Chapter VIII: Instinct

8.

Instinct

Instincts comparable with habits, but different in their origin.

Instincts graduated aphids and ants, instincts variable, domestic instincts, their origin, natural

instincts of the cuckoo, malauthorous, ostrich, and parasitic bees.

Slave-making ants, hive bee, its cell-making instinct, changes of instinct and structure,

not necessarily simultaneous, difficulties of the theory of the natural selection of instincts,

neuter or sterile insects, summary.

Many instincts are so wonderful that their development will probably appear to the reader

a difficulty sufficient to overthrow my whole theory.

I may hear premise that I have nothing to do with the origin of the mental powers, any

more than I have with that of life itself.

We are concerned only with the diversities of instinct and of the other mental faculties

in animals of the same class.

I will not attempt any definition of instinct.

It would be easy to show that several distinct mental actions are commonly embraced by

this term, but everyone understands what is meant, when it is said that instinct impels

the cuckoo to migrate and to lay her eggs in other birds' nests.

An action, which we ourselves require experience to enable us to perform, when performed by

an animal, more especially by a very young one, without experience, and when performed

by many individuals in the same way, without their knowing for what purpose it is performed,

is usually said to be instinctive.

But I could show that none of these characters are universal.

A little dose of judgment or reason, as Pierre Hubert expresses it, often comes into play,

even with animals low in the scale of nature.

Frederick Cuvier and several of the older metaphysicians have compared instinct with habit.

This comparison gives, I think, an accurate notion of the frame of mind under which an

instinctive action is performed, but not necessarily of its origin.

How unconsciously many habitual actions are performed, indeed not rarely in direct opposition

to our conscious will.

Yet they may be modified by the will or reason.

Habits easily become associated with other habits, with certain periods of time and states

of the body.

When once acquired, they often remain constant throughout life.

All other points of resemblance between instincts and habits could be pointed out.

As in repeating a well-known song, so in instincts, one action follows another by a sort of rhythm,

if a person be interrupted in a song, or in repeating anything by rote, he is generally

forced to go back to recover the habitual train of thought, so P.

Hubert found it was with a caterpillar, which makes a very complicated hammock.

For if he took a caterpillar which had completed its hammock up to, say, the sixth stage of construction,

and put it into a hammock completed up only to the third stage, the caterpillar simply

re-performed the fourth, fifth, and sixth stages of construction.

If, however, a caterpillar were taken out of a hammock made up, for instance, to the

third stage, and were put into one finished up to the sixth stage, so that much of its work

was already done for it, far from deriving any benefit from this.

It was much embarrassed, and, in order to complete its hammock, seemed forced to start

from the third stage, where it had left off, and thus tried to complete the already finished

work.

If we suppose any habitual action to become inherited, and it can be shown that this does sometimes

happen, then the resemblance between what originally was a habit and an instinct becomes

so close as not to be distinguished.

If Mozart, instead of playing the pianophore at three years old with wonderfully little

practice, had played a tune with no practice at all, B might truly be said to have done

so instinctively.

But it would be a serious error to suppose that the greater number of instincts have been

acquired by habit in one generation, and then transmitted by inheritance to succeeding

generations.

It can be clearly shown that the most wonderful instincts with which we are acquainted, namely,

those of the hive B and of many ants, could not possibly have been acquired by habit.

It will be universally admitted that instincts are as important as corporeal structures for

the welfare of each species, under its present conditions of life.

Under changed conditions of life, it is at least possible that slight modifications of

instinct might be profitable to a species, and if it can be shown that instincts do very

ever so little, then I can see no difficulty in natural selection preserving and continually

accumulating variations of instinct to any extent that was profitable.

It is thus, as I believe, that all the most complex and wonderful instincts have originated.

As modifications of corporeal structure arise from, and are increased by use or habit,

and are diminished or lost by disuse, so I do not doubt it has been with instincts.

But I believe that the effects of habit are in many cases of subordinate importance to

the effects of the natural selection of what may be called spontaneous variations of instincts,

and is of variations produced by the same unknown causes which produce slight deviations

of bodily structure.

No complex instinct can possibly be produced through natural selection, except by the slow

and gradual accumulation of numerous, slight, yet profitable, variations.

Hence, as in the case of corporeal structures, we ought to find in nature, not the actual

transitional gradations by which each complex instinct has been acquired, for these could

be found only in the lineal ancestors of each species, but we ought to find in the collateral

lines of dissent some evidence of such gradations, or we ought at least to be able to show that

gradations of some kind are possible, and this we certainly can do.

I have been surprised to find, making allowance for the instincts of animals having been but

little observed, except in Europe and North America, and for no instinct being known

among extinct species, how very generally gradations, leading to the most complex instincts,

can be discovered.

Changes of instinct may sometimes be facilitated by the same species having different instincts

at different periods of life, or at different seasons of the year, or when placed under different

circumstances, etc., in which case either the one or the other instinct might be preserved

by natural selection.

From such instances of diversity of instinct in the same species can be shown to occur in nature.

Again, as in the case of corporeal structure, and conformably to my theory, the instinct

of each species is good for itself, but has never, as far as we can judge, been produced

for the exclusive good of others.

One of the strongest instances of an animal apparently performing an action for the soul

good of another, with which I am acquainted, is that of aphids voluntarily yielding,

as was first observed by Hubert, their sweet excretion to ants, that they do so voluntarily,

the following facts show.

I removed all the ants from a group of about a dozen aphids on a dock plant, and prevented

their attendance during several hours.

After this interval, I felt sure that the aphids would want to excrete.

I watched them for some time through a lens, but not one excreted, and then tickled and

stroked them with a hair in the same manner, as well as I could, as the ants do with their

antennae, but not one excreted.

Afterwards, I allowed an ant to visit them, and it immediately seemed, by its eager way

of running about to be well aware what a rich flock it had discovered, it then began

to play with its antennae on the abdomen first of one aphis and then of another, and each,

as soon as it felt the antennae, immediately lifted up its abdomen and excreted a limpid

drop of sweet juice, which was eagerly devoured by the ant.

Given the quite young aphids behaved in this manner, showing that the action was instinctive,

and not the result of experience.

It is certain, from the observations of Huber, that the aphids show no dislike to the ants,

if the latter be not present they are at last compelled to eject their excretion.

But as the excretion is extremely viscid, it is no doubt a convenience to the aphids to

have it removed, therefore probably they do not excrete solely for the good of the ants.

Although there is no evidence that any animal performs an action for the exclusive good

of another species, yet each tries to take advantage of the instincts of others, as each

takes advantage of the weaker bodily structure of other species.

So again certain instincts cannot be considered as absolutely perfect, but as details on this

and other such points are not indispensable, they may be here past over.

As some degree of variation in instincts under a state of nature and the inheritance of

such variations, are indispensable for the action of natural selection, as many instances

as possible ought to be given, but want of space prevents me.

I can only assert that instincts certainly do vary, for instance, the migratory instinct,

both in extent and direction, and in its total loss.

So it is with the nests of birds, which vary partly in dependence on the situations chosen,

and on the nature and temperature of the country inhabited, but often from causes wholly

unknown to us.

Audubon has given several remarkable cases of differences in the nests of the same species

in the northern and southern United States.

Why, it has been asked if instinct be variable, has it not granted to the bee the ability

to use some other material when wax was deficient?

But what other natural material could bees use?

They will work, as I have seen, with wax hardened with vermilion or softened with lard.

Audubon had observed that his bees, instead of laboriously collecting propolis, used a cement

of wax and turpentine, with which he had covered de-corticated trees.

It has lately been shown that bees, instead of searching for pollen, will gladly use a

very different substance, namely, oatmeal.

Fear of any particular enemy is certainly an instinctive quality, as may be seen in nestling

birds, though it is strengthened by experience, and by the sight of fear of the same enemy

in other animals.

The fear of man is slowly acquired, as I have elsewhere shown, by the various animals

which inhabit desert islands, and we see an instance of this, even in England, in the

greater wilderness of all our large birds in comparison with our small birds, for the

large birds have been most persecuted by man.

We may safely attribute the greater wilderness of our large birds to this cause, for an uninhabited

island's large birds are not more fearful than small, and the magpie, so wary in England,

is tame in Norway, as is the hooded crow in Egypt.

That the mental qualities of animals of the same kind, born in a state of nature, very

much, could be shown by many facts.

Several cases could also be adduced of occasional and strange habits in wild animals, which,

if advantageous to the species, might have given rise through natural selection to new instincts.

But I am well aware that these general statements, without the facts in detail, can produce but

a feeble effect on the reader's mind.

I can only repeat my assurance, that I do not speak without good evidence.

The possibility, or even probability, of inherited variations of instinct in a state of nature

will be strengthened by briefly considering a few cases under domestication.

We shall thus be enabled to see the part which habit and the selection of so-called spontaneous

variations have played in modifying the mental qualities of our domestic animals.

It is notorious how much domestic animals vary in their mental qualities.

With cats, for instance, one naturally takes to catching rats, and another mice, and these

tendencies are known to be inherited.

One cat, according to Mr. Estay.

John, always brought home game birds, and other hairs, or rabbits, and another hunted

on marshy ground and almost nightly caught woodcocks or snipes.

A number of curious and authentic instances could be given of various shades of disposition

and taste, and likewise of the oddest tricks, associated with certain frames of mind or periods

of time.

But let us look to the familiar case of the breeds of dogs.

It cannot be doubted that young pointers, I have myself seen striking instances, will

sometimes point and even back other dogs the very first time that they are taken out.

Serving is certainly in some degree inherited by retrievers, and a tendency to run round,

instead of at, a flock of sheep, by shepherd dogs.

I cannot see that these actions, performed without experience by the young, and in nearly

the same manner by each individual, performed with eager delight by each breed, and without

the end being known.

For the young pointer can no more know that he points to aid his master, than the white

butterfly knows why she lays her eggs on the leaf of the cabbage.

I cannot see that these actions differ essentially from true instincts.

If we were to behold one kind of wolf, when young and without any training, as soon as

it sent at its prey, stand motionless like a statue, and then slowly crawl forward with

a peculiar gate, and another kind of wolf rushing round, instead of at, a herd of deer,

and driving them to a distant point, we should assuredly call these actions instinctive.

Instincts, as they may be called, are certainly far less fixed than natural instincts, but

they have been acted on by far less rigorous selection, and have been transmitted for an

incomparably shorter period, under less fixed conditions of life.

How strongly these domestic instincts, habits, and dispositions are inherited, and how curiously

they become mingled, is well shown when different breeds of dogs are crossed.

Thus it is known that a cross with a bulldog has affected for many generations the courage

and obstinacy of greyhounds, and a cross with a greyhound has given to a whole family

of shepherd dogs a tendency to hunt hairs.

These domestic instincts, when thus tested by crossing, resemble natural instincts, which

in a like manner become curiously blended together, and for a long period exhibit traces

of the instincts of either parent, for example, Lou Roy describes a dog, whose great grandfather

was a wolf, and this dog showed a trace of its wild parentage only in one way, by not

coming in a straight line to his master, when called.

Domestic instincts are sometimes spoken of as actions which have become inherited solely

from long continued and compulsory habit, but this is not true.

No one would ever have thought of teaching, or probably could have taught, the tumbler

pigeon to tumble, an action which, as I have witnessed, is performed by young birds,

that have never seen a pigeon tumble.

We may believe that someone pigeon showed a slight tendency to this strange habit, and that

the long continued selection of the best individuals and successive generations made tumblers

what they now are, and near Glasgow there are house tumblers, as I hear from Mr.

Brent, which cannot fly 18 inches high without going head over heels.

It may be doubted whether anyone would have thought of training a dog to point, had not

some one dog naturally shown a tendency in this line, and this is known occasionally to

happen, as I once saw in a pure terrier, the act of pointing is probably.

As many have thought, only the exaggerated pause of an animal preparing to spring on its

prey.

When the first tendency to point was once displayed, methodical selection and the inherited

effects of compulsory training in each successive generation would soon complete the work, and

unconscious selection is still in progress, as each man tries to procure, without intending

to improve the breed, dogs which stand and hunt best.

On the other hand, habit alone in some cases has suffice, hardly any animal is more difficult

to tame than the young of the wild rabbit.

Scarcely any animal is tamer than the young of the tame rabbit, but I can hardly suppose

that domestic rabbits have often been selected for tameness alone, so that we must attribute

at least the greater part of the inherited change from extreme wildness to extreme tameness,

to habit and long continued close confinement.

Animal instincts are lost under domestication, a remarkable instance of this is seen in

those breeds of fowls which very rarely or never become broody, that is, never wish to

sit on their eggs.

Familiarity alone prevents our seeing how largely and how permanently the minds of our domestic

animals have been modified.

It is scarcely possible to doubt that the love of man has become instinctive in the dog.

All wolves, foxes, jackals and species of the cat genus, when kept tame, are most eager

to attack poultry, sheep and pigs, and this tendency has been found incurable in dogs

which have been brought home as puppies from countries such as Tierra del Fuego in Australia,

where the savages do not keep these domestic animals.

How rarely, on the other hand, do our civilized dogs, even when quite young, require to be

taught not to attack poultry, sheep and pigs.

No doubt they occasionally do make an attack and are then beaten, and if not cured, they

are destroyed, so that habit and some degree of selection have probably concurred in civilizing

by inheritance are dogs.

On the other hand, young chickens have lost holy by habit, that fear of the dog and cat

which no doubt was originally instinctive in them.

For I am informed by Captain Hutton that the young chickens of the parent stock, the

Gala Spankiva, when reared in India under a hen, are at first excessively wild.

So it is with young fesans reared in England under a hen.

It is not that chickens have lost all fear, but fear only of dogs and cats, for if the

hen gives the danger chuckle they will run, more especially young turkeys, from under

her and conceal themselves in the surrounding grass or thickets.

And this is evidently done for the instinctive purpose of allowing, as we see in wild ground

birds, their mother to fly away.

But this instinct retained by our chickens has become useless under domestication, for

the mother hen has almost lost by disused the power of flight.

Since, we may conclude that under domestication instincts have been acquired and natural

instincts have been lost, partly by habit and partly by man selecting and accumulating.

During successive generations, peculiar mental habits and actions, which at first appeared

from what we must in our ignorance call an accident.

In some cases compulsory habit alone has suffice to produce inherited mental changes.

In other cases compulsory habit has done nothing, and all has been the result of selection.

We should both methodically and unconsciously, but in most cases habit and selection have

probably concurred.

We shall, perhaps, best understand how instincts in a state of nature have become modified

by selection by considering a few cases.

I will select only three, namely, the instinct which leads the cuckoo to lay her eggs in other

birds' nests, the slave-making instinct of certain ants, and the cell-making power of

the hive bee.

These two latter instincts have generally, and justly been ranked by naturalists as the

most wonderful of all known instincts.

It is supposed by some naturalists that the more immediate cause of the instinct of the

cuckoo is that she lays her eggs, not daily, but at intervals of two or three days, so

that, if she were to make her own nest and sit on her own eggs, those first laid would

have to be left for some time unincubated, or there would be eggs and young birds of different

ages in the same nest.

If this were the case the process of laying and hatching might be inconveniently long,

more especially as she migrates at a very early period, and the first hatched young would

probably have to be fed by the male alone.

But the American cuckoo is in this predicament.

and young successively hatched, all at the same time.

It has been both asserted and denied that the American Kuku occasionally lays her eggs

in other birds' nests, but I have lately heard from DR.

Meryl of Iowa, that he once found an Illinois young Kuku, together with a young J in the

nest of a blue J, Garellus Christatus, and as both were nearly full feathered, there

could be no mistake in their identification.

I could also give several instances of various birds which have been known occasionally to

lay their eggs in other birds' nests.

Now let us suppose that the ancient progenitor of our European Kuku had the habits of the

American Kuku, and that she occasionally laid an egg in another bird's nest.

If the old bird profited by this occasional habit through being enabled to emigrate

earlier or through any other cause, or if the young were made more vigorous by advantage

being taken of the mistaken instinct of another species than when reared by their own mother,

encumbered as she could hardly fail to be by having eggs and young of different ages at

the same time, then the old birds or the fostered young would gain an advantage.

And analogy would lead us to believe that the young thus reared would be apt to follow

by inheritance the occasional and aberrant habit of their mother, and in their turn would

be apt to lay their eggs in other birds' nests, and thus be more successful in rearing

their young.

By a continued process of this nature, I believe that the strange instinct of our Kuku has

been generated.

It has, also recently been ascertained on sufficient evidence, by Edolph Muller, that the

Kuku occasionally lays her eggs on the bare ground, sits on them and feeds her young.

This rare event is probably a case of reversion to the long-lost, aboriginal instinct of

notification.

It has been objected that I have not noticed other related instincts and adaptations of

structure in the Kuku, which are spoken of as necessarily coordinated.

But in all cases, speculation on an instinct known to us only in a single species is useless,

or we have hitherto had no facts to guide us.

Until recently the instincts of the European and of the non-Parasitic American Kuku alone

were known, now, owing to Mr. Ramsey's observations, we have learned something about three

Australian species, which lay their eggs in other birds' nests.

The chief points to be referred to are three, first, that the common Kuku with rare exceptions

lays only one egg in a nest, so that the large and voracious young bird receives ample

food.

Secondly, that the eggs are remarkably small, not exceeding those of the Skylark, a bird

about one-fourth as large as the Kuku.

That the small size of the egg is a real case of adaptation, we may infer from the fact

of the non-Parasitic American Kuku laying full-sized eggs.

Thirdly, that the young Kuku, soon after birth, has the instinct, the strength, and a properly

shaped back for ejecting its foster brothers, which then perish from cold and hunger.

This has been boldly called a beneficent arrangement, in order that the young Kuku may get sufficient

food, and that its foster brothers may perish before they had acquired much feeling.

Turning now to the Australian species, though these birds generally lay only one egg in a nest,

it is not rare to find two and even three eggs in the same nest.

In the bronze Kuku the eggs vary greatly in size, from eight to ten lines in length.

Now, if it had been of an advantage to this species to have laid eggs even smaller than

those now laid, so as to have deceived certain foster parents, or, as is more probable,

to have been hatched within a shorter period.

For it is asserted that there is a relation between the size of eggs and the period of their

incubation, then there is no difficulty in believing that a race or species might have

been formed which would have laid smaller and smaller eggs, for these would have been more.

Safely hatched and reared.

Mr. Ramsay remarks that two of the Australian Kukus, when they lay their eggs in an open nest,

manifest a decided preference for nests containing eggs similar in color to their own.

The European species apparently manifests some tendency towards a similar instinct, but

not rarely departs from it, as is shown by her laying her dull and pale-colored eggs in

the nest of the hedge-warbler with bright greenish blue eggs.

Had our Kuku invariably displayed the above instinct, it would assuredly have been added

to those which it is assumed must all have been acquired together.

The eggs of the Australian bronze Kuku vary, according to Mr. Ramsay, to an extraordinary

degree in color, so that in this respect, as well as in size, natural selection might

have secured and fixed any advantageous variation.

In the case of the European Kuku, the offspring of the foster parents are commonly ejected

from the nest within three days after the Kuku is hatched, and as the latter at this age

is in a most helpless condition, Mr. Gould was formerly inclined to believe that the

act of ejection was performed by the foster parents themselves.

But he has now received a trustworthy account of a young Kuku which was actually seen, while

still blind and not able even to hold up its own head, in the act of ejecting its foster

brothers.

One of these was replaced in the nest by the observer, and was again thrown out.

With respect to the means by which this strange and odious instinct was acquired, if it

were of great importance for the young Kuku, as is probably the case, to receive as much

food as possible soon after birth, I can see no special difficulty in its having gradually

acquired, during successive generations, the blind desire, the strength, and structure

necessary for the work of ejection, for those Kuku's which had such habits and structure

best developed would be the most securely reared.

The first step towards the acquisition of the proper instinct might have been mere unintentional

restlessness on the part of the young bird, when somewhat advanced in age and strength,

the habit having been afterwards improved, and transmitted to an earlier age.

I can see no more difficulty in this than in the unhatched young of other birds acquiring

the instinct to break through their own shells, or than in young snakes acquiring in their

upper jaws, as Owen has remarked, a transitory sharp tooth for cutting through the tough egg

shell.

For if each part is liable to individual variations at all ages, and the variations tend

to be inherited at a corresponding or earlier age, propositions which cannot be disputed,

then the instincts and structure of the young could be slowly modified as surely as those

of the adult, and both cases must stand or fall together with the whole theory of natural

selection.

Some species of Melothrus, a widely distinct genus of American birds, allied to our starlings,

have parasitic habits like those of the Kuku, and the species present an interesting

gradation in the perfection of their instincts.

The sexes of Melothrus Badius are stated by an excellent observer, Mr. Hudson, sometimes

to live promiscuously together in flocks and sometimes to pair.

They either build a nest of their own or seize on one belonging to some other bird, occasionally

throwing out the nestlings of the stranger.

They either lay their eggs in the nest thus appropriated, or oddly enough build one for

themselves on the top of it.

They usually sit on their own eggs and rear their own young, but Mr. Hudson says it is

probable that they are occasionally parasitic, for he has seen the young of the species following

old birds of a distinct kind and clamoring to be fed by them.

The parasitic habits of another species of Melothrus, the M, Boneriancis, are much more

highly developed than those of the last, but are still far from perfect.

This bird, as far as it is known, invariably lays its eggs in the nests of strangers,

but it is remarkable that several together sometimes commence to build an irregular untidy

nest of their own, placed in singular ill-adapted situations, as on the leaves of a large

thistle.

They never, however, as far as Mr. Hudson has ascertained, complete a nest for themselves.

They often lay so many eggs, from 15 to 20, in the same foster nest, that fewer none

can possibly be hatched.

They have, moreover, the extraordinary habit of pecking holes in the eggs, whether of their

own species or of their foster parents, which they find in the appropriated nests.

They drop also many eggs on the bare ground, which are thus wasted.

A third species, the M, Picorus of North America, has acquired instincts as perfect as those

of the cuckoo, for it never lays more than one egg in a foster nest, so that the young

bird is securely reared.

Mr. Hudson is a strong disbeliever in evolution, but he appears to have been so much struck

by the imperfect instincts of the Malawthrus Boneriancis that he quotes my words, and asks,

must we consider these habits, not as especially endowed or created instincts, but as small

consequences of one general law, namely, transition?

These birds, as has already been remarked, occasionally lay their eggs in the nests of

other birds.

This habit is not very uncommon with the Galanesi, and throws some light on the singular instinct

of the ostrich.

In this family several hen birds unite and lay first a few eggs in one nest and then in

another, and these are hatched by the males.

This instinct may probably be accounted for by the fact of the hens laying a large number

of eggs, but, as with the cuckoo, at intervals of two or three days.

The instinct, however, of the American ostrich, as in the case of the Malawthrus Boneriancis,

has not as yet been perfected, for a surprising number of eggs lie strewed over the plains,

so that in one day's hunting I picked up no less than 20 lost and wasted eggs.

Many bees are parasitic, and regularly lay their eggs in the nests of other kinds of

bees.

This case is more remarkable than that of the cuckoo, for these bees have not only had

their instincts but their structure modified in accordance with their parasitic habits,

for they do not possess the pollen-collecting apparatus which would have been indispensable

if they had stored up food for their own young.

Some species of Svegeti, wasp-like insects, are likewise parasitic, and M.

Fabre has lately shown good reason for believing that, although the tacite's nigra generally

makes its own burrow and stores it with paralyzed prey for its own larvae, yet that,

when this insect finds a burrow already made and stored by another's fex, it takes advantage

of the prize, and becomes for the occasion parasitic.

In this case, as with that of the Malawthrus or cuckoo, I can see no difficulty in natural

selection making an occasional habit permanent, if of advantage to the species, and if the

insect whose nest and stored food are feloniously appropriated, be not thus exterminated.

This remarkable instinct was first discovered in the Formica, Polyurges, Rufessens by Pierre

Hubert, a better observer even than his celebrated father.

This ant is absolutely dependent on its slaves, without their aid, the species would certainly

become extinct in a single year.

The males and fertile females do no work of any kind, and the workers or sterile females,

the most energetic and courageous in capturing slaves, do no other work.

They are incapable of making their own nests, or of feeding their own larvae.

When the old nest is found inconvenient and they have to migrate, it is the slaves which

determine the migration, and actually carry their masters in their jaws.

So utterly helpless are the masters, that when Hubert shut up 30 of them without a slave,

but with plenty of the food which they like best, and with their larvae and pupae to stimulate

them to work, they did nothing, they could not even feed themselves, and many perished

of hunger.

Hubert then introduced a single slave, Ffuska, and she instantly set to work, fed and

saved the survivors, made some cells intended the larvae, and put all to rights.

What can be more extraordinary than these well-assertained facts?

If we had not known of any other slave making ant, it would have been hopeless to speculate

how so wonderful an instinct could have been perfected.

In other species, Formika Sengini, was likewise first discovered by P.

Hubert to be a slave making ant.

This species is found in the southern parts of England, and its habits have been attended

to by Mr. F.

Smith, of the British Museum, to whom I am much indebted for information on this and other

subjects.

Although fully trusting to the statements of Hubert and Mr. Smith, I tried to approach the

subject in a skeptical frame of mind, as anyone may well be excused for doubting the existence

of so extraordinary an instinct as that of making slaves.

Hence, I will give the observations which I made in some little detail.

I opened 14 nests of F. Sengini, and found a few slaves in all.

Males and fertile females of the slave species, Ffuska, are found only in their own proper

communities, and have never been observed in the nests of F. Sengini.

The slaves are black and not above half the size of their red masters, so that the contrast

in their appearance is great.

When the nest is slightly disturbed, the slaves occasionally come out, and like their

masters are much agitated and defend the nest, when the nest is much disturbed, and the

larvae and pupae are exposed, the slaves work energetically together with their masters

in carrying them away to a place of safety.

Hence, it is clear that the slaves feel quite at home.

During the months of June and July, on three successive years, I watched for many hours

several nests in Syrian Sussex, and never saw a slave either leave or enter a nest.

As, during these months, the slaves are very few in number, I thought that they might

behave differently when more numerous, but Mr. Smith informs me that he is watched the

nests at various hours during May, June and August, both in Syrian Hampshire, and has

never seen the slaves, though present in large numbers in August either leave or enter

the nest.

Hence, he considers them as strictly household slaves.

The masters, on the other hand, may be constantly seen bringing in materials for the nest and

food of all kinds.

During the year 1860, however, in the month of July, I came across a community with an unusually

large stock of slaves, and I observed a few slaves mingled with their masters leaving

the nest, and marching along the same road to a tall scotch for tree, 25 yards distant,

which they ascended together, probably in search of aphids or coccye.

According to Hubert, who had ample opportunities for observation, the slaves in Switzerland

habitually work with their masters in making the nest, and they alone open and close the

doors in the morning and evening, and, as Hubert expressly states, their principal office

is to search for aphids.

This difference in the usual habits of the masters and slaves in the two countries

probably depends merely on the slaves being captured in greater numbers in Switzerland

than in England.

One day I fortunately witnessed a migration of aph, Sen Guinea from one nest to another,

and it was a most interesting spectacle to behold the masters carefully carrying their

slaves and their jaws instead of being carried by them, as in the case of aph.

Rufessens

Another day my attention was struck by about a score of the slave makers haunting the same

spot, and evidently not in search of food, they approached and were vigorously repulsed

by an independent community of the slave species, F. Fusca, sometimes as many as three of

these ants clinging to the legs of the slave making F. Sen Guinea.

The latter ruthlessly killed their small opponents and carried their dead bodies as food to their

nest, 29 yards distant, but they were prevented from getting any pupey to rear as slaves.

I then dug up a small parcel of the pupey of F. Fusca from another nest, and put them

down on a bear spot near the place of combat, they were eagerly seized and carried off by

the tyrants, who perhaps fancied that, after all, they had been victorious in their late combat.

At the same time I laid on the same place a small parcel of the pupey of another species,

F. Flaiva, with a few of these little yellow ants still clinging to the fragments of their

nest.

These species is sometimes, though rarely, made into slaves, as has been described by

Mr. Smith.

Although so small a species, it is very courageous, and I have seen it ferociously attack other

ants.

In one instance I found to my surprise an independent community of F. Flaiva under a stone beneath

a nest of the slave making F. Sen Guinea.

And when I had accidentally disturbed both nests, the little ants attacked their big neighbors

with surprising courage.

Now I was curious to ascertain whether F. Sen Guinea could distinguish the pupey of F. Fusca,

which they habitually make into slaves, from those of the little and furious F. Flaiva,

which they rarely capture.

And it was evident that they did at once distinguish them, for we have seen that they eagerly

and instantly seized the pupey of F. Fusca, whereas they were much terrified when they came

across the pupey, or even the earth from the nest, of F. Flaiva, and quickly ran away,

but in about a…

After of an hour, shortly after all the little yellow ants had crawled away, they took

heart and carried off the pupey.

One evening I visited another community of F. Sen Guinea, and found a number of these

ants returning home and entering their nests, carrying the dead bodies of F. Fusca, showing

that it was not a migration, and numerous pupey.

I traced a long file of ants burdened with booty, for about 40 yards back, to a very

thick clump of heath.

Whence I saw the last individual of F. Sen Guinea emerged, carrying a pupa, but I was

not able to find the desolated nest in the thick heath.

The nest, however, must have been close at hand.

For two or three individuals of F, Fusca were rushing about in the greatest agitation.

And one was perched motionless with its own pupa and its mouth on the top of a spray of

heath, an image of despair over its ravaged home.

Such are the facts, though they did not need confirmation by me, in regard to the wonderful

instinct of making slaves.

Let it be observed what a contrast the instinctive habits of F. Sen Guinea present with those

of the continental F. Rufessens.

The latter does not build its own nest, does not determine its own migrations, does not

collect food for itself or its young, and cannot even feed itself, it is absolutely dependent

on its numerous slaves.

For Mica Sen Guinea, on the other hand, possesses much fewer slaves, and in the early part

of the summer extremely few.

The masters determine when and where a new nest shall be formed, and when they migrate,

the masters carry the slaves.

Both in Switzerland and England the slaves seem to have the exclusive care of the larvae,

and the masters alone go on slave-making expeditions.

In Switzerland the slaves and masters work together, making and bringing materials for the

nest, both, but chiefly the slaves, tend and milk as it may be called, their aphids,

and thus both collect food for the community.

In England the masters alone usually leave the nest to collect building materials and food

food for themselves, their slaves and larvae, so that the masters in this country receive

much less service from their slaves than they do in Switzerland.

By what steps the instinct of F sanghini originated I will not pretend to conjecture.

But as ants which are not slave makers, will, as I have seen, carry off pupae of other

species, if scattered near their nests, it is possible that such pupae originally stored

as food might become developed, and the foreign ants thus unintentionally reared would then

follow their proper instincts, and do what work they could.

If their presence proved useful to the species which had seized them, if it were more advantageous

to the species, to capture workers than to procreate them, the habit of collecting pupae, originally

for food, might by natural selection be strengthened and rendered permanent for the very different

purpose of raising slaves.

When the instinct was once acquired, if carried out to a much less extent even than in our

British eff, sanghini, which, as we have seen, is less aided by its slaves than the same

species in Switzerland.

Natural selection might increase and modify the instinct, always supposing each modification

to be of use to the species, until an ant was formed as objectively dependent on its

slaves as is the formica rufesans.

I will not here enter on minute details on this subject, but will merely give an outline

of the conclusions at which I have arrived.

He must be a dull man who can examine the exquisite structure of a comb, so beautifully

adapted to its end, without enthusiastic admiration.

We hear from mathematicians that bees have practically solved a recondite problem, and

have made their cells of the proper shape to hold the greatest possible amount of honey,

with the least possible consumption of precious wax in their construction.

It has been remarked that a skillful workman, with fitting tools and measures, would find

it very difficult to make cells of wax of the true form, though this is affected by a

crowd of bees working in a dark hive.

Granting whatever instincts you please, it seems at first quite inconceivable how they

can make all the necessary angles and planes, or even perceive when they are correctly made.

But the difficulty is not nearly so great as it first appears, all this beautiful work

can be shown, I think, to follow from a few simple instincts.

I was led to investigate this subject by Mr. Waterhouse, who has shown that the form

of the cell stands in close relation to the presence of adjoining cells, and the following

view may, perhaps, be considered only as a modification of his theory.

Let us look to the great principle of gradation, and see whether nature does not reveal to

us her method of work.

At one end of a short series we have humble bees, which use their old cocoons to hold

honey, sometimes adding to them short tubes of wax, and likewise making separate and very

irregular rounded cells of wax.

At the other end of the series we have the cells of the hive bee, placed in a double layer,

each cell, as is well known, is in hexagonal prism, with the basal edges of its six sides

beveled so as to join an inverted pyramid of three roms.

These roms have certain angles, and the three which form the pyramidal base of a single

cell on one side of the comb, enter into the composition of the bases of three adjoining

cells on the opposite side.

In the series between the extreme perfection of the cells of the hive bee and the simplicity

of those of the humble bee, we have the cells of the Mexican melapona domestica, carefully

described and figured by Pierre Hubert.

The melapona itself is intermediate in structure between the hive and humble bee, but more

nearly related to the latter, it forms a nearly regular wax and comb of cylindrical cells,

in which the young are hatched, and, in addition, some large cells of wax for holding honey.

These latter cells are nearly spherical and of nearly equal sizes, and are aggregated

into an irregular mass.

But the important point to notice is that these cells are always made at that degree of

nearness to each other that they would have intersected or broken into each other if

the spheres had been completed, but this is never permitted.

The bee's building perfectly flat walls of wax between the spheres which thus tend to

intersect.

Hence, each cell consists of an outer spherical portion, and of two, three, or more flat surfaces,

according as the cell joins two, three, or more other cells.

When one cell rests on three other cells, which, from the spheres being nearly of the

same size, is very frequently and necessarily the case, the three flat surfaces are united

into a pyramid, and this pyramid, as Huber has remarked, is manifestly a gross imitation

of the three-sided pyramidal base of the cell of the hive bee.

As in the cells of the hive bee, so here, the three-plane surfaces in any one cell necessarily

enter into the construction of three adjoining cells.

It is obvious that the melepona saves wax, and what is more important, labor, by this

manner of building.

For the flat walls between the adjoining cells are not double, but are of the same thickness

as the outer spherical portions, and yet each flat portion forms a part of two cells.

Reflecting on this case, it occurred to me that if the melepona had made its spheres at

some given distance from each other, and had made them of equal sizes and had arranged

them symmetrically in a double layer, the resulting structure would have been as perfect

as the comb of the hive bee.

Accordingly I wrote to Professor Miller of Cambridge, and this geometry has kindly read

over the following statement, drawn up from his information, and tells me that it is strictly

correct if a number of equal spheres be described with their centers placed in two parallel

layers, with the center of each sphere at the distance of radius x-sqrt, 2, or radius

x-1.41421, or at some lesser distance, from the centers of the six surrounding spheres

in the same layer, and at the same distance from.

The centers of the adjoining spheres in the other and parallel layer, then, if planes

of intersection between the several spheres in both layers be formed, there will result

a double layer of hexagonal prisms united together by pyramidal bases formed of three

roms, and the roms and the sides of the hexagonal prisms will have every angle identically the

same with the best measurements which have been made of the cells of the hive bee.

But I hear from Professor Wyman, who has made numerous careful measurements, that the

accuracy of the workmanship of the bee has been greatly exaggerated, so much so, that whatever

the typical form of the cell may be, it is rarely, if ever, realized.

Hence we may safely conclude that, if we could slightly modify the instincts already possessed

by the melepona, and in themselves not very wonderful, this bee would make a structure

as wonderfully perfect as that of the hive bee.

We must suppose the melepona to have the power of forming her cells truly spherical, and

of equal sizes, and this would not be very surprising, seeing that she already does so

to a certain extent, and seeing what perfectly cylindrical burrows many insects make in wood,

apparently by turning round on a fixed point.

We must suppose the melepona to arrange her cells in level layers, as she already does

her cylindrical cells, and we must further suppose, and this is the greatest difficulty,

that she can somehow judge accurately at what distance to stand from her fellow laborers

when several are making their spheres.

But she is already so far enabled to judge of distance, that she always describes her

spheres so as to intersect to a certain extent, and then she unites the points of intersection

by perfectly.

Flat surfaces

By such modifications of instincts which in themselves are not very wonderful, hardly

more wonderful than those which guide a bird to make its nest, I believe that the hive

bee has acquired, through natural selection, her inimitable architectural powers.

But this theory can be tested by experiment.

Following the example of Mr.

Tegetmeyer

I separated two combs, and put between them along, thick, rectangular strip of wax, the bees

instantly began to excavate minute circular pits in it, and as they deepened these little

pits, they made them wider and wider until they were converted into shallow basins, appearing

to the eye perfectly true or parts of a sphere, and of about the diameter of a cell.

It was most interesting to observe that, wherever several bees had begun to excavate these

basins near together, they had begun their work at such a distance from each other that

by the time the basins had acquired the above-stated width, i.e. about the width of an ordinary

cell, and were in depth about one-sixth of the diameter of the sphere of which they formed

apart, the rims of the basins intersected or broke into each other.

As soon as this occurred, the bees ceased to excavate, and began to build up flat walls

of wax on the lines of intersection between the basins, so that each hexagonal prism was

built upon the scalloped edge of a smooth basin, instead of on the straight edges of a three

sided pyramid as in the case of ordinary cells.

I then put into the hive, instead of a thick, rectangular piece of wax, a thin and narrow,

knife-edged ridge, colored with vermilion.

The bees instantly began on both sides to excavate little basins near to each other, in

the same way as before, but the ridge of wax was so thin that the bottoms of the basins,

if they had been excavated to the same depth as in the former experiment, would have broken

into each other from the opposite sides.

The bees, however, did not suffer this to happen, and they stopped their excavations in

due time, so that the basins, as soon as they had been a little deepened, came to have

flat bases, and these flat bases, formed by thin little plates of the vermilion wax

left unnaught, were situated, as far as the eye could judge, exactly along the planes

of imaginary intersection between the basins on the opposite side of the ridge of wax.

In some parts, only small portions, in other parts, large portions of a rhombic plate

were thus left between the opposed basins, but the work, from the unnatural state of

things, had not been neatly performed.

The bees must have worked very nearly the same rate in circularly knowing away and deepening

the basins on both sides of the ridge of vermilion wax, in order to have thus succeeded in leaving

flat plates between the basins, by stopping work at the planes of intersection.

Considering how flexible thin wax is, I do not see that there is any difficulty in the

bees, whilst at work on the two sides of a strip of wax, perceiving when they have nought

the wax away to the proper thinness, and then stopping their work.

In ordinary combs it has appeared to me that the bees do not always succeed in working

at exactly the same rate from the opposite sides.

For I have noticed half completed roms at the base of a just commenced cell, which were

slightly concave on one side, where I suppose that the bees had excavated too quickly, and

convex on the opposed side where the bees had worked less quickly.

In one well marked instance, I put the comb back into the hive, and allowed the bees to

go on working for a short time, and again examined the cell, and I found that the rhombic

plate had been completed, and had become perfectly flat.

It was absolutely impossible, from the extreme thinness of a little plate, that they could

have affected this by nought away the convex side, and I suspect that the bees in such cases

stand in the opposed cells and push and bend the ductal and warm wax, which.

As I have tried is easily done, into its proper intermediate plane, and thus flatten it.

In the experiment of the ridge of vermilion wax we can see that, if the bees were to build

for themselves a thin wall of wax, they could make their cells of the proper shape, by standing

at the proper distance from each other, by excavating at the same rate, and by endeavoring

to make equal spherical hollows, but never allowing the spheres to break into each other.

Now bees, as may be clearly seen by examining the edge of a growing comb, do make a rough,

circumferential wall or rim all round the comb, and they nought this away from the opposite

sides, always working circularly as they deepen each cell.

They do not make the whole three-sided pyramidal base of any one cell at the same time, but

only that one rhombic plate which stands on the extreme growing margin, or the two plates,

as the case may be, and they never complete the upper edges of the rhombic plates, until

the hexagonal walls are commenced.

Some of these statements differ from those made by the justly celebrated elder Hubert,

but I am convinced of their accuracy.

And if I had space, I could show that they are conformable with my theory.

Hubert's statement that the very first cell is excavated out of a little parallel-sided

wall of wax, is not, as far as I have seen, strictly correct, the first commencement having

always been a little hood of wax, but I will not hear enter on details.

We see how important a part excavation plays in the construction of the cells, but it

would be a great error to suppose that the bees cannot build up a rough wall of wax in

the proper position, that is, along the plane of intersection between two adjoining spheres.

I have several specimens showing clearly that they can do this.

Even in the rude circumferential rim or wall of wax round a growing comb, flexures may

sometimes be observed, corresponding in position to the planes of the rhombic basal plates

of future cells.

But the rough wall of wax has an every case to be finished off, by being largely not

away on both sides.

The manner in which the bees build is curious, they always make the first rough wall from

10 to 20 times thicker than the excessively thin finished wall of the cell, which will

ultimately be left.

We shall understand how they work, by supposing Mason's first to pile up a broad ridge of cement,

and then to begin cutting it away equally on both sides near the ground, till a smooth

very thin wall is left in the middle.

The Mason's always piling up the cutaway cement, and adding fresh cement on the summit

of the ridge.

We shall thus have a thin wall steadily growing upward, but always crowned by a gigantic

coping.

From all the cells, both those just commenced and those completed, being thus crowned by

a strong coping of wax, the bees can cluster and crawl over the cone without injuring the

delicate hexagonal walls.

These walls, as Professor Miller has kindly ascertained for me, very greatly in thickness,

being, on an average of 12 measurements made near the border of the cone, one-slash 352

of an inch in thickness, whereas the basal rhomboidal plates are thicker, nearly in the proportion

of 3 to 2, having a mean thickness, from 21 measurements, of one-slash 229 of an inch.

By the above singular manner of building, strength is continually given to the cone, with

the utmost ultimate economy of wax.

It seems at first to add to the difficulty of understanding how the cells are made, that

a multitude of bees all work together, one bee after working a short time at one cell

going to another, so that, as Huber has stated, a score of individuals work even at the

commencement of the first cell.

I was able practically to show this fact, by covering the edges of the hexagonal walls

of a single cell, or the extreme margin of the circumferential rim of a growing cone,

with an extremely thin layer of melted vermilion wax, and I invariably found that the color

was most delicately diffused by the bees, as delicately as a painter could have done it

with his brush, by atoms of the colored wax having been taken from the spot on which

it had been placed, and worked into the growing edges of the cells all round.

The work of construction seems to be a sort of balance struck between many bees, all instinctively

standing at the same relative distance from each other, all trying to sweep equal spheres,

and then building up, or leaving undenodd, the planes of intersection between these spheres.

It was really curious to note in cases of difficulty, as when two pieces of combed at an angle,

how often the bees would pull down and rebuild in different ways the same cell, sometimes

recurring to a shape which they had at first rejected.

When bees have a place on which they can stand in their proper positions for working,

for instance, on a slip of wood, placed directly under the middle of a comb growing downwards,

so that the comb has to be built over one face of the slip.

In this case the bees can lay the foundations of one wall of a new hexagon, in its strictly

proper place, projecting beyond the other completed cells.

It suffices that the bees should be enabled to stand at their proper relative distances

from each other and from the walls of the last completed cells, and then, by striking

imaginary spheres, they can build up a wall intermediate between two adjoining spheres,

but, as far as I have seen, they never know a way and finish off the angles of a cell

till a large part both of that cell and of the adjoining cells has been built.

This capacity in bees of laying down under certain circumstances a rough wall in its

proper place between two just commenced cells is important, as it bears on a fact, which

seems at first subversive of the foregoing theory, namely, that the cells on the extreme

margin of wasp combs are sometimes strictly hexagonal, but I have not space here to enter

on this subject.

Nord is there seen to me any great difficulty in a single insect, as in the case of a queen

wasp, making hexagonal cells, if she were to work alternately on the inside and outside

of two or three cells commenced at the same time, always standing at the proper relative

distance from the parts of the cells just begun, sweeping spheres or cylinders, and building

up intermediate planes.

As natural selection acts only by the accumulation of slight modifications of structure or instinct,

each profitable to the individual under its conditions of life, it may reasonably be

asked, how a long and graduated succession of modified architectural instincts, all tending

towards the present perfect plan of construction, could have profited the progenitors of the

hive bee.

I think the answer is not difficult, cells constructed like those of the bee or the wasp

gain in strength, and save much in labor and space, and in the materials of which they

are constructed.

With respect to the formation of wax, it is known that bees are often hard pressed to

get sufficient nectar, and I am informed by Mr.

Tegetmeyer that it has been experimentally proved that from twelve to fifteen pounds

of dry sugar are consumed by a hive of bees for the secretion of a pound of wax, so that

a prodigious quantity of fluid nectar must be collected and consumed by the bees in a hive

for the secretion of the wax necessary for the construction of their combs.

Moreover, many bees have to remain idle for many days during the process of secretion.

A large store of honey is indispensable to support a large stock of bees during the winter,

and the security of the hive is known mainly to depend on a large number of bees being

supported.

Hence the saving of wax by largely saving honey, and the time consumed in collecting the

honey, must be an important element of success any family of bees.

Of course the success of the species may be dependent on the number of its enemies, or

parasites, or on quite distinct causes, and so be altogether independent of the quantity

of honey which the bees can collect.

But let us suppose that this latter circumstance determined, as it probably often has determined,

whether a bee allied to our humble bees could exist in large numbers in any country.

And let us further suppose that the community lived through the winter, and consequently required

a store of honey.

There can in this case be no doubt that it would be an advantage to our imaginary humble

bee if a slight modification of her instincts led her to make her wax and cells near together,

so as to intersect.

A little, for a wall in common even to two adjoining cells would save some little labor and wax.

Hence, it would continually be more and more advantageous to our humble bees, if they

were to make their cells more and more regular, nearer together, and aggregated into a mass,

like the cells of the melepona.

For in this case a large part of the bounding surface of each cell would serve to bound

the adjoining cells, and much labor and wax would be saved.

Again, from the same cause, it would be advantageous to the melepona, if she were to make her cells

closer together, and more regular in every way than it present, for then, as we have seen,

the spherical surfaces would wholly disappear and be replaced by plain surfaces, and the

melepona would make a comb as perfect as that of the hive bee.

Beyond this stage of perfection in architecture, natural selection could not lead, for the comb

of the hive bee, as far as we can see, is absolutely perfect in economizing labor and wax.

Thus, as I believe, the most wonderful of all known instincts that of the hive bee,

can be explained by natural selection having taken advantage of numerous, successive,

slight modifications of simpler instincts, natural selection having, by slow degrees,

more and more perfectly led the bees to sweep equal spheres at a given distance from each

other in a double layer, and to build up and excavate the wax along the planes of intersection.

The bees, though of course, know more knowing that they swept their spheres at one particular

distance from each other, than they know what are the several angles of the hexagonal

prisms and of the basal rhombic plates.

The mode of power of the process of natural selection having been the construction of

cells of due strength and of the proper size and shape for the larvae, this being affected

with the greatest possible economy of labor and wax, that individual swarm which thus made

the best cells with.

Least labor and least waste of honey in the secretion of wax, having succeeded best and having

transmitted their newly acquired economical instincts to new swarms, which in their turn

will have had the best chance of succeeding in the struggle for existence.

It has been objected to the foregoing view of the origin of instincts that the variations

of structure and of instinct must have been simultaneous and accurately adjusted to each

other, as a modification in the one without an immediate corresponding change in the other

would have been fatal.

The force of this objection rests entirely on the assumption that the changes in the instincts

and structure are abrupt.

To take as an illustration the case of the larger titmouse, Paris Major, alluded to in

a previous chapter, this bird often holds the seeds of the hue between its feet on a branch,

and hammers with its beak till it gets at the kernel.

Now what special difficulty would there be in natural selection preserving all the slight

individual variations in the shape of the beak, which were better and better adapted

to break open the seeds, until a beak was formed?

As well constructed for this purpose is that of the nut hatch, at the same time that habit,

or compulsion, or spontaneous variations of taste, led the bird to become more and more

of a seed eater.

In this case the beak is supposed to be slowly modified by natural selection, subsequently

too, but in accordance with, slowly changing habits or taste, but let the feet of the

titmouse vary and grow larger from correlation with the beak, or from any other unknown cause.

It is not improbable that such larger feet would lead the bird to climb more and more until

it acquired the remarkable climbing instinct and power of the nut hatch.

In this case a gradual change of structure is supposed to lead to changed instinctive

habits.

To take one more case, few instincts are more remarkable than that which leads the swift

of the eastern islands to make its nest holy of unspissated saliva.

Some birds build their nests of mud, believed to be moistened with saliva, and one of the

swifts of North America makes its nest, as I have seen, of sticks agglutinated with saliva,

and even with flakes of this substance.

Is it then very improbable that the natural selection of individual swifts, which secreted

more and more saliva, should at last produce a species with instincts leading it to neglect

other materials and to make its nest exclusively of unspissated saliva?

And so in other cases, it must, however, be admitted that in many instances we cannot

conjecture whether it was instinct or structure which first varied.

No doubt many instincts of very difficult explanation could be opposed to the theory of natural

selection, cases, in which we cannot see how an instinct could have originated, cases,

in which no intermediate gradations are known to exist, cases of instincts of such trifling

importance, that they could hardly have been acted on by natural selection, cases of instincts

almost identically the same in animals so remote in the scale of nature that we cannot

account for their similarity by inheritance.

From a common progenitor, and consequently must believe that they were independently acquired

through natural selection.

I will not hear enter on these several cases, but will confine myself to one special difficulty,

which at first appeared to me insuperable, and actually fatal to the whole theory.

I allude to the neuters or sterile females in insect communities, for these neuters often

differ widely in instinct and in structure from both the males and fertile females, and

yet, from being sterile, they cannot propagate their kind.

The subject well deserves to be discussed at great length, but I will here take only

a single case that of working or sterile ants.

How the workers have been rendered sterile is a difficulty, but not much greater than

that of any other striking modification of structure, for it can be shown that some

insects and other articulate animals in a state of nature occasionally become sterile,

and if such insects had been social, and it had been profitable to the community that

a number should have been annually born capable of work, but incapable of procreation, I can

see no a special difficulty in this having been affected through.

Natural selection

But I must pass over this preliminary difficulty.

The great difficulty lies in the working ants differing widely from both the males and

the fertile females in structure, as in the shape of the thorax, and in being destitute

of wings and sometimes of eyes, and in instinct.

As far as instinct alone is concerned, the wonderful difference in this respect between

the workers and the perfect females would have been better exemplified by the hive bee.

If a working ant or other neuter insect had been an ordinary animal, I should have unhesitatingly

assumed that all its characters had been slowly acquired through natural selection, namely,

by individuals having been born with slight profitable modifications, which were inherited

by the offspring, and that these again varied and again were selected, and so onwards.

But with the working ant we have an insect differing greatly from its parents, yet absolutely

sterile, so that it could never have transmitted successively acquired modifications of structure

or instinct to its progeny.

It may well be asked how it is possible to reconcile this case with the theory of natural

selection.

First, let it be remembered that we have innumerable instances, both in our domestic productions

and in those in a state of nature, of all sorts of differences of inherited structure which

are correlated with certain ages and with either sex.

We have differences correlated not only with one sex, but with that short period when the

reproductive system is active, as in the nuptial plumage of many birds, and in the hooked jaws

of the male salmon.

We have even slight differences in the horns of different breeds of cattle in relation

to an artificially imperfect state of the male sex, for oxen of certain breeds have longer

horns than the oxen of other breeds, relatively to the length of the horns in both the bulls

and cows of these same breeds.

Hence, I can see no great difficulty in any character becoming correlated with the sterile

condition of certain members of insect communities.

The difficulty lies in understanding how such correlated modifications of structure could

have been slowly accumulated by natural selection.

This difficulty, though appearing insuperable, is lessened, or, as I believe, disappears

when it is remembered that selection may be applied to the family, as well as to the individual,

and may thus gain the desired end.

Breeders of cattle wish the flesh and fat to be well marbled together.

An animal thus characterized has been slaughtered, but the breeder has gone with confidence to

the same stock and has succeeded.

Such faith may be placed in the power of selection that a breed of cattle, always yielding oxen

with extraordinarily long horns, could, it is probable, be formed by carefully watching

which individual bulls and cows, when matched, produced oxen with the longest horns, and

yet no one ox would ever have propagated its kind.

Here is a better and real illustration, according to M.

Verlet, some varieties of the double annual stock, from having been long and carefully selected

to the right degree, always produce a large proportion of seedlings bearing double and

quite sterile flowers, but they likewise yield some single and fertile plants.

These latter, by which alone the variety can be propagated, may be compared with the

fertile male and female ants, and the double sterile plants with the neuters of the same

community.

As with the varieties of the stock, so with social insects, selection has been applied

to the family, and not to the individual, for the sake of gaining a serviceable end.

Hence, we may conclude that slight modifications of structure or of instinct, correlated

with the sterile condition of certain members of the community, have proved advantageous,

consequently the fertile males and females have flourished, and transmitted to their fertile

offspring attendancy to produce sterile members with the same modifications.

This process must have been repeated many times, until that prodigious amount of difference

between the fertile and sterile females of the same species has been produced which we

see in many social insects.

But we have not as yet touched on the acme of the difficulty, namely, the fact that the

neuters of several ants differ, not only from the fertile females in males, but from each

other, sometimes to an almost incredible degree, and are thus divided into two or even three

casts.

The casts, moreover, do not generally graduate into each other, but are perfectly well-defined,

being as distinct from each other as are any two species of the same genus, or rather

as any two genera of the same family.

Thus, in esoton, there are working in soldier neuters, with jaws and instincts extraordinarily

different.

In cryptoceros, the workers of one cast alone carry a wonderful sort of shield on their

heads, the use of which is quite unknown.

In the Mexican Mermicosistus, the workers of one cast never leave the nest, they are

fed by the workers of another cast, and they have an enormously developed abdomen which

secretes a sort of honey, supplying the place of that excreted by the aphids, or the.

Domestic cattle as they may be called, which are European ants guard and in prison.

It will indeed be thought that I have an overweaning confidence in the principle of natural

selection.

And I do not admit that such wonderful and well-established facts at once annihilate the theory.

In the simpler case of neuter insects all of one cast, which, as I believe, have been

rendered different from the fertile males and females through natural selection, we may

conclude from the analogy of ordinary variations, that the successive, slight, profitable modifications

did not first arise in all the neuters in the same nest, but in some few alone, and that

by the survival of the communities with females which produced most neuters having the advantageous

modification, all the neuters.

Ultimately came to be thus characterized.

According to this view we ought occasionally to find in the same nest neuter insects,

presenting gradations of structure, and this we do find, even not rarely, considering

how few neuter insects out of Europe have been carefully examined.

Mr.

F

Smith has shown that the neuters of several British ants differ surprisingly from each other

in size and sometimes in color, and that the extreme forms can be linked together by individuals

taken out of the same nest, I have myself compared perfect gradations of this kind.

It sometimes happens that the larger or the smaller-sized workers are the most numerous,

or that both large and small are numerous, while those of an intermediate size are scanty

in numbers.

Her Micah Flava has larger and smaller workers, with some few of intermediate size, and,

in this species, as Mr. F.

Smith has observed that the larger workers have simple eyes, Ocelei, which, though small,

can be plainly distinguished, whereas the smaller workers have their Ocelei rudimentary.

Having carefully dissected several specimens of these workers, I can affirm that the eyes

are far more rudimentary in the smaller workers than can be accounted for merely by their

proportionately lesser size, and I fully believe, though I dare not assert so positively,

that the workers of intermediate size have their Ocelei in an exactly intermediate condition.

So that here we have two bodies of sterile workers in the same nest, differing not only

in size, but in their organs of vision, yet connected by some few members in an intermediate

condition.

I may digress by adding that if the smaller workers had been the most useful to the community,

for those males and females had been continually selected, which produced more and more of

the smaller workers, until all the workers were in this condition, we should then have had

a species of ant with neuters in nearly the same condition as those of Mermica.

For the workers of Mermica have not even rudiments of Ocelei, though the male and female ants

of this genus have well developed Ocelei.

I may give one other case, so confidently did I expect occasionally to find gradations

of important structures between the different casts of neuters in the same species, that

I gladly availed myself of Mr. F.

Smith's offer of numerous specimens from the same nest of the driver ant, enama, of West

Africa.

The reader will perhaps best appreciate the amount of difference in these workers by my

giving, not the actual measurements, but a strictly accurate illustration.

The difference was the same as if we were to see a set of workmen building a house, of

whom many were five feet four inches high, and many sixteen feet high.

But we must in addition suppose that the larger workmen had heads four instead of three

times as big as those of the smaller men, and jaws nearly five times as big.

The jaws, moreover, of the working ants of the several sizes differed wonderfully in

shape, and in the form and number of the teeth.

But the important fact for us is that, though the workers can be grouped into casts of different

sizes, yet they graduate insensibly into each other, as does the widely different structure

of their jaws.

I speak confidently on this latter point as Sir J.

Lubbock made drawings for me, with the camera lucida, of the jaws which I dissected from

the workers of the several sizes.

Mr.

Bates, in his interesting naturalist on the Amazon's, has described analogous cases.

With these facts before me, I believe that natural selection, by acting on the fertile

ants or parents, could form a species which should regularly produce neuters, all of large

size with one form of jaw, or all of small size with widely different jaws, or lastly.

And this is the greatest difficulty, one set of workers of one size and structure, and

simultaneously another set of workers of a different size and structure, a graduated

series having first been formed, as in the case of the driver.

And then the extreme forms having been produced in greater and greater numbers, through

the survival of the parents which generated them, until none with an intermediate structure

were produced.

An analogous explanation has been given by Mr.

Wallace, of the equally complex case, of certain male and butterflies regularly appearing

under two or even three distinct female forms, and by Fritz Muller, of certain Brazilian

crustaceans likewise appearing under two widely distinct male forms.

But this subject need not here be discussed.

I have now explained how, I believe, the wonderful fact of two distinctly defined casts of

sterile workers existing in the same nest, both widely different from each other and

from their parents, has originated.

We can see how useful their production may have been to a social community of ants, on

the same principle that the division of labor is useful to civilized man.

Ants, however, work by inherited instincts and by inherited organs or tools, while man

works by acquired knowledge and manufactured instruments.

But I must confess, that, with all my faith and natural selection, I should never have

anticipated that this principle could have been efficient in so high a degree, had not

the case of these neuter insects led me to this conclusion.

I have, therefore, discussed this case, at some little but holy insufficient length,

in order to show the power of natural selection.

And likewise because this is by far the most serious special difficulty which my theory

has encountered.

The case, also, is very interesting, as it proves that with animals, as with plants,

any amount of modification may be affected by the accumulation of numerous, slight, spontaneous

variations, which are in any way profitable, without exercise or habit having been brought

into play.

For peculiar habits, confined to the workers of sterile females, however long they might

be followed, could not possibly affect the males and fertile females, which alone leave

descendants.

I am surprised that no one has advanced this demonstrative case of neuter insects, against

the well-known doctrine of inherited habit, as advanced by Lamarck.

I have endeavored in this chapter briefly to show that the mental qualities of our domestic

animals vary, and that the variations are inherited.

Still more briefly I have attempted to show that instincts vary slightly in a state of nature.

No one will dispute that instincts are of the highest importance to each animal.

Therefore, there is no real difficulty, under changing conditions of life, in natural

selection accumulating to any extent slight modifications of instinct which are in any

way useful.

In many cases habit or use and disuse have probably come into play.

I do not pretend that the facts given in this chapter strengthen in any great degree my

theory, but none of the cases of difficulty, to the best of my judgment, annihilate it.

On the other hand, the fact that instincts are not always absolutely perfect and are

liable to mistakes, that no instinct can be shown to have been produced for the good

of other animals, though animals take advantage of the instincts of others, that the canon

in natural history, of natural non-facet saltum, is applicable to instincts as well as

to corporeal structure, and is plainly explicable on the foregoing views, but is otherwise inexplicable,

all tend to corroborate the theory of natural selection.

This theory is also strengthened by some few other facts in regard to instincts, as by

that common case of closely allied, but distinct these species, when inhabiting distant parts

of the world and living under considerably different conditions of life, yet often retaining

yet often retaining nearly the same instincts. For instance, we can understand, on the principle

of inheritance, how it is that the thrush of tropical South America lines its nest with mud,

in the same peculiar manner as does our British thrush, how it is that the hornbills of Africa and

India have the same extraordinary instinct of plastering up and imprisoning the females in a

hole in a tree, with only a small hole left in the plaster through which the males feed them

and their young one hatched, how it is that the male wrens. Troglidites of North America build

caulknests to roost in like the males of our kitty wrens, a habit wholly unlike that of any other

known bird. Finally, it may not be a logical deduction, but to my imagination it is far more

satisfactory to look at such instincts as the young cuckoo ejecting its foster brothers,

ants making slaves, the larvae of echnomonity feeding within the live bodies of caterpillars,

not as specially endowed or created instincts, but as small consequences of one general law

leading to the advancement of all organic beings, namely, multiply, vary, let the strongest live

and the weakest die.