Auguste Forel, who in 1909 retired from the Chair of Morbid
Psychology in the University of Zürich, was born on September 1,
1848, and is one of the greatest students of the minds and senses
of the lower animals and mankind. Among his most famous works are
his "Hygiene of Nerves and Mind," his great treatise on the whole
problem of sex in human life, of which a cheap edition entitled
"Sexual Ethics" is published, his work on hypnotism, and his
numerous contributions to the psychology of insects. The chief
studies of this remarkable and illustrious student and thinker for
many decades past have been those of the senses and mental
faculties of insects. He has recorded the fact that his study of
the beehive led him to his present views as to the right
constitution of the state--views which may be described as
socialism with a difference. His work on insects has served the
study of human psychology, and is in itself the most important
contribution to insect psychology ever made by a single student.
Only within the last two years has the work of Forel, long famous
on the European Continent, begun to be known abroad.
_I.--Insect Activity and Instinct_
This subject is one of great interest, as much from the standpoint of
biology as from that of comparative psychology. The very peculiar
mechanism of instincts always has its starting-point in sensations. To
comprehend this mechanism it is essential to understand thoroughly the
organs of sense and their special functions.
It is further necessary to study the co-ordination which exists between
the action of the different senses, and leads to their intimate
connection with the functions of the nerve-centres, that is to say, with
the specially instinctive intelligence of insects. The whole question
is, therefore, a chapter of comparative psychology, a chapter in which
it is necessary to take careful note of every factor, to place oneself,
so to speak, on a level with the mind of an insect, and, above all, to
avoid the anthropomorphic errors with which works upon the subject are
filled.
At the same time the other extreme must equally be
avoided--"anthropophobia," which at all costs desires to see in every
living organism a "machine," forgetting that a "machine" which lives,
that is to say, which grows, takes in nutriment, and strikes a balance
between income and expenditure, which, in a word, continually
reconstructs itself, is not a "machine," but something entirely
different. In other words, it is necessary to steer clear of two
dangers. We must avoid (1) identifying the mind of an insect with our
own, but, above all, (2) imagining that we, with what knowledge we
possess, can reconstruct the mind by our chemical and physical laws.
On the other hand, we have to recognise the fact that this mind, and the
sensory functions which put it on its guard, are derived, just as with
our human selves, from the primitive protoplasmic life. This life, so
far as it is specialised in the nervous system by nerve irritability and
its connections with the muscular system, is manifested under two
aspects. These may be likened to two branches of one trunk.
(_a_) _Automatic_ or _instinctive_ activity. This, though perfected by
repetition, is definitely inherited. It is uncontrollable and constant
in effect, adapted to the circumstances of the special life of the race
in question. It is this curious instinctive adaptation--which is so
intelligent when it carries out its proper task, so stupid and incapable
when diverted to some other purpose--that has deceived so many
scientists and philosophers by its insidious analogy with humanly
constructed machines.
But, automatic as it may appear, instinct is not invariable. In the
first place, it presents a racial evolution which of itself alone
already demonstrates a certain degree of plasticity from generation to
generation. It presents, further, individual variations which are more
distinct as it is less deeply fixed by heredity. Thus the divergent
instincts of two varieties, _e.g._, of insects, present more individual
variability and adaptability than do those instincts common to all
species of a genus. In short, if we carefully study the behaviour of
each individual of a species of insects with a developed brain (as has
been done by P. Huber, Lubbock, Wasmann, and myself, among others, for
bees, wasps, and ants), we are not long in finding noteworthy
differences, especially when we put the instinct under abnormal
conditions. We then force the nervous activity of these insects to
present a second and plastic aspect, which to a large extent has been
hidden from us under their enormously developed instinct.
(_b_) The _plastic_ or _adaptive_ activity is by no means, as has been
so often suggested, a derivative of instinct. It is primitive. It is
even the fundamental condition of the evolution of life. The living
being is distinguished by its power of adaptation; even the amoeba is
plastic. But in order that one individual may adapt itself to a host of
conditions and possibilities, as is the case with the higher mammals and
especially with man, the brain requires an enormous quantity of nerve
elements. But this is not the case with the fixed and specialised
adaptation of instinct.
In secondary automatism, or habit, which we observe in ourselves, it is
easy to study how this activity, derived from plastic activity, and ever
becoming more prompt, complex, and sure (technical habits), necessitates
less and less expenditure of nerve effort. It is very difficult to
understand how inherited instinct, hereditary automatism, could have
originated from the plastic activities of our ancestors. It seems as if
a very slow selection, among individuals best adapted in consequence of
fortunate parentage, might perhaps account for it.
To sum up, every animal possesses two kinds of activity in varying
degrees, sometimes one, sometimes the other predominating. In the lowest
beings they are both rudimentary. In insects, special automatic activity
reaches the summit of development and predominance; in man, on the
contrary, with his great brain development, plastic activity is elevated
to an extraordinary height, above all by language, and before all by
written language, which substitutes graphic fixation for secondary
automatism, and allows the accumulation outside the brain of the
knowledge of past generations, thus serving his plastic activity, at
once the adapter and combiner of what the past has bequeathed to it.
According to the families, _genera_, and species of insects, the
development of different senses varies extremely. We meet with most
striking contrasts, and contrasts which have not been sufficiently
noticed. Certain insects, dragon-flies, for instance, live almost
entirely by means of sight. Others are blind, or almost blind, and
subsist exclusively by smell and taste (insects inhabiting caves, most
working ants). Hearing is well developed in certain forms (crickets,
locusts), but most insects appear not to hear, or to hear with
difficulty. Despite their thick, chitinous skeleton, almost all insects
have extremely sensitive touch, especially in the antennæ, but not
confined thereto.
It is absolutely necessary to bear in mind the mental faculties of
insects in order to judge with a fair degree of accuracy how they use
their senses. We shall return to that point when summing up.
_II.--The Vision of Insects_
In vision we are dealing with a certain definite stimulus--light, with
its two modifications, colour and motion. Insects have two sets of
organs for vision, the faceted eye and the so-called simple eye, or
ocellus. These have been historically derived from one and the same
organ. In order to exercise the function of sight the facets need a
greater pencil of light rays by night than by day. To obtain the same
result we dilate the pupil. But nocturnal insects are dazzled by the
light of day, and diurnal insects cannot see by night, for neither
possess the faculty of accommodation. Insects are specially able to
perceive motion, but there are only very few insects that can see
distinctly.
For example, I watched one day a wasp chasing a fly on the wall of a
veranda, as is the habit of this insect at the end of summer and in the
autumn. She dashed violently in flight at the flies sitting on the wall,
which mostly escaped. She continued her pursuit with remarkable
pertinacity, and succeeded on several occasions in catching a fly, which
she killed, mutilated, and bore away to her nest. Each time she quickly
returned to continue the hunt.
In one spot of the wall was stuck a black nail, which was just the size
of a fly, and I saw the wasp very frequently deceived by this nail, upon
which she sprang, leaving it as soon as she perceived her error on
touching it. Nevertheless, she made the same mistake with the nail
shortly after. I have often made similar observations. We may certainly
conclude that the wasp saw something of the size of a fly, but without
distinguishing the details; therefore she saw it indistinctly. Evidently
a wasp does not only perceive motion; she also distinguishes the size of
objects. When I put dead flies on a table to be carried off by another
wasp, she took them, one after another, as well as spiders and other
insects of but little different size placed by their side. On the other
hand, she took no notice of insects much larger or much smaller put
among the flies.
Most entomologists have observed with what ingenuity and sureness
dragon-flies distinguish, follow, and catch the smallest insects on the
wing. Of all insects, they have the best sight. Their enormous convex
eyes have the greatest number of facets. Their number has been estimated
at 12,000, and even at 17,000. Their aerial chases resemble those of the
swallows. By trying to catch them at the edge of a large pond, one can
easily convince oneself that the dragon-flies amuse themselves by making
sport of the hunter; they will always allow one to approach just near
enough to miss catching them. It can be seen to what degree they are
able to measure the distance and reach of their enemy.
It is an absolute fact that dragon-flies, unless it is cold or in the
evening, always manage to fly at just that distance at which the student
cannot touch them; and they see perfectly well whether one is armed with
a net or has nothing but his hands; one might even say that they measure
the length of the handle of the net, for the possession of a long handle
is no advantage. They fly just out of reach of one's instrument,
whatever trouble one may give oneself by hiding it from them and
suddenly lunging as they fly off. Whoever watches butterflies and flies
will soon see that these insects also can measure the distance of such
objects as are not far from them. The males and females of bees and ants
distinguish one another on the wing. It is rare for an individual to
lose sight of the swarm or to miss what it pursues flying. It has been
proved that the sense of smell has nothing to do with this matter. Thus
insects, though without any power of accommodation for light or
distance, are able to perceive objects at different distances.
It is known that many insects will blindly fly and dash against a lamp
at night, until they burn themselves. It has often been wrongly thought
that they are fascinated. We ought first to remember that natural
lights, concentrated at one point like our artificial lights, are
extremely rare in Nature. The light of day, which is the light of wild
animals, is not concentrated at one point. Insects, when they are in
darkness--underground, beneath bark or leaves--are accustomed to reach
the open air, where the light is everywhere diffused, by directing
themselves towards the luminous point. At night, when they fly towards a
lamp, they are evidently deceived, and their small brains cannot
comprehend the novelty of this light concentrated at one spot.
Consequently, their fruitless efforts are again and again renewed
against the flame, and the poor innocents end by burning themselves.
Several domestic insects, which have become little by little adapted to
artificial light in the course of generations, no longer allow
themselves to be deceived thereby. This is the case with house-flies.
Bees distinguish all colours, and seldom confound any but blue and
green; while wasps scarcely react to differences of colour, but note
better the shape of an object, and note, for instance, where the place
of honey is; so that a change of colour on the disc whereon the honey is
placed hardly upsets them. Further, wasps have a better sense of smell
than bees.
The chief discovery regarding the vision of insects made in the last
thirty years is that of Lubbock, who proved that ants perceive the
ultra-violet rays of the spectrum, which we are unable, or almost
unable, to perceive.
It has lately been proved also that many insects appreciate light by the
skin.
They do not see as clearly as we do; but when they possess
well-developed compound eyes they appreciate size, and more or less
distinctly the contours of objects.
Ants have a great faculty for recognition, which probably testifies to
their vision and visual memory. Lubbock observed ants which actually
recognised each other after more than a year of separation.
_III.--Smell, Taste, Hearing, Pain_
Smell is very important in insects. It is difficult for us to judge of,
since man is of all the vertebrates except the whales, perhaps, the one
in which this sense is most rudimentary. We can evidently, therefore,
form only a feeble idea of the world of knowledge imparted by a smell to
a dog, a mole, a hedgehog, or an insect. The instruments of smell are
the antennæ. A poor ant without antennæ is as lost as a blind man who is
also deaf and dumb. This appears from its complete social inactivity,
its isolation, its incapacity to guide itself and to find its food. It
can, therefore, be boldly supposed that the antennæ and their power of
smell, as much on contact as at a distance, constitute the social sense
of ants, the sense which allows them to recognise one another, to tend
to their larvæ, and mutually help one another, and also the sense which
awakens their greedy appetites, their violent hatred for every being
foreign to the colony, the sense which principally guides them--a little
helped by vision, especially in certain species--in the long and patient
travels which they have to undertake, which makes them find their way
back, find their plant-lice, and all their other means of subsistence.
As the philosopher Herbert Spencer has well pointed out, the visceral
sensations of man, and those internal senses which, like smell, can only
make an impression of one kind as regards space--two simultaneous odours
can only be appreciated by us as a mixture--are precisely those by which
we can gain little or no information relative to space. Our vision, on
the contrary, which localises the rays from various distant points of
space on various distinct points of our retina at the same time, is our
most relational sense, that which gives us the most vast ideas of space.
But the antennæ of insects are an olfactory organ turned inside out,
prominent in space, and, further, very mobile. This allows us to suppose
that the sense of smell may be much more relational than ours, that the
sensations thence derived give them ideas of space and of direction
which may be qualitatively different from ours.
Taste exists in insects, and has been very widely written on, but
somewhat inconclusively. The organs of taste probably are to be found in
the jaws and at the base of the tongue. This sense can be observed in
ants, bees, and wasps; and everyone has seen how caterpillars especially
recognise by taste the plants which suit them.
Much has been written on the hearing of insects; but, in my judgment,
only crickets and several other insects of that class appear to perceive
sounds. Erroneous views have been due to confusing hearing with
mechanical vibrations.
We must not forget that the specialisation of the organ of hearing has
reached in man a delicacy of detail which is evidently not found again
in lower vertebrates.
Pain is much less developed in insects than in warm-blooded vertebrates.
Otherwise, one could not see either an ant, with its abdomen or antennæ
cut off, gorge itself with honey; or a humble-bee, in which the antennæ
and all the front of the head had been removed, go to find and pillage
flowers; or a spider, the foot of which had been broken, feed
immediately on this, its own foot, as I myself have seen; or, finally, a
caterpillar, wounded at the "tail" end, devour itself, beginning behind,
as I have observed more than once.
_IV.--Insect Reason and Passions_
Insects reason, and the most intelligent among them, the social
hymenoptera, especially the wasps and ants, even reason much more than
one is tempted to believe when one observes the regularly recurring
mechanism of their instincts. To observe and understand these
reasonings well, it is necessary to mislead their instinct. Further, one
may remark little bursts of plastic judgment, of combinations--extremely
limited, it is true--which, in forcing them an instant from the beaten
track of their automatism, help them to overcome difficulties, and to
decide between two dangers. From the point of view of instinct and
intelligence, or rather of reason, there are not, therefore, absolute
contrasts between the insect, the mammal, and the man.
Finally, insects have passions which are more or less bound up with
their instincts. And these passions vary enormously, according to the
species. I have noted the following passions or traits of character
among ants: choler, hatred, devotion, activity, perseverance, and
gluttony. I have added thereto the discouragement which is sometimes
shown in a striking manner at the time of a defeat, and which can become
real despair; the fear which is shown among ants when they are alone,
while it disappears when they are numerous. I can add further the
momentary temerity whereby certain ants, knowing the enemy to be
weakened and discouraged, hurl themselves alone in the midst of the
black masses of enemies larger than themselves, hustling them without
taking the least further precaution.
When we study the manners of an insect, it is necessary for us to take
account of its mental faculties as well as of its sense organs.
Intelligent insects make better use of their senses, especially by
combining them in various ways. It is possible to study such insects in
their homes in a more varied and more complete manner, allowing greater
accuracy of observations.