[Illustration: _Plate IV_]
AN
INTRODUCTION
TO
ENTOMOLOGY:
OR
ELEMENTS
OF THE
_NATURAL HISTORY OF INSECTS_:
WITH PLATES.
By WILLIAM KIRBY, M.A. F.R. and L.S.
RECTOR OF BARHAM,
AND
WILLIAM SPENCE, ESQ. F.L.S.
IN FOUR VOLUMES.
VOL. II.
_FIFTH EDITION._
LONDON:
PRINTED FOR
LONGMAN, REES, ORME, BROWN, AND GREEN,
PATERNOSTER ROW.
1828.
PRINTED BY RICHARD TAYLOR,
RED LION COURT, FLEET STREET.
CONTENTS OF VOL. II.
Letter
XVI. Societies of Insects. Page
1. Imperfect Societies 1-25
XVII. Societies of Insects continued.
2. Perfect Societies.
_White Ants. Ants_ 26-106
XVIII. Perfect Societies of Insects continued.
_Wasps. Humble-bees_ 107-118
XIX. Perfect Societies of Insects continued.
_Hive-bee_ 119-167
XX. Perfect Societies of Insects concluded.
_Hive-bee_ 168-214
XXI. Means by which Insects defend themselves 215-266
XXII. Motions of Insects.
_Larva and Pupa_ 267-299
XXIII. Motions of Insects continued.
_Imago_ 300-370
XXIV. Noises produced by Insects 371-403
XXV. Luminous Insects 404-424
XXVI. Hybernation and Torpidity of Insects 425-459
XXVII. Instinct of Insects 460-523
AN
INTRODUCTION
TO
ENTOMOLOGY.
LETTER XVI.
_SOCIETIES OF INSECTS._
IMPERFECT SOCIETIES.
I see already, and I see it with pleasure, that you will not content
yourself with being a mere collector of insects. To possess a cabinet
well stored, and to know by what name each described individual which
it contains should be distinguished, will not satisfy the love that
is already grown strong in you for my favourite pursuit; and you now
anticipate with a laudable eagerness, the discoveries that you may
make respecting the history and economy of this most interesting
department of the works of our Creator. I hail with joy this
intention to emulate the bright example, and to tread in the hallowed
steps of Swammerdam, Leeuwenhoek, Redi, Malpighi, Vallisnieri, Ray,
Lister, Reaumur, De Geer, Lyonnet, Bonnet, the Hubers, &c.; and I am
confident that a man of your abilities, discernment, and observation
will contribute, in no small degree, to the treasures already poured
into the general fund by these your illustrious predecessors.
I feel not a little flattered when you inform me that the details
contained in my late letters relative to this subject, have
stimulated you to this noble resolution.--Assure yourself, I shall
think no labour lost, that has been the means of winning over to the
science I love, the exertions of a mind like yours.
But if the facts already related, however extraordinary, have had
power to produce such an effect upon you, what will be the momentum,
when I lay before you more at large, as I next purpose, the most
striking particulars of the proceedings of insects in society,
and show the almost incredibly wonderful results of the combined
instincts and labours of these minute beings? In comparison with
these, all that is the fruit of solitary efforts, though some of
them sufficiently marvellous, appear trifling and insignificant: as
the works of man himself, when they are the produce of the industry
and genius of only one, or a few individuals, though they might be
regarded with admiration by a being who had seen nothing similar
before, yet when contrasted with those to which the union of these
qualities in large bodies has given birth, sink into nothing, and
seem unworthy of attention. Who would think a hut extraordinary by
the side of a stately palace, or a small village when in the vicinity
of a populous and magnificent city?
Insects in society may be viewed under several lights, and their
associations are for various purposes and of different durations.
There are societies the object of which is mutual defence; while that
of others is the propagation of the species. Some form marauding
parties, and associate for prey and plunder;--others meet, as it
should seem, under certain circumstances, merely for the sake of
company;--again, others are brought together by accidental causes,
and disperse when these cease to operate;--and finally, others, which
may be said to form proper societies, are associated for the nurture
of their young, and, by the union of their labours and instincts, for
mutual society, help, and comfort, in erecting or repairing their
common habitation, in collecting provisions, and in defending their
fortress when attacked.
With respect to the _duration_ of the societies of insects, some
last only during their first or larva state; and are occasionally
even restricted to its earliest period;--some again only associate
in their perfect or imago state; while with others, the _proper_
societies for instance, the association is for life. But if I divide
societies of insects into perfect and imperfect, it will, I think,
enable me to give you a clearer and better view of the subject. By
_perfect_ societies I mean those that are associated in all their
states, live in a common habitation, and unite their labours to
promote a common object;--and by _imperfect_ societies, those that
are either associated during part of their existence only, or else do
not dwell in a common habitation, nor unite their labours to promote
a common object. In the present letter I shall confine myself to
giving you some account of _imperfect_ societies.
Imperfect societies may be considered as of five
descriptions:--associations for the sake of company
only--associations of males during the season for
pairing--associations formed for the purpose of travelling or
emigrating together--associations for feeding together--and
associations that undertake some common work.
The first of these associations consists chiefly of insects in their
perfect state. The little beetles called whirlwigs (_Gyrinus_),--which
may be seen clustering in groups under warm banks in every river and
every pool, and wheeling round and round with great velocity; at your
approach dispersing and diving under water, but as soon as you retire
resuming their accustomed movements,--seem to be under the influence of
the social principle, and to form their assemblies for no other purpose
than to enjoy together, in the sunbeam, the mazy dance. Impelled by
the same feeling, in the very depth of winter, even when the earth is
covered with snow, the tribes of _Tipulariæ_ (usually, but improperly,
called gnats) assemble in sheltered situations at midday, when the sun
shines, and form themselves into choirs, that alternately rise and fall
with rapid evolutions[1]. To see these little aëry beings apparently
so full of joy and life, and feeling the entire force of the social
principle in that dreary season, when the whole animal creation appears
to suffer, and the rest of the insect tribes are torpid, always conveys
to my mind the most agreeable sensations. These little creatures may
always be seen at all seasons amusing themselves with these choral
dances; which Mr. Wordsworth, in one of his poems[2], has alluded to in
the following beautiful lines:
"Nor wanting here to entertain the thought,
Creatures that in communities exist,
Less, as might seem, for general guardianship
Or through dependance upon mutual aid,
Than by participation of delight,
And a strict love of fellowship combined.
What other spirit can it be that prompts
The gilded summer flies to mix and weave
Their sports together in the solar beam,
Or in the gloom and twilight hum their joy?"
Another association is that of males during the season of pairing.
Of this nature seems to be that of the cockchafer and fernchafer
(_Melolontha vulgaris_ and _Amphimalla solstitialis_), which, at
certain periods of the year and hours of the day, hover over the
summits of the trees and hedges like swarms of bees, affording,
when they alight on the ground, a grateful food to cats, pigs,
and poultry. The males of another root-devouring beetle (_Hoplia
argentea_) assemble by myriads before noon in the meadows, when in
these infinite hosts you will not find even one female[3]. After
noon the congregation is dissolved, and not a single individual
is to be seen in the air[4]: while those of _M. vulgaris_ and _A.
solstitialis_ are on the wing only in the evening.
At the same time of the day some of the short-lived Ephemeræ assemble
in numerous troops, and keep rising and falling alternately in the
air, so as to exhibit a very amusing scene. Many of these also are
males. They continue this dance from about an hour before sun-set,
till the dew becomes too heavy or too cold for them. In the beginning
of September, for two successive years, I was so fortunate as to
witness a spectacle of this kind, which afforded me a more sublime
gratification than any work or exhibition of art has power to
communicate.--The first was in 1811:--taking an evening walk near
my house, when the sun declining fast towards the horizon shone
forth without a cloud, the whole atmosphere over and near the stream
swarmed with infinite myriads of Ephemeræ and little gnats of the
genus _Chironomus_, which in the sun-beam appeared as numerous and
more lucid than the drops of rain, as if the heavens were showering
down brilliant gems.--Afterwards, in the following year, one Sunday,
a little before sun-set, I was enjoying a stroll with a friend at a
greater distance from the river, when in a field by the road-side
the same pleasing scene was renewed, but in a style of still greater
magnificence; for, from some cause in the atmosphere, the insects
at a distance looked much larger than they really were. The choral
dances consisted principally of _Ephemeræ_, but there were also
some of _Chironomi_; the former, however, being most conspicuous,
attracted our chief attention--alternately rising and falling, in
the full beam they appeared so transparent and glorious, that they
scarcely resembled any thing material--they reminded us of angels
and glorified spirits drinking life and joy in the effulgence of the
Divine favour[5]. The bard of Twickenham, from the terms in which his
beautiful description of his sylphs is conceived in _The Rape of the
Lock_, seems to have witnessed the pleasing scene here described:
"Some to the sun their insect wings unfold,
Waft on the breeze, or sink in clouds of gold;
Transparent forms, too fine for mortal sight,
Their fluid bodies half dissolv'd in light;
Loose to the wind their airy garments flew,
Thin glittering textures of the filmy dew,
Dipt in the richest tincture of the skies,
Where light disports in ever mingling dyes,
While every beam new transient colours flings,
Colours that change whene'er they wave their wings."
I wish you may have the good fortune next year to be a spectator of
this all but celestial dance. In the mean time, in May and June,
their season of love, you may often receive much gratification from
observing the motions of a countless host of little black flies of
the genus _Hilara_, (_H. maura_,) which at this period of the year
assemble to wheel in aëry circles over stagnant waters, with a rush
resembling that of a hasty shower driven by the wind.
The next description of insect associations is of those that
congregate for the purpose of travelling or emigrating together. De
Geer has given an account of the larvæ of certain gnats (_Tipulariæ_)
which assemble in considerable numbers for this purpose, so as to
form a band of a finger's breadth, and of from one to two yards
in length. And, what is remarkable, while upon their march, which
is very slow, they adhere to each other by a kind of glutinous
secretion; but when disturbed they separate without difficulty[6].
Kuhn mentions another of the same tribe (from the antennæ in his
figure, which is very indifferent, it should seem a species of
agaric-gnat (_Mycetophila_)), the larvæ of which live in society
and emigrate in files, like the caterpillar of the procession-moth.
First goes one, next follow two, then three, &c., so as to exhibit a
serpentine appearance, probably from their simultaneous undulating
motion and the continuity of the files; whence the common people in
Germany call them (or rather the file when on march) _heerwurm_, and
view them with great dread, regarding them as ominous of war. These
larvæ are apodes, white, subtransparent, with black heads[7].--But of
insect emigrants none are more celebrated than the locusts, which,
when arrived at their perfect state, assemble as before related,
in such numbers, as in their flight to intercept the sunbeams, and
to darken whole countries; passing from one region to another, and
laying waste kingdom after kingdom:--but upon these I have already
said much, and shall have occasion again to enlarge.--The same
tendency to shift their quarters has been observed in our little
indigenous devourers, the Aphides. Mr. White tells us, that about
three o'clock in the afternoon of the first of August 1785, the
people of the village of Selborne were surprised by a shower of
Aphides or smother-flies, which fell in those parts. Those that
walked in the street at that juncture found themselves covered with
these insects, which settled also upon the hedges and in the gardens,
blackening all the vegetables where they alighted. His annuals were
discoloured by them, and the stalks of a bed of onions quite coated
over for six days after. These armies, he observes, were then, no
doubt, in a state of emigration, and shifting their quarters; and
might have come from the great hop-plantations of Kent or Sussex,
the wind being all that day in the east. They were observed at the
same time in great clouds about Farnham, and all along the vale from
Farnham to Alton[8]. A similar emigration of these flies I once
witnessed, to my great annoyance, when travelling later in the year,
in the Isle of Ely. The air was so full of them, that they were
incessantly flying into my eyes, nostrils, &c.; and my clothes were
covered by them. And in 1814, in the autumn, the Aphides were so
abundant for a few days in the vicinity of Ipswich, as to be noticed
with surprise by the most incurious observers.
As the locust-eating thrush (_Turdus gryllivorus_) accompanies
the locusts, so the lady-birds (_Coccinellæ_) seem to pursue the
Aphides; for I know no other reason to assign for the vast number
that are sometimes, especially in the autumn, to be met with on the
sea-coast or the banks of large rivers. Many years ago, those of
the Humber were so thickly strewed with the common Lady-bird (_C.
septempunctata_), that it was difficult to avoid treading upon them.
Some years afterwards I noticed a mixture of species, collected in
vast numbers, on the sand-hills on the sea-shore, at the north-west
extremity of Norfolk. My friend the Rev. Peter Lathbury made long
since a similar observation at Orford, on the Suffolk coast; and
about five or six years ago they covered the cliffs, as I have
before remarked[9], of all the watering-places on the Kentish and
Sussex coasts, to the no small alarm of the superstitious, who
thought them forerunners of some direful evil. These last probably
emigrated with the Aphides from the hop-grounds. Whether the latter
and their devourers cross the sea has not been ascertained; that the
Coccinellæ attempt it, is evident from their alighting upon ships at
sea, as I have witnessed myself.--This appears clearly to have been
the case with another emigrating insect, the saw-fly (_Athalia?_) of
the turnip (which, though so mischievous, appears never to have been
described; it is nearly related to _A. Centifoliæ_)[10]. It is the
general opinion in Norfolk, Mr. Marshall informs us[11], that these
insects come from over sea. A farmer declared he saw them arrive in
clouds so as to darken the air; the fishermen asserted that they had
repeatedly seen flights of them pass over their heads when they were
at a distance from land; and on the beach and cliffs they were in
such quantities, that they might have been taken up by shovels-full.
Three miles in-land they were described as resembling swarms of
bees. This was in August 1782. Unentomological observers, such as
farmers and fishermen, might easily mistake one kind of insect for
another; but supposing them correct, the swarms in question might
perhaps have passed from Lincolnshire to Norfolk.--Meinecken tells
us, that he once saw in a village in Anhalt, on a clear day, about
four in the afternoon, such a cloud of dragon-flies (_Libellulina_)
as almost concealed the sun, and not a little alarmed the villagers,
under the idea that they were locusts[12]: several instances are
given by Rösel of similar clouds of these insects having been seen in
Silesia and other districts[13]; and Mr. Woolnough of Hollesley in
Suffolk, a most attentive observer of nature, once witnessed such an
army of the smaller dragon-flies (_Agrion_) flying in-land from the
sea, as to cast a slight shadow over a field of four acres as they
passed.--Professor Walch states, that one night about eleven o'clock,
sitting in his study, his attention was attracted by what seemed the
pelting of hail against his window, which surprising him by its long
continuance, he opened the window, and found the noise was occasioned
by a flight of the froth frog-hopper (_Cercopis spumaria_), which
entered the room in such numbers as to cover the table. From this
circumstance and the continuance of the pelting, which lasted at
least half an hour, an idea may be formed of the vast host of this
insect passing over. It passed from east to west; and as his window
faced the south, they only glanced against it obliquely[14]. He
afterwards witnessed, in August, a similar emigration of myriads of
a kind of ground-beetle (_Amara vulgaris_,)[15].--Another writer in
the same work, H. Kapp, observed on a calm sunny day a prodigious
flight of the noxious cabbage-butterfly (_Pontia Brassicæ_), which
passed from north-east to south-west, and lasted two hours[16]. Kalm
saw these last insects midway in the British Channel[17]. Lindley, a
writer in the _Royal Military Chronicle_, tells us, that in Brazil,
in the beginning of March 1803, for many days successively there
was an immense flight of white and yellow butterflies, probably
of the same tribe as the cabbage-butterfly. They were observed
never to settle, but proceeded in a direction from north-west to
south-east. No buildings seemed to stop them from steadily pursuing
their course; which being to the ocean, at only a small distance,
they must consequently perish. It is remarked that at this time no
other kind of butterfly is to be seen, though the country usually
abounds in such a variety[18].--Major Moor, while stationed at
Bombay, as he was playing at chess one evening with a friend in Old
Woman's Island, near that place, witnessed an immense flight of bugs
(_Geocorisæ_), which were going westward. They were so numerous as
to cover every thing in the apartment in which he was sitting.--When
staying at Aldeburgh, on the eastern coast, I have, at certain times,
seen innumerable insects upon the beach close to the waves, and
apparently washed up by them. Though wetted, they were quite alive.
It is remarkable, that of the emigrating insects here enumerated,
the majority--for instance the lady-birds, saw-flies, dragon-flies,
ground-beetles, frog-hoppers, &c.--are not usually social insects,
but seem to congregate, like swallows, merely for the purpose of
emigration. What incites them to this is one of those mysteries
of nature, which at present we cannot penetrate. A scarcity of
food urges the locusts to shift their quarters; and too confined a
space to accommodate their numbers occasions the bees to swarm: but
neither of these motives can operate in causing unsocial insects to
congregate. It is still more difficult to account for the impulse
that urges these creatures, with their filmy wings and fragile form,
to attempt to cross the ocean, and expose themselves, one would
think, to inevitable destruction. Yet, though we are unable to assign
the cause of this singular instinct, some of the reasons which
induced the Creator to endow them with it may be conjectured. This is
clearly one of the modes by which their numbers are kept within due
limits, as, doubtless, the great majority of these adventurers perish
in the waters. Thus, also, a great supply of food is furnished to
those fish in the sea itself, which at other seasons ascend the
rivers in search of them; and this probably is one of the means, if
not the only one, to which the numerous islands of this globe are
indebted for their insect population. Whether the insects I observed
upon the beach wetted by the waves, had flown from our own shores,
and falling into the water had been brought back by the tide; or
whether they had succeeded in the attempt to pass from the continent
to us, by flying as far as they could, and then falling had been
brought by the waves, cannot certainly be ascertained; but Kalm's
observation inclines me to the latter opinion.
The next order of imperfect associations is that of those insects
which feed together:--these are of two descriptions--those that
associate in their _first_ or _last_ state only, and those that
associate in _all_ their states. The first of these associations is
often very short-lived: a patch of eggs is glued to a leaf; when
hatched, the little larvæ feed side by side very amicably, and a
pleasant sight it is to see the regularity with which this work is
often done, as if by word of command; but when the leaf that served
for their cradle is consumed, their society is dissolved, and each
goes where he can to seek his own fortune, regardless of the fate or
lot of his brethren. Of this kind are the larvæ of the saw-fly of
the gooseberry, whose ravages I have recorded before[19], and that
of the cabbage-butterfly; the latter, however, keep longer together,
and seldom wholly separate. In their final state, I have noticed
that the individuals of _Thrips Physapus_, the fly that causes us
in hot weather such intolerable titillation, are very fond of each
other's company when they feed. Towards the latter end of last July,
walking through a wheat-field, I observed that all the blossoms of
_Convolvulus arvensis_, though very numerous, were interiorly turned
quite black by the infinite number of these insects, which were
coursing about within them.
But the most interesting insects of this order are those which
associate in _all_ their states.--Two populous tribes, the great
devastators of the vegetable world, the one in warm and the other
in cold climates, to which I have already alluded under the head
of emigrations--you perceive I am speaking of _Aphides_ and
_Locusts_--are the best examples of this order: although, concerning
the societies of the first, at present we can only say that they are
merely the result of a common origin and station: but those of the
latter, the locusts, wear more the appearance of design, and of being
produced by the social principle.
So much as the world has suffered from these animals[20], it is
extraordinary that so few observations have been made upon their
history, economy, and mode of proceeding. One of the best accounts
seems to be that of Professor Pallas, in his _Travels into the
Southern Provinces of the Russian Empire_. The species to which
his principal attention was paid appears to have been the _Locusta
italica_, in its larva and pupa state. "In serene warm weather,"
says he, "the locusts are in full motion in the morning immediately
after the evaporation of the dew; and if no dew has fallen, they
appear as soon as the sun imparts his genial warmth. At first some
are seen running about like messengers among the reposing swarms,
which are lying partly compressed upon the ground, at the side of
small eminences, and partly attached to tall plants and shrubs.
Shortly after the whole body begins to move forward in one direction
and with little deviation. They resemble a swarm of ants, all taking
the same course, at small distances, but without touching each other:
they uniformly travel towards a certain region as fast as a fly can
run, and without leaping, unless pursued; in which case, indeed, they
disperse, but soon collect again and follow their former route. In
this manner they advance from morning to evening without halting,
frequently at the rate of a hundred fathoms and upwards in the course
of a day. Although they prefer marching along high roads, footpaths,
or open tracts; yet when their progress is opposed by bushes, hedges,
and ditches, they penetrate through them: their way can only be
impeded by the waters of brooks or canals, as they are apparently
terrified at every kind of moisture. Often, however, they endeavour
to gain the opposite bank with the aid of overhanging boughs; and if
the stalks of plants or shrubs be laid across the water, they pass
in close columns over these temporary bridges; on which they even
seem to rest and enjoy the refreshing coolness. Towards sunset the
whole swarm gradually collect in parties, and creep up the plants,
or encamp on slight eminences. On cold, cloudy, or rainy days they
do not travel.--As soon as they acquire wings they progressively
disperse, but still fly about in large swarms[21]."
"In the month of May, when the ovaries of these insects were
ripe and turgid," says Dr. Shaw[22], "each of these swarms began
gradually to disappear, and retired into the Mettijiah, and other
adjacent plains, where they deposited their eggs. These were no
sooner hatched in June, than each of the broods collected itself
into a compact body, of a furlong or more in square; and marching
afterwards directly forwards toward the sea, they let nothing
escape them----_they kept their ranks, like men of war_; climbing
over, as they advanced, every tree or wall that was in their way;
nay, they entered into our very houses and bed-chambers, like
_so many thieves_.----A day or two after one of these hordes was
in motion, others were already hatched to march and glean after
them.----Having lived near a month in this manner----they arrived
at their full growth, and threw off their _nympha-state_ by casting
their outward skin. To prepare themselves for this change, they
clung by their hinder feet to some bush, twig, or corner of a
stone; and immediately, by using an undulating motion, their heads
would first break out, and then the rest of their bodies. The whole
transformation was performed in seven or eight minutes; after which
they lay for a small time in a torpid and seemingly in a languishing
condition; but as soon as the sun and the air had hardened their
wings, by drying up the moisture that remained upon them after
casting their sloughs, they reassumed their former voracity, with an
addition of strength and agility. Yet they continued not long in this
state before they were entirely dispersed." The species Dr. Shaw here
speaks of is probably not the _Locusta migratoria_.
The old Arabian fable, that they are directed in their flights
by a leader or king[23], has been adopted: but I think without
sufficient reason, by several travellers. Thus Benjamin Bullivant,
in his observations on the Natural History of New England[24], says
that "the locusts have a kind of regimental discipline, and as it
were some commanders, which show greater and more splendid wings
than the common ones, and arise first when pursued by the fowls or
the feet of the traveller, as I have often seriously remarked."
And in like terms Jackson observes, that "they have a government
amongst themselves similar to that of the bees and ants; and when the
(_Sultan Jerraad_) king of the locusts rises, the whole body follow
him, not one solitary straggler being left behind[25]." But that
locusts have leaders, like the bees or ants, distinguished from the
rest by the size and splendour of their wings, is a circumstance that
has not yet been established by any satisfactory evidence; indeed,
very strong reasons may be urged against it. The nations of bees and
ants, it must be observed, are housed together in one nest or hive,
the whole population of which is originally derived from one common
mother, and the leaders of the swarms in each are the females. But
the armies of locusts, though they herd together, travel together,
and feed together, consist of an infinity of separate families, all
derived from different mothers, who have laid their eggs in separate
cells or houses in the earth; so that there is little or no analogy
between the societies of locusts and those of bees and ants; and this
pretended sultan is something quite different from the queen-bee or
the female ants. It follows, therefore, that as the locusts have no
common mother, like the bees, to lead their swarms, there is no one
that nature, by a different organization and ampler dimensions,
and a more august form, has destined to this high office. The only
question remaining is, whether one be elected from the rest by common
consent as their leader, or whether their instinct impels them to
follow the first that takes flight or alights. This last is the
learned Bochart's opinion, and seems much the most reasonable[26].
The absurdity of the other supposition, that an election is made,
will appear from such queries as these, at which you may smile.--Who
are the electors? Are the myriads of millions all consulted, or is
the elective franchise confined to a few? Who holds the courts and
takes the votes? Who casts them up and declares the result? When is
the election made?--The larvæ appear to be as much under government
as the perfect insect.--Is the monarch then chosen by his peers
when they first leave the egg and emerge from their subterranean
caverns? or have larva, pupa, and imago each their separate king? The
account given us in Scripture is certainly much the most probable,
that the locusts have no king, though they observe as much order
and regularity in their movements as if they were under military
discipline, and had a ruler over them[27]. Some species of ants, as
we learn from the admirable history of them by M. P. Huber, though
they go forth by common consent upon their military expeditions, yet
the order of their columns keeps perpetually changing; so that those
who lead the van at the first setting out, soon fall into the rear,
and others take their place: their successors do the same; and such
is the constant order of their march. It seems probable, as these
columns are extended to a considerable length, that the object of
this successive change of leaders is to convey constant intelligence
to those in the rear, of what is going forward in the van. Whether
any thing like this takes place for the regulation of their motions
in the innumerable locust-armies, which are sometimes co-extensive
with vast kingdoms; or whether their instinct simply directs them
to follow the first that moves or flies, and to keep their measured
distance, so that, as the prophet speaks, "one does not thrust
another, and they walk every one in his path[28]," must be left to
future naturalists to ascertain. And I think that you will join with
me in the wish that travellers, who have a taste for Natural History,
and some knowledge of insects, would devote a share of attention to
the proceedings of these celebrated animals, so that we might have
facts instead of fables.
The last order of imperfect associations approaches nearer to perfect
societies, and is that of those insects which the social principle
urges to unite in some common work for the benefit of the community.
Amongst the _Coleoptera_, _Ateuchus pilularius_, a beetle before
mentioned, acts under the influence of this principle. "I have
attentively admired their industry and mutual assisting of each
other," says Catesby, "in rolling those globular balls from the
place where they made them, to that of their interment, which is
usually the distance of some yards, more or less. This they perform
breech foremost, by raising their hind parts, forcing along the ball
with their hind feet. Two or three of them are sometimes engaged
in trundling one ball, which, from meeting with impediments from
the unevenness of the ground, is sometimes deserted by them: it is
however attempted by others with success, unless it happens to roll
into some deep hollow chink, where they are constrained to leave it;
but they continue their work by rolling off the next ball that comes
in their way. None of them seem to know their own balls, but an equal
care for the whole appears to affect all the community[29]."
Many larvæ also of _Lepidoptera_ associate with this view, some of
which are social only during part of their existence, and others
during the whole of it. The first of these continue together while
their united labours are beneficial to them; but when they reach a
certain period of their life, they disperse and become solitary.
Of this kind are the caterpillars of a little butterfly (_Melitæa
Cinxia_) which devour the narrow-leaved plantain. The families
of these, usually amounting to about a hundred, unite to form a
pyramidal silken tent, containing several apartments, which is
pitched over some of the plants that constitute their food, and
shelters them both from the sun and the rain. When they have consumed
the provision which it covers, they construct a new one over other
roots of this plant; and sometimes four or five of these encampments
may be seen within a foot or two of each other. Against winter they
weave and erect a stronger habitation of a rounder form, not divided
by any partitions, in which they lie heaped one upon another, each
being rolled up. About April they separate, and continue solitary
till they assume the pupa.
Reaumur, to whom I am indebted for this account, has also given
us an interesting history of another insect, the gold-tail-moth
(_Arctia chrysorhœa_) before mentioned, whose caterpillars are of
this description. They belong to that family of _Bombycidæ_, which
envelop their eggs in hair plucked from their own body. As soon
as one of these young caterpillars is disclosed from the egg, it
begins to feed; another quickly joins it, placing itself by its
side; thus they proceed in succession till a file is formed across
the leaf:--a second is then begun; and after this is completed, a
third--and so they proceed till the whole upper surface of the leaf
is covered:--but as a single leaf will not contain the whole family,
the remainder take their station upon the adjoining ones. No sooner
have they satisfied the cravings of hunger, than they begin to think
of erecting a common habitation, which at first is only a vaulted
web, that covers the leaf they inhabit, but by their united labours
in due time grows into a magnificent tent of silk, containing various
apartments sufficient to defend and shelter them all from the attack
of enemies and the inclemency of the seasons. As our caterpillars,
like eastern monarchs, are too delicate to adventure their feet
upon the rough bark of the tree upon which they feed, they lay a
silken carpet over every road and pathway leading to their palace,
which extends as far as they have occasion to go for food. To the
habitation just described they retreat during heavy rains, and
when the sun is too hot:--they likewise pass part of the night in
them;--and, indeed, at all times some may usually be found at home.
Upon any sudden alarm they retreat to them for safety, and also when
they cast their skins:--in the winter they are wholly confined to
them, emerging again in the spring: but in May and June they entirely
desert them; and, losing all their love for society, live in
solitude till they become pupæ, which takes place in about a month.
When they desert their nests, the spiders take possession of them;
which has given rise to a prevalent though most absurd opinion, that
they are the parents of these caterpillars[30].
With other caterpillars the association continues during the whole of
the larva state. De Geer mentions one of the saw-flies (_Serrifera_)
of this description which form a common nidus by connecting leaves
together with silken threads, each larva moreover spinning a tube of
the same material for its own private apartment, in which it glides
backwards and forwards upon its back[31]. I have observed similar
nidi in this country; the insects that form them belong to the
Fabrician genus _Lyda_.
The most remarkable insects, however, that arrange under this class
of imperfect associates, are those that observe a particular order
of march. Though they move without beat of drum, they maintain as
much regularity in their step as a file of soldiers. It is a most
agreeable sight, says one of Nature's most favoured admirers, Bonnet,
to see several hundreds of the larvæ of _Trichoda Neustria_ marching
after each other, some in straight lines, others in curves of various
inflection, resembling, from their fiery colour, a moving cord of
gold stretched upon a silken ribband of the purest white; this
ribband is the carpeted causeway that leads to their leafy pasture
from their nest. Equally amusing is the progress of another moth,
the _Pityocampa_, before noticed; they march together from their
common citadel, consisting of pine leaves united and inwoven with
the silk which they spin, in a single line: in following each other
they describe a multitude of graceful curves of varying figure, thus
forming a series of living wreaths, which change their shape every
moment:--all move with a uniform pace, no one pressing too forward or
loitering behind; when the first stops, all stop, each defiling in
exact military order[32].
A still more singular and pleasing spectacle, when their regiments
march out to forage, is exhibited by the caterpillars of the
_Processionary_ moth _Lasiocampa processionea_. This moth,
which is a native of France, and has not yet been found in this
country, inhabits the oak. Each family consists of from 600 to 800
individuals. When young, they have no fixed habitation, but encamp
sometimes in one place and sometimes in another, under the shelter of
their web: but when they have attained two-thirds of their growth,
they weave for themselves a common tent, before described[33].
About sun-set the regiment leaves its quarters; or, to make the
metaphor harmonize with the trivial name of the animal, the monks
their cœnobium. At their head is a chief, by whose movements their
procession is regulated. When he stops, all stop, and proceed when
he proceeds; three or four of his immediate followers succeed in the
same line, the head of the second touching the tail of the first:
then comes an equal series of pairs, next of threes, and so on as
far as fifteen or twenty. The whole procession moves regularly on
with an even pace, each file treading upon the steps of those that
precede it. If the leader, arriving at a particular point, pursues
a different direction, all march to that point before they turn.
Probably in this they are guided by some scent imparted to the tracks
by those that pass over them. Sometimes the order of procession
is different; the leader, who moves singly, is followed by two,
these are succeeded by three, then come four, and so on. When the
leader,--who in nothing differs from the rest, and is probably the
caterpillar nearest the entrance to the nest, followed, as I have
described,--has proceeded to the distance of about two feet, more
or less, he makes a halt; during which those which remain come
forth, take their places, the company forms into files, the march is
resumed, and all follow as regularly as if they kept time to music.
These larvæ may be occasionally found at mid-day out of their nests,
packed close one to another without making any movement; so that,
although they occupy a space sufficiently ample, it is not easy to
discover them. At other times, instead of being simply laid side by
side, they are formed into singular masses, in which they are heaped
one upon another, and as it were interwoven together. Thus also they
are disposed in their nests. Sometimes their families divide into two
bands, which never afterwards unite[34].
I have nothing further of importance to communicate to you on
imperfect societies: in my next I shall begin the most interesting
subject that Entomology offers; a subject, to say the least,
including as great a portion both of instruction and amusement as
any branch of Natural History affords;--I mean those _perfect_
associations which have for their great object the multiplication of
the species, and the education, if such a term may be here employed,
of the young. This is too fertile a theme to be confined to a single
letter, but must occupy several.
I am, &c.
FOOTNOTES:
[1] See also Markwick in White's _Nat. Hist._ ii. 256.
[2] _The Excursion._
[3] The females (_Scarabæus argenteus_, Marsh.) have red legs, and
the males (_Scarabæus pulverulentus_, Marsh.) black.
[4] Kirby in _Linn. Trans._ v. 256.
[5] The authors of this work were the witnesses of the magnificent
scene here described. It was on the second of September. The first
was on the ninth of that month.
[6] De Geer, vi. 338.
[7] _Naturforsch._ xvii. 226.
[8] _Nat. Hist._ ii. 101.
[9] VOL. I. 265--.
[10] _Fn. Germ. Init._ xlix. 18.
[11] _Philos. Trans._ lxxiii. 217.
[12] _Naturforsch._ vi. 110.
[13] ii. 135.
[14] _Naturforsch._ vi. 111.
[15] Ibid. xi. 95.
[16] Ibid. 94.
[17] _Travels_, i. 13.
[18] _R. Milit. Chron._ for March 1815, p. 452.
[19] VOL. I. 197.
[20] See VOL. I. 215.
[21] Pallas, ii. 422-6.
[22] _Travels_, 187.
[23] Bochart, _Hierozoic._ ii. l. 4. c. 2. 460.
[24] In _Philos. Trans._ for 1698.
[25] Jackson's _Marocco_, 51.
[26] Bochart, _Hierozoic._ ubi supra.
[27] Proverbs xxx. 27.
[28] Joel ii. 8.
[29] Catesby's _Carolina_, ii. 111. See above, VOL. I. 51.
[30] Vol. I. 473. Reaumur, ii. 125.
[31] De Geer, ii. 1029.
[32] Bonnet, ii. 57.
[33] VOL. I. 475.
[34] Reaumur, ii. 180.
LETTER XVII.
_SOCIETIES OF INSECTS CONTINUED._
PERFECT SOCIETIES. (_White Ants and Ants._)
The associations of insects of which my last letter gave you a
detail, were of a very imperfect kind, both as to their object and
duration: but those which I am now to lay before you exhibit the
semblance of a nearer approach, both in their principle and its
results, to the societies of man himself. There are two kindred
sentiments, that in these last act with most powerful energy--desire
and affection.--From the first proceed many wants that cannot
be satisfied without the intercourse, aid, and co-operation of
others; and by the last we are impelled to seek the good of certain
objects, and to delight in their society. Thus self-love combines
with philanthropy to produce the social principle, both desire and
love alternately urging us to an intercourse with each other; and
from these in union originate the multiplication and preservation
of the species. These two passions are the master-movers in this
business; but there is a third subsidiary to them, which, though it
trenches upon the social principle, considered abstractedly, is often
a powerful bond of union in separate societies--you will readily
perceive that I am speaking of fear;--under the influence of this
passion these are drawn closer together, and unite more intimately
for defence against some common enemy, and to raise works of munition
that may resist his attack.
The main instrument of association is language, and no association
can be perfect where there is not a common tongue. The origin of
nationality was difference of speech: at Babel, when tongues were
divided, nations separated. Language may be understood in a larger
sense than to signify inflections of the voice,--it may well include
all the means of making yourself understood by another, whether by
gestures, sounds, signs, or words: the two first of these kinds may
be called natural language, and the two last arbitrary or artificial.
I have said that perfect societies of insects exhibit the _semblance_
of a nearer approach, both in their principle and its results, to
the societies of man himself, because, unless we could perfectly
understand what instinct is, and how it acts, we cannot, without
exposing ourselves to the charge of temerity, assert that these are
precisely the same.
But when we consider the object of these societies, the preservation
and multiplication of the species; and the means by which that object
is attained, the united labours and co-operation of perhaps millions
of individuals, it seems as if they were impelled by passions very
similar to those main-springs of human associations, which I have just
enumerated. Desire appears to stimulate them--love to allure them--fear
to alarm them. They want a habitation to reside in, and food for their
subsistence. Does not this look as if desire were the operating cause,
which induces them to unite their labours to construct the one and
provide the other? Their nests contain a numerous family of helpless
brood. Does not love here seem to urge them to that exemplary and fond
attention, and those unremitted and indefatigable exertions manifested
by the whole community for the benefit of these dear objects? Is it
not also evidenced by their general and singular attachment to their
females, by their mutual caresses, by their feeding each other, by
their apparent sympathy with suffering individuals and endeavours to
relieve them, by their readiness to help those that are in difficulty,
and finally by their sports and assemblies for relaxation? That fear
produces its influence upon them seems no less evident, when we see
them, agitated by the approach of enemies, endeavour to remove what
is most dear to them beyond their reach, unite their efforts to
repel their attacks, and to construct works of defence. They appear
to have besides a common language; for they possess the faculty, by
significative gestures and sounds, of communicating their wants and
ideas to each other[35].
There are, however, the following great differences between human
societies and those of insects. Man is susceptible of individual
attachment, which forms the basis of his happiness, and the source
of his purest and dearest enjoyments:--whereas the love of insects
seems to be a kind of instinctive patriotism that is extended to the
whole community, never distinguishing individuals, unless, as in the
instance of the female bee, connected with that great object.
Man also, endowed with reason, forms a judgement from circumstances,
and by a variety of means can attain the same end. Besides
the language of nature, gestures, and exclamations, which the
passions produce, he is gifted with the divine faculty of speech,
and can express his thoughts by articulate sounds or artificial
language.--Not so our social insects. Every species has its peculiar
mode of proceeding, to which it adheres as to the law of its nature,
never deviating but under the control of imperious circumstances;
for in particular instances, as you will see when I come to treat of
their instincts, they know how to vary, though not very materially,
from the usual mode[36]. But they never depart, like man, from the
general system; and, in common with the rest of the animal kingdom,
they have no articulate language.
Human associations, under the direction of reason and revelation,
are also formed with higher views,--I mean as to government, morals,
and religion:--with respect to the last of these, the social insects
of course can have nothing to do, except that by their wonderful
proceedings they give man an occasion of glorifying his great
Creator; but in their instincts, extraordinary as it may seem, they
exhibit a semblance of the two former, as will abundantly appear in
the course of our correspondence.
I shall not detain you longer by prefatory remarks from the amusing
scene to which I am eager to introduce you; but the following
observations of M. P. Huber on this subject are so just and striking,
that I cannot refrain from copying them.