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].
Our more dainty and delicate fruits, at least such as are usually so
accounted, the apricot, the peach, and the nectarine, originally of
Asiatic origin, are not less subject to the empire of insects than
the homelier natives of Europe. Certain Aphides form a convenient
and sheltered habitation for themselves, by causing portions of the
leaves to rise into hollow red convexities; in these they reside,
and, with their rostrum pumping out the sap, in time occasion them to
curl up, and thus deform the tree and injure the produce. The fruit
is attacked by various other enemies of this class, against which we
find it not easy to secure it: wasps, earwigs, flies, wood-lice, and
ants, which last communicate to it a disagreeable flavour, all share
with us these ambrosial treasures; the first of them as it were opening
the door, by making an incision in the rind, and letting in all the
rest.--The nucleus of the apricot is also sometimes inhabited by the
caterpillar of a moth, which devouring the kernel causes the fruit to
fall prematurely[344].--In this country, however, these fruits may
be regarded as mere luxuries, and therefore are of less consequence;
but in North America they constitute an important part of the general
produce, at least the peach, serving both as food for swine, and
furnishing by distillation a useful spirit. The ravages committed upon
them there by insects are so serious, that premiums have been offered
for extirpating them. A species of weevil, perhaps a _Rynchites_,
enters the fruit when unripe, probably laying its eggs within the
stone, and so destroys them. And two kinds of _Zygæna_, by attacking
the roots do a still greater injury to the trees[345].--A Coccus, as it
should seem from the description, imported about thirty years ago from
the Mauritius, or else with the Constantia vine from the Cape of Good
Hope, has destroyed nearly nine-tenths of the peach-trees in the Island
of St. Helena, where formerly they were so abundant, that, as in North
America, the swine were fed with them. Various means have been employed
to destroy this plague, but hitherto without success[346].--The
imperial pine-apple, the glory of our stoves, and the most esteemed
of the gifts of Pomona, cannot, however precious, be defended from
the injuries of a singular species of mite, the _red Spider_[347] of
gardeners, (_Erythræus telarius_) which covers them, and other stove
plants, with a most delicate but at the same time very pernicious
web.--The olive-tree, so valuable to the inhabitants of the warmer
regions of Europe, often nourishes in its berries the destructive
maggot of a fly (_Oscinis Oleæ_); and the caterpillar of a little
moth (_Tinea Oleella_), which preys upon the kernel of the nucleus,
occasions them to fall before they are ripe.--Every one who eats nuts
knows that they are very often inhabited by a small white grub; this
is the offspring of a weevil (_Balaninus Nucum_) remarkable for its
long and slender rostrum, with which it perforates the shell when young
and soft, and deposits an egg in the orifice.--In France it sometimes
happens, when the chestnuts promise an abundant crop, that the fruit
falls before it comes to maturity, scarcely any remaining upon the
trees. The caterpillar of a moth which eats into its interior is the
cause of this disappointment[348].--Of fruits the date has the hardest
nucleus; yet an insect of the same tribe with the above, that feeds
upon its kernel, is armed with jaws sufficiently strong to perforate
it, that it may make its escape when the time of its change is arrived,
and assume the pupa between the stone and the flesh. The date is eaten
also by a beetle which Hasselquist calls a _Dermestes_[349].
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.
Having now conducted you round and exhibited to you the melancholy
proofs of the universal dominion of insects over our vegetable
treasures, while growing or endued with the principle of vitality,
in their separate departments,--I must next introduce you to a pest
worse than all put together, which indiscriminately attacks and
destroys every vegetable substance that the earth produces, and
which, wherever it prevails, carries famine, pestilence and death in
its train. Happily for this country--and we cannot be too thankful
for the privilege, we know this scourge of nations only by report.
The name of _Locust_, which has been such a sound of horror in other
countries, here only suggests an object of interesting inquiry. But
the ravages of locusts are so copious a theme that they merit to be
considered in a separate letter.
I am, &c.
FOOTNOTES:
[270] _Linn. Trans._ ix. 156-61.
[271] Germar's _Mag. der Ent._ i. 1-10. Mr. Stephens, in his
_Illustrations of British Entomology_ (No. I. p. 4.), very
judiciously asks, "May not these herbivorous larvæ have been the
principal cause of the mischief to the wheat, while those of the
_Zabrus_ contributed rather to lessen their numbers than to destroy
the corn." But this query does not account for their being found,
when in the perfect state, attacking the ear. I have seen cognate
beetles devouring the seeds of umbelliferous plants.
[272] _Act. Stockh._ 1778. 3. n. 11. and 4. n. 4. Marsham in _Linn.
Trans._ ii. 79.
[273] _Linn. Trans._ ii. 76-80.
[274] _Encyclopæd. Britann._ viii. 480-95.
[275] Young's _Annals of Agriculture_, xi. 471.
[276] _Tipula Tritici_, K., belonging to Latreille's genus
_Cecidomyia_. (See above, p. 28. note^a.) Marsham and Kirby in _Linn.
Trans._ iii. 242-5. iv. 225-39. v. 96-110.
[277] Oliv. ii. n. 19. 3-4.
[278] _Curculio testaceus_, _Ent. Brit._
[279] Marsham in _Linn. Trans._ ii. 80. De Geer notices the injury
done by this fly to rye, and observes that before it had been
attributed to frost. ii. 68.
[280] _Act. Stockh._ 1750. 128. Reaum. ii. 480, &c.
[281] This insect was taken in maize by Mr. Sparshall of Norwich.
[282] Smith's Abbott's _Insects of Georgia_, 191.
[283] I say this upon the authority of Mr. Wolnough of Hollesley
(late of Boyton) in Suffolk, an intelligent agriculturist, and a most
acute and accurate observer of nature.
[284] Reaum. vi. 566.
[285] Kalm's _Travels_, i. 173.
[286] Amoreux, 288.
[287] I have raised plants from this seed, which appear from the
foliage to belong either to _Phaseolus_ or _Dolichos_.
[288] Markwick, Marsham and Lehmann in _Linn. Trans._ vi. 142-. and
Kirby in ditto, ix. 37. 42. n. 19. 23.
[289] PLATE XVII. FIG. 12.
[290] _Philos. Trans._ 1741. 581.
[291] De Geer, ii. 341. _Amœn. Acad._ iii. 355.
[292] _Farmer's Mag._ iii. 487.
[293] Pallas's _Travels in South Russia_, i. 30.
[294] PLATE XVIII. FIG. 4.
[295] Marsham in _Communications to the Board of Agriculture_, iv.
412. _Plate_ xviii. _fig_. 4. and _Linn. Trans._ ix. 60.
[296] PLATE XXIV. FIG. 3.
[297] The wire-worm is particularly destructive for a few years in
gardens recently converted from pasture ground. In the Botanic Garden
at Hull thus circumstanced a great proportion of the annuals sown in
1813 were destroyed by it. A very simple and effectual remedy in such
cases was mentioned to me by Sir Joseph Banks. He recommended that
slices of potato stuck upon skewers should be buried near the seeds
sown, examined every day, and the wire-worms which collect upon them
in great numbers destroyed.