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Ants and Some Other Insects

An Inquiry into

The Psychic Powers of these Animals

With an Appendix on

The Pecularities of Thetr Olfactory Sense

By

Dr. August Forel
Late Professor of Psychiatry at ua: University of Zurich

Translated from the German
By
Prof. William Morton Wheeler
American Museum of Natural History, New York

Chicago
The Open Court Publishing Company

London
Kegan Paul, Trench, Triibner & Co, Ltd.

1904

YS Ve

aS ia

ANTS AND SOME OTHER INSECTS.

HEN discussing the ant-mind, we must consider that these
small animals, on the one hand, differ very widely from our-
selves in organisation, but on the other hand, have come, through
so-called convergence, to possess in the form of a social common-

wealth a peculiar relationship to us. My subject, however, requires

the discussion of so many complicated questions that I am com-

pelled to assume acquaintance with the work of others, especially

the elements of psychology, and in addition the works of P. Huber,

Wasmann, von Buttel-Reepen, Darwin, Romanes, Lubbock, my
Fourmis de la Suisse, and many others. Since the functions ot the
sense-organs constitute the basis of comparative psychology, I
must also refer to a series of articles entitled ‘‘Sensations des In-
sectes”’ which I have recently published (1g00-1g01) in the R7v7sta
de Biologia Generale, edited by Dr. P. Celesia. In these papers I
have defined my position with respect to various authors, especially
Plateau and Bethe.

Very recently Bethe, Uexkull, and others have denied the ex-
istence of psychic powers in invertebrate animals. They explain
the latter as reflex-machines, and take their stand on the ground of
the so-called psycho-physical parallelism for the purpose of demon-
strating our inability to recognise mental qualities in these animals.
They believe, however, that they can prove the mechanical regu-
larity of behavior, but assume unknown forces whenever they are
left in the lurch in their explanations. They regard the mind as
first making its appearance in the vertebrates, whereas the old Car-
tesians regarded all animals, in contradistinction to man, as mind-

less (unconscious) machines.

2 ANTS AND SOME OTHER INSECTS.

The Jesuit father E. Wasmann and von Buttel-Reepen are
willing, on the other hand, to accept the inductive inference from
analogy as a valid scientific method. Like Lubbock, the lecturer
and others, they advocate a comparative psychology of the inverte-
brates and convincingly demonstrate the existence of psychic facul-
ties in these animals. 'Wasmann, however,-puts a very low esti-
mate on the mental powers of the higher vertebrates and, in my
opinion, improperly, denies to them any ability of drawing infer-
ences from experience when in the presence of new conditions (this
alone he designates as intelligence); he believes that man alone
possesses an immortal soul (independent of natural laws?) in addi-
tion to the animal mind.

It is necessary, first of all, to arrive at some common under-
standing concerning the obscure notion ‘‘psychic” in order that
we may avoid logomachy, and carrying on theology in the sense of
Goethe’s Mephistopheles. Two concepts are confounded in an
obscure manner in the word ‘‘psychic”’: first, the abstract concept
of introspection, or subjectivism, i. e., observation from within,
which every person knows only, and can know only, in and by him-
self. For this let us reserve the term ‘‘consciousness.’? Second,
the ‘‘activity” of the mind or that which determines the contents
of the field of consciousness, This has been included without fur-
ther ado with consciousness in the wider sense, and thence has
arisen the confusion of regarding consciousness as an attribute of
the mind. In another place I have designated the molecular wave
of activity of the neural elements as ‘‘neurocyme.”

We cannot speak of the consciousness of human beings other
than ourselves without drawing an inference from analogy; quite
as little ought we to speak of a consciousness of forgotten things.
The field of our consciousness is constantly changing. Things ap-
pear in it and disappear from it. Memory, through association,
enables us to recall, more or less directly and with more or less diffi-
culty, things which appear to be momentarily absent from con-
sciousness. Moreover, both the experience of self-observation and
the phenomena of hypnotism teach us experimentally that many
things of which we seem to be unconscious, are nevertheless pres-

ANTS AND SOME OTHER INSECTS. 3

ent in consciousness or have been. Indeed, certain sense-impres-

, sions remain, at the moment of their occurrence, unconscious so
far as our ordinary consciousness or superconsciousness is con-
cerned, although they can be subsequently recalled into conscious-
ness by suggestion. Whole chains of brain-activities, (dreams,
somnambulism, or secondary consciousness) seem ordinarily to be
excluded from the superconsciousness, but may subsequently be
associated by suggestion with the remembered contents of con-
sciousness. In all these cases, therefore, what seems to be uncon-
scious is after all proved to be conscious. The above-mentioned
phenomena have frequently led to mystical interpretations, but
they are explainable on a very simple assumption. Let us assume
—and this is quite in harmony with observation—that the fields of
the introspectively conscious brain-activities are limited by so-called
association or dissociation processes, i. e., that we are unable ac-

- tively to bring them all into connection at the same time, and that
therefore all that seems to us unconscious has also in reality a con-

- sciousness, in other words, a subjective reflex, then the following
results: Our ordinary waking consciousness or superconsciousness
is merely an inner subjective reflex of those activities of attention
which are most intimately connected with one another, i. e., of the
more intensively concentrated maxima of our cerebral activities
during waking. There exist, however, other consciousnesses, partly
forgotten, partly only loosely or indirectly connected with the con-
tents of the superconsciousness, in contradistinction to which these
may be designated as subconsciousness. They correspond to other
less concentrated or otherwise associated cerebral activities. We
are bound to assume the existence of still more remotely intercon-
nected subconsciousnesses for the infra-cortical (lower) brain-
centers, and so on.

It is easy to establish the fact that the maximum of our psychic
activity, namely, attention, passes every moment from one percep-
tion or thought to another. These objects of attention, as visual
or auditory images, will-impulses, feelings or abstract thoughts,
come into play—and of this there is no doubt—in different brain-
regions or neuron-complexes. We can therefore compare attention

4 ANTS AND SOME OTHER INSECTS.

to a functional macula /utea wandering in the brain, or with a wan-
dering maximal intensity of neurocymic activity. But it is quite as
satisfactorily established that other psychic phenomena external to
attention are likewise present in consciousness, though in a feebler
condition. Finally, it is well known that all that has been in con-
sciousness—even that which is now more, now less, forgotten—is
included in the psychic, i. e., in the contents of consciousness. On
superficial consideration this appears to satisfy theoretical require-

ments. But in fact and in truth there are innumerable processes

of which we are feebly conscious for only a scarcely appreciable
instant and which anon disappear from consciousness. Here and
not in the strong and repeated ‘‘psychomes”—lI beg your indul-
gence for this word, with which I would for the sake of brevity
designate each and every psychic unit—are we to seek the transi-
tion from the conscious to the apparently unconscious. Even in
this case, however, the feeble condition of consciousness is only
apparent, because the inner reflex of these processes can merely
echo faintly in the field of a strongly diverted attention. This,
therefore, in no wise proves that such half conscious processes are
in and for themselves so feebly represented in consciousness, since
a flash of attention is sufficient subsequently to give them definite
shape in consciousness. Only in consequence of the diversion of
the attention do they lose more and more their connection with the
chain of intensity-maxima which, under ordinary circumstances,
constitute the remembered contents of our superconsciousness.
The more feebly, however, they are bound to the latter, with the
more difficulty are such half-conscious processes later associated
anew through memory with the dominant chain. Of such a nature
are all dreams, all the subordinate circumstances of our lives, all
automatised habits, all instincts. But if there exists between the
clearly conscious and the unconscious, a half-conscious brain-life,
whose consciousness appears to us so feeble merely on account of
the deviation of our ordinary train of memories, this is an unequiv-
ocal indication that a step further on the remaining connection
would be completely severed, so that we should no longer have the
right to say that the brain-activities thus fading away nebulously

7
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ANTS AND SOME OTHER INSECTS. 5

from our superconsciousness do not have consciousness in and for
themselves. For the sake of brevity and simplicity we will ascribe
subconsciousness to these so-called unconscious brain-processes.

If this assumption is correct—and all things point in this di-
rection—we are not further concerned with consciousness. It does
not at all exist as such, but only through the brain-activity of which
it is the inner reflex. With the disappearance of this activity, con-
sciousness disappears. When the one is complicated, the other,
too, is complicated. When the one is simple, the other is corre-
spondingly simple. If the brain-activity be dissociated, conscious-
ness also becomes dissociated. Consciousness is only an abstract
concept, which loses all its substance with the falling away of
‘fconscious”’ brain-activity. The brain-activity reflected in the
mirror of consciousness appears therein subjectively as a summary
synthesis, and the synthetical summation grows with the higher
complications and abstractions acquired through habit and prac-
tice, so that details previously conscious (e. g., those involved in
the act of reading) later become subconscious, and the whole takes
on the semblance of a psychical unit.

Psychology, therefore, cannot restrict itself merely to a study
of the phenomena of our superconsciousness by means of intro-
spection, for the science would be impossible under.such circum-
stances. Everybody would have only his own subjective psychol-
ogy, after the manner of the old scholastic spiritualists, and would
therefore be compelled to doubt the very existence of the external
world and his fellow-men. Inference from analogy, scientific in-
duction, the comparison of the experiences of our five senses, prove
to us the existence of the outer world, our fellow-men and the psy-
chology of the latter. They also prove to us that there is such a
thing as comparative psychology, a psychology of animals. Finally
our own psychology, without reference to our brainsactivity, is an
incomprehensible patchwork full of contradictions, a patchwork
which above all things seems to contradict the law of the conser-
vation of energy.

It follows, furthermore, from these really very simple reflections
that a psychology that would ignore brain-activity, is a monstrous

6 ANTS AND SOME OTHER INSECTS.

impossibility. The contents of our superconsciousness are con-
tinually influenced and conditioned by subconscious brain-activi-
ties. Without these latter it can never be understood.~ On the
other hand, we understand the full value and the ground of the
complex organisation of our brain only when we observe it in the
inner light of consciousness, and when this observation is supple-
mented by a comparison of the consciousness of our fellow-men as
this is rendered possible for us through spoken and written lan-
guage by means of very detailed inferences from analogy. The
mind must therefore be studied simultaneously from within and
from without. Outside ourselves the mind can, to be sure, be
studied only through analogy, but we are compelled to make use of
this the only method which we possess.

Some one has said that language was given to man not so
much for the expression as for the concealment of his thoughts. It
is also well known that different men in all honesty attribute very
different meanings to the same words. A savant, an artist, a
peasant, a woman, a wild Wedda from Ceylon, interpret the same
words very differently. Even the same individual interprets them
differently according to his moods and their context. Hence it
follows that to the psychologist and especially to the psychiatrist—
and as such I am here speaking—the mimetic expression, glances
and acts of a man often betray his true inner being better than his
spoken language. Hence also the attitudes and behavior of ani-
mals have for us the value of a ‘‘language,” the psychological im-
portance of which must not be underestimated. Moreover, the
anatomy, physiology and pathology of the animal and human brain
have yielded irrefutable proof that our mental faculties depend on
the quality, quantity, and integrity of the living brain and are one
with the same. It is just as impossible that there should exist a
human brain without a mind, as a mind without a brain, and to
every normal or pathological change in the mental activity, there
corresponds a normal or pathological change of the neurocymic ac-
tivity of the brain, i. e., of its nervous elements. Hence what we
perceive introspectively in consciousness is cerebral activity.

As regards the relation of pure psychology (introspection) to

ANTS AND SOME OTHER INSECTS. 7

the physiology of the brain (observation of brain-activity from with-
out), we shall take the theory of identity for granted so long as it
is in harmony with the facts. The word identity, or monism, im-
plies that every psychic phenomenon is the same real thing as the
molecular or neurocymic activity of the brain-cortex coinciding
with it, but that this may be viewed from two standpoints. The
phenomenon alone is dualistic, the thing itself is monistic. - If this
were otherwise there would result from the accession of the purely
psychical to the physical, or cerebral, an excess of energy which
would necessarily contradict the law of the conservation of energy.
Such a contradiction, however, has never been demonstrated and
would hold up to derision all scientific experience. In the mani-
festations of our brain-life, wonderful as they undoubtedly are,
there is absolutely nothing which contradicts natural laws and jus-
tifies us in postulating the existence of a mythical, supernatural
‘< psyche.”

On this account I speak of monistic identity and not of psycho-
physical parallelism. A thing cannot be parallel with itself. Of
course, psychologists of the modern school, when they make use of
this term, desire merely to designate a supposed parallelism of
phenomena without prejudice either to monism or dualism. Since,
however, many central nervous processes are accessible neither to
physiological nor to psychological observation, the phenomena ac-
cessible to us through these two methods of investigation are not
in the least parallel, but separated from one another very unequally
by intermediate processes. Moreover, inasmuch as the dualistic
hypothesis is scientifically untenable, it is altogether proper to
start out from the hypothesis of identity.

It is as clear as day that the same activity in the nervous sys-
tem of an animal, or even in my own nervous system, observed by
myself, first by means of physiological methods from without, and
second, as reflecting itself in my consciousness, must appear to me
to be totally different, and it-would indeed be labor lost to try to
convert the physiological into psychological qualities or vice versa.
We cannot even convert one psychological quality into another, so
far as the reality symbolised by both is concerned; e. g., the tone,

8 ANTS AND SOME OTHER INSECTS.

the visual and tactile sensation, which a uniform, low, tuning-fork
vibration produces on our three corresponding senses. Neverthe-
less, we may infer inductively that it is the same reality, the same
vibration which is symbolised for us in these three qualitatively
and totally different modes; i. e., produces in us these three differ-

ent psychical impressions which cannot be transformed into one.

another. These impressions depend on activities in different parts
of the brain and are, of course, as such actually different from one
another in the brain. We speak of psycho-physiological identity
only when we mean, on the one hand, the cortical neurocyme which
directly conditions the conscious phenomena known to us, on the
other hand, the corresponding phenomena of consciousness.

And, in fact, a mind conceived as dualistic could only be de-
void of energy or energy-containing. If it be conceived as devoid
of energy (Wasmann), 1. e., independent of the laws of energy,
we have arrived at a belief in the miraculous, a belief which coun-
tenances the interference with and arbitrary suspension of the laws
of nature. If it be conceived as energy-containing, one is merely
playing upon words, for a mind which obeys the law of energy is
only a portion of the cerebral activities arbitrarily severed from its
connections and dubbed ‘‘psychic essence,” only that this may be
forthwith discredited. Energy can only be transformed qualita-
tively, not quantitatively. A mind conceived as dualistic, if sup-
posed to obey the law of energy, would have to be transformed
completely into some other form of energy. But then it would no
longer be dualistic, i. e., no longer essentially different from the
brain-activities.

Bethe, Uexkull, and others would require us to hold fast to
the physiological method, because it alone is exact and restricts it-
self to what can be weighed and measured. This, too, is an error
which has been refuted from time immemorial. Only pure mathe-
matics is exact, because in its operations it makes use solely of
equations of abstract numbers. The concrete natural sciences can
never be exact and are as unable to subsist without the inductive
method of inference from analogy as a tree without its roots. Bethe
and Uexkull do not seem to know that knowledge is merely rela-

ee

ANTS AND SOME OTHER INSECTS. 9

tive. They demand absolute exactitude and cannot understand
that such a thing is impossible. Besides, physiology has no reason
to pride itself upon the peculiar exactitude of its methods and re-
sults. |

Although we know that our whole psychology appears as the
activity of our cerebrum in connection with the activities of more
subordinate nerve-centers, the senses and the muscles, nevertheless
for didactic purposes it may be divided into the psychology of cog-
nition, of feeling and volition. Relatively speaking, this subdivi-
sion has an anatomico-physiological basis. Cognition depends, in
the first instance, on the elaboration of sense-impressions by the
brain; the will represents the psycho- or cerebrofugal resultants of
cognition and the feelings together with their final transmission to
the muscles. The feelings represent general conditions of excita-
tion of a central nature united with elements of cognition and with
cerebrofugal impulses, which are relatively differentiated and re-
fined by the former, but have profound hereditary and phylogenetic
origins and are relatively independent. There is a continual inter-
action of these three groups of brain-activities upon one another.
Sense-impressions arouse the attention; this necessitates move-
ments; the latter produce new sense-impressions and call for an
active selection among themselves. Both occasion feelings of pleas-
ure and pain and these again call forth movements of defense,
flight, or desire, and bring about fresh sense-impressions, etc.
Anatomically, at least, the sensory pathways to the brain and their
cortical centers are sharply separated from the centers belonging
to the volitional pathways to the muscles. Further on in the cere-
brum, however, all three regions merge together in many neurons
of the cortex. 3

Within ourselves, moreover, we are able to observe in the three
above-mentioned regions all varieties and degrees of so-called
psychic dignity, from the simplest reflex to the highest mental
manifestations. The feelings and impulses connected with self-
preservation (hunger, thirst, fear) and with reproduction (sexual
love and its concomitants) represent within us the region of long-
inherited, profoundly phyletic, fixed, instinct-life. These instincts

Io ANTS AND SOME OTHER INSECTS.

are nevertheless partially modified and partly kept within due
bounds through the interference of the higher cerebral activities.
The enormous mass of brain-substance, which in man stands in no
direct relation to the senses and musculature, admits not only of
an enormous storing up of impressions and of an infinite variety of
motor innervations, but above all, of prodigious combinations of
these energies among themselves through their reciprocal activities
and the awakening of old, so-called memory images through the
agency of new impressions. In contradistinction to the compul-
sory, regular activities of the profoundly phyletic automatisms, I
have used the term ‘‘plastic” to designate those combinations and
individual adaptations which depend on actual interaction in the
activities of the cerebrum. Its loftiest and finest expression is the
plastic imagination, both in the province of cognition and. in the
province of feeling, or in both combined. In the province of the
will the finest plastic adaptability, wedded to perseverance and
firmness, and especially when united with the imagination, yields
that loftiest mental condition which gradually brings to a conclu-
sion during the course of many years decisions that have been long
and carefully planned and deeply contemplated. Hence the plas-
tic gift of combination peculiar to genius ranks much higher than
any simpler plastic adaptability.

The distinction between automatism and plasticity in brain-
activity is, however, only a relative one and one of degree. In the
most different instincts which we are able to influence through our
cerebrum, i. e., more or less voluntarily, like deglutition, respira-
tion, eating, drinking, the sexual impulse, maternal affection, jeal-
ousy, we observe gradations between compulsory heredity and plas-
tic adaptability, yes, even great individual fluctuations according
to the intensity of the corresponding hereditary predispositions.

Now it is indisputable that the individual Pithecanthropus or
allied being, whose cerebrum was large enough gradually to con-
struct from onomatopceas, interjections and the like, the elements
of articulate speech, must thereby have acquired a potent means of
exploiting his brain. Man first fully acquired this power through
written language. Both developed the abstract concept symbolised

ANTS AND SOME OTHER INSECTS. II

by words, as a higher stage in generalisation. All these things
give man a colossal advantage, since he is thereby enabled to stand
on the shoulders of the written encyclopzdia of his predecessors.
This is lacking in all animals living at the present time. Hence, if
we would compare the human mind with the animal mind, we must
turn, not to the poet or the savant, but to the Wedda or at any rate
to the illiterate. These people, like children and animals, are very
simple and extremely concrete in their thinking. The fact that it
is impossible to teach a chimpanzee brain the symbols of language
proves only that it is not sufficiently developed for this purpose.
‘But the rudiments are present nevertheless. Of course the ‘‘lan-
guage” of parrots is no language, since it symbolises nothing. On
the other hand, some animals possess phyletic, i. e., hereditarily
and instinctively fixed cries and gesture, which are as instinctively
understood. Such instinctive animal languages are also very widely
distributed and highly developed among insects, and have been
fixed by heredity for each species. Finally it is possible to develop
by training in higher animals a certain mimetic and acoustic conven-
tional language-symbolism, by utilising for this purpose the pecu-
liar dispositions of such species. Thus it is possible to teacha
dog to react in a particular manner to certain sounds or signs, but
it is impossible to teach a fish or an ant these things. The dog
comprehends the sign, not, of course, with the reflections of human
understanding, but with the capacity of a dog’s brain. And it is,
to be sure, even more impossible to teach its young an accomplish-
ment so lofty for its own brain as one which had to be acquired by
training, than for the Wedda or even the negro to transmit his ac-
quired culture by his own impulse. Even the impulse to do this is
entirely lacking. Nevertheless, every brain that is trained by man
is capable of learning and profiting much from the experience of
its own individual life. And one discovers on closer examination
that even lower animals may become accustomed to some extent to
one thing or another, and hence trained, although this does not
amount to an understanding of conventional symbols.

In general we may say, therefore, that the central nervous sys-

tem operates in two ways: automatically and plastically.

I2 ANTS AND SOME OTHER INSECTS.

The so-called reflexes and their temporary, purposefully adap-
tive, but hereditarily stereotyped combinations, which respond
always more or less in the same manner to the same stimuli, con-
stitute the paradigm of automatic activities. These have the de-
ceptive appearance of a ‘‘machine” owing to the regularity of their
operations. But a machine which maintains, constructs, and re-
produces itself is not a machine. In order to build such a machine
we should have to possess the key of life, i. e., the understanding
of the supposed, but by no means demonstrated, mechanics of liv-
ing protoplasm. Everything points to the conclusion that the in-
stinctive automatisms. have been gradually acquired and heredita-
rily fixed by natural selection and other factors of inheritance. But
there are also secondary automatisms or habits which arise through
the frequent repetition of plastic activities and are therefore espe-
cially characteristic of man’s enormous brain-development.

In all the psychic provinces of intellect, feeling, and will,
habits follow the constant law of perfection through repetition.
Through practice every repeated plastic brain-activity gradually
becomes automatic, becomes ‘‘second nature,” i. e., similar to in-
stinct. Nevertheless instinct is not inherited habit, but phylogenet-
ically inherited intelligence which has gradually become adapted
and crystalised by natural selection or by some other means.

Plastic activity manifests itself, in general, in the ability of the
nervous system to conform or adapt itself to new and unexpected
conditions and also through its faculty of bringing about internally
new combinations of neurocyme. Bethe calls this the power of
modification. But since, notwithstanding his pretended issue with
anthropomorphism, he himself continually proceeds in an anthro-
pomorphic spirit and demands human ratiocination of animals, if
they are to be credited with plasticity (power of modification),—he
naturally overlooks the fact that the beginnings of plasticity are
primordial, that they are in fact already present in the Ameeba,
which adapts itself to its environment. Nor is this fact to be con-
jured out of the world by Loeb’s word ‘‘tropisms.”

Automatic and plastic activities, whether simple or complex,
are merely relative antitheses. They grade over into each other,

—eE—— Oe ee

ANTS AND SOME OTHER INSECTS. 13

e. g., in the formation of habits but also in instincts. In their ex-
treme forms they resemble two terminal branches of a tree, but
they may lead to similar results through so-called convergence of
the conditions of life (slavery and cattle-keeping among ants and
men). The automatic may be more easily derived from the plastic
activities than wice versa. One thing is established, however: since
a tolerably complicated plastic activity admits of many possibilities
of adaptation in the individual brain, it requires much more nerv-
ous substance, many more neurons, but has more resistances to
overcome in order to attain a complicated-result. The activities
of an Amceba belong therefore rather to the plasticity of living
molecules, but not as yet to that of codperating nerve-elements; as
cell-plasticity it should really be designated as ‘‘ undifferentiated.”
There are formed in certain animals specially complex automatisms,
or instincts, which require relatively little plasticity and few neu- -
rons. In others, on the contrary, there remains relatively consider- —
able nerve-substance for individual plasticity, while the instincts
are less complicated. Other animals, again, have little besides the
lower reflex centers and are extremely poor in both kinds of com-
plex activities. Still others, finally, are rich in both. Strong so-
called ‘‘hereditary predispositions” or unfinished instincts consti-
tute the phylogenetic transitions between both kinds of activity
and are of extraordinarily high development in man.

Spoken and especially written language, moreover, enable man
to exploit his brain to a wonderful extent. This leads us to under-
estimate animals. Both in animals and man the true value of the
brain is falsified by training, i. e., artificially heightened. We
overestimate the powers of the educated negro and the trained dog
and underestimate the powers of the illiterate individual and the
wild animal.

I beg your indulgence for this lengthy introduction to my sub-

11f I expressly refrain from accepting the premature and unjustifiable identifi-
cation of cell-life with a ‘‘machine,” I nevertheless do not share the so-called vital-
istic views. It is quite possible that science may sometime be able to produce liv-
ing protoplasm from inorganic matter. The vital forces have undoubtedly origi-
nated from physico-chemical forces. But the ultimate nature of the latter and of
the assumed material atoms is, of course, metaphysical, i. e., unknowable.

I4 ANTS AND SOME OTHER INSECTS.

ject, but it seemed necessary that we should come to some under-
standing concerning the validity of comparative psychology. My
further task now consists in demonstrating to you what manner of ©
psychical faculties may be detected in insects. Of course, I shall
select in the first place the ants as the insects with which I am
most familiar. Let us first examine the brain of these animals.

In order to determine the psychical value of a central nervous
system it is necessary, first, to eliminate all the nerve-centers which
subserve the lower functions, above the immediate innervation of
the muscles and sense-organs as first centers. The volume of such
neuron-complexes does not depend on the intricacy of mental work
but on the number of muscle-fibres concerned in it, the sensory
surfaces, and the reflex apparatus, hence above all things on the

‘size of the animals. Complex instincts already require the inter-
vention of much more plastic work and for this purpose such nerve-
centers alone would be inadequate.

A beautiful example of the fact that complex mental combina-
tions require a large nerve-center dominating the sensory and mus-
cular centers is furnished by the brain of the ant. The ant-colony
commonly consists of three kinds of individuals: the queen, or
female (largest), the workers which are smaller, and the males
which are usually larger than the workers. The workers excel in
complex instincts and in clearly demonstrable mental powers
(memory, plasticity, etc.). These are much less developed in the
queens. The males are incredibly stupid, unable to distinguish
friends from enemies and incapable of finding their way back to
their nest. Nevertheless the latter have very highly developed
eyes and antennae, i. e., the two sense-organs which alone are con-
nected with the brain, or supra-oesophageal ganglion and enable
them to possess themselves of the females during the nuptial flight.
No muscles are innervated by the supra-oesophageal ganglion.
These conditions greatly facilitate the comparison of the percep-
tive organs, 1. e., of the brain (corpora pedunculata) in the three
sexes. This is very large in the worker, much srraller in the fe-
male, and almost vestigial in the male, whereas the optic and

olfactory lobes are very large in the latter. The cortical portion

ANTS AND SOME OTHER INSECTS. 15

of the large worker brain is, moreover, extremely rich in cellular
_ elements. In this connection I would request you to glance at the
figures and their explanation.

Very recently, to be sure, it has come to be the fashion to un-
derestimate the importance of brain-morphology in psychology and
even in nerve-physiology. But fashions, especially such absurd
ones as this, should have no influence on true investigation. Of
course, we should not expect anatomy to say what it was never in-
tended to say.

In ants, injury to the cerebrum leads to the same results as in-
jury to the brain of the pigeon.

In this place I would refer you for a fuller account of the de-
tails of sensation and the psychic peculiarities of insects to my
more extended work above mentioned: Sensations des Insectes.

It can be demonstrated that insects possess the senses of
sight, smell, taste, and touch. The auditory sense is doubtful.
Perhaps a sense of touch modified for the perception of delicate
vibrations may bear a deceptive resemblance to hearing. A sixth

sense has nowhere been shown to occur. A photodermatic sense,
- modified for light-sensation, must be regarded as a form of the tac-
tile sense. It occursin many insects. This sense is in no respect
of an optic nature. In aquatic insects the olfactory and gustatory
senses perhaps grade over into each other somewhat (Nagel), since
both perceive chemical substances dissolved in the water.

The visual sense of the facetted eyes is especially adapted for
seeing movements, i. e., for perceiving relative changes of position
in the retinal image. In flight it is able to localise large spatial
areas admirably, but must show less definite contours of the ob-
jects than our eyes. The compound eye yields only a single up-
right image (Exner), the clearness of which increases with the
number of facets and the convexity of the eye. Exner succeeded
in photographing this image in the fire-fly (Lampyris). As the
eyes are immovable the sight of resting objects soon disappears so
far as the resting insect is concerned. For this reason resting in-
sects are easily captured when very slowly approached. In flight

insects orient themselves in space by means of their compound

Fig.

ee ees Game 2

EXPLANATION OF THE FIGURES.

Brain (supra-cesophageal ganglion) of an ant (Zaszus fuliginosus), magnified
60 diameters, seen from above.

Fig. W. Brain of the Worker.
Fig. 7. Brain of the Queen (Female)
Fig. JZ. Brain of the Male.

S¢.=Brain trunk. JZ. 0Z.=Lobus opticus (optic lobe). JZ. oJf.=Lobus olfac-
torius sive antennalis (olfactory lobe). M.=Facetted eye. WV. o/f.=Nervus olfac-
torius sive antennalis (olfactory nerve). O.=Ocelli, or simple eyes with their
nerves (present only in the male and queen). 7. =Cellular brain cortex (developed
only in the worker and queen). C. .=Corpora pedunculata, or fungiform bodies
(developed only in the worker and queen). #.=Rudimental cortex of male.

The length of the whole ant is :

in the worker 4.5 mm;
in the queen 6.0 mm;
in the male 4.5 mm.

N. B. The striation of the corpora pedunculata and their stems is represented
diagrammatically, for the purpose of indicating rather coarsely their extremely
delicate fibrillar structure.

16 ANTS AND SOME OTHER INSECTS.

eyes. Odor, when perceived, merely draws these animals in a
particular direction. When the compound eyes are covered, all
powers of orientation in the air are lost. Many insects can adapt
their eyes for the day or night by a shifting of the pigment. Ants
see the ultra-violet with their eyes. Honey-bees and humble-bees
can distinguish colors, but obviously in other tones than we do,
since they cannot be deceived by artificial flowers of the most skil-
ful workmanship. This may be due to admixtures of the ultra-violet
rays which are invisible to our eyes.

The ocelli (simple eyes) play a subordinate réle, and probably
serve as organs of sight for objects situated in the immediate vicin-
ity and in dark cavities.

The olfactory sense has its seat in the antennez, usually in the
club-shaped flagellum, or rather in the pore-plates and olfactory
rods of these portions of the antennz. On account of its external
and moveable position at the tip of the antenna, the olfactory or-
gan possesses two properties which are lacking in the vertebrates,
and particularly in man. These are:

1. The power of perceiving the chemical nature of a body by
direct contact (contact-odor);

2. The power of space-perception and of perceiving the form
of objects and that of the animal’s own trail by means of odor, and
the additional property of leaving associated memories.

The olfactory sense of insects, therefore, gives these animals

definite and clear-cut perceptions of space-relations, and enables.

the animal while moving on the surface of the ground to orient it-
self with facility. I have designated this sense, which is thus quali-
tatively, i. e., in its specific energy, very different from our olfac-
tory sense, as the topochemical (olfactory) sense. Probably the
pore-plates are used for perceiving odor at a distance and the olfac-
tory rods for contact-odor, but this is pure conjecture. Extirpation
of the antenne destroys the power of distinguishing friends from
enemies and deprives the ant of the faculty of orienting itself on
the ground and of finding its way, whereas it is possible to cut off

three legs and an antenna without seriously impairing these powers.

The topochemical sense always permits the ant to distinguish be-

ANTS AND SOME OTHER INSECTS. 17

tween the directions of its trail, a faculty which Bethe attributes to
a mysterious polarisation. The ability to sense different odors
varies enormously in different insects. An object possessing odor
for one species is often odorless for other species (and for ourselves)
and vice versa.

The gustatory organs are situated on the mouth-parts. Among
insects the reactions of this sense are very similar to our own. Will
accustomed some wasps to look ina particular place for honey,
which he afterwards mixed with quinine. The wasps detected the
substance at once, made gestures of disgust, and never returned to
the honey. Mixing the honey with alum had the same result. At
first they returned, but after the disagreeable gustatory experience
they failed to reappear. Incidentally this is also a proof of their
gustatory memory and of their powers of association.

Several organs have been found and described as auditory.
But after their removal the supposed reaction to sounds persists.
This would seem to indicate that a deceptive resemblance to hear-
ing may be produced by the perception of delicate vibrations
through the tactile sense (Dugés).

The tactile sense is everywhere represented by tactile hairs
and papilla. It reacts more especially to delicate tremors of the
atmosphere or soil. Certain arthropods, especially the spiders,
orient themselves mainly by means of this sense.

It may be demonstrated that insects, according to the species
and conditions of life, use their different senses in combination for
purposes of orienting themselves and for perceiving the external
world. Many species lack eyes and hence also the sense of sight.
In others, again, the olfactory sense is obtuse; certain other forms
lack the contact-odor sense (e. g., most Diptera).

It has been shown that the superb powers of orientation ex-
hibited by certain aerial animals, like birds (carrier-pigeons), bees,
etc., depend on vision and its memories. Movement in the air
gives this sense enormous and manifold values. The semi-circular
canals of the auditory organ are an apparatus of equilibrium in
vertebrates and mediate sensations of acceleration and rotation
(Mach-Breuer), but do not give external orientation. For the dem-

~

18 ANTS AND SOME OTHER INSECTS.

onstration of these matters I must refer you to my work above-
cited. A specific, magnetic, or other mode of orientation, indepen-
dent of the known senses, does not exist. ;

The facts above presented constitute the basis of insect psy-
chology. The social insects are especially favorable objects for
study on account of their manifold reciprocal relationships. If in
speaking of their behavior I use terms borrowed from human life,
I request you, once for all, to bear in mind that these are not to
be interpreted in an anthropomorphic but in an analogous sense.

THE PROVINCE OF COGNITION.

Many insects (perhaps all, in a more rudimental condition)
possess memory, i. e., they are able to store up sense-impressions
in their brains for subsequent use. Insects are not merely attracted
directly by sensory stimuli, as Bethe imagines. Huber, myself,
Fabre, Lubbock, Wasmann, Von Buttel-Reepen, have demonstrated
this fact experimentally. That bees, wasps, etc., can find their way
in flight through the air, notwithstanding wind and rain (and hence
under circumstances precluding the existence of any possible odor-
iferous trail), and even after the antenne have been cut off, toa
concealed place where they have found what they desired, though
this place may be quite invisible from their nest, and this even
after the expiration of days and weeks, is a fact of special impor-
tance as proof of the above assertion. It can be shown that these
insects recognise objects by means of their colors, their forms, and
especially by their position in space. Position they perceive
through the mutual relations and succession of the large objects in

space, as these are revealed to them in their rapid change of place

during flight in their compound eyes (shifting of retinal images).
Especially the experiments performed by Von Buttel-Reepen and
myself leave no doubt concerning this fact. Additional proof of a
different nature is furnished by Von Buttel, who found that ether or
chloroform narcosis deprives bees of all memory. By this means
enemies can be converted into friends. Under these circumstances,
too, all memory of locality is lost and must be reacquired by means

whet Cen

EE se

ANTS AND SOME OTHER INSECTS. Ig

of a new flight of orientation. An animal, however, certainly can-
not forget without having remembered.

The topochemical antennal sense also furnishes splendid proofs
of memory in ants, bees, etc. An ant may perform an arduous
journey of thirty meters from her ruined nest, there find a place
suitable for building another nest, return, orienting herself by
means of her antennz, seize a companion who forthwith rolls her-
self about her abductrix, and is carried to the newly selected spot.
The latter then also finds her way to the original nest, and both

|

each carry back another companion, etc. The memory of the suit- |

able nature of the locality for establishing a new nest must exist in
the brain of the first ant or she would not return, laden with a com-
panion, to this very spot. The slave-making ants (Polyergus) un-
dertake predatory expeditions, led by a few workers, who for days
and weeks previously have been searching the neighborhood for
nests of Formica fusca. The ants often lose their way, remain
standing and hunt about for a long time till one or the other finds
the topochemical trail and indicates to the others the direction to
be followed by rapidly pushing ahead. Then the pupz of the For-
mica fusca nest, which they have found, are brought up from the
depths of the galleries, appropriated and dragged home, often a
distance of forty meters or more. If the plundered nest still con-
tains pupe, the robbers return on the same or following days and
carry off the remainder, but if there are no pup@ left they do not
return. How do the Polyergus know whether there are pupz re-
maining? It can be demonstrated that smell could not attract them
from such a distance, and this is even less possible for sight or any
other sense. Memory alone, i. e., the recollection that many pupz
still remain behind in the plundered nest can induce them to re-

turn. I have carefully followed a great number of these predatory |

expeditions.

While Formica species follow their topochemical trail with
great difficulty over new roads, they nevertheless know the imme-
diate surroundings of their nest so well that even shovelling away
the earth can scarcély disconcert them, and they find their way at
once, as Wasmann emphatically states and as I myself have often

20 ANTS AND SOME OTHER INSECTS.

observed. That this cannot be due to smelling at long range can
be demonstrated in another manner, for the olfactory powers of the
genus Formica, like those of honey-bees, are not sufficiently acute
for this purpose, as has been shown in innumerable experiments by
all connoisseurs of these animals. Certain ants can recognise friends
even after the expiration of months. In ants and bees there are
very complex combinations and mixtures of odors, which Von But-
tel has very aptly distinguished as nest-odor, colony- (family-) odor,
and individual odor. In ants we have in addition a species-odor,
while the queen-odor does not play the same réle as among bees.

It follows from these and many other considerations that the
social Hymenoptera can store up in their brains visual images and
topochemical odor-images and combine these to form perceptions
or something of a similar nature, and that they can associate such
perceptions, even those of different senses, especially sight, odor,
and taste, with one another and thereby acquire spatial images.

Huber as well as Von Buttel, Wasmann, and myself have
always found that these animals, through frequent repetition of an
activity, journey, etc., gain in the certainty and rapidity of the ex-
ecution of their instincts. Hence they form, very rapidly to be
sure, habits. Von Buttel gives splendid examples of these in the
robber-bees, i. e., in some of the common honey-bees that have
acquired the habit of stealing the honey from the hives of strangers.
At first the robbers display some hesitation, though later they be-
come more and more impudent. But he who uses the term habit,
must imply secondary automatism and a pre-existing plastic adapt-
ability. Von Buttel adduces an admirable proof of this whole mat-
ter and at the same time one of the clearest and simplest refuta-
tions of Bethe’s innumerable blunders, when he shows that bees
that have never flown from the hive, even though they may be
older than others that have already flown, are unable to find their
way back even from a distance of a few meters, when they are un-
able to see the hive, whereas old bees know the whole environ-
ment, often to a distance of six or seven kilometers.

It results, therefore, from the unanimous observations of all
) the connoisseurs that sensation, perception, and association, infer-

‘wedi. Get hs = Qe ess tei ed A he ——_

—E———— ee SL Oe

ANTS AND SOME OTHER INSECTS. 2I

ence, memory and habit follow in the social insects on the whole
the same fundamental laws as in the vertebrates and ourselves.
Furthermore, attention is surprisingly developed in insects, often
taking on an obsessional character and being difficult to divert.

On the other hand, inherited automatism exhibits a colossal
preponderance. The above-mentioned faculties are manifested
only in an extremely feeble form beyond the confines of the in-
stinct-automatism stereotyped in the species.

An insect is extraordinarily stupid and inadaptable to all things
not related to its instincts. Nevertheless I succeeded in teaching
a water-beetle (Dy¢iscus marginalis) which in nature feeds only in
the water, to eat on my table. While thus feeding, it always exe-
cuted a clumsy flexor-movement with its fore-legs which brought it
over on its back. The insect learned to keep on feeding while on
its back, but it would not dispense with this movement, which is
adapted to feeding in the water. On the other hand, it always at-
tempted to leap out of the water (no longer fleeing to the bottom
of the vessel) when I entered the room, and nibbled at the tip of
my finger in the most familiar manner. Now these are certainly
plastic variations of instinct. In a similar manner some large
Algerian ants which I transplanted to Zurich, learned during the
course of the summer months to close the entrance of their nest
with pellets of earth, because they were being persecuted and an-
noyed by our little Zaszus niger. In Algiers I always saw the nest-
opening wide open. There are many similar examples which go
to show that these tiny animals can utilise some few of their expe-
riences even when this requires a departure from the usual in-
stincts.

That ants, bees, and wasps are able to exchange communica-
tions that are understood, and that they do not merely titillate one
another with their antennze as Bethe maintains, has been demon-
strated in so many hundred instances, that it is unnecessary to
waste many words on this subject. The observations of a single
_ predatory expedition of Polyergus, with a standing still of the whole
army and a seeking for the lost trail, is proof sufficient of the above
statement. But, of course, this is not language in the human sense!

22 ANTS AND SOME OTHER INSECTS.

There are no abstract concepts corresponding to the signs. We
are here concerned only with hereditary, instinctively automatic
signs. The same is true of their comprehension (pushing with the
head, rushing at one another with wide-open mandibles, titillation
with the antennez, stridulatory movement of the abdomen, etc.).
Moreover, imitation plays a great rdle. Ants, bees, etc., imitate
and follow their companions. Hence it is decidedly erroneous (and
in this matter Wasmann, Von Buttel, and myself are of but one
opinion) to inject human thought-conception and human ratiocina-
tion into this instinct-language, as has been done to some extent,
at least, even by Pierre Huber, not to mention others. It is even
very doubtful whether a so-called general sensory idea (i. e., a gen-
eral idea of an object, like the idea ‘‘ant,” ‘*enemy,” ‘‘nest,”
‘‘pupa”) can arise in the emmet brain. This is hardly capable of
demonstration. Undoubtedly perception and association can be
carried on in a very simple way, after the manner of insects, with-
out ever rising to such complex results. At any rate proofs of such
an assumption are lacking. But what exists is surely in itself suffi-
ciently interesting and important. It gives us at least an insight
into the brain-life of these animals.

Better than any generalisations, a good example will show
what I mean.

Plateau had maintained that when Dahlia blossoms are covered
with green leaves, bees nevertheless return to them at once. At
first he concealed his Dahlias incompletely (i. e., only their ray-
florets), afterwards completely, but still in an unsatisfactory man-
ner, and inferred from the results that bees are attracted by odor
and not by sight.

a. In a Dahlia bed visited by many bees and comprising about
forty-three floral heads of different colors, I covered first seventeen
and then eight at 2.15 P. M., September roth, with shel bain
bent around them and fastened with pins.

6. Of four I covered only the yellow disc;

c. Of one, on the other hand, I covered only the outer ray-

florets, leaving the disc visible.

ANTS AND SOME OTHER INSECTS. 23

So many bees were visiting the Dahlias that at times there
were two or three to a flower.

Result: Immediately all the completely covered flowers ceased
to be visited by the bees. Dahlia (c) continued to be visited like
those completely visible. The bees often flew to Dahlias (4) but at
once abandoned them; a few, however, succeeded in finding the
disc beneath the leaves.

Then as soon as I removed the covering from a red Dahlia the
bees at once flew to it; and soon a poorly concealed specimen was
detected and visited. Later an inquisitive bee discovered the en-
trance to a covered Dahlia from the side or from below. Thence-
forth this bee, but only this one, returned to this same covered
flower.

Nevertheless several bees seemed to be seeking the Dahlias
which had so suddenly disappeared. Towards 5.30 o’clock some
of them had detected the covered flowers. Thenceforth these in-
sects were rapidly imitated by the other bees, and in a short time
the hidden flowers were again being visited. As soon as a bee had
discovered my imposition and found the entrance to a hidden
flower, she flew in her subsequent journeys, without hesitation to
the’ concealed opening of the grape-leaf. As long asa bee had
merely made the discovery by herself, she remained unnoticed by
the others. When this was accomplished by several, however, (usu-
ally by four or five,) the others followed their example.

Plateau, therefore, conducted his experiments in a faulty man-
ner and obtained erroneous results. The bees still saw the Dahlias
which he at first incompletely concealed. Then, by the time he
had covered them up completely, but only from above, they had
already detected the fraud and saw the Dahlias also from the side.
Plateau had failed to take into consideration the bee’s memory and
attention.

September 13th I made some crude imitations of Dahlias by
sticking the yellow heads of Hieracium (hawkweed) each in a Pe-
tunia flower, and placed them among the Dahlias. Neither the
Petunias nor the Hieracium had been visited by the bees. Never-
theless many of the honey and humble-bees flew at first to the arte-

24 ANTS AND SOME OTHER INSECTS.

facts in almost as great numbers as to the Dahlias, but at once
abandoned the flowers when they had detected the error, obviously
by means of their sense of smell. The same results were produced
by a Dahlia, the disc of which had been replaced by the disc of a
Hieracium.

As a control experiment I had placed a beautiful, odorous
Dahlia disc among the white and yellow Chrysanthemums which
had been neglected by the bees. Fora whole half hour the bees
flew by only a few centimeters above the disc without noticing it;
not till then was it visited by a bee that happened to be followed
by a second. From this moment the Dahlia disc which lay in the
path of flight was visited like the others, whereas on the other hand
the Petunia-Hieracium artefacts, now known to be fraudulent, were
no longer noticed.

Plateau has demonstrated that artificial flowers, no matter how
carefully copied from the human standpoint, are not noticed by in-
sects. I placed artefacts of this description among the Dahlias.
They remained in fact entirely neglected. Perhaps, as above sug-
gested, the bees are able to distinguish the chlorophyll colors from
other artificial hues, owing to admixtures of the ultra-violet rays,
or by some other means. But since Plateau imagines that the arti-
ficial flowers repel insects, I cut out, Sept. 19th, the following
rather crude paper-flowers :

a. A red flower;

B. A white flower ;

y. A blue flower ;

6 A blue flower, with a yellow center made from a dead leaf;

«. A rose-colored piece of paper with a dry Dahlia disc;

¢. A green Dahlia leaf (unchanged).

It was nine o’clock in the morning. I placed a drop of honey
on each of the six artefacts mounted among the Dahlias. For a
quarter of an hour many bees flew past, very close to my artefacts
but without perceiving and hence without smelling the honey. I
went away for an hour. On my return artefact 6 was without honey,
and must therefore have been discovered by the bees. All the
others had remained quite untouched and unnoticed.

” ee i setae

el lle tains

ANTS AND SOME OTHER INSECTS. 25

With some difficulty I next undertook to bring artefact a very
close to a bee resting on a Dahlia. But the attention of the bee
was so deeply engrossed by the Dahlia that I had to repeat the ex-
periment four or five times till I succeeded in bringing the honey
within reach of her proboscis. The insect at once began to suck
up the honey from the paper-flower. I marked the bee’s back with

blue paint so that I might be able to recognise her, and repeated

the experiment with 8 and ec. In these cases one of the bees was
painted yellow, the other white.

Soon the blue bee, which had in the meantime gone to the
hive, returned, flew at once to a, first hovering about it dubiously,
then to 6, where she fed, then again toa, but not to the Dahlias.
Later the yellow bee returned to B and fed, and flew to a and 8
where she again fed, but gave as little heed to the Dahlias as did
the blue bee.

Thereupon the white bee returned seeking e¢, but failing to find
it, at once went to feeding on some of the Dahlias. But she tarried
only a moment on each Dahlia as if tortured by the zdée fixe of
honey. She returned to the artefacts, the perception of which,
however, she was not quite able to associate with the memory of
the honey flavor. At last she found a separate piece of «, which
happened to be turned down somewhat behind, and began lapping
up the honey.

Thenceforth the three painted bees, and these alone, returned
regularly to the artefacts and no longer visited the Dahlias. The
fact is of great importance that the painted bees entirely of their
own accord, undoubtedly through an instinctive inference from
analogy, discovered the other artefacts as soon as their attention ~
had been attracted by the honey on one of them, notwithstanding
the fact that the artefacts were some distance from one another and
of different colors. For were not the Dahlias, too, which they had
previously visited, of different colors? Thus the blue bee flew to
a, B, y, and 4, the yellow to £, a, 6, and y, the white «, a, B, and 8.
Matters continued thus for half an hour. The hidden green ¢ was
not found, evidently because it was indistinguishable from the green

foliage.

26 ANTS AND SOME OTHER INSECTS.

Finally one bee, by herself, having had in all probability her
attention attracted by the three others, came to 6 and fed. I marked
her with carmine. Thereupon she flew to a and drove the blue bee
away. Another bee was attracted to e of her own accord and was
painted with cinnobar. Still another bee came by herself to B and
was painted green. It was now 12.30 o’clock. The experiment
had therefore lasted more than three hours, and during this time
only six bees had come to know the artefacts, while the great ma-
jority still kept on visiting the Dahlias. But now the other bees
began to have their attention attracted by the visitors to the arte-
facts. One, then two, then three, and finally more new ones fol-
lowed, and I had not sufficient colors with which to mark them.
Every moment I was obliged to replenish the honey. Then I went
to dinner and returned at 1.25. At this moment seven bees were
feeding on £, two ona, one on y, three on 6, the white one alone
one. More than half of all these were new, unpainted followers.
Now a veritable swarm of bees threw themselves on the artefacts
and licked up the last traces of the honey. Then for the first time,
after more than four hours, a bee from the swarm discovered the
honey on the artefact £, which on account of its color had remained
concealed up to this time!

As a pack of hounds throws itself on an empty skeleton, the
swarm of bees, now completely diverted from the Dahlias, cast
themselves on the completely empty artefacts and vainly searched
every corner of them for honey. It was 1.55 P. M. The bees be-
gan to scatter and return to the Dahlias. Then I replaced a and
8B by a red and white paper respectively, which had never come in
contact with honey and could not therefore smell of the substance.
These pieces of paper, nevertheless, were visited and examined by
various bees, whose brains were still possessed with the fixed idea
of the flavor of honey. The white bee, e. g., investigated the white
paper very carefully for a period of three to four minutes. There
could, of course, be no such thing as an unknown force or attrac-
tion of odor, or brilliancy of floral colors. This fact can only be
explained by an association of space, form, and color memories with

memories of taste.

ANTS AND SOME OTHER INSECTS. 27

Thereupon I took all the artefacts in my left hand for the pur-
pose of carrying them away. Two or three bees followed me, hov-
ering about my left hand, and tried to alight on the empty artefacts.
The space-image had changed and only the color and form could
any longer be of service to the bees in their recognition of these
objects.

This experiment is so clear and unequivocal that I mention it
here among many others. It demonstrates:

1. The space, form, and color perceptions of the honey-bee.
That these are possible only through the agency of the compound
eyes is proved by other experiments (varnishing the eyes, extirpa-
tion of the antennez, mouth-parts, etc.).

2. The memory of the honey-bee, in particular her visual and
gustatory memory.

3. Her power of associating gustatory with visual memories.

4. Her ability instinctively to draw inferences from analogy:
If she has once been offered honey in an artefact, she will investi-
gate others, even those of a different color and hitherto unnoticed.
These she compares by means of the visual sense, since they are
relatively similar, and recognises them as similar though such ob-
jects are most unusual in the bee’s experience.

5. Her poor olfactory sense, which is useful only at very close
range.

6. The onesidedness and narrow circle of her attention.

7. The rapid formation of habits.

8. The limits of imitation of bees by one another.

Of course, I should not allow myself to draw these conclusions
from a single experiment, if they had not been confirmed by in-
numerable observations by the ablest investigators in this field.
Lubbock showed clearly that it is necessary to train a bee for some
time to go to a particular color if one wishes to compel her to pay
no attention to other colors. This is the only way in which it is
possible to demonstrate her ability to distinguish colors. My bees,
on the contrary, had been trained on differently colored objects
(Dahlias and artefacts) and therefore paid no attention to differ-
ences in color. It would bea fallacy to conclude from this that

28 © ANTS AND SOME OTHER INSECTS.

they do not distinguish colors. On the contrary, by means of other
experiments I have fully confirmed Lubbock’s results. _

By 2.20 P. M. all of my bees, even the painted onés, had re-
turned to the Dahlias.

On September 27, a week later, I wished to perform a fresh
experiment with the same bees. I intended to make them distin-
guish between differently colored discs, placed at different points on
a long scale, representing on a great sheet of paper, varying intensi-
ties of light from white through gray to black. First, I wished to
train a bee toasingle color. But I had calculated without the
bee’s memory, which rendered the whole experiment impracticable.
Scarcely had I placed my paper with the discs on the lawn near
the Dahlia bed, and placed one or two bees on the blue discs and
marked them with colors, when they began to investigate all the
red, blue, white, black and other discs with or without honey. After
a few moments had elapsed, other bees came from the Dahlia bed
and in a short time a whole swarm threw itself on the paper discs.
Of course, those that had been provided with honey were most vis-
ited, because they detained the bees, but even the discs without
honey were stormed and scrutinised by bees following one another
in their flight. The bees besieged even the paint-box. Among
these there was one that I had previously deprived of her antenne.
She had previously partaken of the honey on the blue discs and
had returned to the hive. This bee examined the blue piece of
paint in the color-box.

In brief, my experiment was impossible, because all the bees
still remembered from a former occasion the many-colored artefacts
provided with honey, and therefore examined all the paper discs
no matter of what color. The association between the taste of the
honey and the paper discs had been again aroused by the sight-
perception of the latter, and had acquired both consistency and
rapid and powerful imitation, because honey happened to be actually
found on some of the discs.

Together with the perceptive and associative powers, the
power of drawing simple, instinctive inferences from analogy is
also apparent. Without this, indeed, the operation of perception

ge eT ee ee ae

ANTS AND SOME OTHER INSECTS. 29

and memory would be inconceivable! We have just given an ex-
ample. I have shown on a former occasion that humble-bees,
whose nest I had transferred to my window, when they returned
home often confounded other windows of the same facade and ex-
amined them for a long time before they discovered the: right one.
Lubbock reports similar facts. Von Buttel shows that bees that
-are accustomed to rooms and windows, learn to examine the rooms
and windows in other places, i. e., other houses. When Pissot
suspended wire netting with meshes twenty-two mm. in diameter
in front of a wasp nest, the wasps hesitated at first, then went
around the netting by crawling along the ground or avoided it in
some other way. But they soon learned to fly directly through the
meshes. The sense of sight, observed during flight, is particularly
well adapted to experiments of this kind, which cannot therefore
be performed with ants. But the latter undoubtedly draw similar
inferences from the data derived from their topochemical antennal
sense. The discovery of. prey or other food on a plant or an ob-
ject induces these insects to examine similar plants or objects and
to perform other actions of a like nature.

There are, on the other hand, certain very stupid insects, like
the males of ants, the Diptera and may-flies (Ephemerids) with
rudimental brains, incapable of learning anything or of combining
sense-impressions to any higher degree than as simple automatisms,
and without any demonstrable retention of memory-images. Such
insects lead a life almost exclusively dominated by sensory stimuli;
but their lives are adapted to extremely simple conditions. In
these very instances the difference is most striking, and they dem-
onstrate most clearly through comparison and contrast the jlus
possessed by more intelligent insects.

THE REALM OF WILL.

The notion of volition, in contradistinction to the notion of
reflex action, presupposes the expiration of a certain time interval
and the operation of mediating and complex brain-activities be-
tween the sense-impression and the movement which it conditions.
In the operation of the purposeful automatisms of instinct which

30 ANTS AND SOME OTHER INSECTS.

arouse one another into activity in certain sequences, there.is also
a time interval, filled out by internal, dynamic brain-processes as
in the case of the will. Hence these are not pure reflexes. They
may for a time suffer interruption and then be again continued.
But their operation is brought about in great measure by a con-
catenation of complicated reflexes which follow one another in a
compulsory order. ' On this account the term automatism or in-
stinct is justifiable. f

If we are to speak of will in the narrower sense, we must be
able to establish the existence of individual decisions, which can be
directed according to circumstances, i. e., are modifiable, and may,
for a certain period, remain dormant in the brain to be still per-
formed notwithstanding. Such volition may be very different from
the complex volition of man, which consists of the resultants of
prodigiously manifold components that have been long preparing
and combining. The ants exhibit positive and negative volitional
phenomena, which cannot be mistaken. The ants of the genus
Formica Linné are particularly brilliant in this respect, and they
also illustrate the individual psychical activities most clearly. The
above-mentioned migrations from nest to nest show very beauti-
fully the individual plans of single workers carried out with great
tenacity. For hours at a time an ant may try to overcome a multi-
tude of difficulties for the purpose of attaining an aim which she
has set herself. This aim is not accurately prescribed by instinct,
as the insect may be confronted with several possibilities, so that
it often happens that two ants may be working in opposition to
each other. This looks like stupidity to the superficial observer.
But it is just here that the ant’s plasticity reveals itself. Fora
time the two little animals interfere with each other, but finally
they notice the fact, and one of them gives in, goes away, or assists
the other.

These conditions are best observed during the building of nests
or roads, e. g., in the horse-ant (Formica rufa) and still better in
F. pratensis. It is necessary, however, to follow the behavior of a
few ants for hours, if one would have a clear conception of this
matter, and for this much patience and much time are necessary.

— a es

ANTS AND SOME OTHER INSECTS. 31

The combats between ants, too, show certain very consistent aims
of behavior, especially the struggles which I have called chronic
combats (combats @ froid). After two parties (two colonies brought
together) have made peace with each other, one often sees a few
individuals persecuting and maltreating certain individuals of the
opposite party. They often carry their victims a long distance off,
for the purpose of excluding them from the nest. If the ant that
has been borne away returns to the nest and is found by her perse-
cutrix, she is again seized and carried away to a still greater dis-
tance. In one such case in an artificial nest of a small species of
Leptothorax, the persecuting ant succeeded in dragging her victim
to the edge of my table. She then stretched out her head and
allowed her burden to fall on the floor. This was not chance, for
she repeated the performance twice in succession after I had again
placed the victim on the table. Among the different individuals of
the previously hostile, but now pacified opposition, she had con-
centrated her antipathy on this particular ant and had tried to make
her return to the nest impossible. One must have very strong pre-
conceived opinions if in such and many similar cases one would
maintain that ants are lacking in individual decision and execution.
Of course, all these things happen within the confines of the in-
stinct-precincts of the species, and the different stages in the exe-
tion of a project are instinctive. Moreover, I expressly defend my-
self against the imputation that I am importing human reflection
and abstract concepts into this volition of the ant, though we must
honestly admit, nevertheless, that in the accomplishment of our
human decisions both hereditary and secondary automatisms are
permitted to pass unnoticed. While I am writing these words, my
eyes operate with partially hereditary, and my hand with secondary
automatisms. But it goes without saying that only a human brain
is capable of carrying out my complex innervations and my con-
comitant abstract reflections. But the ant must, nevertheless, as-
sociate and consider somewhat in a concrete way after the manner
of an ant, when it pursues one of the above-mentioned aims and
combines its instincts with this special object in view. While,

however, the instinct of the ant can be combined for only a few

32 ANTS AND SOME OTHER INSECTS.

slightly different purposes, by means of a small number of plastic
adaptations or associations, individually interrupted in their con-
catenation or vice versa, in the thinking human being both inherited
and secondary automatisms are only fragments or instruments in
the service of an overwhelming, all-controlling, plastic brain-activ-
ity. It may be said incidentally that the relative independence of
the spinal chord and of subordinate brain-centers in the lower ani-
mals (and even in the lower mammals) as comparcd with the cere-
brum, may be explained in a similar manner if they are compared
with the profound dependence of these organs and their functions
on the massive cerebrum in man and even to some extent in the
apes. The cerebrum splits up and controls its automatisms (dvide
el impera).

While success visibly heightens both the audacity and tenacity
of the ant-will, it is possible to observe after repeated failure or in
consequence of the sudden and unexpected attacks of powerful en-
emies a form of abulic dejection, which may lead to a neglect of
the most important instincts, to cowardly flight, to the devouring
or casting away of offspring, to neglect of work, and similar condi-
tions. There is a chronically cumulative discouragement in degen-
erate ant-colonies and an acute discouragement when a combat is
lost. In the latter case one may see troops of large powerful ants
fleeing before a single enemy, without even attempting to defend
themselves, whereas the latter a few moments previously would
have been killed by a few bites from the fleeing individuals. It is
remarkable how soon the victor notices and utilises this abulic dis-
couragement. The dejected ants usually rally after the flight and
soon take heart and initiative again. But they offer but feeble re-
‘sistance, e. g., to a renewed attack from the same enemy on the
following day. Even an ant’s brain does not so soon forget the
defeats which it has suffered.

In bitter conflicts between two colonies of nearly equal strength
the tenacity of the struggle and with it the will to conquer increases
till one of the parties is definitively overpowered. In the realm of
will imitation plays a great rdle. Even among ants protervity and
dejection are singularly contagious.

— a

ANTS AND SOME OTHER INSECTS. 33

THE REALM OF FEELING.

It may perhaps sound ludicrous to speak of feelings in insects.
But when we stop to consider how profoundly instinctive and
fixed is our human life of feeling, how pronounced are the emotions
in our domestic animals, and how closely interwoven with the im-
pulses, we should expect to encounter emotions and feelings in
animal psychology. And these may indeed be recognised so clearly
that even Uexkuell would have to capitulate if he should come to
know them more accurately. We find them already interwoven
with the will as we have described it. Most of the emotions of in-
sects are profoundly united to the instincts. Of such a nature is
the jealousy of the queen bee when she kills the rival princesses,
and the terror of the latter while they are still within their cells;
such is the rage of fighting ants, wasps, and bees, the above-men-
tioned discouragement, the love of the brood, the self-devotion of
the worker honey-bees, when they die of hunger while feeding their
queen, and many other cases of a similar description. But there
are also individual emotions that are not compelled altogether by
instinct, e. g., the above-mentioned mania of certain ants for mal-
treating some of their antagonists. On the other hand, as I have
shown, friendly services (feeding), under exceptional circum-
stances, may call forth feelings of sympathy and finally of partner-
ship, even between ants of differents species. Further than this,
feelings of sympathy, antipathy, and anger among ants may be in-
tensified by repetition and by the corresponding activities, just as
in other animals and man.

The social sense of duty is instinctive in ants, though they ex-
hibit great individual, temporary, and occasional deviations, which

betray a certain amount of plasticity.

PSYCHIC CORRELATIONS.

I have rapidly reviewed the three main realms of ant-psychol-
ogy. It is self-evident that in this matter they no more admit of

34 ANTS AND SOME OTHER INSECTS.

sharp demarcation from one another than elsewhere. The will
consists of centrifugal resultants of sense-impressions and feelings
and in turn reacts powerfully on both of these.

It is of considerable interest to observe the antagonism be-
tween different perceptions, feelings, and volitions in ants and
bees, and the manner in which in these animals the intensely fixed
(obsessional) attention may be finally diverted from one thing to
another. Here experiment is able to teach us much. While bees
are busy foraging on only one species of flower, they overlook
everything else, even other flowers. If their attention is diverted
by honey offered them directly, although previously overlooked,
they have eyes only for the honey. An intense emotion, like the
swarming of honey-bees (von Buttel) compells these insects to
forget all animosities and even the old maternal hive to which they
no longer return. But if the latter happens to be painted blue,
and if the swarming is interrupted by taking. away the queen, the
bees recollect the blue color of their old hive and fly to hives that
are painted blue. ‘Two feelings often struggle with each other in
bees that are ‘‘crying’” and without a queen: that of animosity
towards strange bees and the desire for a queen. Nowif they be
given a strange queen by artificial means, they kill or maltreat her,
because the former feeling at first predominates. For this reason
the apiarist encloses the strange queen in awire cage. Then the
foreign odor annoys the bees less because it is further away and
they are unable to persecute the queen. Still they recognise the
specific queen-odor and are able to feed her through the bars of the
cage. This suffices to pacify the hive. Then the second feeling
quickly comes to the front; the workers become rapidly inured to
the new odor and after three or four days have elapsed, the queen
may be liberated without peril.

It is possible in ants to make the love of sweets struggle with
the sense of duty, when enemies are made to attack a colony and
honey is placed before the ants streaming forth to defend their
nest. I have done this with Formica pratensis. At first the ants
partook of the honey, but only for an instant. The sense of duty
conquered and all of them without exception, hurried forth to battle

— se

ss, a. a ee

ae aT ery

wat. a Se

“gtk Dias, 8 ek

. se

So ©

ANTS AND SOME OTHER INSECTS. 35

and most of them to death. In this case a higher decision of in-
stinct was victorious over the lower impulse.

In résumé I would lay stress on the following general conclu-
sions:

1. From the standpoint of natural science we are bound to
hold fast to the psychophysiological theory of identity (Monism) in
contradistinction to dualism, because it alone is in harmony with
the facts and with the law of the conservation of energy.

Our mind must be studied simultaneously both directly from

within and indirectly from without, through biology and the condi- | |

tions of its origin. Hence there is such a thing as comparative ||

psychology of other individuals in addition to that of self, and in
like manner we are led to a psychology of animals. Inference from
analogy, applied with caution, is not. only permissible in this sci-
ence, but obligatory.

2. The senses of insects are our own. Only the auditory sense
still remains doubtful, so far as its location and interpretation are
concerned. A sixth sense has not yet been shown to exist, and a
special sense of direction and orientation is certainly lacking. The
vestibular apparatus of vertebrates is merely an organ of equilibra-
tion and mediates internal sensations of acceleration, but gives no
orientation in space outside of the body. On the other hand the
visual and olfactory senses of insects present varieties in the range
of their competency and in their specific energies (vision of ultra-
violet, functional peculiarities of the facetted eye, topochemical
antennal sense and contact-odor).

3. Reflexes, instincts, and plastic, individually adaptive, cen-
tral nervous activities pass over into one another by gradations.
Higher complications of these central or psychic functions corre-
spond to a more complicated apparatus of superordinated neuron-
complexes (cerebrum).

4. Without becoming antagonistic, the central nervous activ-
ity in the different groups and species of animals complicates itself
in two directions: (@) through inheritance (natural selection, etc.)
of the complex, purposeful automatisms, or instincts; (4) through
the increasingly manifold possibilities of plastic, individually adap-

~~.

|
|

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|

36 ANTS AND SOME OTHER INSECTS.

tive activities, in combination with the faculty of gradually devel-
oping secondary individual automatisms (habits).

The latter mode requires many more nerve-elements. Through
hereditary predispositions (imperfect instincts) of greater or less
stability, it presents transitions to the former mode.

5. In social insects the correlation of more developed psychic
powers with the volume of the brain may be directly observed.

6. In these animals it is possible to demonstrate the existence
of memory, associations of sensory images, perceptions, attention,
habits, simple powers of inference from analogy, the utilisation of
individual experiences and hence distinct, though feeble, plastic;
individual deliberations or adaptations.

7. It is also possible to detect a corresponding, simpler form
of volition, i. e., the carrying out of individual decisions in a more
or less protracted time-sequence, through different concatenations
of instincts; furthermore different kinds of discomfort and pleasure
emotions, as well as interactions and antagonisms between these di-
verse psychic powers.

8. In insect behavior the activity of the attention is one-sided
and occupies a prominent place. It narrows the scope of behavior
and renders the animal temporarily blind (inattentive) to other
sense-impressions. |

Thus, however different may be the development of the auto-
matic and plastic, central neurocyme activities in the brains of dif-
ferent animals, it is surely possible, nevertheless, to recognise cer-
tain generally valid series of phenomena and their fundamental
laws.

Even to-day I am compelled to uphold the seventh thesis
which I established in 1877 in my habilitation as privat-docent in
the University of Munich:

‘‘All the properties of the human mind may be derived from
the properties of the animal mind.”

I would merely add to this:

‘‘And all the mental attributes of higher animals may be de-

| rived from those of lower animals.”’ In other words: The doctrine

of evolution is quite as valid in the province of psychology as it is

donee, MPs

ANTS AND SOME OTHER INSECTS, 37

in all the other provinces of organic life. Notwithstanding all the
differences presented by animal organisms and the conditions of
their existence, the psychic functions of the nerve-elements seem
nevertheless, everywhere to be in accord with certain fundamental
laws, even in the cases where this would be least expected on ac-
count of the magnitude of the differences.

APPENDIX.

THE PECULIARITIES OF THE OLFACTORY SENSE IN INSECTS.

Our sense of smell, like our sense of taste, is a chemical sense.
But while the latter reacts only to substances dissolved in liquids
and with but few (about five) different principal qualities, the
olfactory sense reacts with innumerable qualities to particles of the
most diverse substances dissolved in the atmosphere. - Even to our
relatively degenerate human olfactories, the number of these odor-
qualities seems to be almost infinite. |

In insects that live in the air and on the earth the sense of
taste seems to be located, not only like our own, in the mouth-
parts, but also'to exhibit the same qualities and the corresponding
reactions. At any rate it is easy to show that these animals are
usually very fond of sweet, and dislike bitter things, and that they
perceive these two properties only after having tasted of the re-
spective substances. F. Will, in particular, has published good
experiments on this subject. f

In aquatic insects the conditions are more complicated. Nagel,
who studied them more closely, shows how difficult it is in these
cases to distinguish smell from taste, since substances dissolved in
water are more or less clearly perceived or discerned from a dis-
tance by both senses and sought or avoided in consequence. Nagel,
at any rate, succeeded in showing that the palpi, which are of less
importance in terrestrial insects, have an important function in
aquatic forms.

In this place we are concerned with an investigation of the

sense of smell in terrestrial insects. Its seat has been proved to be

38 ANTS AND SOME OTHER INSECTS.

in the antennz. A less important adjunct to these organs is located,
as Nagel and Wasmann have shown, in the palpi. In the antenne
it is usually the club or foliaceous or otherwise formed dilatations
which accommodate the cellular ganglion of the antennary nerve.
I shall not discuss the histological structure of the nerve-termina-
tions but refer instead to Hicks, Leydig, Hauser, my own investi-
gations and the other pertinent literature, especially to K. Kraepe-
lin’s excellent work. I would merely emphasise the following
points:

1. All the olfactory papille of the antenne are transformed,
hair-like pore-canals.

2. All of these present a cellular dilatation just in front of the
nerve-termination.

3. Tactile hairs are found on the antenne together with the
olfactory papille.

4. The character and form of the nerve-terminations are highly
variable, but they may be reduced to three principal types: pore-
plates, olfactory rods, and olfactory hairs. The two latter are
often nearly or quite indistinguishable from each other. The nerve-
termination is always covered with a cuticula which may be never
so delicate.

Other end-organs of the Hymenopteran antenna described by
Hicks and myself, are still entirely obscure, so far as their function
is concerned, but they can have nothing to do with the sense of
smell, since they are absent in insects with a delicate sense of smell
(wasps) and accur in great numbers in the honey-bees, which have
obtuse olfactories. | |

That the antenne and not the nerve-terminations of the mouth
and palate function, as organs of smell, has been demonstrated by
my control experiments, which leave absolutely no grounds for
doubt and have, moreover, been corroborated on all sides. Ter-
restrial insects can discern chemical substances at a distance by
means of their antennz only. But in touch, too, these organs are
most important and the palpi only to a subordinate extent, namely
in mastication. The antenne enable the insect to perceive the
‘chemical nature of bodies and in particular, to recognise and dis-

ANTS AND SOME OTHER INSECTS. 39

tinguish plants, other animals and food, except in so far as the
visual and gustatory senses are concerned in these activities. These
two senses may be readily eliminated, however, since the latter
functions only during feeding and the former can be removed by
varnishing the eyes or by other means. Many insects, too, are
blind and find their way about exclusively by means of their an-
tennz. This is the case, e. g., with many predatory ants of the
genus Eciton.

But I will here assume these questions to be known and an-
swered, nor will I indulge in polemics with Bethe and his asso-
ciates concerning the propriety of designating the chemical anten-
nal sense as ‘‘smell.” I have discussed this matter elsewhere.!
What I wish to investigate in this place is the psychological quality
of the antennal olfactory sense, how it results in part from observa-
tion and in part from the too little heeded correlative laws of the
psychological exploitation of each sense in accordance with its
structure. I assume as known the doctrines of specific energies
and adequate stimuli, together with the more recent investigations
on the still undifferentiated senses, like photodermatism and the
like, and would refer, moreover, to Helmholtz’s Die Thatsachen in
der Wahrnehmung, 1879. Hirschwald, Berlin.

When in our own human subjective psychology, which alone
is known to us directly, we investigate the manner in which we in-
terpret our sensations, we happen upon a peculiar fact to which
especially Herbert Spencer has called attention. We find that so-
called perceptions consist, as is well known, of sensations which
are bound together sometimes firmly, sometimes more loosely. The
more intimately the sensations are bound together to form a whole,
the easier it is for us to recall in our memory the whole froma
part. Thus, e. g., it is easy for me to form an idea from the thought
of the head of an acquaintance as to the remainder of his body. In
the same manner the first note of a melody or the first verse of a
poem brings back the remainder of either. But the thought of an

1‘** Sensations des Insectes,” Rzvzsta di Biologia Generale, Como, 1900-1901.
For the remainder see also A. Forel, Mitth. des Miinchener entom. Vereins, 1878,
and Recueil. Zool. Suisse, 1886-1887.

40 ANTS AND SOME OTHER INSECTS.

odor of violets, a sensation of hunger, or a stomach-ache, are in-
capable of recalling in me either simultaneous or subsequent odors
or feelings. |

These latter conditions call up in my consciousness much
more easily certain associated visual, tactile, or auditory images
(e. g., the visual image of a violet, a table set fora meal). As
ideas they are commonly to be represented in consciousness only
with considerable difficulty, and sometimes not at all, and they are
scarcely capable of association among themselves. We readily ob-
serve, moreover, that visual images furnish us mainly with space
recollections, auditory images with sequences in time, and tactile
images with both, but less perfectly. These are indubitable and
well-known facts.

But when we seek for the wherefore of these phenomena, we
find the answer in the structure of the particular sense-organ and
in its manner of functioning.

It is well known that the eye gives us a very accurate image
of the external world on our retina. Colors and forms are there
depicted in the most delicate detail, and both the convergence of
our two eyes and their movement and accommodation gives us be-
sides the dimensions of depth through stereoscopic vision. What-
ever may be still lacking or disturbing is supplied by instinctive
inferences acquired by practice, both in memory and direct per-
ception (like the lacunz of the visual field), or ignored (like the
turbidity of the corpus vitreum). But the basis of the visual im-
age is given in the codrdinated tout ensemble of the retinal stimuli,
namely the retinal image.!_ Hence, since the retina furnishes us
with such spatial projections, and these in sharp details, or rela-
tions, definitely codrdinated with one another, the sense of sight
gives us knowledge of space. For this reason, also, and solely on
this account, we find it so easy to supply through memory by asso-

1It is well known that in this matter the movements of the eyes, the move-
ments of the body and of external objects play an essential part, so that without
these the eye would fail to give us any knowledge of space. But I need not discuss
this further, since the antenne of ants are at least quite as moveable and their
olfactory sense is even more easily educated in unison with the tactile sense.

2 th a i i, i

a? pac]8. cam dw ae a kd te

- ae,

i< 2

ANTS AND SOME OTHER INSECTS. 41

ciation the missing remnant of a visual spatial image. For this
reason, too, the visual sensations are preéminently associative or
relational in space, to use Spencer’s expression. For the same

reason. the insane person so readily exhibits halucinations of com-

plicated spatial images in the visual sphere. This would be im-
possible in the case of the olfactory sense.

Similarly, the organ of Corti in the ear gives us tone or sound
scales in accurate time-sequence, and hence also associations of
sequence much more perfectly than the other senses. Its associa-
tions are thus in the main associations of sequence, because the
end-apparatus registers time-sequences in time-intervals and not
as space images. |

The corresponding cortical receptive areas are capable, in the
first instance, merely of registering what is brought to them by the
sense-stimuli and these are mainly associated spatial images for
sight and tone or sound-sequences for hearing.

Let us consider fora moment how odors strike the mucous
membranes of our choane. They are wafted towards us as wild
mixtures in an airy maelstrom, which brings them to the olfactory
terminations without order in the inhaled air or in the mucous of
the palate. They come in such a way that there cannot possibly
be any spatial association of the different odors in definite relation-
ships. In time they succeed one another slowly and without order,
according to the law of the stronger element in the mixture, but
without any definite combination. If, after one has been inhaling
the odor of violets, the atmosphere gradually becomes charged
with more roast meat than violet particles, the odor of roast suc-
ceeds that of violet. But nowhere can we perceive anything like a
definitely associated sequence, so that neither our ideas of time nor
those of space comprise odors that revive one another through as-
sociation. By much sniffing of the surface of objects we could at
most finally succeed in forming a kind of spatial image, but this
would be very difficult owing to man’s upright posture. Neverthe-
less it is probable that dogs, hedge-hogs, and similar animals ac-
quire a certain olfactory image by means of sniffing. The same
conditions obtain in the sphere of taste and the visceral sensations

42 ANTS AND SOME OTHER INSECTS.

for the same reasons. None of these senses furnish us with any
sharply defined qualitative relations either in space or time. On
this account they furnish by themselves no associations, no true
perceptions, no memory images, but merely sensations, and these
often as mixed sensations, which are vague and capable of being
associated only with associative senses. The hallucinations of
smell, taste, and of the splanchnic sensations, are not deceptive
perceptions, since they cannot have a deceptive resemblance to ob-
jects. They are simply paresthesias or hyperesthesias, i. e., path-
ological sensations of an elementary character either without ade-
quate stimulus or inadequate to the stimulus.

The tactile sense furnishes us with a gross perception of space
and of definite relations, and may, therefore, give rise to hallucina-
tions, or false perceptions of objects. By better training its asso-
ciative powers in the blind may be intensified. The visual sensa-
tions are usually associated with tactile localisations.

Thus we see that there is a law according to which the psy-
chology of a sense depends not only on its specific energy but also
on the manner in which it is able to transmit to the brain the rela-
tions of its qualities in space and time. On this depends the
knowledge we acquire concerning time and space relations through
a particular sense and hence also its ability to form perceptions
and associations in the brain. More or less experience is, of course,
to be added or subtracted, but this is merely capable of enriching
the knowledge of its possessor according to the measure of the re-
lations of the particular sense-stimuli in space and time.

I would beg you to hold fast to what I have said and then to
picture to yourselves an olfactory sense, i. e., a chemical sense
effective at a distance and like our sense of smell, capable of re-
ceiving impressions from particles of the most diverse substances
diffused through the atmosphere, located not in your nostrils, but
on your hands. For of such a nature is the position of the olfac-
tory sense on the antennal club of the ant.

Now imagine your olfactory hands in continual vibration, touch-
ing all objects to the right and to the left as you walk along, thereby
rapidly locating the position of all odoriferous objects as you ap-

ANTS AND SOME OTHER INSECTS. 43

proach or recede from them, and perceiving the surfaces both simul-
taneously and successively as parts of objects differing in odor and
position. It is clear from the very outset that such sense-organs
would enable you to construct a veritable odor-chart of the path
you had traversed and one of double significance:

1. Aclear contact-odor chart, restricted, to be sure, to the
immediate environment and giving the accurate odor-form of the
objects touched (round odors, rectangular odors, elongate odors,
etc.) and further hard and soft odors in combination with the tac-
tile sensations.

2. A less definite chart which, however, has orienting value
for a certain distance, and produces emanations which we may pic-
ture to ourselves like the red gas of bromine which we can actually
see.

If we have demonstrated that ants perceive chemical qualities
through their antennz both from contact and from a distance, then
the antennz must give them knowledge of space, if the above for-
mulated law is true, and concerning this there can be little doubt.
This must be true even from the fact that the two antenne simul-
taneously perceive different and differently odoriferous portions of
space.) _

| They must therefore also transmit perceptions and topograph-
ically associated memories concerning a path thus touched and
smelled. Both the trail of the ants themselves and the surround-
ing objects must leave in their brains a chemical (odor-) space-
form with different, more or less definitely circumscribed qualities,
i. e., an odor-image of immediate space, and this must render as-
sociated memories possible. Thus an ant must perceive the forms
of its trail by means of smell. This is impossible, at least for the
majority of the species, by means of the eyes. If this is true, an
ant will always be able, no matter where she may be placed on her

1Tt is not without interest to compare these facts with Condillac’s discussion
(Treatise on the Sensations) concerning his hypothetical statue. Condillac shows
that our sense of smell is of itself incapable of giving us space knowledge. But it
is different in the case of the topochemical sense of smell in combination with the
antennary movements. Here Condillac’s conditions of the gustatory sense are ful-
filled.

44 ANTS AND SOME OTHER INSECTS.

trail, to perceive what is to the right, left, behind or before her,
and consequently what direction she is to take, according to whether
she is bound for home, or in the opposite direction to-a tree in-
fested with Aphides, or the like.

Singularly enough, I had established this latter fact in my
‘‘Etudes Myrmécologiques en.1886” (Annales de la Societé Ento-
mologique de Belgique) before I had arrived at its theoretical inter-
pretation. But I was at once led by this discovery in the same
work to the interpretation just given. Without knowing of my
work in this connection, A. Bethe has recently established (dis-
covered, as he supposes) this same fact, and has designated it as
‘¢polarisation of the ant-trail.””. He regards this as the expression
of a mysterious, inexplicable force, or polarisation. As we have
seen, the matter is not only no enigma, but on the contrary, a nec-
essary psychological postulate. We should rather find the absence
of this faculty incomprehensible.

But everything I have just said presupposes a receptive brain.
The formation of lasting perceptions and associations cannot take
place without an organ capable of fixing the sense-impressions and
of combining them among themselves. Experience shows that the
immediate sensory centers are inadequate to the performance of
this task. Though undoubtedly receptive, they are, nevertheless,
incapable of utilising what has been received in the development
of more complex instincts and can turn it to account only in the
grosser, simpler reflexes and automatisms. To be sure, a male
ant has better eyes than a worker ant, and probably quite as good
antennz, but he is unable to remember what he has seen and is
especially incapable of associating it in the form of a trail-image,
because he is almost devoid of a brain. For this reason he is un-
able to find his way back to the nest. On the other hand, it is well
known that the brain of a man who has lost a limb or whose hear-
ing is defective, will enable him to paint pictures with his foot,
write with the stump of an arm or construct grand combinations
from the images of defective senses.

I venture, therefore, to designate as topochemical the olfactory
antennal sense of honey-bees, humble-bees, wasps, etc.

F
3

ere ey ee

bg

Afr

eer ae in ic

—— sh ee oe

See a

ANTS AND SOME OTHER INSECTS. 45

Can we generalise to such an extent as to apply this term with-
out further investigation to all arthropods? To a considerable ex-
tent this must be denied. |

In fact, the multiformity in the structure and development of
the arthropod sense-organs is enormous, and we must exercise cau-
tion in making premature generalisations.

It is certain that in some aerial insects the olfactory sense has
dwindled to a minimum, e. g., in those species in which the male
recognises and follows the female exclusively by means of the eyes,
as in the Odonata (dragon-flies). To insects with such habits an
olfactory sense would be almost superfluous. Here, too, the an-
tennze have dwindled to diminutive dimensions.

But there are insects whose antennz are immovable and quite
unable to touch objects. This is the case in most Diptera (flies).
Still these antennz are often highly developed and present striking
dilatations densely beset with olfactory papille. By experiment I
have demonstrated the existence of an olfactory sense in such
Dipteran antenne, and I have been able to show that, e. g., in
Sarcophaga vivipara and other carrion flies, the egg-laying instinct
is absolutely dependent on the sensation of the odor of carrion and
the presence of the antennz. In these cases'the contact-odor sense
is undoubtedly absent. More or less of a topochemical odor-sense
at long range must, of course, be present, since the antennz are
external, but the precision of the spatial image must be very im-
perfect, owing to the immobility of the antennze. Nevertheless,
flies move about so rapidly in the air that they must be able by
means of their antennz to distinguish very quickly the direction
from which odors are being wafted. These insects do, in fact, find
the concealed source of odors with great assurance. But this is no
great art, for even we ourselves are able to do the same by sniffing
or going to and fro. But the flies find their way through the air
with their eyes and not at all by means of their sense of smell.
Hence their olfactory powers probably constitute a closer psycho-
logical approximation to those of mammals than to the topochemi-
cal odor-sense of ants, for they can hardly furnish any constant and
definite space-relations.

46 ANTS AND SOME OTHER INSECTS.

Even in many insects with movable antenne and of less erial

habits, e. g., the chafers and bombycid moths, the antennal olfac-

tory sense is evidently much better adapted to function at a dis-

tance, i. e., to the perception of odors from distant objects, than»

to the perception of space and trails. Such insects find their way
by means of their eyes, but fly in the direction whence their an-
tenne perceive an odor that is being sought.

A genuine topochemical antennal sense is, therefore, probably
best developed in all arthropods, whose antenne are not only mov-
able in the atmosphere, but adapted to feeling of objects. In these
cases the still imperfect topochemical oder-sense for distances can
be momentarily controlled by the contact-odor-sense and defini-
tively fixed topographically, i. e., topochemically, as we see so ex-
tensively practised in the ants.

It would be possible to meet this view with the objection that
a contact-odor sense could not accomplish much more than the
tactile sense.- I have made this objection to myself. But in the
first place it is necessary to reckon with the facts. Now it is a fact
that insects in touching objects with their antennze mainly perceive
and distinguish the chemical constitution of the objects touched
and heed these very much more than they do the mechanical im-
pacts also perceived at the same time. Secondly, the tactile sense
gives only resistance and through this, form. On the other hand,
the multiplicity of odors is enormous, and it is possible to demon-
strate, as I have done for the ants, and Von Buttel-Reepen for the
bees, that these animals in distinguishing their different nest-mates
and their enemies, betray nothing beyond the perception of ex-
tremely delicate and numerous gradations in the qualities of odors.

In combination with topochemical space-perception, these
numerous odor-qualities must constitute a spatial sense which is
vastly superior to the tactile sense. The whole biology of the so-
cial Hymenoptera furnishes the objective proof of this assertion.

It would certainly be well worth while to investigate this mat-
ter in other groups of arthropods which possess complex instincts.

In conclusion I will cite an example, which I have myself ob-

ee a a

"ae.

_—

s-* he ae,

ANTS AND SOME OTHER INSECTS. 47

served, for the purpose of illustrating the capacity of the topo-
chemical olfactory sense.

The American genus Eciton comprises predatory ants that
build temporary nests from which they undertake expeditions for
the purpose of preying on all kinds of insects. The Ecitons follow
one another in files, like geese, and are very quick to detect new
hunting grounds. As ‘‘ants of visitation,” like the Africo-Indian
species of Dorylus, they often take possession of human dwellings,
ferret about in all the crevices of the walls and rooms for spiders,
roaches, mice, and even rats, attack and tear to pieces all such
vermin in the course of a few hours and then carry the booty home.
They can convert a mouse into a clean skeleton. They also attack
other ants and plunder their nests.

Now all the workers of the African species of Dorylus and of
many of the species of Eciton are totally blind, so that they must
orient themselves exclusively by means of their antennal sense.

In 1899 at Faisons, North Carolina, I was fortunate enough to
find a temporary nest of the totally blind little Eczton carolinense in
a rotten log. I placed the ants in a bag and made them the sub-
ject of some observations. The Eciton workers carry their elon-
gate larve in their jaws and extending back between their legs in
such a position that the antennz have full play in front.

Their ability to follow one another and to find their way about
rapidly and unanimously in new territory without a single ant go-
ing astray, is incredible. I threw a handful of Ecitons with their
young into a strange garden in Washington, i. e., after a long rail-
way journey and far away from their nest. Without losing a mo-
ment’s time, the little animals begam to form in files which were
fully organised in five minutes. Tapping the ground continually
with their antenne, they took up their larve and moved away in
order, reconnoitering the territory in all directions. Nota pebble,
not a crevice, not a plant was left unnoticed or overlooked. The
| place best suited for concealing their young was very soon found,
whereas most of our European ants under such conditions, i. e., in
a completely unknown locality, would probably have consumed at
least an hour in accomplishing the same result. The order and

48 ANTS AND SOME OTHER INSECTS.

dispatch with which such a procession is formed in the midst of a
totally strange locality is almost fabulous. I repeated the experi-
ment in two localities, both times with the same result. ~The an-
tenneze of the Ecitons are highly developed, and it is obvious that
their brain is instinctively adapted to such rapid orientation in
strange places.

In Colombia, to be sure, I had had opportunities of observing,
not the temporary nests, but the predatory expeditions of larger
Ecitons (2. Burchelli and hamatum) possessing eyes. But these
in no respect surpassed the completely blind Z. carolinense in their
power of orientation and of keeping together in files. As soon as
an ant perceives that she is not being followed, she turns back and
follows the others. But the marvellous fact is the certainty of this
recognition, the quickness and readiness with which the animals
recognise their topochemical trail without hesitation. There is
none of the groping about and wandering to and fro exhibited by
most of our ants. Our species of Tapinoma and Polyergus alone
exhibit a similar but less perfect condition. It is especially inter-
esting, however, to watch the serpetuum mobile of the antenne of
the Ecitons, the lively manner in which these are kept titillating
the earth, all objects, and their companions.

All this could never be accomplished by a tactile sense alone.
Nor could it be brought about by an olfactory sense which furnished
no spatial associations. As soon as an Eciton is deprived of its
two antennz it is utterly lost, like any other ant under the same
circumstances. It is absolutely unable to orient itself further or to
recognise its companions.

In combination with the powerful development of the cere-
brum (corpora pedunculata) the topochemical olfactory sense of the
antenne constitutes the key to ant psychology. Feeling obliged
to treat of the latter in the preceeding lecture, I found it necessary
here to discuss in detail this particular matter which is so often
misunderstood.

[In his latest Souvenirs entomologiques (Seventh Series) J. H. Fabre has
recorded a number of ingenious experiments showing the ability of the males of

Saturnia and Bombyx to find their females at great distances and in concealment.

re Ase

ANTS AND SOME OTHER INSECTS. 49

He tried in vain (which was to have been foreseen) to conceal the female by odors
which are strong even to our olfactories. The males came notwithstanding. He
established the following facts: (1) Even an adverse wind does not prevent the
males from finding their way ; (2) if the box containing the female is loosely closed,
the males come nevertheless ; (3) if it is hermetically closed (e. g., with wadding or
soldered) they no longer come; (4) the female must have settled for some time on
a particular spot before the males come; (5) if the female is then suddenly placed
under a wire netting or a bell-jar, though still clearly visible, the males neverthe-
less do not fly to her, but pass on to the spot where she had previously rested
and left her odor ; (6) the experiment of cutting off the antennz proves very little.
The males without antennz do not, of course, come again; but even the other
males usually come only once: their lives are too short and too soon exhausted.

At first Fabre did not wish to believe in smell, but he was compelled finally,
as a result of his own experiments, to eliminate sight and hearing. Now he makes
a bold hypothesis: the olfactory sense of insects has two energies, one (ours),
which reacts to dissolved chemical particles, and another which receives ‘' physical
odor-waves,”’ similar to the waves of light and sound. He already foresees how
science will provide us with a ‘‘radiography of odors” (after the pattern of the
Roentgen rays). But his own results, enumerated above under (4) and (5) contra-
dict this view. The great distances from which the Bombyx males can discern
their females is a proof to him that this cannot be due to dissolved chemical par-
ticles. And these same animals smell the female only after a certain time and
smell the spot where she had rested, instead of the female when she is taken away!
This, however, would be inconceivable on the theory of a physical wave-sense,
while it agrees very well with that of an extremely delicate, chemical olfactory
sense.

It is a fact that insects very frequently fail to notice odors which we perceive
as intense, and even while these are present, detect odors which are imperceptible
to our olfactories. We must explain this as due to the fact that the olfactory pa-
pillz of different species of animals are especially adapted to perceiving very differ-
ent substances. All biological observations favor this view, and our psycho-chem-
ical theories will have to make due allowance for the fact. ]

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The Kingdom of Protista. By Pror, Ernst Hazcxer, ‘The Open Court,” No. 394.

“The Cellular Soul. By Pror, Ernst Haecke. From Haeckel’s ‘‘Phylogenie.” ‘‘’'The
Open Court,” No. 396.

The Phylogeny of the Plant-Soul. By Pror. Ernst Haecxet, From the ‘“ Phylogenie.”
«*The Open Court,” No, 398.

Epigenesis or Preformation. By Pror. Bawst Hacker, “The Open Court,” No. 405.

5

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