should belong to the tribe of _Geocorisæ_, Latr.; but it seems very difficult to conceive how an insect that lives by suction, and has no mandibles, could destroy these plants so totally.

When the wheat blossoms, another marauder, to which Mr. Marsham first called the attention of the public, takes its turn to make an attack upon it, under the form of an orange-coloured gnat, which introducing its long retractile ovipositor into the centre of the corolla, there deposits its eggs. These being hatched, the larvæ, perhaps by eating the pollen, prevent the impregnation of the grain, and so in some seasons destroy the twentieth part of the crop[276].

One would think, when laid up in the barn or in the granary, that wheat would be secure from injury; but even there the weevil (_Calandra granaria_), in its imago as well as in its larva state, devours it; and sometimes this pest becomes so infinitely numerous, that a sensible man, engaged in the brewing trade, once told me, speaking perhaps rather hyperbolically, that they collected and destroyed them by bushels; and no wonder, for a single pair of these destroyers may produce in one year above 6000 descendants.--There are three other insects that attack the stored wheat, which are more injurious to it than even the weevil. One is a minute species of moth (_Tinea granella_), happily not much if at all known in this country; of which Leeuwenhoek has given us a full history under the name of the wolf. Another is a species of the same genus, at present not named, which, as we are informed by Du Hamel, at one time committed dreadful ravages in the province of Angoumois in France. The third is _Trogosita caraboides_, a kind of beetle, the grub of which called _Cadelle_, Olivier tells us, did more damage to the housed grain in the southern provinces of France than either the weevil or the wolf[277].--Here I may just mention a few other insects which devour grains that are the food of man, concerning which I have collected no other facts. The rice-weevil (_Calandra Oryzæ_) is very injurious to the useful grain after which it is named, as is likewise another small beetle, _Lyctus dentatus_, F. (_Sylvanus_, Latr.): and an Indian grain called in the country _Joharré_, which appears to be a species of Holcus or Milium, is the appropriate food of another species of Calandra[278], which I found abundant in it.

_Rye_, in this island, is an article of less importance than wheat; but in some parts of the continent it forms a principal portion of the bread-corn. Providence has also appointed the insect means of causing a scarcity of this species of food. The fly before noticed (_Oscinis Pumilionis_) introduces its eggs into the heart of the shoots of rye, and occasions so many to perish, that from eight to fourteen are lost in a square of two feet.--A small moth also (_Margaritia Secalis_) which eats the culm of this plant within the vagina, thus destroys many ears[279]. In common with wheat and barley it also suffers from Leeuwenhoek's wolf and the weevil.

_Barley_ likewise, another of our most valuable grains, has several insect foes. The gelatinous larva of a saw-fly (_Tenthredo_, L.) preys upon the upper surface of the leaves, and so occasions them to wither. _Musca Hordei_ of Bierkander also assails the plant. A tenth part of the produce of this grain, Linné affirms, is annually destroyed in Sweden by another fly, not yet discovered in Britain, (_Oscinis Frit_,) which does the mischief by getting into the ear, as does likewise _O. lineata_, F.--A small species of moth described by Reaumur, though not named by Linné, which may be called _Tinea Hordei_, (_Ypsolophus granellus?_) devours the grain when laid up in the granary. This fly deposits several eggs, perhaps twenty or thirty, on a single grain; but as one grain only is to be the portion of one larva, they disperse when hatched, each selecting one for itself, which it enters from without at a place more tender than the rest;--and this single grain furnishes a sufficient supply of food to support the caterpillar till it is ready to assume the pupa. Concealed within this contracted habitation, the little animal does nothing that may betray it to the watchful eye of man, not even ejecting its excrements from its habitation; so that there may be millions within a heap of corn, where you would not suspect there was one[280].

I have not observed that _oats_ suffer from insects, except from the universal subterranean destroyer of the grasses, the wire-worm, of which I shall give you a more full account hereafter; and occasionally from an Aphis. The only important grain that now remains unnoticed is the _maize_ or Indian corn. Besides the chintz-bug-fly, a little beetle[281] (_Phaleria cornuta_) appears to devour it; and it has probably other unrecorded enemies. The Guinea corn of America (_Holcus bicolor_), as well as other kinds of grain, is, according to Abbott, often much injured by the larva of a moth (_Noctua frugiperda_, Smith), which feeds upon the main shoot[282].

Next to grain _pulse_ is useful to us both when cultivated in our gardens and in our fields. Peas and beans, which form so material a part of the produce of the farm, are exposed to the attack of a numerous host of insect depredators; indeed the former, on account of their ravages, is one of the most uncertain of our crops. The animals from which in this country both these plants suffer most are the _Aphides_, commonly called leaf-lice, but which properly should be denominated plant-lice.--As almost every animal has its peculiar _louse_, so has almost every plant its peculiar _plant-louse_; and, next to locusts, these are the greatest enemies of the vegetable world, and like them are sometimes so numerous as to darken the air[283]. The multiplication of these little creatures is infinite and almost incredible. Providence has endued them with privileges promoting fecundity, which no other insects possess: at one time of the year they are viviparous, at another oviparous; and, what is most remarkable and without parallel, the sexual intercourse of one original pair serves for all the generations which proceed from the female for a whole succeeding year. Reaumur has proved that in five generations one Aphis may be the progenitor of 5,904,900,000 descendants; and it is supposed that in one year there may be twenty generations[284]. This astonishing fecundity exceeds that of any known animal; and we cannot wonder that a creature so prolific should be proportionably injurious; some species, however, seem more so than others. Those that attack wheat, oats, and barley, of which there are more kinds than one, seldom multiply so fast as to be very noxious to those plants; while those which attack pulse spread so rapidly, and take such entire possession, that the crop is greatly injured, and sometimes destroyed by them. This was the case with respect to peas in the year 1810, when the produce was not much more than the seed sown; and many farmers turned their swine into their pea-fields, not thinking them worth harvesting. The damage in this instance was caused solely by the Aphis, and was universal throughout the kingdom, so that a sufficient supply for the navy could not be obtained. The earlier peas are sown, the better chance they stand of escaping, at least in part, the effects of this vegetable Phthiriasis.--Beans are also often great sufferers from another species of plant-louse, in some districts from its black colour called the _Collier_, which begins at the top of the plant, and so keeps multiplying downwards. The best remedy in this case, which also tends to set the beans well, and improves both their quality and quantity, is to top them as soon as the Aphides begin to appear, and carrying away the tops to burn or bury them.--In a late stage of growth great havoc is often made in peas by the grub of a small beetle (_Bruchus granarius_), which will sometimes lay an egg in every pea of a pod, and thus destroy it.--Something similar I have been told (I suspect it is a short-snouted weevil) occasionally injures beans. In this country, however, the mischief caused by the Bruchus is seldom very serious; but in North America another species (_B. Pisi_) is most alarmingly destructive, its ravages being at one time so universal as to put an end in some places to the cultivation of that favourite pulse. No wonder then that Kalm should have been thrown into such a trepidation upon discovering some of these pestilent insects just disclosed in a parcel of peas he had brought from that country, lest he should be the instrument of introducing so fatal an evil into his beloved Sweden[285]. In the year 1780 an alarm was spread in some parts of France, that people had been poisoned by eating worm-eaten peas; and they were forbidden by authority to be exposed for sale in the market: but the fears of the public were soon removed by the examination of some scientific men, who found the cause of the injury to be the insect of which I am now speaking[286]. Another species of Bruchus (_B. pectinicornis_) devours the peas in China and Barbary. A leguminous seed, much used when boiled as food for horses in India, known to Europeans by the name of _Gram_, but in the Tamul dialect called _Koloo_, and by the Moors _Cooltee_, is the appropriate food of a fourth kind of Bruchus, related to the last, but having the antennæ, which in the male are pectinated, much shorter than the body. It is, perhaps, _B. scutellaris_. A parcel of this seed[287] given me by Captain Green was full of this insect, several grains containing two. Molina, in his History of Chili, tells us of a beetle, which he names _Lucanus Pilmus_, that infests the beans in that country;--a circumstance quite at variance with the habits of the _Lucanidæ_, which all prey upon timber. This insect was probably a _Phaleria_, in which genus the mandibles are protruded from the head like those of _Lucanus_; and one species, as we have seen above, feeds upon maize.

Great profits are sometimes derived by farmers from their crops of _clover-seed_: but this does not happen very often; for a small weevil, (_Apion flavifemoratum_,) which abounds every where at almost all times of the year, feeds upon the seed of the purple clover, and in most seasons does the crop considerable damage; so that a plant of the fairest appearance will, in consequence of the voracity of this little enemy, produce scarcely any thing. Another species (_Apion flavipes_) infests the Dutch or white clover[288]. The young plants of purple clover, when just sprung, are often, as Mr. Joseph Stickney pointed out to me, much injured by the same little jumping beetles (_Haltica_) that attack the turnips.

But not only, if let loose to the work of destruction, might insects annihilate our grain and pulse; they would also deprive the earth of that beautiful green carpet which now covers it, and is so agreeable and so refreshing to the sight. When you see a large tract of land lying fallow, as is sometimes the case in open districts, with no intervening patches of verdure, how unpleasant and uncomfortable is it to your eye! What then would be your sensations, were the whole face of the earth bare, and not dressed by Flora? But such a state of things would soon take place, if to punish us, or to teach us thankfulness to the great Arbiter of our fate, the insects that feed upon the _grass_ of our pastures were to become as generally numerous as they are occasionally permitted to do. One of the worst of these ravagers is the grub of the common cock-chafer (_Melolontha vulgaris_.)[289] This insect, which is found to remain in the _larva_ state four years, sometimes destroys whole acres of grass, as I can aver from my own observation. It undermines the richest meadows, and so loosens the turf that it will roll up as if cut with a turfing-spade. These grubs did so much injury about seventy years ago to a poor farmer near Norwich, that the court of that city, out of compassion, allowed him 25_l._, and the man and his servant declared that he had gathered eighty bushels of the beetle[290]. In the year 1785 many provinces of France were so ravaged by them, that a premium was offered by the government for the best mode of destroying them. They do not confine themselves to grass, but eat also the roots of corn; and it is to feast upon this grub more particularly that the rooks follow the plough.

The larva also of another species of a cognate genus (_Hoplia pulverulenta_) is extremely destructive in moist meadows, rooting under the herbage, so that, the soil becoming loose, the grass soon withers and dies. Swine are very fond of these grubs, and will devour vast numbers of them, and the rooks lend their assistance.

Amongst the _Lepidoptera_, the greatest enemy of our pastures is the _Charæas Graminis_, which, however, is said not to touch the foxtail grass. In the years 1740, 1741, 1742, 1748, 1749, they multiplied so prodigiously and committed such ravages in many provinces of Sweden, that the meadows became quite white and dry as if a fire had passed over them[291]. This destructive insect, though found in this country, is luckily scarce amongst us; but our northern neighbours appear occasionally to have suffered greatly from it. In 1759, and again in 1802, the high sheep farms in Tweedale were dreadfully infested by a caterpillar, which was probably the larva of this moth; spots of a mile square were totally covered by them, and the grass devoured to the root[292].

Most of the insects I have hitherto mentioned attack our crops partially, confining themselves to one or two kinds only; but there are some species which extend their ravages indifferently to _all_. Of this description is the _Pyralis? frumentalis_, which moth, Pallas tells us, is an almost universal pest in the government of Kasan in Russia, often eating the greater part of the spring corn to the root[293]. To this we are fortunately strangers; but another, well known by the name of the wire-worm, causes annually a large diminution of the produce of our fields, destroying indiscriminately wheat, rye, oats, and grass[294]. This insect, which has its name apparently from its slender form, and uncommon hardness and toughness, is the grub of one of the elastic beetles termed by Linné _Elater lineatus_, but by Bierkander, to whom we are indebted for its history, _E. Segetis_[295], which name is now generally adopted. The late ingenious Mr. Paul of Starston in Norfolk, (well known as the inventor of a machine[296] to entrap the turnip-beetle, which may be applied by collectors with great advantage to general purposes,) has also succeeded in tracing this insect from the larva to the imago state. His grubs produced _Elater obscurus_ of Mr. Marsham, which however comes so near to _E. Segetis_ that it is doubtful whether it be more than a variety. The other species, however, of the genus have similar grubs, many of which probably contribute to the mischief. When told that it lives in its first (or feeding) state not less than five years, during the greatest part of which time it is supported by devouring the roots of grain, you will not wonder that its ravages should be so extensive, and that whole crops should sometimes be cut off by it. As it abounds chiefly in newly broken-up land, though the roots of the grasses supply it with food, it probably does not do any great injury to our meadows and pastures[297].

Here also may be included the larva of the long-legged gnat (_Tipula oleracea_), known in many parts by the name of _the grub_, which is sometimes very prejudicial to the grass in marshy lands, and at others not less so to corn. Reaumur informs us, that in Poitou, in certain years, the grass of whole districts has been so destroyed by it, as not to produce the food necessary for the sustenance of the cattle[298]. In many parts of England, in Holderness particularly, it cuts off a large proportion of the wheat crops, especially if sown upon clover-lays[299]. Reaumur concludes from the observations he made that it lives solely upon earth, and consequently that the injury which it occasions, arises from its loosening the roots of corn and grass by burrowing amongst them: but my friend Mr. Stickney, the intelligent author of a treatise upon this insect, is inclined to think from his experiments that it feeds on the roots themselves. However this may be, the evil produced is evident; and it appears too from the observations of the gentleman last mentioned, that this animal is not killed by lime applied in much larger doses than usual[300].

Our national beverage ale, so valuable and heartening to the lower orders, and so infinitely preferable to ardent spirits and tea, is indebted to another vegetable, the _hop_, for its agreeable conservative bitter. This plant so precious has numberless enemies in the Lilliputian world to which I am introducing you. Its roots are subject to the attack of the caterpillar of a singular species of moth (_Hepiolus Humuli_), known to collectors by the name of the ghost, that sometimes does them considerable injury[301].--A small beetle also (_Haltica concinna_) is particularly destructive to the tender shoots early in the year; and upon the presence or absence of Aphides, known by the name of _the fly_, as in the case of peas, the crop of every year depends; so that the hop-grower is wholly at the mercy of insects. They are the barometer that indicates the rise and fall of his wealth.

If the beer-drinker be thus interested in the history of these animals, equally so is the drinker of tea. Indeed _sugar_ is an article so universally useful and agreeable, that what concerns the cane that produces it seems to concern every one. This also affords a tempting food to insects. The caterpillar of a white moth, called the borer, for destroying which a reward of fifty guineas is offered by the Society of Arts, is in this respect a great nuisance, as is an unknown species of horned beetle[302]. An ant also (_Formica analis_) makes a lodgement in the interior of the sugar-cane in Guinea, and destroys it.--But the creature of this class most destructive to the sugar-cane, is one of the latter genus that does not devour it, and is therefore improperly called _Formica saccharivora_ by Linné; but, by making its nest for shelter under the roots, so injures the plants that they become unhealthy and unproductive. These insects about seventy years ago appeared in such infinite hosts in the island of Granada, as to put a stop to the cultivation of this plant; and a reward of 20,000_l._ was offered to any one who should discover an effectual mode of destroying them. Their numbers were incredible. They descended from the hills like torrents, and the plantations, as well as every path and road for miles, were filled with them. Many domestic quadrupeds perished in consequence of this plague. Rats, mice, and reptiles of every kind became an easy prey to them; and even the birds, which they attacked whenever they alighted on the ground in search of food, were so harassed as to be at length unable to resist them. Streams of water opposed only a temporary obstacle to their progress, the foremost rushing blindly on to certain death, and fresh armies instantly following, till a bank was formed of the carcases of those that were drowned sufficient to dam up the waters, and allow the main body to pass over in safety below. Even the all-devouring element of fire was tried in vain. When lighted to arrest their route, they rushed into the blaze in such myriads of millions as to extinguish it. Those that thus patriotically devoted themselves to certain death for the common good, were but as the pioneers or advanced guard of a countless army, which by their self-sacrifice was enabled to pass unimpeded and unhurt. The intire crops of standing canes were burnt down, and the earth dug up in every part of the plantations. But vain was every attempt of man to effect their destruction, till in 1780 it pleased Providence at length to annihilate them by the torrents of rain which accompanied a hurricane most fatal to the other West India Islands. This dreadful pest was thought to have been imported[303]. Besides these enemies, the sugar-cane has also its Aphis, which sometimes destroys the whole crop[304]; and according to Humboldt and Bonpland the larva of _Elater noctilucus_ feeds in it[305].

Two other vegetable productions of the New World, _cotton_ and _tobacco_, which are also valuable articles of commerce, receive great injury from the depredations of insects. M'Kinnen, in his Tour through the West Indies, states that in 1788 and 1794 two-thirds of the crop of cotton in Crooked Island, one of the Bahamas, was destroyed by the _chenille_ (probably a lepidopterous larva); and the _red bug_, an insect equally noxious, stained it so much in some places as to render it of little or no value. Browne relates that in Jamaica a bug destroys whole fields of this plant, and the caterpillar of that beautiful butterfly _Helicopis Cupido_ also feeds upon it[306]. That of a hawk-moth, _Sphinx Carolina_, is the great pest of Tobacco; and it is attacked likewise by the larva of a moth, _Phalæna Rhexiæ_, Smith[307], and by other insects of the names and kind of which I am ignorant.

_Roots_ are another important object of agriculture, which, however, as to many of them, they may seem to be defended by the earth that covers them, do not escape the attack of insect enemies.--The carrot, which forms a valuable part of the crop of the sand-land farms in Suffolk, is often very much injured, as is also the parsnip, by a small centipede (_Geophilus electricus_), and another polypod (_Polydesmus complanatus_), which eat into various labyrinths the upper part of their roots; and they are both sometimes totally destroyed by the maggot of some dipterous insect, probably one of the _Muscidæ_. I had an opportunity of noticing this in the month of July, in the year 1812, in the garden of our valued friend the Rev. Revett Sheppard of Offton in Suffolk. The plants appeared many of them in a dying state; and upon drawing them out of the ground to ascertain the cause, these larvæ were found with their head and half of their body immersed in the root in an oblique direction, and in many instances they had eaten off the end of it.

America has made us no present more extensively beneficial, compared with which the mines of Potosi are worthless, than the _potato_. This invaluable root, which is now so universally cultivated, is often, in this country, considerably injured by the two insects first mentioned as attacking the carrot. The Death's-head-hawk-moth (_Acherontia Atropos_) in its larva state feeds upon its leaves, though without much injury. In America it is said to suffer much from two beetles (_Cantharis cinerea_ and _vittata_), of the same genus with the blister-beetle[308]; and in the island of Barbadoes some hemipterous insect, supposed to be a Tettigonia, occasionally attacks them. In 1734 and 1735 vast swarms of them devoured almost every vegetable production of that island, particularly the potato, and thus occasioned such a failure of this excellent esculent, especially in one parish, that a collection was made throughout the island for the relief of the poor, whose principal food it forms.

The chief dependence of our farmers for the sustenance of their cattle in the winter is another most useful root, the _turnip_. And they have often to lament the distress occasioned by a failure in this crop, of which these minor animals are the cause. On its first coming up, as soon as the cotyledon leaves are unfolded, a whole host of little jumping beetles, composed chiefly of _Haltica Nemorum_, called by farmers the _fly_[309] and _black jack_, attack and devour them; so that on account of their ravages the land is often obliged to be resown, and frequently with no better success. It has been calculated by an eminent agriculturist, that from this cause alone the loss sustained in the turnip crops in Devonshire in 1786 was not less than 100,000_l._[310] Almost as much damage is sometimes occasioned by a little weevil (_Ceutorhynchus contractus_) which in the same manner pierces a hole in the cuticle. When the plant is more advanced, and out of danger from these pygmy foes, the black larva of a saw-fly takes their place, and occasionally does no little mischief, whole districts being sometimes nearly stripped by them; so that in 1783 many thousand acres were on this account ploughed up[311].--The caterpillar of the cabbage-butterfly (_Pontia Brassicæ_) is also sometimes found upon the turnip in great numbers; and Sir Joseph Banks informs me that forty or fifty of the insects before mentioned[312], called by Mr. Walford the wire-worm, have been discovered in October just below the leaves in a single bulb of this plant.--The small knob or tubercle often observable on these roots is inhabited by a _grub_, which, from its resemblance to one found in similar knobs on the roots of _Sinapis arvensis_, from which I have bred _Ceutorhynchus contractus_ (_Curculio_ Marsh) and _C. assimilis_, small weevils nearly related to each other[313]. This, however, does not seem to affect their growth. Great mischief is occasionally done to the young plants by the wire-worm. I was shown a field last summer in which they had destroyed one-fourth of the crop, and the gentleman who showed them to me calculated that his loss by them would be 100_l._ One year he sowed a field thrice with turnips, which were twice wholly, and the third time in great part, cut off by this insect.--Whether the disease to which turnips are subject, in some parts of the kingdom, from the form of the excrescences into which the bulb shoots, called _fingers and toes_, be occasioned by insects, is not certainly known[314].

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We have wandered long enough about the fields to observe the progress of insect devastation; let us now return home to visit the domains of Flora and Pomona, that we may see whether their subjects are exposed to equal maltreatment. If we begin with the _kitchen-garden_, we shall find that its various productions, ministering so materially to our daily comfort and enjoyment, almost all suffer more or less from the attack of the animals we are considering.--Thus, the earliest of our table dainties, radishes, are devoured by the maggot of a fly (_Anthomyia Radicum_), and our lettuces by the caterpillars of several species of moth; one of which is the beautiful tiger-moth (_Euprepia Caja_), another the pot-herb-moth (_Mamestra oleracea_), a third anonymous, described by Reaumur as beginning at the root, eating itself a mansion in the stem, and so destroying the plant before it cabbages[315]. And when they are come to their perfection and appear fit for the table, their beauty and delicacy are often marred by the troublesome earwig, which, insinuating itself into them, defiles them with its excrements.--What more acceptable vegetable in the spring than broccoli? Yet how dreadfully is its foliage often ravaged in the autumn by numerous hordes of the cabbage-butterfly! so that, in an extensive garden, you will sometimes see nothing left of the leaves except the veins and stalks.--What more useful, again, than the cabbage? Besides the same insect, which injures them in a similar way, in some countries they are infested by the caterpillar of a most destructive moth (_Mamestra Brassicæ_), to which indeed I have before alluded[316]; which, not content with the leaves, penetrates into the very heart of the plant[317].--One of the most delicate and admired of all table vegetables, concerning which gardeners are most apt to pride themselves, and bestow much pains to produce in perfection, I mean the cauliflower, is often attacked by a fly, which ovipositing in that part of the stalk covered by the earth, the maggots when hatched occasion the plant to wither and die, or to produce a worthless head[318]. Even when the head is good and handsome, if not carefully examined previous to being cooked, it is often rendered disgusting by earwigs that have crept into it, or the green caterpillar of _Pontia Rapæ_.

Our peas, beans, carrots, parsnips, turnips, and potatos are attacked in the garden by the same enemies that injure them in the fields[319]; I shall therefore dismiss them without further notice, and point out those which infest another of our most esteemed kinds of pulse, kidney beans. These are principally Aphides, which in dry seasons are extremely injurious to them. The fluid which they secrete, falling upon the leaves, causes them to turn black as if sprinkled with soot; and the nutriment being subtracted from the pods by their constant suction, they are prevented from coming to their proper size or perfection. The beans also which they contain are sometimes devoured by the caterpillar of a small moth[320].--Onions, which add a relish to the poor man's crusts and cheese, and form so material an ingredient in the most savory dishes of the rich, are also the favourite food of the maggot of a fly, that often does considerable damage to the crop.--From this maggot (for a supply of onions containing which I have to thank my friend Mr. Campbell, surgeon, of Hedon near Hull, where it is very injurious, particularly in light soils,) I have succeeded in breeding the fly, which proves of that tribe of the Linnean genus _Musca_, now called _Scatophaga_. Being apparently undescribed, and new to my valued correspondent Count Hoffmansegg to whom I sent it, I call it _S. Ceparum_[321].--The diuretic asparagus, towards the close of the season, is sometimes rendered unpalatable by the numerous eggs of the asparagus beetle (_Lema Asparagi_), and its larvæ feed upon the foliage after the heads branch out.--Cucumbers with us enjoy an immunity from insect assailants; but in America they are deprived of this privilege, an unascertained species, called there the cucumber-fly, doing them great injury[322].--And, to name no more, mushrooms, which are frequently cultivated and much in request, often swarm with the maggots of various _Diptera_ and _Coleoptera_.

The insects just enumerated are partial in their attacks, confining themselves to one or two kinds of our pulse or other vegetables. But there are others that devour more indiscriminately the produce of our gardens; and of these in certain seasons and countries we have no greater and more universal enemy than the caterpillar of a moth called by entomologists _Plusia Gamma_, from its having a character inscribed in gold on its primary wings, which resembles that Greek letter. This creature affords a pregnant instance of the power of Providence to let loose an animal to the work of destruction and punishment. Though common with us, it is seldom the cause of more than trivial injury; but in the year 1735 it was so incredibly multiplied in France as to infest the whole country. On the great roads, whereever you cast your eyes, you might see vast numbers traversing them in all directions to pass from field to field; but their ravages were particularly felt in the kitchen-gardens, where they devoured every thing, whether pulse or pot-herbs, so that nothing was left besides the stalks and veins of the leaves. The credulous multitude thought they were poisonous, report affirming that in some instances the eating of them had been followed by fatal effects. In consequence of this alarming idea, herbs were banished for several weeks from the soups of Paris. Fortunately these destroyers did not meddle with the corn, or famine would have followed in their train. Reaumur has proved that a single pair of these insects might in one season produce 80,000; so that, were the friendly Ichneumons removed, to which the mercy of Heaven has given it in charge to keep their numbers within due limits, we should no longer enjoy the comfort of vegetables with our animal food, and probably soon become the prey of scorbutic diseases[323].--I must not overlook that singular animal the mole-cricket, (_Gryllotalpa vulgaris_,) which is a terrible devastator of the produce of the kitchen-garden. It burrows under ground, and devouring the roots of plants thus occasions them to wither, and even gets into hot-beds. It does so much mischief in Germany, that the author of an old book of gardening, after giving a figure of it, exclaims, "Happy are the places where this pest is unknown!"

The _flowers_ and _shrubs_, that form the ornament of our parterres and pleasure-grounds, seem less exposed to insect depredation than the produce of the kitchen-garden; yet still there are not a few that suffer from it. The foliage of one of our greatest favourites, the _rose_, often loses all its loveliness and lustre from the excrements of the Aphides that prey upon it. The leaf-cutter bee also (_Megachile[324] centuncularis_), by cutting pieces out to form for its young its cells of curious construction, disfigures it considerably; and the froth frog-hopper (_Cercopis spumaria_) aided by the saw-fly of the rose (_Hylotoma Rosæ_) contributes to check the luxuriance of its growth, and to diminish the splendour of its beauty.--Reaumur has given the history of a fly (_Merodon Narcissi_) whose larva feeds in safety within the bulbs of the Narcissus, and destroys them; and also of another, though he neglects to describe the species, which tarnishes the gay parterre of the florist, whose delight is to observe the freaks of nature exhibited in the various many-coloured streaks which diversify the blossom of the tulip, by devouring its bulbs[325].--Ray notices another mentioned by Swammerdam, probably _Bibio hortulana_, which he calls the deadliest enemy of the flowers of the spring. He accuses it of despoiling the gardens and fields of every blossom, and so extinguishing the hope of the year[326]. But you must not take up a prejudice against an innocent creature, even under the warrant of such weighty authority; for the insect which our great naturalist has arraigned as the author of such devastation is scarcely guilty, if it be at all a culprit, in the degree here alleged against it. As it is very numerous early in the year, it may perhaps discolour the vernal blossoms, but its mouth is furnished with no instrument to enable it to devour them.

In our _stoves_ and _greenhouses_ the Aphides often reign triumphant; for, if they be not discovered and destroyed when their numbers are small, their increase becomes so rapid and their attack so indiscriminate, that every plant is covered and contaminated by them, beauty being converted into deformity, and objects before the most attractive now exciting only nausea and disgust. The Coccus (_C. Hesperidum_) also, which looks like an inanimate scale upon the bark, does considerable injury to the two prime ornaments of our conservatories, the orange and the myrtle; drawing off the sap by its pectoral rostrum, and thus depriving the plant of a portion of its nutriment, at the same time that it causes unpleasant sensations in the beholder from its resemblance to the pustule of some cutaneous disease.

I must next conduct you from the garden into the _orchard_ and _fruitery_; and here you will find the same enemies still more busy and successful in their attempts to do us hurt.--The strawberry, which is the earliest and at the same time most grateful of our fruits, enjoys also the privilege of being almost exempt from insect injury. A jumping weevil (_Orchestes Fragariæ_) is said by Fabricius to inhabit this plant; but as the same species is abundant in this country upon the beech, the beauty of which it materially injures by the numberless holes which it pierces in the leaves, and has I believe never been taken upon the strawberry, it seems probable that Smidt's specimens might have fallen upon the latter from that tree[327]. The only insect I have observed feeding upon this fruit is the ant, and the injury that it does is not material.--The raspberry, the fruit of which arrives later at maturity, has more than one species of these animals for its foes. Its foliage sometimes suffers much from the attack of _Melolontha horticola_[328], a little beetle related to the cockchafer: when in flower the footstalks of the blossom are occasionally eaten through by a more minute animal of the same order, _Byturus tomentosus_, which I once saw prove fatal to a whole crop; and bees frequently anticipate us, and by sucking the fruit with their proboscis spoil it for the table.--Gooseberries and currants, those agreeable and useful fruits, a common object of cultivation both to poor and rich, have their share of enemies in this class. The all-attacking Aphides do not pass over them, and the former especially are sometimes greatly injured by them; their excrement falling upon the berries renders them clammy and disgusting, and they soon turn quite black from it. In July 1812 I saw a currant-bush miserably ravaged by a species of Coccus, very much resembling the Coccus of the vine. The eggs were of a beautiful pink, and enveloped in a large mass of cotton-like web, which could be drawn out to a considerable length. Sir Joseph Banks lately showed me a branch of the same shrub perforated down to the pith by the caterpillar of _Æegeria tipuliformis_: the diminished size of the fruit points out, he observes, where this enemy has been at work. In Germany, where perhaps this insect is more numerous, it is said to destroy not seldom the larger bushes of the red currant[329]. The foliage of these fruits often suffers much from the black and white caterpillar of _Abraxas grossulariata_; (this was the case last spring at Hull;) but their worst and most destructive enemy, particularly of the gooseberry, is that of a small saw-fly. This larva is of a green colour, shagreened as it were with minute black tubercles, which it loses at its last moult. The fly attaches its eggs in rows to the underside of the leaves. When first hatched, the little animals feed in society; but having consumed the leaf on which they were born, they separate from each other, and the work of devastation proceeds with such rapidity, that frequently, where many families are produced on the same bush, nothing of the leaves is left but the veins, and all the fruit for that year is spoiled[330].

Upon the leaves of the cherry, which usually succeeds the gooseberry, in common with those of the pear and several other fruit-trees, the slimy larva of another saw-fly (_Tenthredo Cerasi_) makes its repast, yet without being the cause of any very material injury. But in North America a second species nearly related to it, known there by the name of the _slug-worm_, has become prevalent to such a degree as to threaten the destruction not only of the cherry, but also of the pear, quince, and plum. In 1797 they were so numerous that the smaller trees were covered by them; and a breeze of air passing through those on which they abounded became charged with a very disagreeable and sickening odour. Twenty or thirty were to be seen on a single leaf; and many trees, being quite stripped, were obliged to put forth fresh foliage, thus anticipating the supply of the succeeding year and cutting off the prospect of fruit[331].--In some parts of Germany the cherry-tree has an enemy equally injurious. A splendid beetle of the weevil tribe (_Rynchites Bacchus_) bores with its rostrum through the half-grown fruit into the soft stone, and there deposits an egg. The grub produced from it feeds upon the kernel, and, when about to become a pupa, gnaws its way through the cherry, and sometimes not one in a thousand escapes[332]. This insect is fortunately rare with us, and has usually been found upon the black-thorn. The cherry-fly also (_Tephritis Cerasi_) provides a habitation for its maggot in the same fruit, which it invariably spoils[333].

The different varieties of the plum are every year more or less injured by Aphides; and a Coccus (_C. Persicæ?_) sometimes so abounds upon them that every twig is thickly beaded with the red semiglobose bodies of the gravid females, whose progeny in spring exhaust the trees by pumping out the sap.

The blossoms of our pear-trees, as we learn from Mr. Knight, are often rendered abortive by the grub of a brown beetle: and a considerable quantity of its fruit is destroyed by that of a small four-winged fly, which occasions it to drop off prematurely[334]. This would seem to be a saw-fly, and is probably the species which Reaumur saw enter the blossom of a pear before it was quite open, doubtless to deposit its eggs in the embryo fruit. He often found in young pears, on opening them, a larva of this genus[335].--A little moth likewise is mentioned by Mr. Forsyth as very injurious to this tree[336].

But of all our fruits none is so useful and important as the apple, and none suffers more from insects, which according to Mr. Knight[337] are a more frequent cause of the crops failing than frost. The figure-of-eight moth (_Episema cæruleocephala_), Linné denominates the pest of Pomona and the destroyer of the blossoms of the apple, pear, and cherry.--He also mentions another (_Tinea Corticella_) as inhabiting apple-bearing trees under the bark.--And Reaumur has given us the history of a species common in this country, and producing the same effect, often to the destruction of the crop, the caterpillar of which feeds in the centre of our apples, thus occasioning them to fall[338]. Even the young grafts, I am informed by an intelligent friend[339], are frequently destroyed, sometimes many hundreds in one night, in the nurseries about London, by _Curculio Vastator_, Marsh., (_Otiorhynchus? picipes_) one of the short-snouted weevils; and the foundation of canker in full-grown trees is often laid by the larvæ of _Semasia Wœberana_[340]. The sap too is often injuriously drawn off by a minute Coccus, of which the female has the exact shape of a muscle-shell (_C. arborum linearis_, Geoffr.), and which Reaumur has accurately described and figured[341]. This species so abounded in 1816 on an apple-tree in my garden, that the whole bark was covered with it in every part; and I have since been informed by Joshua Haworth, jun. Esq. of Hull, that it equally infests other trees in the neighbourhood. Even the fruit of a golden pippin which he sent me were thickly beset with it.--But the greatest enemy of this tree, and which has been known in this country only since the year 1787, is the apple-aphis, called by some the _Coccus_, and by others the _American blight_. This is a minute insect, covered with a long cotton-like wool transpiring from the pores of its body, which takes its station in the chinks and rugosities of the bark, where it increases abundantly, and by constantly drawing off the sap causes ultimately the destruction of the tree. Whence this pest was first introduced is not certainly known. Sir Joseph Banks traced its origin to a nursery in Sloane Street; and at first he was led to conclude that it had been imported with some apple-trees from France. On writing, however, to gardeners in that country, he found it to be wholly unknown there. It was therefore, if not a native insect, most probably derived from North America, from whence apple-trees had also been imported by the proprietor of that nursery. Whatever its origin, it spread rapidly. At first it was confined to the vicinity of the metropolis, where it destroyed thousands of trees. But it has now found its way into other parts of the kingdom, particularly into the cyder counties; and in 1810 so many perished from it in Gloucestershire, that, if some mode of destroying it were not discovered, it was feared the making of cyder must be abandoned. This valuable discovery, it is said, has since been made; the application of the spirit of tar to the bark being recommended as effectual[342]. Sir Joseph Banks long ago extirpated it from his own apple-trees, by the simple method of taking off all the rugged and dead old bark, and then scrubbing the trunk and branches with a hard brush[343].