being the true parents of the colony. The state-apartments are
situated in the centre of the hive, and are strictly guarded by
workers. Both king and queen are wingless, and are of larger size than
their subjects. The queen engages in a continual round of maternal
duties, the eggs deposited by the sovereign-mother being at once
seized by the workers and conveyed to special or "nursery cells,"
where the young are duly tended and brought up. Once a year, at the
beginning of the rainy season, winged termites appear in the hive as
developments of certain of the eggs laid by the queen-termite. These
latter are winged males and females (Fig. 1, 1), the two sexes being
present in equal numbers. Some of these, after shedding their wings,
become the founders--kings and queens--of new communities, the
privilege of sex being thus associated with the important and
self-denying work of perpetuating the species or race in time. Sooner
or later--a termite family takes about a year to grow--a veritable
exodus of the young winged termites takes place; and just before this
emigration movement occurs, a hive may be seen to be stocked with
"termites" of all castes and in all stages of development. The workers
never exhibit a change of form during their growth; the soldiers begin
to differ from the workers in the possession of larger heads and jaws;
whilst the young which are destined to become the winged males and
females are distinguished by the early possession of the germs of
wings which become larger as the skin is successively moulted. Amongst
the bees, blind Huber supposed that an ordinary or neuter egg develops
into a queen bee if the larva is fed upon a special kind of
food--"royal food," as it is called. Although some entomological
authorities differ from Huber with regard to the exact means by which
the queen bee is reared and specialized from other larvae, yet the
opinion thus expressed possesses a large amount of probability.
Whatever may be the exact method or causes through or by which the
queen bee is developed, Mr. Bates strongly asserts that the
differences between the soldiers and worker termites are distinctly
marked from the egg. This latter observer maintains that the
difference is not due to variations in food or treatment during their
early existence, but is fixed and apparent from the beginning of
development. This fact is worthy of note, for it argues in favor of
the view that if, as is most likely, the differences between the
grades of termites may have originally been produced by natural
selection or other causes, these differences have now become part and
parcel of the constitution of these insects, and are propagated by the
ordinary law of heredity. Thus acquired conditions have become in time
the natural "way of life" of these animals.
Mr. Bates has also placed on record the noteworthy fact that a species
of termites exists in which the members of the soldier class did not
differ at all from the workers "except in the fighting instinct." This
observation, if it may be used at all in elucidation of the origin of
the curious family life of these insects, points not to sudden
creation, but to gradual acquirement and modification as having been
the method of development of the specialized classes and castes in
termite society. Firstly, we may thus regard the beginnings of the
further development of a colony to appear in a nest in which workers
and soldiers are alike, as stated by Mr. Bates. Then, through the
practice of the fighting instinct, we may conceive that natural
selection would be competent to adapt the soldiers more perfectly for
their duties militant, by developing the head and jaws as offensive
weapons. Possibly, were our knowledge of the termites at all complete,
we should meet with all stages in the development and specialization
of the various grades of society amongst these insects--at least the
present state of our knowledge would seem to lead to such a conclusion
as being much more feasible than the theory of special or sudden
creation of the peculiarities of the race. It is admitted that the
termites are in many respects inferior in structure to the bees and
wasps, whilst the white ants themselves are the superiors of their own
order--that of the _Neuroptera_. That the termites preceded the bees
and their neighbors, the common ants, in the order of development of
social instincts, is a conclusion supported by the fact that the
_Neuroptera_ form the first group of insects which are preserved to us
in the "records of the rocks." Fossil _Neuroptera_ occur in the
Devonian rocks of North America; the first traces of insects allied to
the bees and wasps being geologically more recent, and appearing in
the oolitic strata. The occurrence of high social instincts in an
ancient group of insects renders the repetition of these instincts in
a later and higher group the less remarkable. The observation,
however, does not of necessity carry with it any actual or implied
connection between the termites and their higher neighbors, although,
indeed, the likeness between the social life of the two orders of
insects might warrant such a supposition.
[Illustration: FIG. 3. RED, OR HORSE-ANT (_Formica rufa_.) a, male; b,
female, winged; c, worker.]
The common ants (Fig. 3), the study of which in their native haunts is
a matter of no great difficulty, and one which will fully reward the
seeking mind, like the termites, possess three grades of individuals.
In a single ant's nest more than One female may be found, the ants
differing from the bees in this respect; and in the nests of some
species of ants there are apparently "soldiers" resembling the
military termites in the possession of large heads and well-developed
jaws. Very amazing differences are to be perceived amongst the various
species of ants. Differences in size are of common occurrence, but
naturalists have actually succeeded in classifying ants in a general
way, by differences in manner and disposition. We know, for example,
that the horse-ant (_Formica rufa_, Fig. 3) has little _individual_
intelligence, but is extremely socialistic, and moves and acts _en
masse_ with precision and tact. Another species (_F. fusca_) is timid
and retiring. _F. pratensis_ is a revengeful creature, since it
"worries" its fallen foes; _F. cinerea_ is bold and audacious; others
are termed "thieves" and "cowards"; some are phlegmatic; and to
complete the list of failings and traits which are human enough in
character, one species is said to present an invariable greediness as
its prevailing characteristic. The common ants resemble the termites
in the general details of their life. We see in an ant's nest the same
restless activity of the workers, the same earnest attention paid to
the young and pupae, the same instinct in shielding the young from
danger, and much the same general routine of development. Certain
rather special, and it may be said extraordinary, habits of ants may,
however, demand notice before we attempt a brief survey of their
instincts at large. Few readers are unacquainted with the _Aphides_,
or plant-lice, those little wingless insects which infest our plants
and herbs in myriads in summer. It is a fact now well known to
naturalists, and first placed on record by Huber, that between the
ants and plant-lice, relations of a very friendly and, as far as the
ants are concerned, advantageous character have become established.
Ants have been observed to stroke the tips of the bodies of the
plant-lice with their antennae, this act causing the plant-lice to
exude drops of a clear, sweet fluid, of which the ants are extremely
enamoured. The ants would thus appear to habitually "milk" their
insect-neighbors, and, as far as observation goes, some ants seem not
merely to keep the plant-lice in their nests so as to form a veritable
dairy establishment, but also to make provision in the future by
securing the eggs of the aphides, and bringing up the young as we rear
calves.
[Illustration: FIG 4. APPLE APHIS (_Eriosoma Mali_).]
That the relation between the ants and plant-lice are of very stable
kind is proved by the interesting remarks of Mr. Darwin, who "removed
all the ants from a group of about a dozen aphides on a dock-plant,
and prevented their attendance during several hours." Careful watching
showed that the plant-lice after this interval did not excrete the
sweet fluid. Mr. Darwin then stroked the plant-lice with a hair,
endeavoring thus to imitate the action of the ant's feelers, but not a
single plant-louse seemed disposed to emit the secretion. Thereafter a
single ant was admitted to their company, the insect, in Mr. Darwin's
words, appearing, "by its eager way of running about, to be well aware
what a rich flock it had discovered." The ant first stroked one aphis
and then another, each insect excreting a drop of the sweet juice "as
soon as it felt the antennae;" and "even the quite young aphides
behaved in this manner, showing that the action was instinctive, and
not the result of experience." If, as Mr. Darwin remarks, it is a
convenience for the aphides to have the sweet secretion removed, and
that "they do not excrete solely for the food of the ants," the
observation does not in any degree lessen the curious nature of the
relationship which has become established between the ants and their
neighbors, or the interesting features in ant life which have
inaugurated and perpetuated the habit.
Not less remarkable are the "slave-making" instincts of certain
species of ants. It may be safely maintained that the slave-making
habit forms a subject of more than ordinary interest not merely to
naturalists but to metaphysicians given to speculate on the origin and
acquirement of the practices of human existence. Pierre Huber, son of
the famous entomologist, was the first to describe the slave-making
instincts in a species (_Polyergus rufescens_) noted for its
predaceous instincts, and subsequent observations have shown that
other species participate in these habits. _Polyergus_ is thoroughly
dependent on slaves. Without these bonds-men it is difficult to see
how the ants could exist. Huber tells us that the workers of this
species perform no work save that of capturing slaves. Use and wont,
and the habit of depending entirely on their servitors, have produced
such changes in the structure of the ants that they are unable to help
themselves. The jaws of these ants are not adapted for work; they are
carried by their slaves from an old nest to a new one; and, more
extraordinary still, they require to be fed by their slaves, even with
plenty of food close at hand. Out of thirty of these ants placed by
Huber in a box, with some of their larvae and pupae, and a store of
honey, fifteen died in less than two days of hunger and of sheer
inability to help themselves. When, however, one of their slaves was
introduced, the willing servitor "established order, formed a chamber
in the earth, gathered together the larvae, extricated several young
ants that were ready to quit the condition of pupae, and preserved the
life of the remaining Amazons." It must be noted that there are very
varying degrees in the dependence of the ant-masters on their slaves.
In the recognition of this graduated scale of relationship and
dependence, indeed, will be found the clue to the acquirement of this
instinct. The horse-ant (_Formica rufa_) will carry off the larvae and
pupae of other ants _for food_, and it sometimes happens that some of
these captives, spared by their cannibal neighbors, will grow up in
the nest of their captor. A well-known ant, the _Formica sanguinea_,
found in the South of England, is however, a true slave-making
species, but exhibits no such utter dependence on its servitors as
does _Polyergus_. The slave-making habit is not only typically
developed in the _Sanguineas_, but the bearing of the captives to
their masters indicate a degree of relationship and organization such
as could hardly be conceived to exist outside human experience. The
_Sanguineas_ make periodical excursions, and, like a powerful
predatory clan, carry off the pupae or chrysalides of a neighboring
species, _F. fusca_. Thus the children of the latter race are born
within the nest of their captors in an enslaved condition. As slaves
"born and bred," so to speak, they fall at once into the routine of
their duties, assist their masters in the work of the nest, and tend
and nurse the young of the family. The slaves, curiously enough in
this instance, are black in color, whilst the masters are twice the
size of the servitors, and are red in color, and that the slaves are
true importations is proved by the fact that males and females of the
slave species are never developed within the nest of the masters, but
only within those of their own colonies. The slaves in this instance
rarely leave the nest, the masters foraging for food, and employing
their captives in household work, as it were; whilst, when the work of
emigration occurs, the masters carry the slaves in their mouths like
household goods and chattels, instead of being carried by them, as in
the case of _Polyergus_.
Mr. Darwin gives an interesting account of the different attitudes
exhibited by the _Sanguineas_ toward species of ants other than the
black race from which their slaves are usually drawn. A few pupae of
the yellow ant (_F. flava_), a courageous and pugnacious little
species, were placed within the reach of the slave-making
_Sanguineas_. A like chance presented with the pupae of their slave
race was eagerly seized, and the chrysalides carried off. The pupae of
the yellow ants, however, were not merely left untouched, but the
slave-makers exhibited every system of terror and alarm at the sight
of the chrysalides of their yellow neighbors. Such an instance
demonstrates the existence not merely of perception but also of the
memory of past experience, probably of not over agreeable kind, of
encounters with the yellow ants. When, on the contrary, a nest of the
slaves is attacked, the _Sanguineas_ are both bold and wary. Mr.
Darwin traced a long file of _Sanguineas_ for forty yards backward to
a clump of heath, whence he perceived the last of the invaders
marching homeward with a slave pupa in its mouth. Two or three
individuals of the attacked and desolate nest were rushing about in
wild despair, and "one," adds Mr. Darwin, "was perched motionless,
with its own pupa in its mouth, on the top of a spray of heath, an
image of despair over its ravaged home." The picture thus drawn is not
the less eloquent because its subject is drawn from lower existence;
although the pains and sorrows of ant life may not legitimately be
judged by the standard of human woe.
The explanation of the slave-making instinct in ants begins with the
recognition of the fact that many ants, not slave-makers, store up
pupae of other species for food. If we suppose that some of the pupae,
originally acquired through a cannibal-like instinct, came to maturity
within the nest of their captors, and in virtue of their own inherited
instincts engaged in the work of the hive, we may conceive of a
rational beginning of the slave-making instinct. If, further, the
captors learned to appreciate the labors of their captives, as
lightening their own work, the habit of collecting pupae as slaves
might succeed and supersede that of collecting them for food. In any
case, we should require to postulate on the part of the slave-makers a
degree of instinct altogether unusual in insects, or, indeed, in
higher animals; but that such instinct is developed in ants other than
slave-makers admits of no dispute. The strengthening, through
repetition, of a habit useful to the species may thus be credited with
the beginning of the practice of slavery amongst ants; whilst special
circumstances--such as the number of the slaves as compared with the
number of masters--would tend to develop a greater or less degree of
dependence of the captors or their servitors.
Huber, for instance, informs us that the _Fusca_-slaves of the
_Sanguineas_ of Switzerland work with their masters in building the
nest; they close and open the doors of the hive; but their chief
office appears to be that of hunting for plant-lice. In England, on
the contrary, the slaves are strictly household servants, rarely
venturing out of doors. Such differences depend most probably on the
fact that a greater number of slaves occur in Swiss than in English
nests, and they may therefore be employed in a wider range of duties
on the Continent than at home. A fewer number of slaves, a greater
aptitude on the part of the slaves for their duties, the inability of
the masters to perform the duties of the slaves--each or all of these
causes combined would serve to increase the value of the servitors,
and at the same time to reduce the independence of the masters.
This increase of the value of the slaves as active factors in the ant
community might at length proceed to such extremes as we see
exemplified in the _Polyergus_, already referred to--a race which has
become literally unable to feed itself, and to discharge the simplest
duties of ant existence, and whose actual life is entirely spent in
marauding expeditions on the nests of its neighbors.
The subject of the general intelligence of ants, and of their ability
to adapt themselves to awkward and unusual circumstances, may be
briefly touched upon by way of conclusion.
Between the reason and intelligence of higher animals and the
"instinct" of ants there is unquestionably a great gulf fixed. I make
this statement unhesitatingly, notwithstanding that I should no more
willingly attempt to define "instinct" than to give an exact
definition of "insanity." In the latter case one may make the
definition so limited as practically to exclude all save one class of
cases, or so wide as to include even the judge on the bench. In the
case of instinct, the rigid definition of one authority might cause us
to regard it as the exclusive property of lower forms and as having no
relationship whatever with the mental powers of higher beings; or, on
the other hand, as being but a modified form of, or in some respects
identical with, these very powers. We know too little respecting the
so-called "automatic" powers and ways, even of higher animals, to
dogmatize regarding the acts of lower animals, but we may safely
assume that one apparent ground or distinction between instinct and
reason may be found in the common incompetence of instinct to move out
of the beaten track of existence, and in the adaptation of reason,
through the teachings of experience, to new and unwonted
circumstances. Let Dr. Carpenter speak as an authority on such a
subject. "The whole nervous system of invertebrated animals, then, may
be regarded as ministering entirely to _automatic_ action; and its
highest development, as in the class of insects, is coincident with
the highest manifestations of the 'instinctive' powers, which, when
carefully examined, are found to consist entirely in movements of the
excito-motor and sensori-motor kinds. (The terms '_excito-motor_' and
'_sensori-motor_' are applied to nervous actions resulting in
movements of varying kinds, and produced by impressions made on
nervous centres, but without any necessary emotion, reason, or
consciousness.) When we attentively consider the habits of these
animals, we find that their actions, though evidently adapted to the
attainment of certain ends, are very far from evincing a _designed_
adaptation on the part of the beings that perform them.... For, in the
first place, these actions are invariably performed in the same manner
by all the individuals of a species, when the conditions are the same;
and thus are obviously to be attributed rather to a uniform impulse
than to a free choice, the most remarkable example of this being
furnished by the economy of bees, wasps, and other 'social' insects,
in which every individual of the community performs its appropriated
part with the exactitude and method of a perfect machine. The very
perfection of the adaptation, again, is often of itself a sufficient
evidence of the unreasoning character of the beings which perform the
work; for if we attribute it to their own intelligence, we must admit
that this intelligence frequently equals, if it does not surpass, that
of the most accomplished Human Reasoner."
Appealing to the most recent observations on ants, we may find
evidence of the truth of Dr. Carpenter's statements, whilst at the
same time we may also detect instances of the development of higher
powers which are hardly to be classed as "automatic," and which, in
certain species (as in the _Ecitons_, charmingly described by Mr. Belt
in "The Naturalist in Nicaragua"), may be said to be elevated above
the common instincts of the race. Dr. Henry Maudsley has also well
summed up the relationship of the acts of these insects to the acts of
higher forms, and to new adaptations when he says: "I do not say that
the ant and the bee are entirely destitute of any power of adaptation
to new experiences in their lives--that they are, in fact, purely
organized machines, acting always with unvarying regularity; it would
appear, indeed, from close observation, that these creatures do
sometimes discover in their actions traces of a sensibility to strange
experiences, and of corresponding adaptations of movements. We cannot,
moreover, conceive how the remarkable instincts which they manifest
can have been acquired originally, except by virtue of some such
power. But the power in them now is evidently of a rudimentary kind,
and must remain so while they have not those higher nerve-centres in
which the sensations are combined into ideas, and perceptions of the
relations of things are acquired. Granting, however, that the bee or
ant has these traces of adaptive action, it must be allowed that they
are truly rudiments of functions, which in the supreme nerve-centres
we designate as reason and volition. Such a confession might be a
trouble to a metaphysical physiologist, who would thereupon find it
necessary to place a metaphysical entity behind the so-called
instincts of the bee, but can be no trouble to the inductive
physiologist--he simply recognizes an illustration of a physiological
diffusion of properties, and of the physical conditions of primitive
volition, and traces in the evolution of mind and its organs, as in
the evolution of other functions and their organs, a progressive
specialization and increasing complexity."
The recently published experiments of Sir John Lubbock show that ants
under certain circumstances are both stupid and devoid of any
intelligent comprehension in the way of surmounting difficulties; but
this distinguished observer has also shown that as regards
communication between ants, and in the regulation of the ordinary
circumstances of their lives, these insects evince a high degree of
intelligence, and exhibit instincts of a very highly developed kind.
Still, making every allowance for the development of extraordinary
mental power in some species of ants, there can be little doubt of the
purely automatic beginnings and nature of most, if not all, of the
acts of ordinary ant existence. The young ant, wasp, or bee, will
begin its labors and discharge them as perfectly at the beginning of
its existence as a perfect insect, as at the close of life. Here there
is no experience, no tuition, no consciousness, no reason, and no
powers save such as have been transferred to the insect as a mere
matter of heredity and derivation from its ancestors, who lived by an
unconscious rule of thumb, so to speak. It is very hard at first to
convince one's self, when watching an ant's nest, that intelligence
and consciousness play little or no part in the apparently intelligent
operation of these insects. But to assume the contrary would be to
maintain that the insect stands on an equal footing to man himself,
and for such a supposition there is neither lawful ground nor
sympathy. The marvellous instinct of lower life stands on a platform
of its own, has its own phases of development, and probably its own
unconscious way of progress. The higher reason and intellect of
humanity similarly possesses its own peculiar standard, rate, and
method of culture. A man may seek and find in the ways of lower
existence not merely a lesson in the ordering of his existence, but
some comfort, also, in the thought that the progress of lower nature
is not unknown in the domain of human hopes and aspirations.
[Illustration: RETURN OF ANTS AFTER A BATTLE.]
THE WILD LLAMA
(FROM A JOURNAL OF RESEARCHES, ETC.)
BY CHARLES DARWIN.
[Illustration: HEAD OF GUANACO.]
The guanaco, or wild Llama, is the characteristic quadruped of the
plains of Patagonia; it is the South American representative of the
camel in the East. It is an elegant animal in a state of nature, with
a long slender neck and fine legs. It is very common over the whole of
the temperate parts of the continent, as far south as the islands near
Cape Horn. It generally lives in small herds of from half a dozen to
thirty in each; but on the banks of the St. Cruz we saw one herd which
must have contained at least five hundred.