filthy the substances which they inhabit, yet they so manage as
to keep themselves personally neat. Several, however, by no means
deserve this character; and I fear you will scarcely credit me when
I tell you that some shelter themselves under an umbrella formed of
their own excrement! You will exclaim, perhaps, that there is no
parallel case in all nature;--it may be so;--yet as I am bound to
confess the faults of insects as well as to extol their virtues, I
must not conceal from you this opprobrium. Beetles of three different
genera are given to this Hottentot habit. The first to which I shall
introduce you is one that has long been celebrated under the name
of the beetle of the lily (_Lema merdigera_, _Cantaride de' Gigli_,
Vallisn.) The larvæ of this insect have a very tender skin, which
appears to require some covering from the impressions of the external
air and from the rays of the sun; and it finds nothing so well
adapted to answer these purposes, and probably also to conceal itself
from the birds, as its own excrement, with which it covers itself
in the following manner. Its anus is remarkably situated, being on
the back of the last segment of the body, and not at or under its
extremity, as obtains in most insects. By means of such a position,
the excrement when it issues from the body, instead of being pushed
away and falling, is lifted up above the back in the direction of the
head. When entirely clear of the passage, it falls, and is retained,
though slightly, by its viscosity. The grub next, by a movement
of its segments, conducts it from the place where it fell to the
vicinity of the head. It effects this by swelling the segment on
which the excrement is deposited, and contracting the following one,
so that it necessarily moves that way. Although, when discharged, it
has a longitudinal direction, by the same action of the segments the
animal contrives to place every grain transversely. Thus, when laid
quite bare, it will cover itself in about two hours. There are often
many layers of these grains upon the back of the insect, so as to
form a coat of greater diameter than its body. When it becomes too
heavy and stiff, it is thrown off, and a new one begun[381].--The
larvæ of the various species of the tortoise-beetles (_Cassida_,
L.) have all of them, as far as they are known, similar habits, and
are furnished besides with a singular apparatus, by means of which
they can elevate or drop their stercorarious parasol so as most
effectually to shelter or shade them. The instrument by which they
effect this is an anal fork, upon which they deposit their excrement,
and which in some is turned up and lies flat upon their backs; and in
others forms different angles, from very acute to very obtuse, with
their body; and occasionally is unbent and in the same direction with
it[382]. In some species the excrement is not so disgusting as you
may suppose, being formed into fine branching filaments. This is the
case with _C. maculata_, L.[383].--In the cognate genus _Imatidium_,
the larvæ also are merdigerous; and that of _I. Leayanum_, Latr.,
taken by Major-General Hardwicke in the East Indies, also produces an
assemblage of very long filaments, that resemble a dried fucus or a
filamentous lichen.--The clothing of the _Tineæ_, clothes-moths and
others, and also of the case-worms, having enlarged upon in a former
letter[384], I need not describe here.
Some insects, that they may not be discovered and become the prey of
their enemies when they are reposing, conceal themselves in flowers.
The male of a little bee (_Heriades_[385] _Campanularum_), a true
Sybarite, dozes voluptuously in the bells of the different species of
_Campanula_--in which, indeed, I have often found other kinds asleep.
Linné named another species _florisomnis_ on account of a similar
propensity. A third, a most curious and rare species (_Andrena_[386]
_spinigera_), shelters itself when sleeping, at least I once found it
there so circumstanced, in the nest-like umbel of the wild carrot.
You would think it a most extraordinary freak of Nature, should any
quadruped sleep suspended by its jaws, (some birds however are said,
I think, to have such a habit, and _Sus Babyroussa_ one something
like it,)--yet insects do this occasionally. Linné informs us that
a little bee (_Epeolus_[387] _variegatus_) passes the night thus
suspended to the beak of the flowers of _Geranium phæum_: and I once
found one of the vespiform bees (_Nomada_[388] _Goodeniana_) hanging
by its mandibles from the edge of a hazel-leaf, apparently asleep,
with its limbs relaxed and folded. On being disengaged from its
situation it became perfectly lively.
There is no period of their existence in which insects usually are
less able to help themselves, than during that intermediate state of
repose which precedes their coming forth in their perfect forms. I
formerly explained to you how large a portion of them during this
state cease to be locomotive, and assume an appearance of death[389].
In this helpless condition, unless Providence had furnished them
with some means of security, they must fall an easy prey to the most
insignificant of their assailants. But even here they are taught
to conceal themselves from their enemies by various and singular
contrivances. Some seek for safety by burying themselves, previously
to the assumption of the pupa, at a considerable depth under the
earth; others bore into the heart of trees, or into pieces of timber;
some take their residence in the hollow stalks of plants; and many
are concealed under leaves, or suspend themselves in dark places,
where they cannot readily be seen. But in this state they are not
only defended from harm by the situation they select, but also by
the covering in which numbers envelop themselves; for, besides the
leathery case that defends the yet tender and unformed imago, many of
these animals know how to weave for it a costly shroud of the finest
materials, through which few of its enemies can make their way;--and to
this curious instinct, as I long since observed, we owe one of the most
valuable articles of commerce, the silk that gives lustre to the beauty
of our females. These shrouds are sometimes double. Thus the larvæ of
certain saw-flies spin for themselves a cocoon of a soft, flexible, and
close texture, which they surround with an exterior one composed of a
strong kind of net-work, which withstands pressure like a racket[390].
Here nature has provided that the inclosed animal shall be protected
by the interior cocoon from the injury it might be exposed to from
the harshness of the exterior, while the latter by its strength and
tension prevents it from being hurt by any external pressure.
But of all the contrivances by which insects in this state are secured
from their enemies, there is none more ingenious than that to which
the may-flies (_Trichoptera_) have recourse for this purpose. You have
heard before that these insects are at first aquatic, and inhabit
curious cases made of a variety of materials, which are usually open
at each end[391]. Since they must reside in these cases, when they are
become pupæ, till the time of their final change approaches, if they
are left open, how are the animals, now become torpid, to keep out
their enemies? Or, if they are wholly closed, how is the water, which
is necessary to their respiration and life, to be introduced? These
sagacious creatures know how to compass both these ends at once. They
fix a grate or portcullis to each extremity of their fortress, which at
the same time keeps out intruders and admits the water. These grates
they weave with silk spun from their anus into strong threads, which
cross each other, and are not soluble in water. One of them, described
by De Geer, is very remarkable. It consists of a small, thickish,
circular lamina of brown silk, becoming as hard as gum, which exactly
fits the aperture of the case, and is fixed a little within the margin.
It is pierced all over with holes disposed in concentric circles, and
separated by ridges which go from the centre to the circumference, but
often not quite so regularly as the radii of a circle or the spokes of
a wheel. These radii are traversed again by other ridges, which follow
the direction of the circles of holes; so that the two kinds of ridges
crossing each other form compartments, in the centre of each of which
is a hole[392].
Under this head I shall call your attention to another circumstance
that saves from their enemies innumerable insects:--I mean their coming
forth for flight or for food only in the night, and taking their
repose in various places of concealment during the day. The infinite
hosts of moths (_Phalæna_, L.),--amounting in this country to more
than a thousand species,--with few exceptions, are all night-fliers.
And a considerable proportion of the other orders,--exclusive of the
_Hymenoptera_ and _Diptera_, which are mostly day-fliers,--are of the
same description. Many _larvæ_ of moths also come out only in the night
after their food, lying hid all day in subterraneous or other retreats.
Of this kind is that of _Fumea pulla_ and _Nycterobius_, whose
proceedings have been before described[393]. The caterpillar of another
moth (_Noctua subterranea_, F.) never ascends the stems of plants, but
remains, a true Troglodyte, always in its cell under ground, biting the
stems at their base, which falling, bring thus their foliage within its
reach[394].
The habitations of insects are also usually places of retreat,
which secure them from many of their enemies:--but I have so fully
enlarged upon this subject on a former occasion[395], that it would
be superfluous to do more than mention it here.
I am now to lay before you some examples of the contrivances, requiring
skill and ingenuity, by which our busy animals occasionally defend
themselves from the designs and attack of their foes. Of these I
have already detailed to you many instances, which I shall not here
repeat; my history therefore will not be very prolix.--I observed
in my account of the societies of wasps, that they place sentinels
at the mouth of their nests. The same precaution is taken by the
hive-bees, particularly in the night, when they may expect that
the great destroyers of their combs, _Galleria mellonella_ and its
associates[396], will endeavour to make their way into the hive.
Observe them by moonlight, and you will see the sentinels pacing about
with their antennæ extended, and alternately directed to the right
and left. In the mean time the moths flutter round the entrance; and
it is curious to see with what art they know how to profit of the
disadvantage that the bees, which cannot discern objects but in a
strong light, labour under at that time. But should they touch a moth
with these organs of nice sensation, it falls an immediate victim
to their just anger. The moth, however, seeks to glide between the
sentinels, avoiding with the utmost caution, as if she were sensible
that her safety depended upon it, all contact with their antennæ. These
bees upon guard in the night, are frequently heard to utter a very
short low hum; but no sooner does any strange insect or enemy touch
their antennæ, than the guard is put into a commotion, and the hum
becomes louder, resembling that of bees when they fly, and the enemy is
assailed by workers from the interior of the hive[397].
To defend themselves from the death's-head hawk-moth, they have
recourse to a different proceeding. In seasons in which they are
annoyed by this animal, they often barricade the entrance of their
hive by a thick wall made of wax and propolis. This wall is built
immediately behind and sometimes in the gateway, which it entirely
stops up; but it is itself pierced with an opening or two sufficient
for the passage of one or two workers. These fortifications are
occasionally varied: sometimes there is only one wall, as just
described, the apertures of which are in arcades, and placed in
the upper part of the masonry. At others many little bastions, one
behind the other, are erected. Gateways masked by the anterior
walls, and not corresponding with those in them, are made in the
second line of building. These casemated gates are not constructed
by the bees without the most urgent necessity. When their danger
is present and pressing, and they are as it were compelled to seek
some preservative, they have recourse to this mode of defence[398],
which places the instinct of these animals in a wonderful light,
and shows how well they know how to adapt their proceedings to
circumstances. Can this be merely sensitive? When attacked by strange
bees, they have recourse to a similar manœuvre; only in this case
they make but narrow apertures, sufficient for a single bee to pass
through.--Pliny affirms that a sick bear will provoke a hive of bees
to attack him in order to let him blood[399]. What will you say, if
humble-bees have recourse to a similar manœuvre? It is related to
me by Dr. Leach, from the communications of Mr. Daniel Bydder--an
indefatigable and well-informed collector of insects, and observer of
their proceedings--that _Bombus_[400] _terrestris_, when labouring
under _Acariasis_[401] from the numbers of a small mite (_Gamasus
Gymnopterorum_) that infest it, will take its station in an ant-hill;
where beginning to scratch, and kick, and make a disturbance, the
ants immediately come out to attack it, and falling foul of the
mites, they destroy or carry them all off; when the bee, thus
delivered from its enemies, takes its flight.
In this long detail, the first idea that will, I should hope, strike
the mind of every thinking being, is the truth of the Psalmist's
observation--that the tender mercies of God are over all his works.
Not the least and most insignificant of his creatures is, we see,
deprived of his paternal care and attention; none are exiled from his
all-directing providence. Why then should man, the head of the visible
creation, for whom all the inferior animals were created and endowed;
for whose well-being, in some sense, all these wonderful creatures with
their miraculous instincts, whose history I am giving you, were put in
action,--why should he ever doubt, if he uses his powers and faculties
rightly, that his Creator will provide him with what is necessary for
his present state?--Why should he imagine that a Being, whose very
essence is LOVE, unless he compels him by his own wilful and obdurate
wickedness, will ever cut him off from his care and providence?
Another idea that upon this occasion must force itself into our mind
is, that nothing is made in vain. When we find that so many seemingly
trivial variations in the colour, clothing, form, structure, motions,
habits, and economy of insects are of very great importance to them,
we may safely conclude that the peculiarities in all these respects,
of which we do not yet know the use, are equally necessary: and we
may almost say, reversing the words of our Saviour, that not a _hair_
is given to them without our Heavenly Father.
I am, &c.
FOOTNOTES:
[289] Fabr. _Vorlesungen_, 321.
[290] _Cimic. Helvet._ _t._ iii. _f._ 3.
[291] _Hist. of Chili_, i. 172.
[292] Since the first edition of this volume was printed, a lady from
the West Indies looking at my cabinet, upon being shown this insect,
exclaimed "Oh, that is _The Devil's Horse_!"
[293] Brahm _Insekten Kalender_, ii. 383.
[294] Hence we have _Locusta citrifolia_, _laurifolia_,
_camellifolia_, _myrtifolia_, _salvifolia_, &c. which, I believe, all
belong to a genus I have named _Pterophylla_.
[295] _Voyage_, &c. ii. 16.
[296] _Brit. Ent._ _t._ 154.
[297] Oliv. _Entomolog._ i. no. 8. 17.
[298] PLATE XIX. Fig. 11. VOL. I. 267. Latreille _Gen. Crust. et
Ins._ iv. 322.
[299] _Apis._ * * e. 2. K.
[300] Dr. Fleming however, _in Literis_, doubts whether the reason
here assigned is the cause of the resemblance between the _Bombus_
and _Volucella_; he thinks if a bee knows a stranger of its own
species, it could not be deceived by a fly in the disguise of a bee.
But the fact that these insects lay their eggs in their nests, and
that they resemble humble-bees, seems to justify the conclusion drawn
in the text. They must get in often undiscovered.
[301] Latreille, _Annal. du Mus._ 1810. 5.
[302] One would almost wish that the same superstition prevailed here
which Sparrman observes is common in Sweden, with respect to these
animals. "Simple people," says he, "believe that their sins will be
forgiven if they set a cockchafer on its legs." _Voyage_, i. 28.
[303] _Cigales_, _f._ 85.
[304] Ibid. _f._ 115. Coquebert, _Illustr. Ic._ ii. _t._ xxviii. _f._ 5.
[305] Stoll, _Cigales_, _f._ 163. Comp. Pallas, _Spicil. Zool._ _t._
i. _f._ 12.
[306] Reaum. v. 94.
[307] This was first pointed out to me by Mr. Briggs of the
Post-office, who sent me an accurate drawing of the animal and of
one of its hairs. I did not at that time discover that it had been
figured by De Geer, iv. _t._ viii. _f._ 1-7.
[308] VOL. I. p. 130.
[309] _Insect. Surinam._ _t._ 57. Two different species of
caterpillars apparently related to this of Madame Merian were in the
late Mr. Francillon's cabinet, and are now in my possession.
[310] VOL. I. p. 149.
[311] To this genus belongs the apple Aphis, called _A. lanigera_.
[312] _Nat. Hist. of the Slug-worm_, 7.
[313] The penetrating genius of Lord Verulam discovered in a great
degree the cause of this vitality. "They stirre," says he, speaking
of insects, "a good while after their heads are off, or that they be
cut in pieces; which is caused also for that their vital spirits are
more diffused thorowout all their parts, and lesse confined to organs
than in perfect creatures." _Sylv. Sylvar. cent._. vii. § 697.
[314] Leeuw. _Epist._ 77, 1694.
[315] De Geer, vii. 127.
[316] _Bib. Nat._ ii. c. 3. VOL. I. p. 399.
[317] _Linn. Trans._ vi. 84.
[318] J. Mason Good's _Anniversary Oration, delivered March_ 8, 1808,
_before the Medical Society of London_, p. 31.
[319] De Geer, vi. 355; comp. 320, and Reaum. ii. 141-147.
[320] Hill's _Swamm._ i. 174.
[321] _Ann. du Mus._ 1810. 5.
[322] VOL. I. p. 426.
[323] De Geer, iv. 229.
[324] Smellic, _Phil. of Nat. Hist._ i. 150.
[325] Rös. I. v. 27.
[326] PLATE I. FIG. 7. _Linn. Trans._ x. 404--.
[327] Reaum. ii. 253.
[328] Reaum. ii. 260. _t._ 20. _f._ 10. 11. Compare Sepp. IV. _t._ i.
_f._ 3-7.
[329] Ibid. i. 100.
[330] Smith's _Abbot's Ins. of Georgia_, ii. 121.
[331] De Geer, iv. 74.
[332] _Nat. Hist._ ii. 268.
[333] P. Huber in _Linn. Trans._ vi. 219. Kirby, _Mon. Ap. Angl._ i.
201.
[334] Kirby in _Linn. Trans._ xi. 87, note *.
[335] VOL. I. p. 164.
[336] Ibid. 34.
[337] Huber appears to be of this opinion; he does not, however, lay
great stress upon it. Yet there seems no other way of accounting for
the impunity with which this animal commits its depredations. Huber,
ii. 299--.
[338] _Hist. Nat._ l. xxix. c. 6.
[339] iv. 86.
[340] De Geer, iii. 249. 374.
[341] Ibid. 611.
[342] VOL. I. 480.
[343] Kirby, _Mon. Ap. Angl._ i. 136. note _a._
[344] De Geer, vi. 134. Meigen _Dipt._ v. 12.
[345] De Geer, vi. 135. 33.
[346] Ibid. vii. 581.
[347] PLATE XIX. FIG. 1. a.
[348] Merian _Surinam._ 17. Jones in _Linn. Trans._ ii. 64.
[349] De Geer, ii. 989-- _t._ xxxvii. _f._ 6.
[350] De Geer, v. 291. Compare Ray's _Letters_, 43. See PLATE XVIII.
FIG. 1.
[351] _Ann. du Mus._ xviii. 70.
[352] Lesser _L._ i. 284, note 6.
[353] _De Araneis_ 27.
[354] This gentleman is of opinion that spiders possess the means of
re-dissolving their webs. He observed one, when its net was broken
run up its thread, and gathering a considerable mass of the web into
a ball, suddenly dissolve it with fluid. He also observes, that when
winding up a powerful prey, a spider can form its threads into a
broad sheet.
[355] Jurine _Hymenopt._ _t._ vi. _f._ 8.
[356] De Geer, ii. 971.
[357] I owe the knowledge of this circumstance to Mr. MacLeay.
[358] De Geer, iv. 86. Geoffr. i. 141.
[359] De Geer, ii. 734.
[360] Reaumur. v. 96.
[361] De Geer, ii. 937--.
[362] Rösel, iv. 162. De Geer, i. 273.
[363] Rai. _Hist. Ins._ 94. _n._ 3.
[364] De Geer, i. 324--.
[365] Ibid. i. 208.
[366] De Geer, i. 322--.
[367] _Ins. Surinam._ t. viii. xxiii. xxxii.
[368] I. iv. 122.
[369] Reaum. ii. 155. _t._ vii. _f._ 4-7.
[370] Lewin's _Prodromus_.
[371] De Geer, i. 149--.
[372] Mr. MacLeay relates to me, from the communications of Mr. E.
Forster, the following particulars respecting the history of _Mutilla
coccinea_, which from this account appears to be one of the most
redoubtable of stinging insects. The females are most plentiful in
Maryland in the months of July and August, but are never very numerous.
They are very active, and have been observed to take flies by surprise.
A person stung by one of them lost his senses in five minutes, and was
so ill for several days that his life was despaired of.
[373] Hedcorne near Sittingbourne.
[374] Dr. Long in Ray's _Letters_, 370.
[375] Lesser _L._ i. 263. Note ‡.
[376] Huber, _Nouv. Obs._ ii. 301--.
[377] Bingley, _Animal Biogr._ iii. 1st Ed. 247--. White, _Nat. Hist._
ii. 82.
[378] In the former Editions of this work this insect was stated to
be synonymous with _Trox dubius_ of Panzer, which it much resembles,
except in the sculpture of the prothorax, (_Fn. Ins. Germ. Init._
lxii. _t._ 5.); but as Schönherr and Gyllenhal, who had better
means of ascertaining the point, regard _Georyssus pygmæus_, Latr.,
as Panzer's insect, the reference is now omitted. _G. areniferus_
differs considerably from _G. pygmæus_, as described by Gyllenhal
(_Insect. Suec._ I. iii. 675.) The front is not rugulose, the vertex
is channeled, the antennæ shorter than the head; the prothorax is
rather shining, marked anteriorly with several excavations, in
the middle of which is a channel forming a reversed cross with a
transverse impression.
[379] De Geer, iii. 283-- Geoffr. _Hist. Ins._ i. 437.
[380] Reaum. iii. 391.
[381] Reaum. iii. 220-- Compare Vallisnieri _Esperienz. ed Osservaz._
195. Ed. 1726.
[382] Reaum. 233--.
[383] Kirby in _Linn. Trans._ iii. 10.
[384] VOL. I. 457-67.
[385] _Apis._ **. c. 2. γ. K.
[386] _Melitta._ **. c. K.
[387] _Apis._ **. b. K.
[388] _Apis._ b. *. K.
[389] VOL. I. 64--.
[390] Reaum. v. 100.
[391] VOL. I. 464--.
[392] Reaum. iii. 170. De Geer, ii. 519. 545. PLATE XVII. FIG. 11.
[393] VOL. I. 453.
[394] Fab. _Ent. Syst. Em._ iii. 70. 200.
[395] VOL. I. 432--.
[396] VOL. I. 165.
[397] Huber, _Nouv. Obs._ ii. 412.
[398] Huber, _Nouv. Obs._ ii. 294--.
[399] _Hist. Nat._ l. viii. c. 36.
[400] _Apis._ * *. e. 2. K.
[401] VOL. I. 97--.
LETTER XXII.
_MOTIONS OF INSECTS._ (_Larva and Pupa._)
Amongst the means of defence to which insects have recourse, I have
noticed their _motions_. These shall be the subject of the present
letter. I shall not, however, confine myself to those by which
they seek to escape from their enemies; but take a larger and more
comprehensive survey of them, including not only every species of
locomotion, but also the movements they give to different parts of
their body when in a state of repose: and in order to render this
survey more complete, I shall add to it some account of the various
organs and instruments by which they move.
Whenever you go abroad in summer, wherever you turn your eyes and
attention, you will see insects in motion. They are flying or sailing
every where in the air; dancing in the sun or in the shade; creeping
slowly, or marching soberly, or running swiftly, or jumping upon the
ground; traversing your path in all directions; coursing over the
surface of the waters, or swimming at every depth beneath; emerging
from a subterranean habitation, or going into one; climbing up the
trees, or descending from them; glancing from flower to flower; now
alighting upon the earth and waters, and now leaving them to follow
the impulse of their various instincts; sometimes travelling singly;
at other times in countless swarms: these the busy children of the
day, and those of the night. If you return to your apartment--there
are these ubiquitaries--some flying about--others pacing against
gravity up the walls or upon the ceiling--others walking with ease
upon the glass of your windows, and some even venturing to take their
station on your own sacred person, and asserting their right to the
lord of the creation.