[234] _Insect. Theatr._ 36. Schirach, 241.
[235] VOL. I. 496.
[236] Reaum. _ubi supr._ 437--.
[237] _Philos. Trans._ 1807, 242.
[238] xxxi. 148.
[239] Knight in _Philos. Trans._ for 1807, 237. Marshall, _Agricult.
of Norfolk_.
[240] It has been supposed, and the supposition was adopted
originally in this work (VOL. I. 1st Ed. p. 371), that the object in
this case is brooding the eggs; but upon further consideration we
incline to Huber's opinion, that it has no connexion with it, the
ordinary temperature of the hive being sufficient for this purpose;
and the circumstance of their entering unoccupied cells proves that
this attitude has no particular connexion with the eggs. _Huber_, i.
212.--"When large pieces of comb," says Wildman (p. 45), "were broken
off and left at the bottom of the hive, a great number of bees have
gone and placed themselves upon them." This looks like incubation.
Reaumur however affirms (p. 591) that if part of a comb falls and
loses its perpendicular direction, the bees, as if conscious that
they would come to nothing, pull out and destroy all the larvæ. They
might perhaps remain perpendicular in the case observed by Wildman.
[241] Reaum. v. 431. Huber, ii. 212.
[242] Reaum. v. 432--.
[243] Reaum. v. 434--.
[244] VOL. I. 331, Reaum. v. 698--.
[245] _Philos. Trans._ 1792, 160. Comp. Reaum. v. 450.
[246] Reaum. _ibid._ 591-- Hunter, _ibid._ 161--.
[247] Reaum. _ibid._ 697.
[248] Reaum. v. 602.
[249] Ibid. 656.
[250] ii. 339.
[251] Reaum. v. 672.
[252] Huber, ii. 338-362.
[253] Huber, ii. 359--.
[254] Reaum. v. 442.
[255] Bonner _On Bees_, 102.
[256] Reaum. _ubi supr._ 580-600.
[257] In _Philos. Trans._ 1807, 239.
[258] Huber, ii. 407--.
[259] Ibid. 375.
[260] Thorley, 16-- The Psalmist alludes to the fury of these
creatures, when he says of his enemies, "They compassed me about like
bees." _Ps._ cxviii. 12.
[261] Park's _Last Mission_, 153. 297, Comp. _Journal_, 331.
[262] Thorley 150--.
[263] Lesser, _L._ ii. 171.
[264] See above, p. 126.
[265] Reaum. v. 360-365.
[266] _Philos. Trans._ 1807, 234--.
[267] 166.
[268] Thorley, _ibid._ Comp. Mills _On Bees_, 63.--The following
account of an apiarian battle was copied from the _Carlisle Patriot_
Newspaper:--On Saturday last, in the village of Cargo, a combat of a
truly novel description was witnessed. A hive of bees belonging to a
professional gentleman of this city, swarmed on Thursday last, after
which they were hived in the regular way, and appeared to be doing
well. On the Saturday after, a swarm of bees, from some neighbouring
hive, appeared to be flying over the garden in which the hive
above-mentioned was placed, when they instantly darted down upon the
hive of the new settlers, and completely covered it: in a little time
they began to enter the hive, and poured into it in such numbers that
it soon became completely filled. A loud humming noise was heard, and
the work of destruction immediately ensued; the winged combatants
sallied forth from the hive, until it became entirely empty; and a
furious battle commenced in "upper air," between the besiegers and
the besieged. A spectator informs us, that these intrepid little
warriors were so numerous, that they literally darkened the sky
overhead like a cloud; meanwhile the destructive battle raged with
fury on both sides, and the ground beneath was covered with the
wounded and the slain, hundreds of them were lying dead, or crawling
about, disabled from re-ascending to the scene of action. To one
party, however, the palm of victory was at last awarded, and they
settled upon the branch of an adjoining apple-tree, from which they
were safely placed in the empty hive, which had been the object of
their valiant contention, and where they now continue peacefully and
industriously employed in adding to the stores of their commonwealth.
[269] Comp. Schirach, 49. Mills, 62-- Thorley, 163--.
[270] 51.
[271] ii. 380--.
[272] VOL. I. 163, and 281, 289.
[273] Schirach, 52.
[274] 170.
[275] Reaum. v. 710.
[276] Thorley, 171.
[277] White's _Nat. Hist._ 8vo. i. 339--.
[278] Swamm. _Bib. Nat._ Ed. Hill. i. 160.
[279] _ubi supr._ 665.
[280] 178--.
[281] _Theatr. Ins._ 21.
[282] Reaum. v. 540--.
[283] January 11, 1818. My bees were out, and very alert this day.
The thermometer stood abroad in the shade at 51-1/2°. When the sun
shone there was quite a cluster of them at the mouth of the hives,
and great numbers were buzzing about in the air before them.
[284] v. 671.
[285] i. 354. Note *.
[286] _ubi supr._
[287] Reaum. v. 672.
[288] Huber, i. 313.
LETTER XXI.
_MEANS BY WHICH INSECTS DEFEND
THEMSELVES._
When a country is particularly open to attack, or surrounded by
numerous enemies, who from cupidity or hostile feelings are disposed
to annoy it, we are usually led to inquire what are its means of
_defence?_ whether natural, or arising from the number, courage, or
skill of its inhabitants. The insect tribes constitute such a nation:
with them infinite hosts of enemies wage continual war, many of whom
derive the whole of their subsistence from them: and amongst their
own tribes there are numerous civil broils, the strong often preying
upon the weak, and the cunning upon the simple: so that unless a
watchful Providence (which cares for all its creatures, even the
most insignificant,) had supplied them with some mode of resistance
or escape, this innumerable race must soon be extirpated. That such
is the case, it shall be my endeavour in this letter to prove; in
which I shall detail to you some of the most remarkable means of
defence with which they are provided. For the sake of distinctness
I shall consider these under two separate heads, into which indeed
they naturally divide themselves:--_Passive_ means of defence, such
as are independent of any efforts of the insect; and _active_ means
of defence, such as result from certain efforts of the insect in the
employment of those instincts and instruments with which Providence
has furnished it for this purpose.
I. The principal _passive_ means of defence with which insects are
provided, are derived from their colour and form, by which they
either deceive, dazzle, alarm, or annoy their enemies; or from their
substance, involuntary secretions, vitality, and numbers.
They often _deceive_ them by imitating various substances. Sometimes
they so exactly resemble the soil which they inhabit, that it must be
a practised eye which can distinguish them from it. Thus, one of our
scarcest British weevils (_Curculio nebulosus_), by its gray colour
spotted with black, so closely imitates the soil consisting of white
sand mixed with black earth, on which I have always found it, that
its chance of escape, even though it be hunted for by the lyncean eye
of an entomologist, is not small. Another insect of the same tribe
(_Thylacites scabriculus_), of which I have observed several species
of ground-beetles, (_Harpalus_, &c.) make great havoc, abounds in
pits of a loamy soil of the same colour precisely with itself; a
circumstance that doubtless occasions many to escape from their
pitiless foes.--Several other weevils, for instance _Chlorima nivea_
and _cretacea_, resemble chalk, and perhaps inhabit a chalky or white
soil.
Many insects also are like pebbles and stones, both rough and
polished, and of various colours; but since this resemblance
sometimes results from their attitudes, I shall enlarge upon it under
my second head: whether, however, it be merely passive, or combined
with action, we may safely regard it as given to enable them to elude
the vigilance of their enemies.
A numerous host of our little animals escape from birds and other
assailants by imitating the colour of the plants, or parts of them,
which they inhabit; or the twigs of shrubs and trees; their foliage,
flowers, and fruit. Many of the mottled moths, which take their
station of diurnal repose on the north side of the trunks of trees,
are with difficulty distinguished from the gray and green lichens
that cover them. Of this kind are _Miselia aprilina_ and _Acronycta
Psi_. The caterpillar of _Pœcilia? Algæ_, when it feeds on the
yellow _Lichen juniperinus_, is always yellow; but when upon the
gray _Lichen saxatilis_ its hue becomes gray[289]. This change is
probably produced by the colour of its food. _Leptocerus atratus_,
a kind of may-fly, frequents the black flower-spikes of the common
sedge (_Carex riparia_), which fringes the banks of our rivers. I
have often been unable to distinguish it from them, and the birds
probably often make the same mistake and pass it by.--A jumping bug,
very similar to one figured by Schellenberg[290], also much resembles
the lichens of the oak on which I took it.
The Spectre tribe (_Phasma_) go still further in this mimicry,
representing a small branch with its spray. I have one from Brazil
eight inches long, that, unless it was seen to move, could scarcely
be conceived to be any thing else; the legs as well as the head,
having their little snags and knobs, so that no imitation can be more
accurate. Perhaps this may be the species mentioned by Molina[291],
which the natives of Chili call "The Devil's Horse[292]."
Other insects, of various tribes, represent the leaves of plants,
living, decaying, and dead; some in their colour, and some both in
their colour and shape. The caterpillar of a moth (_Hadena Ligustri_)
that feeds upon the privet, is so exactly of the colour of the
underside of the leaf, upon which it usually sits in the day-time,
that you may have the leaf in your hand and yet not discover
it[293].--The tribe of grasshoppers, called _Locustæ_ by Fabricius,
though the true _Locust_ does not belong to it, in the veining,
colour, and texture of their elytra, resemble green leaves[294].--The
tribe of _Phasmina_--named praying-insects and spectres--also of
the _Orthoptera_ order, often exhibit the same peculiarity.--Others
of them, by the spots and mixtures of colour observable in these
organs, represent leaves that are decaying in various degrees.--Those
of several species of _Mantidæ_ likewise imitate dry leaves, and so
exactly, by their opacity, colour, rigidity, and veins, that, were
no other part of the animal visible, even after a close examination,
it would be generally affirmed to be nothing but a dry leaf. Of this
nature is the _Phyllium siccifolium_, and two or three Brazilian
species in my cabinet, that seem undescribed, which I will show
you when you give me an opportunity. But these imitations of dry
leaves are not confined to the _Orthoptera_ order solely. Amongst
the _Hemiptera_, the _Acanthia paradoxa_, a kind of bug, surprised
Sparrman not a little. He was sheltering himself from the mid-day
sun, when the air was so still and calm as scarcely to shake an aspen
leaf, and saw with wonder what he mistook for a little withered,
pale, crumpled leaf, eaten as it were by caterpillars, fluttering
from the tree. The sight appeared to him so very extraordinary, that
he left his place of shelter to contemplate it more nearly; and could
scarcely believe his eyes, when he beheld a living insect, in shape
and colour resembling a fragment of a withered leaf with the edges
turned up and eaten away as it were by caterpillars, and at the same
time all over beset with prickles[295].--A British insect, one of
our largest moths (_Gastropacha quercifolia_), called by collectors
the _Lappet-moth_, affords an example from the _Lepidoptera_ order
of the imitation in question, its wings representing, both in shape
and colour, an arid brown leaf. Some bugs, belonging to the genus
_Dictyonota_ of Mr. Curtis[296], simulate portions of leaves in a
still further state of decay, when the veins only are left. For, the
thorax and elytra of these insects being reticulated, with the little
areas or meshes of the net-work transparent, this circumstance gives
them exactly the appearance of small fragments of skeletons of leaves.
But you have probably heard of most of these species of imitation: I
hope, therefore, you will give credit to the two instances to which
I shall next call your attention, of insects that even mimic flowers
and fruit. With respect to the former, I recollect to have seen in
a collection made by Mr. Masson at the Cape of Good Hope, a species
of the orthopterous genus _Pneumora_, the elytra of which were of a
rose- or pink-colour, which shrowding its vesiculose abdomen, gave it
much the appearance of a fine flower--A most beautiful and brilliant
beetle, of the genus _Chlamys_, (_Ch. Bacca_,) found by Captain
Hancock in Brazil, by the inequalities of its ruby-coloured surface,
strikingly resembles some kinds of fruit.--And to make the series
of imitations complete, a minute black beetle, with ridges upon its
elytra, (_Onthophilus sulcatus_[297],) when lying without motion, is
very like the seed of an umbelliferous plant. The dog-tick is not
unlike a small bean; which resemblance has caused a bean, commonly
cultivated as food for horses, to be called the _tick-bean_. The
Palma Christi, also, had probably the name of _Ricinus_ given to it
from the similitude of its seed to a tick.
Another tribe of these little animals, before alluded to, is secured
from harm by a different kind of imitation, and affords a beautiful
instance of the wisdom of Providence in adapting means to their end.
Some singular larvæ, with a radiated anus[298], live in the nests of
humble-bees, and are the offspring of a particular genus of flies,
(_Volucella_,) many of the species of which strikingly resemble
those bees in shape, clothing, and colour. Thus has the Author of
nature provided that they may enter these nests and deposit their
eggs undiscovered. Did these intruders venture themselves amongst
the humble-bees in a less kindred form, their lives would probably
pay the forfeit of their presumption. Mr. Sheppard once found one of
these larvæ in the nest of _Bombus_[299] _Raiellus_, but we could not
ascertain what the fly was. Perhaps it might be _Volucella bombylans_,
which resembles those humble-bees that have a red anus[300].
The brilliant colours in which many insects are arrayed, may decorate
them with some other view than that of mere ornament. They may _dazzle_
their enemies. The radiant blue of the upper surface of the wings of
a giant butterfly, abundant in Brazil (_Morpho Menelaus_), which from
its size would be a ready prey for any insectivorous birds, by its
splendour (which I am told, when the insect is flying in the sunshine,
is inconceivably bright,) may produce an effect upon the sight of such
birds, that may give it no small chance of escape. Latreille has a
similar conjecture with respect to the golden wasps (_Chrysis_, L.).
These animals lay their eggs in the nests of such _Hymenoptera_, wasps,
bee-wasps (_Bembex_), and bees,--as are redoubtable for their stings;
and therefore have the utmost occasion for protection against these
murderous weapons. Amongst other defences the golden wasps are adorned
with the most brilliant colours, which by their radiance, especially
in the sunny situations frequented by these insects, may dazzle the
eyes of their enemies, and enable them to effect unhurt the purpose for
which they were created[301].
The frightful aspect of certain insects is another passive mean
of defence by which they sometimes strike beholders, especially
children, often great insect tormentors, with _alarm_, and so
escape. The terrific and protended jaws of the stag-beetle (_Lucanus
Cervus_) in Europe, and of the stag-horn capricorn beetle (_Prionus
cervicornis_) in America, may save them from the cruel fate of the
poor cockchafer[302], whose gyrations and motions, when transfixed
by a pin, too often form the amusement of ill-disciplined children.
The threatening horns also, prominent eyes, or black and dismal hue
of many other _Coleoptera_ belonging to Linné's genera _Scarabæus_,
_Cicindela_, and _Carabus_, may produce the same effect.
But the most striking instances of armour are to be found amongst the
homopterous _Hemiptera_. In some of these, the horns that rise from
the thorax are so singular and monstrous, that nothing parallel to
them can be found in nature. Of this kind is the _Cicada spinosa_,
Stoll[303], the _Centrotus clavatus_[304], and more particularly the
_Centrotus globularis_[305], so remarkable for the extraordinary
apparatus of balls and spines, which it appears to carry erect,
like a standard, over its head. What is the precise use of all the
varieties of armour with which these little creatures are furnished
it is not easy to say, but they may probably defend them from the
attack of some enemies.
Under this head I may mention the long hairs, stiff bristles, sharp
spines, and hard tubercular prominences with which many caterpillars
are clothed, bristled, and studded. That these are means of defence
is rendered more probable by the fact that, in several instances,
the animals so distinguished, at their last moult, previous to their
assuming the pupa, (in which state they are protected by other
contrivances,) appear with a smooth skin, without any of the tubercles,
hairs, or spines for which they were before remarkable[306]. Wonderful
are the varieties of this kind which insects exhibit:--but upon these
I shall treat more at large on a future occasion. I shall only here
select a few facts more particularly connected with my present subject.
The caterpillar of the great tiger-moth (_Euprepia Caja_), which is
beset with long dense hairs, when rolled up--an attitude it usually
assumes if alarmed--cannot then be taken without great difficulty,
slipping repeatedly from the pressure of the fingers. If its hairs do
not render it distasteful, this may often be the mean of its escape
from the birds.--That little destructive beetle, _Anthrenus Musorum_,
which so annoys the entomologist, if it gets into his cabinets, when
in the larva state being covered with bunches of diverging hairs,
glides from between your fingers as if it were lubricated with oil.
The two tufts of hairs near the tail of this are most curious in their
structure, being jointed through their whole length, and terminating
in a sharp halberd-shaped point[307].--I have a small lepidopterous
caterpillar from Brazil, the upper side of which is thickly beset with
strong, sharp, branching spines, which would enter into the finger, and
would probably render it a painful morsel to any minor enemy.
The powers of _annoyance_, by means of their hairs, with which the
moth of the fir, and the procession-moth, before noticed[308], are
gifted, are doubtless a defensive armour to them.--Madame Merian has
figured an enormous caterpillar of this kind,--which unfortunately
she could not trace to the perfect insect,--by the very touch of
which her hands, she says, were inflamed, and that the inflammation
was succeeded by the most excruciating pain[309]. The vesicatory
beetles, likewise, (_Cantharis vesicatoria_, &c.) are not improbably
defended from their assailants by the remarkable quality, so useful
to suffering mortals, that distinguishes them.
Your own observation must have proved to you, that insects often
escape great perils, from the crush of the foot, or of superincumbent
weights, by the hardness of the _substance_ that covers great numbers
of them. The elytra of many beetles of the genus _Hister_ are so
nearly impenetrable, that it is very difficult to make a pin pass
through them; and the smaller stag-beetle (_Dorcus parallelopipedus_)
will bear almost any weight--the head and trunk forming a slight
angle with the abdomen--which passes over it upon the ground. Other
insects are protected by the toughness of their skin. A remarkable
instance of this is afforded by the common forest-fly (_Hippobosca
equina_), which, as was before observed[310], can scarcely be killed
by the utmost pressure of the finger and thumb.
The _involuntary secretions_ of these little beings may also be
regarded as means of defence, which either conceal them from their
enemies, make them more difficult to be attacked, or render them less
palatable. Thus, the white froth often observable upon rose-bushes,
and other shrubs and plants, called by the vulgar frog-spittle,--but
which, if examined, will be found to envelop the larva of a small
hemipterous insect (_Cercopis spumaria_), from whose anus it exudes,
although it is sometimes discovered even in this concealment by the
indefatigable wasps, and becomes their prey,--serves to protect the
insect, which soon dies when exposed, not only from the heat of the
sun and from violent rains, but also to hide it from the birds and
its other foes.--The cottony secretion that transpires through the
skin of _Myzoxyla_[311], and some species of _Coccus_, and in which
the eggs of the latter are often involved, may perhaps be of use to
them in this view; either concealing them--for they look rather like
little locks of cotton, or feathers, than any thing animated--or
rendering them distasteful to creatures that would otherwise prey
upon them.--The same remark may apply to the slimy caterpillars of
some of the saw-flies (_Tenthredo Cerasi_, _Allantus Scrophulariæ_
&c.) The coat of slime of these animals, as Professor Peck
observes[312], retains its humidity though exposed to the fiercest
sun.--Under this head I shall also mention the phosphoric insects:
the glow-worm (_Lampyris_); the lantern-fly (_Fulgora_); the fire-fly
(_Elater_); and the electric centipede (_Geophilus electricus_);
since the light emitted by these animals may defend them from the
attack of some enemies. Mr. Sheppard once noticed a Carabus running
round the last-mentioned insect, when shining, as if wishing but
afraid to attack it.
Various insects, doubtless, find the wonderful _vitality_[313] with
which they are endowed another mean of defence; at least of obviating
the effects of an attack. So that, when to all appearance they are
mortally wounded, they recover, and fulfil the end of their creation.
Indeed female _Lepidoptera_, especially of the larger kinds, will
scarcely die, do what you will, till they have laid their eggs.--Dr.
Arnold, a most acute observer, relates to Mr. MacLeay, that having
pinned _Scolia quadrimaculata_, a hymenopterous insect, down in
the same box with many others, amongst which was the humming-bird
hawk-moth (_Macroglossa stellatarum_), its proper food; it freed
itself from the pin that transfixed it, and, neglecting all the other
insects in the box, attacked the Sphinx, and pulling it to pieces
devoured a large portion of its abdomen.