from particular organs. Of these, some are furnished with a kind of
scent-vessels, which I shall call _osmateria_; while in others it
issues from the intestines at the ordinary passage. In the former
instance the organ is usually retractile within the body, being only
exerted when it is used: it is generally a bifid vessel, something
in the shape of the letter Y. Linné, in his generic character of the
rove-beetles (_Staphylinidæ_), mentions two oblong vesicles as proper
to this genus. These organs,--which are by no means common to the
whole genus, even as restricted by late writers,--are its _osmateria_,
and give forth the scent for which some species, particularly
_Ocypus brunnipes_, are remarkable. If you press the abdomen hard,
you will find that these vesicles are only branches from a common
stem; and you may easily ascertain that the smell of this insect,
which mixes something extremely fetid with a spicy odour, proceeds
from their extremity.--A similar organ, half an inch in length, and
of the same shape, issues from the neck of the caterpillar of the
swallow-tail-butterfly (_Papilio Machaon_)[347]. When I pressed this
caterpillar, says Bonnet, near its anterior part, it darted forth
its horn as if it meant to prick me with it, directing it towards
my fingers; but it withdrew it as soon as I left off pressing it.
This horn smells strongly of fennel, and probably is employed by the
insect, by means of its powerful scent, to drive away the flies and
ichneumons that annoy it. A similar horn is protruded by the slimy
larva of _P. Anchises_, as also _Parnassius Apollo_ and many other
_Equites_[348].--Another insect, the larva of a species of saw-fly
described by De Geer, is furnished with osmateria, or scent-organs,
of a different kind. They are situated between the five first pair of
intermediate legs, which they exceed in size, and are perforated at
the end like the rose of a watering-pot. If you touch the insect, they
shoot out like the horns of a snail, and emit a most nauseous odour,
which remains long upon the finger; but when the pressure is removed
they are withdrawn within the body[349].--The grub of the poplar-beetle
(_Chrysomela Populi_) also is remarkable for similar organs. On each
of the nine intermediate dorsal segments of its body is a pair of
black, elevated, conical tubercles, of a hard substance; from all of
these when touched the animal emits a small drop of a white milky
fluid, the smell of which, De Geer observes, is almost insupportable,
being inexpressibly strong and penetrating. These drops proceed at
the same instant from all the eighteen scent-organs; which forms a
curious spectacle. The insect, however, does not waste this precious
fluid: each drop instead of falling, after appearing for a moment and
dispensing its perfume, is withdrawn again within its receptacle, till
the pressure is repeated, when it reappears[350].
I shall now introduce you to the true counterparts of the skunk,
which explode a most fetid vapour from the ordinary passage. I have
lately hinted that the scent of many _Eutrechina_ is thus emitted.
_Anchomenus prasinus_, a beetle of this tribe, combats its enemies
with repeated discharges of smoke and noise: but the most famous
for their exploits in this way are those, which on this account
are distinguished by the name of bombardiers (_Brachinus_). The
most common species (_B. crepitans_), which is found occasionally
in many parts of Britain, when pursued by its great enemy,
_Calosoma Inquisitor_, seems at first to have no mode of escape:
when suddenly a loud explosion is heard, and a blue smoke attended
by a very disagreeable scent, is seen to proceed from its anus,
which immediately stops the progress of its assailant: when it has
recovered from the effect of it, and the pursuit is renewed, a
second discharge again arrests its course. The bombardier can fire
its artillery twenty times in succession if necessary, and so gain
time to effect its escape.--Another species (_B. Displosor_) makes
explosions similar to those of _B. crepitans_: when irritated it
can give ten or twelve good discharges; but afterwards, instead of
smoke it emits a yellow or brown fluid. By bending the joints of its
abdomen it can direct its smoke to any particular point. M. Leon
Dufour observes that this smoke has a strong and pungent odour,
which has a striking analogy with that exhaled by the Nitric Acid.
It is caustic, reddening white paper, and producing on the skin the
sensation of burning, and forming red spots, which pass into brown,
and though washed remain several days[351].
Another expedient to which insects have recourse to rid themselves
of their enemies, is the emission of disagreeable _fluids_. These
some discharge from the mouth; others from the anus; others again
from the joints of the limbs and segments of the body; and a few from
appropriate organs.
You have doubtless often observed a black beetle crossing pathways
with a slow pace, which feeds upon the different species of bedstraw
(_Galium_), called by some the bloody-nose beetle (_Timarcha
tenebricosa_). This insect, when taken, usually ejects from its mouth
a clear drop or two of red fluid, which will stain paper of an orange
colour. The carrion-beetles (_Silpha_ and _Necrophorus_), as also
the larger _Carabi_, defile us, if handled roughly, with brown fetid
saliva. Mr. Sheppard having taken one of the latter (_C. violaceus_),
applied it in joke to his son's face, and was surprised to hear him
immediately cry out as if hurt: repeating the experiment with another
of his boys, he complained of its making him smart: upon this he
touched himself with it, and it caused as much pain as if, after
shaving, he had rubbed his face with spirits of wine. This he observed
was not invariably the case with this beetle, its saliva at other times
being harmless. Hence he conjectures that its caustic nature, in the
instance here recorded, might arise from its food; which he had reason
to think had at that time been the electric centipede (_Geophilus
electricus_).--Lesser having once touched the anal horn of the
caterpillar of some sphinx, suddenly turning its head round it vomited
upon his hand a quantity of green viscous and very fetid fluid, which,
though he washed it frequently with soap and fumed it with sulphur,
infected it for two days[352].--Lister relates that he saw a spider,
when upon being provoked it attempted to bite, emit several times small
drops of very clear fluid[353].--Mr. Briggs observed a caterpillar
caught in the web of one of our largest spiders, by means of a fluid
which it sent forth entirely dissolve the great breadth of threads with
which the latter endeavoured to envelop it, as fast as produced, till
the spider appeared quite exhausted[354].--The caterpillars also of a
particular tribe of saw-flies, remarkable for the beautiful pennated
antennæ of the males (_Pteronus_)[355], when disturbed eject a drop of
fluid from their mouth. Those of one species inhabiting the fir-tree
(_Pt. Pini_) are ordinarily stationed on the narrow leaves of that
tree--which they devour most voraciously in the manner that we eat
radishes--with their head towards the point. Sometimes two are engaged
opposite to each other on the same leaf. They collect in groups often
of more than a hundred, and keep as close to each other as they can.
When a branch is stripped they all move together to another. If one of
these caterpillars be touched or disturbed, it immediately with a twist
lifts the anterior part of its body, and emits from its mouth a drop of
clear resin, perfectly similar both in odour and consistence to that of
the fir[356]. What is still more remarkable, no sooner does a single
individual of the group give itself this motion, than all the rest, as
if they were moved by a spring, instantaneously do the same[357]. Thus
these animals fire a volley as it were at their annoyers, the scent of
which is probably sufficient to discomfit any ichneumons, flies, or
predaceous beetles that may be desirous of attacking them.
Amongst those which annoy their enemies by the emission of fluids
from their anus are the larger Carabi. These, if roughly handled,
will spirt to a considerable distance an acrid, caustic, stinking
liquor, which if it touch the eyes or the lips occasions considerable
pain[358].--The rose-scented capricorn (_Cerambyx moschatus_)
produced a similar effect upon Mr. Sheppard by similar means. The
fluid in this had a powerful odour of musk.--The acid of ants has
long been celebrated, and is one of their most powerful means of
defence. When the species that have no sting make a wound with their
jaws, they insinuate into it some of this acid, the effluvia produced
by which are so subtile and penetrating, that it is impossible to
hold your head near the nest of the hill-ant (_Formica rufa_), when
the ants are much disturbed, without being almost suffocated. This
odour thus proceeding from myriads of ants, is powerful enough, it is
said, to kill a frog, and is probably the means of securing the nest
from the attack of many enemies.--Dr. Arnold observed a species of
bug (_Scutellera_) abundant upon some polygamous plant which he could
not determine, and in all their different states. They were attended
closely by hosts of ants, and when disturbed emitted a very strong
smell. One of these insects ejected a minute drop of fluid into one
of his eyes, which occasioned for some hours considerable pain and
inflammation. In the evening, however, they appeared to subside;--but
on the following morning the inflammation was renewed, became worse
than ever, and lasted for three days.
Other insects, when under alarm, discharge a fluid from the joints
and segments of their body. You have often seen what has been called
the unctuous or oil beetle (_Meloe Proscarabæus_), and I dare say,
when you took it, have observed orange-coloured or deep-yellow drops
appear at its joints. As these insects feed upon acrid plants, the
species of crowfoot or _Ranunculus_, it is probable that this fluid
partakes of the nature of their food and is very acrimonious--and
thus may put to flight its insect assailants or the birds, from
neither of which it could otherwise escape, being a very slow and
sluggish and at the same time very conspicuous animal. Another beetle
(_Ellenophorus collaris_) has likewise this faculty.--The lady-bird,
we know, has been recommended as a cure for the tooth-ache. This
idea may have taken its rise from a secretion of this kind being
noticed upon it. I have observed that one species (_Coccinella
bipunctata_) when taken ejects from its joints a yellow fluid
which yields a powerful but not agreeable scent of opium.--_Asilus
crabroniformis_, a dipterous insect, once when I took it, emitted
a white milky fluid from its proboscis, the joints of the legs and
abdomen, and the anus.--The common scorpion-fly, likewise, upon the
same occasion ejects from its proboscis a brown and fetid drop[359].
Some insects have peculiar organs from which their fluids issue, or
are ejaculated. Thus the larvæ of saw-flies when taken into the hand
cover themselves with drops, exuding from all parts of their body,
of an unpleasant penetrating scent[360]. That of _Cimbex lutea_, of
the same tribe, from a small hole just above each spiracle, syringes
a similar fluid in horizontal jets of the diameter of a thread,
sometimes to the distance of more than a foot[361].--The caterpillar
of the great emperor moth (_Saturnia Pyri_,) also spirts out, when
the spines that cover them are touched, clear lymph from its pierced
tubercles[362].--Willughby has remarked a curious circumstance with
respect to a water-beetle (_Acilius sulcatus_), which ought not to be
overlooked. A transverse line of a pale colour is observable upon the
elytra of the male; where this line terminates certain oblong pores
are visible, from which he affirms he has often seen a milky fluid
exuding[363]; and what may confirm his statement, I have more than
once observed such a fluid issue from the male of this genus.--The
caterpillar of the puss-moth (_Cerura vinula_), as well as those of
several other species, has a cleft in the neck between the head and
the first pair of legs. From this issues, at the will of the animal,
a singular syringe, laterally bifid; the branches of which are
terminated by a nipple perforated like the rose of a watering-pot.
By means of this organ, when touched, it will syringe a fluid to a
considerable distance, which, if it enters the eyes, gives them acute
but not lasting pain. The animal when taken from the tree on which
it feeds, though supplied with its leaves, loses this faculty, with
which it is probably endowed to drive off the ichneumons that infest
it[364].--And, to name no more, the great tiger-moth (_Euprepia
Caja_), when in its last or perfect state, has near its head a
remarkable tuft of the most brilliant carmine, from amongst the hairs
of which, if the thorax be touched, some minute drops of transparent
water issue, doubtless for some similar purpose[365].
The next active means of defence with which Creative Wisdom has
endowed these busy tribes, are those _limbs_ or _weapons_ with which
they are furnished. The insect lately mentioned, the puss-moth,
besides the syringes just described, is remarkable for its singular
forked tail, entirely dissimilar to the anal termination of the
abdomen of most other caterpillars. This tail is composed of two
long cylindrical tubes moveable at their base, and beset with a
great number of short stiff spines. When the animal walks, the two
branches of the tail are separated from each other, and at every
step are lowered so as to touch the plane of position; hence we may
conclude that they assist it in this motion and supply the place of
hind legs. If you touch or otherwise incommode it, from each of the
above branches there issues a long, cylindrical, slender, fleshy, and
very flexible organ of a rose colour, to which the caterpillar can
give every imaginable curve or inflection, causing it sometimes to
assume even a spiral form. It enters the tube, or issues from it, in
the same manner as the horns of snails or slugs. These tails form a
kind of double whip, the tubes representing the handle, and the horns
the thong or lash with which the animal drives away the ichneumons
and flies that attempt to settle upon it. Touch any part of the body,
and immediately one or both the horns will appear and be extended;
and the animal will, as it were, lash the spot where it feels that
you incommode it. De Geer, from whom this account is taken, says
that this caterpillar will bite very sharply[366].--Several larvæ
of butterflies, distinguished at their head by a semicoronet of
strong spines, figured by Madame Merian, are armed with singular
anal organs[367], which may have a similar use. Rösel when he first
saw the caterpillar of the puss-moth, stretched out his hand with
great eagerness, so he tells us, to take the prize; but when in
addition to its grim attitude he beheld it dart forth these menacing
catapults, apprehending they might be poisonous organs, his courage
failed him. At length, without touching the monster, he ventured to
cut off the twig on which it was, and let it drop into a box[368]!
The caterpillar of the gold-tail moth (_Arctia chrysorhœa_) has a
remarkable aperture, which it can open and shut, surrounded by a rim
on the upper part of each segment. This aperture includes a little
cavity, from which it has the power of darting forth small flocks
of a cottony matter that fills it[369]. This manœuvre is probably
connected with our present subject, and employed to defend it from
its enemies. It also ejects a fluid from its anus.
There is a moth in New Holland, the larva of which annoys its foes
in a different way: from eight tubercles in its back it darts forth,
when alarmed, as many bunches of little stings, by which it inflicts
very painful and venomous wounds[370].
The caterpillar of the moth of the beech (_Stauropus Fagi_),
called the lobster, is distinguished by the uncommon length of its
anterior legs. Mr. Stephens, an acute entomologist, relates to me
that he once saw this animal use them to rid itself of a mite that
incommoded it. They are probably equally useful in delivering it from
the ichneumon and its other insect enemies.--Dr. Arnold has made
a curious observation (confirmed by Dr. Forsström with respect to
others of the genus) on the use of the long processes or tails that
distinguish the secondary wings of _Thecla Iarbas_. These processes,
he remarks, resemble antennæ, and when the butterfly is sitting it
keeps them in constant motion; so that at first sight it appears to
have a head at each extremity; which deception is much increased by a
spot resembling an eye at the base of the processes. These insects,
perhaps, thus perplex or alarm their assailants.--Goedart pretended
that the anal horn with which the caterpillars of so many hawk-moths
(_Sphingidæ_) are armed, answers the end of a sting instilling a
dangerous venom: but the observations of modern entomologists have
proved that this is altogether fabulous, since the animal has not
the power of moving them[371]. Their use is still unknown.
Whether the long and often threatening horns on the head, thorax,
and even elytra, with which many insects are armed, are beneficial
to them in the view under consideration, is very uncertain. They are
frequently sexual distinctions, and have a reference probably rather
to sexual purposes and the economy of the animal, than to any thing
else. They may, however, in some instances deter enemies from attacking
them, and therefore it was right not to omit them wholly, though I
shall not further enlarge upon them.--Their mandibles or upper jaws,
though principally intended for mastication,--and in the case of the
_Hymenoptera_, as instruments for various economical and mechanical
uses,--are often employed to annoy their enemies or assailants. I once
suffered considerable pain from the bite of the common water-beetle
(_Dytiscus marginalis_), as well as from that of the great rove-beetle
(_Goerius olens_); but the most tremendous and effectual weapon with
which insects are armed--though this, except in the case of the
scorpion, is also a sexual instrument, and useful to the females in
oviposition--is their sting. With this they keep not only the larger
animals, but even man himself, in awe and at a distance. But on these I
enlarged sufficiently in a former letter[372].
These weapons, fearful as they are, would be of but little use to
insects if they had not courage to employ them: in this quality,
however, they are by no means deficient; for, their diminutive size
considered, they are, many of them, the most valiant animals in
nature. The giant bulk of an elephant would not deter a hornet, a
bee, or even an ant, from attacking it, if it was provoked. I once
observed a small spider walking in my path. On putting my stick
to it, it immediately turned round as if to defend itself. On the
approach of my finger, it lifted itself up and stretched out its legs
to meet it.--In Ray's Letters mention is made of a singular combat
between a spider and a toad fought at Hetcorne near Sittinghurst[373]
in Kent; but as the particulars and issue of this famous duel are
not given, I can only mention the circumstance, and conjecture that
the spider was victorious[374]! Terrible as is the dragon-fly to the
insect world in general, putting to flight and devouring whole hosts
of butterflies, may-flies, and others of its tribes, it instills no
terror into the stout heart of the scorpion-fly (_Panorpa communis_),
though much its inferior in size and strength. Lyonnet saw one attack
a dragon-fly of ten times its own bigness, bring it to the ground,
pierce it repeatedly with its proboscis; and had he not by his
eagerness parted them, he doubts not it would have destroyed this
tyrant of the insect creation[375].
When the death's-head-hawk-moth was introduced by Huber into a nest
of humble-bees, they were not affected by it, like the hive-bees,
but attacked it and drove it out of their nest, and in one instance
their stings proved fatal to it[376].--A black ground-beetle devours
the eggs of the mole cricket, or _Gryllotalpa_. To defend them, the
female places herself at the entrance of the nest--which is a neatly
smoothed and rounded chamber protected by labyrinths, ditches, and
ramparts--and whenever the beetle attempts to seize its prey, she
catches it and bites it asunder[377].
I know nothing more astonishing than the wonderful muscular strength
of insects, which in proportion to their size exceeds that of any
other class of animals, and is likewise to be reckoned amongst their
means of defence. Take one of the common chafers or dung-beetles
(_Geotrupes stercorarius_, or _Copris lunaris_), into your hand,
and observe how he makes his way in spite of your utmost pressure;
and read the accounts which authors have left us of the very great
weights that a flea will easily move, as if a single man should draw
a waggon with forty or fifty hundred weight of hay:--but upon this I
shall touch hereafter, and therefore only hint at it now.
We are next to consider the modes of _concealment_ to which insects
have recourse in order to escape the observation of their enemies.
One is by covering themselves with various substances. Of this
description is a little water-beetle (_Elophorus aquaticus_), which
is always found covered with mud, and so when feeding at the bottom
of a pool or pond can scarcely be distinguished, by the predaceous
aquatic insects, from the soil on which it rests. Another very minute
insect of the same order (_Limnius æneus_) that is found in rivulets
under stones and the like, sometimes conceals its elytra with a
thick coating of sand, that becomes nearly as hard as stone. I never
met with these animals so circumstanced but once; then, however,
there were several which had thus defended themselves, and I can
now show you a specimen.--A species of a minute coleopterous genus
(_Georyssus areniferus_[378]), which lives in wet spots where the
toad-rush (_Juncus bufonius_) grows, covers itself with sand; and
another nearly related to it (_Chætophorus cretiferus_, K.) which
frequents chalk, whitens itself all over with that substance. As this
animal, when clean, is very black, were it not for this manœuvre, it
would be too conspicuous upon its white territory to have any chance
of escape from the birds and its other assailants.--No insect is
more celebrated for rendering itself hideous by a coat of dirt than
the _Reduvius personatus_, a kind of bug sometimes found in houses.
When in its two preparatory states, every part of its body, even
its legs and antennæ, is so covered with the dust of apartments,
consisting of a mixture of particles of sand, fragments of wool or
silk, and similar matters, that the animal at first would be taken
for one of the ugliest spiders. This grotesque appearance is aided
and increased by motions equally awkward and grotesque, upon which
I shall enlarge hereafter. If you touch it with a hair-pencil or a
feather, this clothing will soon be removed, and you may behold the
creature unmasked, and in its proper form. It is an insect of prey;
and amongst other victims will devour its more hateful congener the
bed-bug[379]. Its slow movements, combined with its covering, seem to
indicate that the object of these manœuvres is to conceal itself from
observation, probably, both of its enemies and of its prey. It is
therefore properly noticed under my present head.
As Hercules, after he had slain the Nemean lion, made a doublet of
its skin, so the larva of another insect (_Hemerobius Chrysops_, a
lace-winged fly with golden eyes,) covers itself with the skins of
the luckless Aphides that it has slain and devoured. From the head to
the tail, this pygmy destroyer of the helpless is defended by a thick
coat, or rather mountain composed of the skins, limbs, and down of
these creatures. Reaumur, in order to ascertain how far this covering
was necessary, removed it, and put the animal into a glass, at one
time with a silk cocoon, and at another with raspings of paper. In
the first instance, in the space of an hour it had clothed itself
with particles of the silk: and in the second, being again laid bare,
it found the paper so convenient a material, that it made of it a
coat of unusual thickness[380].