One of the most delicious, and at the same time most useful, of all our fruits is the grape: to this, as you know, we are indebted for our raisins, for our currants, for our wine, and for our brandy; you cannot therefore but feel interested in its history, and desire to be informed, whether, like those before enumerated, this choice gift of Heaven, whose produce "cheereth God and man[350]," must also be the prey of insects. There is a singular beetle, common in Hungary, (Lethrus cephalotes) which gnaws off the young shoots of the vine, and drags them backward into its burrow, where it feeds upon them: on this account the country people wage continual war with it, destroying vast numbers[351].—Three other beetles also attack this noble plant: two of them, mentioned by French authors, (Rynchites Bacchus and Eumolpus Vitis,) devour the young shoots, the foliage and the footstalks of the fruit, so that the latter is prevented from coming to maturity[352]; and a third (C. Corruptor, Host,) by a German, which seems closely allied to Otiorhynchus? picipes before mentioned, if it be not the same insect. This destroys the young vines, often killing them the first year; and is accounted so terrible an enemy to them, that not only the animals but even their eggs are searched for and destroyed, and to forward this work people often call in the assistance of their neighbours[353].—In the Crimea the small caterpillar of a Procris or Ino (lepidopterous genera separated from Sphinx, L.) related to I. Statices, is a still more destructive enemy. As soon as the buds open in the spring, it eats its way into them, especially the fruit buds, and devours the germ of the grape. Two or three of these caterpillars will so injure a vine, by creeping from one germ to another, that it will bear no fruit nor produce a single regular shoot the succeeding year[354].—Vine leaves in France are also frequently destroyed by the larva of a moth (Tortrix vitana); in Germany another species does great injury to the young bunches, preventing their expansion by the webs in which it involves them[355]; and a third (Tortrix fasciana) makes the grapes themselves its food: a similar insect is alluded to in the threat contained in Deuteronomy[356].—The worst pest of the vine in this country is its Coccus (C. Vitis). This animal, which fortunately is not sufficiently hardy to endure the common temperature of our atmosphere, sometimes so abounds upon those that are cultivated in stoves and greenhouses, that their stems seem quite covered with little locks of white cotton; which appearance is caused by a filamentous secretion transpiring through the skin of the animal, in which they envelop their eggs. Where they prevail they do great injury to the plant by subtracting the sap from its foliage and fruit, and causing it to bleed.—And to close the list, you are perfectly aware of the eagerness with which wasps, flies, and other insects, attack the grapes when ripe, often leaving nothing but the mere skin for their lordly proprietor.
There are some of these creatures that attack indiscriminately all fruit-trees. One of these is the Cicada septendecim, (so called because, according to Kalm, it appears only once in seventeen years[357].) The female oviposits in the pith of the twigs of trees, where the grubs are hatched, and do infinite damage both to fruit- and forest-trees[358].—Another, the caterpillar of the butterfly of the hawthorn, (Pieris Cratægi) which in 1791, in some parts of Germany, stripped the fruit-trees in general of their foliage[359].—In France also in 1731 and 1732 that of a moth which seems related to the brown-tail moth (Arctia phæorhœa), whose history has been given by the late Mr. Curtis, was so numerous as to occasion a general alarm. The oaks, elms, and white-thorn hedges looked as if some burning wind had passed over them and dried up their leaves; for, the insect devouring only one surface of them, that which is left becomes brown and dry. They also laid waste the fruit-trees, and even devoured the fruit; so that the parliament published an edict to compel people to collect and destroy them; but this would in a great measure have been ineffectual, had not some cold rains fallen, which so completely annihilated them, that it was difficult to meet with a single individual[360].
If we quit the orchard and fruit-garden for a walk in our plantations and groves, we shall still be forced to witness the sad effects of insect devastation; and when we see, as sometimes happens, the hedges and trees entirely deprived of their foliage, and ourselves of the shade we love from the fervid beam of the noon-day sun; when the singing birds have deserted them; and all their music, which has so often enchanted us by its melody, variety, and sweetness, has ceased—we shall be tempted in our hearts to wish the whole insect race was blotted from the page of creation. Numerous are the agents employed in this work of destruction. Amongst the beetles, various cockchafers (Melolontha vulgaris, Amphimalla solstitialis, and Phyllopertha horticola) in their perfect state act as conspicuous a part in injuring the trees, as their grubs do in destroying the herbage. Besides the leaves of fruit-trees, they devour those of the sycamore, the lime, the beech, the willow, and the elm. They are sometimes, especially the common one, astonishingly numerous. Mouffet relates (but one would think that there must be some mistake in the date, since they are never so early in their appearance,) that on the 24th of February 1574 such a number of them fell into the river Severn as to stop the wheels of the water-mills[361]. It is also recorded in the Philosophical Transactions, that in 1688 they filled the hedges and trees of part of the county of Galway in such infinite numbers, as to cling to each other in clusters like bees when they swarm; on the wing they darkened the air, and produced a sound like that of distant drums. When they were feeding, the noise of their jaws might be mistaken for the sawing of timber. Travellers and people abroad were very much annoyed by their continual flying in their faces; and in a short time the leaves of all the trees for some miles round were so totally consumed by them, that at Midsummer the country wore the aspect of the depth of winter[362].
But the criminals to whom it is principally owing that our groves are sometimes stripped of the green robe of summer, are the various tribes of Lepidoptera, especially the night-fliers or moths, myriads of whose caterpillars, in certain seasons, despoil whole districts of their beauty, and our walks of all their pleasure. In 1731 the oaks in France were terribly devastated by the larva of Hypogymna dispar[363], and in 1797 many of the pine forests about Bayreuth suffered a similar injury from that of H. Monacha[364]. Those of Germany are also sometimes laid waste by the caterpillar of a beautiful moth belonging to the Noctuidæ (Achatea spreta[365]), which has been taken in England. Cheimatobia brumata is likewise a fearful enemy to the foliage of almost every kind of tree[366]. The woods in certain provinces of North America are in some years entirely stripped by that of another moth, which eats all kinds of leaves. This happening at a time of the year when the heat is most excessive is attended by fatal consequences. For, being deprived of the shelter of their foliage, whole forests are sometimes entirely dried up and ruined[367].—The brown-tail moth, before alluded to, which occasionally bares our hawthorn hedges, has been rendered famous by the alarm it caused to the inhabitants of the vicinity of the metropolis in 1782, when rewards were offered for collecting the caterpillars, and the churchwardens and overseers of the parishes attended to see them burnt by bushels.—You may have observed perhaps in some cabinets of foreign insects an ant, the head of which is very large in proportion to the size of its body, with a piece of leaf in its mouth many times bigger than itself. These ants, called in Tobago parasol ants (Œcodoma cephalotes), cut circular pieces out of the leaves of various trees and plants, which they carry in their jaws to their nests, and they will strip a tree of its leaves in a night, a circumstance which has been confirmed to me by Captain Hancock[368]. Stedman mentions another very large ant, being at least an inch in length, which has the same instinct. It was a pleasant spectacle, he observes, to behold this army of ants marching constantly in the same direction, and each individual with its bit of green leaf in its mouth[369]. The injury thus caused to trees by insects is not confined to the mere loss of their leaves for one season; for it occasions them to draw upon the funds of another, by sending forth premature shoots and making gems unfold, that, in the ordinary course, would not have put forth their foliage till the following year.
Other insects, though they do not entirely devour the leaves of trees and plants, yet considerably diminish their beauty. Thus, for instance, sometimes the subcutaneous larvæ undermine them, when the leaf exhibits the whole course of their labyrinth in a pallid, tortuous, gradually dilating line—at others the Tortrices disfigure them by rolling them up, or the leaf-cutter bees by taking a piece out of them, or certain Tineæ again by eating their under surface, and so causing them to wither either partially or totally. You have doubtless observed what is called the honey-dew upon the maple and other trees, concerning which the learned Roman naturalist Pliny gravely hesitates whether he shall call it the sweat of the heavens, the saliva of the stars, or a liquid produced by the purgation of the air[370]!! Perhaps you may not be aware that it is a secretion of Aphides, whose excrement has the privilege of emulating sugar and honey in sweetness and purity. It however often tarnishes the lustre of those trees in which these insects are numerous, and is the lure that attracts the swarms of ants which you may often see travelling up and down the trunk of the oak and other trees. The larch in particular is inhabited by an Aphis transpiring a waxy substance like filaments of cotton: this is sometimes so infinitely multiplied upon it as to whiten the whole tree, which often perishes in consequence of its attack. The beech is infested by a similar one. Some animals also of this genus inhabiting the poplar, elm, lime, and willow, reside in galls they have produced, that disfigure the leaves or their footstalks. Perhaps those resembling fruit, or flowers, or moss, produced by the Aphis of the fir (Aphis Abietis), the different species of gall-gnats (Cecidomyia), or occasioned by the puncture and oviposition of the various kinds of gall-flies (Cynips), may be regarded rather as an ornament than as an injury to a tree or shrub; yet when too numerous they must deprive it of its proper nutriment, and so occasion some defect. And probably the enormous wens, and other monstrosities and deformities observable in trees, may have been originally produced by the bite or incision of insects.
Besides exterior insect enemies, living trees are liable to the ravages of many that are interior. The caterpillar of the great goat-moth (Cossus ligniperda[371]), of the hornet hawk-moth (Sesia crabroniformis, F.), and of two beetles (Nitidula grisea, and Cryptorhynchus Lapathi), devour the wood of the willow and sallow, which thus in time often become so hollow as to be easily blown down. The bee hawk-moth (Sesia apiformis[372]), and probably Rynchites Populi, a brilliant green weevil, feeds upon the poplar—Prionus coriarius is sometimes found in the oak and sometimes in the elm, and Hylurgus piniperda[373], in the Scotch fir. Mr. Stephens informs me that the fir-trees in a plantation of Mr. Foljambe's in Yorkshire were destroyed by a hymenopterous insect (Sirex Gigas), while those of another belonging to the same gentleman in Wiltshire met with a similar fate from the attack of Sirex Juvencus. The elm also suffers dreadfully from the attack of another minute beetle (Scolytus destructor), related to the last[374].—When the sap flows from wounds in a tree it is attended by various other beetles, (I have observed Cetonia aurata, and several Nitidulæ and Brachyptera busy in this way,) which prevent it from healing so soon as it would otherwise do; and if the bark be any where separated from the wood, a numerous army of wood-lice, earwigs, spiders, field-bugs, and similar subcortical insects take their station there and prevent a re-union.
The mischief however produced by any or all of these, is not to be compared with that sometimes sustained in Germany from the attacks of a small beetle, (Bostrichus Typographus) so called on account of a fancied resemblance between the paths it erodes and letters, which bores into the fir. This insect, in its preparatory state, feeds upon the soft inner bark only: but it attacks this important part in such vast numbers, 80,000 being sometimes found in a single tree, that it is infinitely more noxious than any of those that bore into the wood: and such is its vitality, that though the bark be battered and the tree plunged into water, or laid upon the ice or snow, it remains alive and unhurt. The leaves of the trees infested by these insects first become yellow, the trees themselves then die at the top, and soon entirely perish. Their ravages have long been known in Germany under the name of Wurm trökniss (decay caused by worms); and in the old liturgies of that country the animal itself is formally mentioned under its vulgar appellation, "The Turk." This pest was particularly prevalent and caused incalculable mischief about the year 1665. In the beginning of the last century it again showed itself in the Hartz forests—it reappeared in 1757, redoubled its injuries in 1769, and arrived at its height in 1783, when the number of trees destroyed by it in the above forests alone, was calculated at a million and a half, and the inhabitants were threatened with a total suspension of the working of their mines, and consequent ruin. At this period these Bostrichi, when arrived at their perfect state, migrated in swarms like bees into Suabia and Franconia. At length, between the years 1784 and 1789, in consequence of a succession of cold and moist seasons, the numbers of this scourge were sensibly diminished. It appeared again however in 1790, and so late as 1796 there was great reason to fear for the few fir-trees that were left[375].
The seeds of forest- as well as of fruit-trees are doubtless subject to injuries from the same quarter, but these being more out of the reach of observation, have not been much noticed. Acorns, however, a considerable article with nurserymen, are said to have both a moth and a beetle that prey upon them; and what is remarkable, though sometimes one larva of each is found in the same acorn, yet two of either kind are never to be met with together[376]. The beetle is probably the Curculio Glandium (Balaninus) of Mr. Marsham, and is nearly related to the species whose grub inhabits the nut.