REMAINING ARTICULATA.
THE Hymenoptera being so much the most intelligent order, not merely of
insects, but of Invertebrata, and the Arachnida having been now
considered, very little space need be occupied with the remaining
classes of the Articulata.
_Coleoptera._
Sir John Lubbock, in his first paper on Bees and Wasps, quotes the
following case from Kirby and Spence, with the remarks which I append:--
The first of these anecdotes refers to a beetle
(_Ateuchus pilularius_) which, having made for the
reception of its eggs a pellet of dung too heavy for
it to move, repaired to an adjoining heap, and soon
returned with three of his companions. 'All four now
applied their united strength to the pellet, and at
length succeeded in pushing it out; which being done,
the three assistant beetles left the spot and returned
to their own quarters.' This observation rests on the
authority of an anonymous German artist; and though we
are assured that he was a 'man of strict veracity,' I
am not aware that any similar fact has been recorded
by any other observer.
Catesby, however, says:--
I have attentively admired their industry, and their
mutual assisting of each other in rolling these
globular balls from the place where they made them, to
that of their interment, which is usually a distance
of some yards, more or less. This they perform back
foremost, by raising their hind parts and pushing away
the ball with their hind feet. Two or three of them
are sometimes engaged in trundling one ball, which
from meeting with impediments, on account of the
unevenness of the ground, is sometimes deserted by
them. It is, however, attempted by others with
success, unless it happen to roll into some deep
hollow or ditch, where they are accustomed 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. They form
these pellets while the dung remains moist, and leave
them to harden in the sun before they attempt to roll
them. In their rolling of them from place to place,
both they and the balls may frequently be seen
tumbling about over the little eminences that are in
their way. They are not, however, easily discouraged,
and by repeating their attempts usually surmount the
difficulties.[90]
Büchner speaks of the fact that dung-beetles co-operate in their work as
one that is well established, but gives no authorities or references.[91]
A friend of my own, however, informs me that she has witnessed the fact;
and in view of analogous observations made on other species of
Coleoptera, I see no reason to doubt this one. Some of these
observations I may here append.
Herr Gollitz writes to Büchner thus:--
Last summer, in the month of July, I was one day in my
field, and found there a mound of fresh earth like a
molehill, on which a striped black and red beetle,
with long legs, and about the size of a hornet, was
busy taking away the earth from a hole that led like a
pit into the mound, and levelling the place. After I
had watched this beetle for some time, I noticed a
second beetle of the same kind, which brought a little
lump of earth from the interior to the opening of the
hole, and then disappeared again in the mound; every
four or five minutes a pellet came out of the hole,
and was carried away by the first-named beetle. After
I had watched these proceedings for about half an
hour, the beetle which had been working underground
came out and ran to its comrade. Both put their heads
together, and clearly held a conversation, for
immediately afterwards they changed work. The one
which had been working outside went into the mound,
the other took the outside labour, and all went on
vigorously. I watched the affair still for a little
longer, and went away with the notion that these
insects could understand each other just like men.
Klingelhöffer, of Darmstadt (in Brehm, _loc. cit._,
ix., p. 86), says:--A golden running beetle came to a
cockchafer lying on its back in the garden, intending
to eat it, but was unable to master it; it ran to the
next bush, and returned with a friend, whereupon the
two overpowered the cockchafer, and pulled it off to
their hiding-place.
Similarly, there is no doubt that the burying beetles (_Nicrophorus_)
co-operate.
Several of them unite together to bury under the
ground, as food and shelter for their young, some dead
animal, such as a mouse, a toad, a mole, a bird, &c.
The burial is performed because the corpse, if left
above ground, would either dry up, or grow rotten, or
be eaten by other animals. In all these cases the
young would perish, whereas the dead body lying in the
earth and withdrawn from the outer air lasts very
well. The burying beetles go to work in a very
well-considered fashion, for they scrape away the
earth lying under the body, so that it sinks of itself
deeper and deeper. When it is deep enough down, it is
covered over from above. If the situation is stony,
the beetles with united forces and great efforts drag
the corpse to some place more suitable for burying.
They work so diligently that a mouse, for instance, is
buried within three hours. But they often work on for
days, so as to bury the body as deeply as possible.
From large carcasses, such as those of horses, sheep,
&c., they only bury pieces as large as they can
manage.[92]
Lastly, Clarville gives a case of a burying beetle which wanted to carry
away a dead mouse, but, finding it too heavy for its unaided strength,
went off, like the beetles previously mentioned, and brought four others
to its assistance.[93]
A friend of Gleditsch fastened a dead toad, which he desired to dry,
upon the top of an upright stick. The burying beetles were attracted by
the smell, and finding that they could not reach the toad, they
undermined the stick, so causing it to fall with the toad, which was
then buried safe out of harm's way.[94]
A converse exemplification of beetle-intelligence is given by G.
Berkeley.[95] He saw a beetle carrying a dead spider up a heath plant,
and hanging it upon a twig of the heath in so secure a position, that
when the insect had left it Mr. Berkeley found that a sharp shake of the
heather would not bring the dead spider down. As the burying beetle
preserves its treasure by hiding it out of sight below ground, so this
beetle no doubt secured the same end but by other means; 'seeing,' as
Mr. Berkeley observes, 'that if it did not hang up its prey, it might
fall into the hands of other hunters, it took all possible pains to find
out the best store-room for it.'
The above instances of beetle-intelligence lead me to credit the
following, which has been communicated to me by Dr. Garraway, of
Faversham. On a bank of moss in the Black Forest he saw a beetle alight
with a caterpillar which it was carrying, and proceed to excavate a
cylindrical hole in the peat, about an inch and a half deep, into which,
when completed, it dropped the caterpillar, and then flew away through
the pines. 'I was struck,' says my correspondent, 'with the creature's
folly in leaving the whole uncovered, as every curious wayfaring insect
would doubtless be tempted to enter therein. However, in about a minute
the beetle returned, this time carrying a small pebble, of which there
were none in the immediate vicinity, and having carefully fitted this
into the aperture, fled away into space.'
_Earwig._
I must devote a short division of this chapter to the earwig. M. Geer
describes a regular process of incubation as practised by the mother
insect. He placed one with her eggs in a box, and scattered the eggs on
the floor of the latter. The earwig, however, carried them one by one
into a certain part of the box, and then remained constantly sitting
upon the heap without ever quitting it for a moment. When the eggs were
hatched, the young earwigs kept close to their mother, following her
about everywhere, and often running under her abdomen, just as chickens
run under a hen.[96]
A young lady, who objects to her name being published, informs me that
her two younger sisters (children) are in the habit of feeding every
morning with sugar an earwig, which they call 'Tom,' and which crawls up
a certain curtain regularly every day at the same hour, with the
apparent expectation of getting its breakfast. This resembles analogous
instances which, have been mentioned in the case of spiders.
_Dipterous Insects._
The gad-fly, whose eggs are hatched out in the intestines of the horse,
exhibits a singular refinement of instinct in depositing them upon those
parts of the horse which the animal is most likely to lick. For,
according to Bingley and other writers, 'the inside of the knee is the
part on which these flies principally deposit their eggs; and next to
this they fix them upon the sides, and the back part of the shoulder;
but almost always in places liable to be licked by the tongue.' The
female fly deposits her eggs while on the wing, or at least scarcely
appears to settle when she extends her ovidepositor to touch the horse.
She lays only a single egg at a time--flying away a short distance after
having deposited one in order to prepare another, and so on.
The following anecdote, which I quote from Jesse, seems to indicate
no small degree of intelligence on the part of the common
house-fly--intelligence, for instance, the same both in kind and degree
as that which was displayed by Sir John Lubbock's pet wasp already
mentioned:
Slingsby, the celebrated opera dancer, resided in the
large house in Cross-deep, Twickenham, next to Sir
Wathen Waller's, looking down the river. He was fond
of the study of natural history, and particularly of
insects, and he once tried to tame some house-flies,
and preserve them in a state of activity through the
winter. For this purpose, quite at the latter end of
autumn, and when they were becoming almost helpless,
he selected four from off his breakfast-table, put
them upon a large handful of cotton, and placed it in
one corner of the window nearest the fireplace. Not
long afterwards the weather became so cold that all
flies disappeared except these four, which constantly
left their bed of cotton at his breakfast-time, came
and fed at the table, and then returned to their home.
This continued for a short time, when three of them
became lifeless in their shelter, and only one came
down. This one Slingsby had trained to feed upon his
thumb-nail, by placing on it some moist, sugar mixed
with a little butter. Although there had been at
intervals several days of sharp frost, the fly never
missed taking his daily meal in this way till after
Christmas, when, his kind preserver having invited a
friend to dine and sleep at his house, the fly, the
next morning, perched upon the thumb of the visitor,
who, being ignorant that it was a pet of his host's,
clapped his hand upon it, and thus put an end to Mr.
Slingsby's experiment.[97]
_Crustacea._
There is no doubt that these are an intelligent group of animals,
although I have been able to collect but wonderfully little information
upon the subject. Mr. Moseley, F.R.S., in his very interesting work,
'Notes by a Naturalist on the _Challenger_,' says (p. 70):--
In the tropics one becomes accustomed to watch the
habits of various species of crabs, which there live
so commonly an aërial life. The more I have seen of
them, the more have I been astonished at their
sagacity.
And again (pp. 48-9):--
A rock crab (_Grapsus stringosus_) was very abundant,
running about all over the rocks, and making off into
clefts on one's approach. I was astonished at the keen
and long sight of this crab. I noticed some made off
at full speed to their hiding-places at the instant
that my head showed above a rock fifty yards
distant. . . .
At Still Bay, on the sandy beach of which a heavy surf
was breaking, I encountered a sand crab (_[OE]cypoda
ippeus_), which was walking about, and got between it
and its hole in the dry sand above the beach. The crab
was a large one, at least three inches in breadth of
its carapace. . . . With its curious column-like eyes
erect, the crab bolted down towards the surf as the
only escape, and as it saw a great wave rushing up the
shelving shore, dug itself tight into the sand, and
held on to prevent the undertide from carrying it into
the sea. As soon as the wave had retreated, it made
off full speed for the shore. I gave chase, and
whenever a wave approached, the crab repeated the
manoeuvre. I once touched it with my hand whilst it
was buried and blinded by the sandy water, but the
surf compelled me to retreat, and I could not snatch
hold of it for fear of its powerful claws. At last I
chased it, hard pressed, into the surf in a hurry, and
being unable to get proper hold in time, it was washed
into the sea. The crab evidently dreaded going into
the sea. . . . They soon die when kept a short time
beneath the water.
The land crabs of the West Indies and North America descend from their
mountain home in May and June, to deposit their spawn in the sea. They
travel in such swarms that the roads and woods are covered with them.
They migrate in a straight line, and rather than allow themselves to be
deflected from it, 'they scale the houses, and surmount every other
obstacle that lies in their way' (Kirby). They travel chiefly by night,
and when they arrive at the sea-shore they 'bathe three or four
different times,' and then 'commit their eggs to the waves.' They return
to the mountains by the same route, but only the most vigorous survive
the double journey.
Prof. Alex. Agassiz details some interesting observations on the
behaviour of young hermit crabs reared by himself 'from very young
stages,' when first presented with shells of mollusks. 'A number of
shells, some of them empty, others with the animal living, were placed
in a glass dish with the young crabs. Scarcely had the shells reached
the bottom before the crabs made a rush for the shells, turned them
round and round, invariably at the mouth, and soon a couple of the crabs
decided to venture in, which they did with remarkable alacrity.' The
crabs which obtained for their share the shells still inhabited by
living mollusks, 'remained riding round upon the mouth of their future
dwelling, and, on the death of the mollusk, which generally occurred
soon after in captivity, commenced at once to tear out the animal, and
having eaten him, proceeded to take its place within the shell.'[98]
There is a species of small crustacean (_Podocerus capillatus_)
described by Mr. Bates, which builds a nest to contain its eggs. The
nest is in the form of a hollow cone, built upon seaweed, and composed
of fine thread-like material closely interlaced. 'These nests,' says Mr.
Bates, 'are evidently used as a place of refuge and security, in which
the parent protects and keeps her brood of young until they are old
enough to be independent of the mother's care.'
Dr. Erasmus Darwin tells us, on the authority of a friend on whose
competency as an observer he relied, that the common crab during the
moulting season stations as sentinel an unmoulted or hard-shelled
individual, to prevent marine enemies from injuring moulted individuals
in their unprotected state. While thus mounting guard the hard-shelled
crab is much more courageous than at other times, when he has only his
own safety to consider. But these observations require to be
corroborated.
In 'Nature' (xv., p. 415) there is a notice of a lobster (_Homarus
marinus_) in the Rothesay Aquarium which attacked a flounder that was
confined in the same tank with him, and having devoured a portion of his
victim, buried the rest beneath a heap of shingle, on which he 'mounted
guard.' 'Five times within two hours was the fish unearthed, and as
often did the lobster shovel the gravel over it with his huge claws,
each time ascending the pile and turning his bold defensive front to his
companions.'
The following is quoted from Mr. Darwin's 'Descent of Man' (pp.
270-1):--
A trustworthy naturalist, Mr. Gardner, whilst watching
a shore-crab (_Gelasimus_) making its burrow, threw
some shells towards the hole. One rolled in, and three
other shells remained within a few inches of the
mouth. In about five minutes the crab brought out the
shell which had fallen in, and carried it away to the
distance of a foot; it then saw the three other shells
lying near, and evidently thinking that they might
likewise roll in, carried them to the spot where it
had laid the first. It would, I think, be difficult to
distinguish this act from one performed by man by the
aid of reason.
Mr. Darwin also alludes to the curious instinctive habits of the large
shore-crab (_Birgus latro_), which feeds on fallen cocoa-nuts 'by
tearing off the husk fibre by fibre; and it always begins at that end
where the three eye-like depressions are situated. It then breaks
through one of these eyes by hammering with its heavy front pincers, and
turning round, extracts the albuminous core with its narrow posterior
pincers.'
Remarkable cases occur of commensalism between certain crabs and
sea-anemones, and they betoken much intelligence. Thus Professor Möbius
says in his 'Beiträge zur Meeresfauna der Insel Mauritius' (1880) that
there are two crabs belonging to different genera which have the habit
of firmly grasping a sea-anemone in each claw and carrying them about,
presumably to secure some benefit to themselves. The more familiar case
of the species of anemone which lives on the shells tenanted by hermit
crabs is of special interest to us on account of a remarkable
observation published by Mr. Gosse, F.R.S. (_Zoologist_, June, 1859). He
found that on his detaching the anemone (_Adamsia_) from the shell, the
hermit crab always took it up in its claws and held it against the shell
'for the space of ten minutes at a time, until fairly attached by a good
strong base.' It was said by the late Dr. Robert Ball that when the
common _Sagartia parasitica_ is attached to a stone and a hermit crab is
placed in its vicinity, the anemone will leave the stone and attach
itself to the hermit's shell (_Critic_, March 24, 1860).
_Intelligence of Larvæ of Certain Insects._
I shall now allude to some of the more interesting facts touching the
psychology of insects when in their immature or larval state. This is an
interesting topic from the point of view which we occupy as
evolutionists, because a caterpillar is really a locomotive and
self-feeding embryo, whose entire mental constitution is destined to
undergo a metamorphosis no less complete and profound than that which is
also destined to take place in its corporeal structure. Yet although the
caterpillar has an embryo psychology, its instincts and even
intelligence often seem to be higher or more elaborated than is the case
with the imago form. Where such is the case the explanation of course
must be that it is of more importance to the species that the larval
form should be in a certain measure intelligent than that the imago form
should be so. Every larva is a potential imago, or breeding individual;
therefore its life is of no less value to the species during its larval
than during its adult existence; and if certain instincts or grades of
intelligence are of more use to it during the former than during the
latter period, of course natural selection would determine the unusual
event which we seem here in some cases to see--namely, that the embryo
should stand on a higher level of psychological development than the
adult.
I may most fitly begin under this heading with the remarkable instincts
of the so-called 'ant-lion,' which is the larva of a neuropterous
insect, the common _Myrmeleon_ (_M. formicarium_). I quote the following
account of its habits from Thompson's 'Passions of Animals' (p. 258):--
The devices of the ant-lion are still more
extraordinary if possible. He forms, with astonishing
labour and perseverance, a pit in the shape of a
funnel, in a dry sandy soil, under some old wall or
other spot protected from the wind. His pit being
finished, he buries himself among the sand at the
bottom, leaving only his horns visible, and thus waits
patiently for his prey. When an ant or any other small
insect happens to walk on the edge of the hollow, it
forces down some of the particles of sand, which gives
the ant-lion notice of its presence. He immediately
throws up the sand which covers his head to overwhelm
the ant, and with its returning force brings it to the
bottom. This he continues to do till the insect is
overcome and falls between his horns. Every endeavour
to escape, when once the incautious ant has stepped
within the verge of the pit, is vain, for in all its
attempts to climb the side the deceptive sand slips
from under its feet, and every struggle precipitates
it still lower. When within reach its enemy plunges
the points of its jaws into its body, and having
sucked out all its juices, throws out the empty skin
to some distance.
According to Bingley, if the ant-lion, while excavating its pitfall,--
Comes to a stone of some moderate size, it does not
desert the work on this account, but goes on,
intending to remove that impediment the last. When the
pit is finished, it crawls backward up the side of the
place where the stone is; and, getting its tail under
it, takes great pains and time to get it on a true
poise, and then begins to crawl backward with it up
the edge to the top of the pit, to get it out of the
way. It is a common thing to see an ant-lion labouring
in this manner at a stone four times as big as its own
body; and as it can only move backwards, and the poise
is difficult to keep, especially up a slope of such
crumbling matter as sand, which moulders away from
under its feet, and necessarily alters the position of
its body, the stone very frequently rolls down, when
near the verge, quite to the bottom. In this case the
animal attacks it again in the same way, and is often
not discouraged by five or six miscarriages, but
continues its struggle so long that it at length gets
over the verge of the place. When it has done this, it
does not leave it there, lest it should roll in again;
but is always at the pains of pushing it further on,
till it has removed it to a necessary distance from
the edge of the pit.[99]
Passing on now to the intelligence of caterpillars, Mr. G. B. Buckton,
F.R.S., writing from Haslemere, says:--
Many caterpillars of _Pieris rapæ_ have, during this
autumn, fed below my windows. On searching for
suitable positions for passing into chrysalides, some
eight or ten individuals, in their direct march
upwards, encountered the plate-glass panes of my
windows; on these they appeared to be unable to stand.
Accordingly in every case they made silken ladders,
some of them five feet long, each ladder being formed
of a single continuous thread, woven in elegant loops
from side to side. . . . The reasoning, however, seems
to be but narrow, for one ladder was constructed
parallel to the window-frame for nearly three feet,
on which secure footing could be had by simply
diverting the track two inches.[100]
In this case it appears clear that we have to do with instinct, and not
with reason. No doubt it is the congenital habit of these caterpillars
to overcome impediments in this way; but the instinct is one of
sufficient interest to be here stated.
The following is quoted from Kirby and Spence:--
A caterpillar described by Bonnet, which, from being
confined in a box, was unable to obtain a supply of
the bark with which its ordinary instinct directs it
to make its cocoon, substituted pieces of paper that
were given to it, tied them together with silk, and
constructed a very passable cocoon with them. In
another instance the same naturalist having opened
several cocoons of a moth (_Noctura verbasci_), which
are composed of a mixture of grains of earth and silk,
just after being finished, the larvæ did not repair
the injury _in the same manner_. Some employed both
earth and silk; others contented themselves with
spinning a silken veil before the opening.[101]
The same authorities state, as result of their own observation, that
the--
Common cabbage caterpillar, which, when building web
under stone or wooden surfaces, previously covers a
space with a web to form a base for supporting its
dependent pupa, when building a web beneath a muslin
surface dispenses with this base altogether: it
perceives that the woven texture of the muslin forms
facilities for attaching the threads of the cocoon
securely enough to support the weight of the cocoon
without the necessity of making the usual square inch
or so of basal support.[102]
The instincts of the larva of the _Tinea_ moth are thus described by
Réaumur:--
It feeds upon the elm, using the leaves both as food
and clothing. To do this it only eats the parenchyma
of the leaf, preserving the upper and under epidermal
membranes, between which it then insinuates itself as
it progressively devours the parenchyma. It, however,
carefully avoids separating these membranes where they
unite at the extreme edge of the leaf, which is
designed to form 'one of the seams of its coat.' The
cavity when thus excavated between the two epidermal
membranes is then lined with silk, made cylindrical in
shape, cut off at the two ends and all along the side
remote from the 'seam,' and then the two epidermal
membranes sewn together along the side where they have
had to be cut in order to separate them from the tree.
The larva now has a coat exactly fitting its body, and
open at each end. By the one opening it feeds, and by
the other discharges its excrement, 'having on one
side a nicely jointed seam--that which is commonly
applied to its back--composed of the natural marginal
junction of the membranes of the leaf.'
Réaumur cut off the edge of a newly finished coat, so as to expose the
body of the larva at that point. The animal did not set about making a
new coat _ab initio_, as we might expect that it would on the popular
supposition that a train of instinctive actions is always as mechanical
as the running down of a set of cog-wheels, and that wherever a novel
element is introduced the machinery must be thrown out of gear, so that
it cannot meet a new emergency of however simple a character, and must
therefore re-start the whole process over again from the beginning. In
this case the larva sewed up the rent; and not only so, but 'the
scissors having cut off one of the projections intended to enter into
the construction of the triangular end of the case, it entirely changed
the original plan, and made that end the head which had been first
designed for the tail.'
Another remarkable case of the variation of instinct in the Lepidoptera
is stated by Bonnet. There are usually, he says, two generations of the
Angoumois moth: the first appear in early summer, and lay their eggs
upon the ears of wheat in the fields; the second appear later in the
summer, or in the autumn, and these lay their eggs upon wheat in the
granaries; from these eggs there comes the first generation of next
year's moths. This is a highly remarkable case--supposing the facts to
be as Bonnet states; for it seems that the early summer moths, although
born in the granaries, immediately fly to the unreaped fields to lay
their eggs in the standing corn, while the autumn moths never attempt to
leave the granaries, but lay their eggs upon the stored wheat.[103]
Westwood says that--
A species of Tasmanian caterpillar (_Noctua Ewingii_)
swarms over the land in enormous companies, which
regularly begin to march at four o'clock in the
morning, and as regularly halt at midday. _Liparis
chrysorrhaca_, a kind of caterpillar, spins for the
winter a common web, in which several hundred
individuals find a common shelter.[104]
According to Kirby and Spence,--
The larva of the ichneumon, while feeding upon its
caterpillar host, spares the walls of the intestines
until it is time for it to escape, when, the life of
the caterpillar being no longer necessary to its
development, it perforates these walls.[105]
The larvæ _Theda isocrates_ live in a group of seven
or eight in the fruit of pomegranate. In consequence
of their excavations within the fruit, the latter is
apt to fall; and to prevent its doing so the larvæ
throw out a thread of attachment wherewith to secure
the fruit to the branch, so that if the stalk withers,
this thread serves to suspend the fruit.[106]
The caterpillar of the Bombyx moth, which is a native
of France, exhibits very wonderful instincts. The
larva is gregarious in its habits, each society
(family) consisting of perhaps 600 or 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. About sunset the
regiment leaves its quarters. . . . 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 in
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.[107]
The following additional facts concerning these remarkable habits may be
quoted. I take them from the account published by Mr. Davis in
'Loudoun's Magazine of Natural History:'--
The caterpillars, he observed, were Bombyces, and were
seen crossing a road in single file, each so close to
its predecessor that the line was quite continuous,
'moving like a living cord.' The number of
caterpillars was 154, and the length of the line 27
feet. When Mr. Davis removed one from the line the
caterpillar immediately in front suddenly stood still,
then the next, and next, and so on to the leader.
Similarly, those behind the point of interruption
successively halted. After a pause of a few moments,
the first caterpillar behind the break in the line
endeavoured to fill up the vacant space, and so
recover contact or communication, which after a time
it succeeded in doing, when the information that the
line was again closed was passed forward in some way
from caterpillar to caterpillar till it reached the
leader, when the whole fine was again put in motion.
The individual which had been abstracted remained
rolled up and motionless; but on being placed near the
moving column it immediately unrolled, and made every
attempt to get readmitted into the procession. After
many endeavours it succeeded, the one below falling
into the rear of the interloper. On repeating the
experiment by removing a caterpillar fifty from the
head of the procession, Mr. Davis found that it took
just thirty seconds by his watch for information of
the fact to reach the leader. All the same results
followed as in the previous case. It was observable
that the animals were guided neither by sight nor
smell while endeavouring to close up the interrupted
line; for the caterpillar next behind the
interruption, on whom the duty of closing up devolved,
'turned right and left, and often in a wrong
direction, when within half an inch of the one
immediately before him; when he at last touched the
object of his search, the fact was communicated again
by signal; and in thirty seconds the whole line was in
rapid march.' This gentleman adds that the object of
the march was the search for new pasture. The
caterpillars feed on the Eucalyptus, and when they
have completely stripped one tree of its leaves, they
all congregate on the trunk, and proceed as described
to another tree.
De Villiers[108] gives an account of his observations on the manner in
which these caterpillars (_Cnethocampii pitzocampa_) are able to pass
information, which does not quite agree with the above observation of
Mr. Davis. For he says that, in a train of 600 caterpillars,
interference by him in any part of the train was communicated through
the whole series instantaneously--all the 600 caterpillars stopping
immediately and with one consent like a single organism.
According to Kirby and Spence there is a kind of caterpillar (_Pieris
cratægi_) which lives in little colonies of ten or twelve in common
chambers lined with silk. In one part they make of the same material a
little bag or pocket, which is used by the community or household as a
water-closet. When full of excrement the caterpillars empty it by
turning out the pellets with their feet.[109]
Only two other instances of noteworthy intelligence as exhibited by
larvæ have fallen within my reading. One of these is mentioned by
Réaumur, who says that the larvæ of _Hemerobius chrysops_ chase aphides,
and having killed them, clothe themselves in their skins; and the other
case is the very remarkable one mentioned in his newly published work by
W. MacLachlan, F.R.S., of caddis-worms adjusting the specific gravity of
their tubes to suit that of the water in which they live, by attaching
heavy or light material to them according as they require sinking or
flotation.
FOOTNOTES:
[90] Quoted by Bingley, _Animal Biography_, vol. iii., p. 118.
[91] _Loc. cit._, p. 344.
[92] Büchner, _loc. cit._, p. 344.
[93] Quoted in Strauss, _Insects_, s. 389.
[94] Kirby and Spence, _loc. cit._, pp. 321-2.
[95] _Life and Recollections_, vol. ii., p. 356.
[96] Quoted by Bingley, _loc. cit._, vol. iii., pp. 150-51.
[97] _Gleanings_, vol. ii., pp. 165-6.
[98] _American Journ. Sc. and Art_, vol. x., Oct. 1875.
[99] _Animal Biography_, vol. iii., pp. 244-5.
[100] _Nature_, vii., p. 49.
[101] _Intr. to Ent._, ii., p. 475.
[102] _Ibid._, p. 475.
[103] _[OE]uvres_, ix., p. 370.
[104] _Trans. Ent. Soc._, vol. ii.
[105] _Introd. Ent._, Letter xi.
[106] Westwood, _Trans. Ent. Soc._, vol. ii., p. 1.
[107] Kirby and Spence, _Entomology_, Letter xvi.
[108] _Trans. Ent. Soc. France_, vol. i., p. 201.
[109] _Introduction to Entomology_, Letter xxvi.