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TIWAIUSS ll,

Feter Smit del. et hth, : AR Mintern Bros, Chromo,
A group of protectively coloured avimals.

ANIMAL COLORATION

AN ACCOUNT OF

The Principal Facts and Theories

RELATING TO THE

COLOURS AND MARKINGS OF ANIMALS

BY

FRANK E. BEDDARD, M.A. Oxon., F.R.S.E., Ere.

Prosector to the Zoological Society of London, Lecturer on Biology at Guy's Hospital

With Kowr Coloured Plates; and Wloodeuts in the Test

LONDON: SWAN SONNENSCHEIN & CO.
NEW YORK: MACMILLAN & CO.
1892,

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ie We A Shh.

BO, | \ey om?)

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Printed by Hazell, Watson, & Viney, La, London and Aylesbury.

PREFACE.
—- &—

THe present volume has grown out of materials which I
had collected for the ‘“ Davis Lectures,” delivered by me
in the Zoological Society’s Gardens during the spring of
Iso. This book is addressed, as were the lectures, to persons
having no special knowledge of zoology, but that general
interest in the facts and problems of the science, which is now
su widely spread. It contains hardly anything novel, but
professes to give some account of the principal phenomena
of coloration exhibited by animals. Some of the facts and
theories, however, have not, so far as I am aware, as yet
found their way into works of a popular character; I refer
particularly to the ingenious theories of Dr. Eisig and
M. Stolzmanu. Inasmuch as Mr. Poulton’s work upon the
Colours of Animals, recently published as one of the volumes
of the ‘International Neientific Series,” and Mr. Wallace’s
sketel of coloration in his ‘ Darwinism,” deal with colour
almost entirely from the point of view of natural selection,
I have attempted to lay some stress upon other aspects of
the question. The literature relating to animal coloration is
enormous ; xo much so that it is really beyond the powers of
any person who cannot give up lus whole time to abstract
it thoroughly. To write an exhaustive work upon Animal
Coloration requires a sort of naturalist that now hardly can

exist—a specialist in every group. However, all that I have

iv PREFACE.

aimed at is to furnish a general notion of the facts and
theories relating to Animal Coloration, and I trust that
nothing of great importance has been omitted. Many of my
examples have been selected from animals that may be usually
seen in the Zoological Society’s Gardens. I have not used
insects so much as has Mr. Poulton ; this is not in the least
because I do not regard them as furnishing such good material
for the exposition of the phenomena and theories of colour ; it
is simply because Mr. Poulton’s book is, or ought to be, in the
hands of every one interested in the subject; and acting on
this supposition I have thought it advisable to draw more
largely upon other groups. Nevertheless it is impossible not
to devote a good deal of space to insects. The theory of
Mimicry, for instance, is almost entirely supported by evideuce
furnished from that group. I am much indebted to Mr.
Bateson for numerous references tu papers bearing upon the
subject of animal coloration, and to Prof. Flower for kindly
permitting me to have drawings made of some of the beautiful
preparations, illustrating animal coloration, which he had
caused to he prepared for the national museum at South
Kensington. Other assistance I shall acknowledge in the
course of the following pages.

TABLE OF CONTENTS.

CHAPTER I.
INTRODUCTORY.

The Colours of Animals.— Colours caused by Absorption of Light due to the
Presence of Pigments.—Colours associated with Substances of Physio-
logical Importance to the Animal.—Ha:moglobin.—Chlorophyll.—
Other Pigments of Physiological Importance.—The Coloration of
Animals.—Vlan of Coloration not always Useful to the Animal.—
Constancy of Coloration.—The Action of Natural Selection in pro-
ducing Colour Vhanges must be strictly Limited.—Comparative Con-
stancy of Colour in Genera and Species.—The same Plan of Coloration
often found in Distantly-related Animals.—Relation between Colora-
tion and Structure-——Changes of Colour during Lifetime.—Absence
of Brilliant Coloration among Mammals.—The Colours of Deep-sea
Animals.—Change of Colour after Death—Connection between In-
tegumental] Piements and lixcretory Products.

CHAPTER II.
COLORATION AFFECTED BY THE ENVIRONMENY.

Local Colour Varielies.—Geographical Distribution of Colour.-—Additional
Justances of an Apparent Connection between Colour aud Locality.—
Effects of Food upon Colour.—Hffects of Temperature and Moisture.—
Lixamples of Mclanic Varieties found upon Islands.—Further Examples
of Effects of Temperature and Moisture.—Influcnce of Light.—Absence
of Colour in Animals which live in Darkness not always due tou Absence
of Light.—Colour sometimes Dependent upon Light.—Bright Colours in
Subterranean Animals.— Influence of Light upon Colours of Flat-fish.—
Absence of Colour in Cave Animals.—Seasonal Change in Colour.—
Seasonal Change in Orthoptera.—Seasunal Change in a Bectie.—Change
of Colour in Arctic Animals.—Seasonal Dimorphism

vl CONTENTS.

CHAPTER IL.
PROTECTIVE COLORATION,

Special Colour Resemblances.—Protection afforded by Resemblances of this
kind chiefly efficacious against Vertebrate Enemies.—Some Evidence
showing that Caterpillars are concealed by Protective Coloration from
Enemies.—Protective Coloration of the Iguana.—Protective Colora-
tion occasionally appears to be Superfluous.—Protective Resemblance
in an Annelid.---Protective Coloration the prevailing device among
Leaf-feeding Caterpillars Protective Coloration in Man.—Green
Colour of the Moth.—Longitudinal Striping of Caterpillars.—Longi-
tudinal Striping found in all the species of the Butterfly Family
Satyride.—These Larve usually feed by Night and often conceal
themselves by Day.—Internal-feeding Larvz sometimes Striped.—
Striping sometimes occurs in Certain Species Only of a Genera,.—
Striped Larve do not always feed on or among Grasses.— Occasional
Absence of Coloration in Internal-feeding Caterpillars—-The Resem-
blance of the Larve of Geometers tv Twigs.—Comparative Rarity of
Green Trec-frequenting Animals an Argument in favour of Selection.—
Deceptively-coloured African Mantis.—Protective Coloration in Spiders.
—Do Animals select Resting-places which are in Harmony with
their Colour /—Indifferent Colours.—Certain apparently Protectively
Coloured Animals probably do not owe their Coloration to Natural
Selection.—Specific Characters retained even in Insects which imi-
tate the same Environment.—Protection often due to Multiplicity of
Surroundings——Colours of Pelagic Organisms.—Protective Resem-
blances due to Causes other than Natural Selection.—Combination
of Many Methods of Defence.—Dimorphism in Coloration.—Variable
Protective Resemblances in Chrysalids.— Variable Protective Coloration
in Vertebrates.

CHAPTER Iv.
WARNING COLORAITON.

The Magpie-moth Caterpillar as an Instance of Warning Colours.—Karlier
Experiments with Warningly-coloured Insects.—Some Experiments
upon the Palatability of Various Animals.— Warning Colours can only
be safely adopted by a comparatively Small Number of Animals.—
Objections to the Current Theory of Warning Coloration.—The Wings
of some Inedible Butterflies resist Injury.—Dr. Fisig’s Theory of
Warning Colours,—Connection between Integumental Pigment and
Excretory Products.—Warning Colours of N udibranchs.— Warnine
Coloration in Wasps.—Dr. Hisig’s View not universally applicable.—
The Warning Coloration of the Skunk.—Warning Coloration in Other
Mammals.— Warning Coloration in Reptiles. —Warning Coloration in
Amphibia.—Bright Colours not always used as a Warning.—Instance
of Alluring Coloration ina Lizard.-—Other Examples of Alluring Colours.
—Bright Colours and Large Size of the Fins in certain Fish may haye
iw Protective Value.

83

11s

CONTENTS. vii

CHAPTER V.
PROTECTIVE MIMICRY.

Mr. Bates’ Theory.—-Mimicry often found only in Females.—Are the
Danaidz strongly scented, like the Heliconidw ?—Distastefulness
sometimes limited to a Few Individuals.—Resistent Structure of the
Wings in Danaids an Additional Defence.—Mimicry between Pro-
tected Forms.—Mimicry between Insects belonging to Different
Orders.—A Protected Insect sometimes Mimicked by more than
one Species.—Mimicry of Vertebrates by Insects and of Insects by
Vertebrates.—Mr. Wallace’s statement of the Conditions under which
Protective Mimicry occurs.—Objections to the Theory of Mimicry.—
Resemblances among more or less remotely allied Animals which
perhaps cannot be put down to Mimicry.—Instances of Developing
Mimicry in Butterflies—Butterflies more attacked by Birds in the
Tropics than in Temperate Regions.—Spiders mimicking Ants.—
Difficulty of distinguishing between Mimicry and Warning Colora-
tion.—Resemblances hetween Insects occurring in Different Countries.
—Mimicry possibly originated between forms much alike to start
with.—Cases of apparently Useless Mimicry.—Mimicry of Hymeno-
ptera by Volucella is Difficult to account for.—Vision of Tnsects.—
Cases of Mimicry in which the Mimicking Form is equally abundant
with the Model.—Criticism of an apparent case of Mimicry.—
Mimicry in some cases possibly only a Resemblance due to Affinity.
—Mimicry among Mammals.—Mimicry among Birds.—Mimicry may
be in certain cases even Disadvantageous.—Mimicry not always De-
ceptive.—The Occasional Limitation of Mimicry to the Female Insect.
—Mimicry between Unprotected Forms.—Relative Unimportance of
the Imago Stage in Butterflies—Summary, : ‘ . 198

CHAPTER VI.
SEXUAL COLORATION.

Sexual Dimorphism in Colour,—Sexual Dimorphism of Colour most marked
in Birds and Butterflies. Slight Development of Colour Dimorphism
in Mammals.—Dependence of Sexual Dimorphism from the Generat-
ing Laws.—The Theory of Sexual Selection.—-Difficulty of Believing
in a highly-developed Asthetic Sense.— A‘sthetic Sense of Butterflies. —
Objections to the Theory of Sexual Selection.—Excitability at Breed-
ing Scason of Animals among which there is no Pairing.—Some
arguments in favour of Sexual Selection.—The Courtship of Spiders,
- Sexual Dimorphism partly due to a Need for Protection on the
part of the Female.--Mr, Stoltzmann’s Views.—Mr. Wallace’s Views.
Summary

GUNERAL INDEX. s 4 f ‘i P . 7 ~ BRA

INDUX OF AUTHOR'S NAMES, : ‘ i j « DST

LIST OF ILLUSTRATIONS.

PLATES.

PLATE I.—A Group of Protectively Coloured Animals To face page 108
» IL—Kallima butterfly ‘ * : 139
, IlL—Group of Animals Exhibiting Warning Colours 150
, IV.—Volucellz and Bees o ss 225
WOODCOUTS.
FIG. : PAGE | FIG. PAGE
1, Arctic Fox 74 18, Swallowtail Butterfly and
2. Ermine . 75 Larva lv
3. Orange Tip 87 | 19. (Fig. 10 repeated) 215
4, Lappet Moth . 88 7 20. Coral Snake 181
5, Sloth 96 | 21. Salamander 184
6. Delphinus delphis . 115 | 22. Fishing Frog . 189
7. Aptenodytes patagonica 116 | 23. Flying Gurnard 192
8. Phronima sedentaria 124 | 24. Leptalis and Ithomia 194
9. Mysis. si 5 : 125 | 25. Hornet Clearwing . 203
10, EHolis and Dendronotus . 128 | 25. Cladohates 236
11. Puss Moth and Caterpillar 134 | 27. Bee Hawk Moth 245
12. Chameleons 142 | 28. Female and Larvae of Psyche. 254
13. The Horned Toad (Phryno- 29. Bird of Paradise 257
soma) 144 | 30. Humming Bird 258
14, Tree Frogs , . 145 | 31. Argus Pheasant 258
15. Buff Tip Moth and Cater- 32. Cincinnurus regius 250
pillar 151 33, Night-Jar 270
16. Leopard Moth 158 | 34. Winter Moth . 271
17. Vapourer Moth: male, female, 35. Winter Moth, Maleand Female 271
and larva 160 | 386, Gypsy Moth , , 292

4

ANIMAL COLORATION.

———>—-
CHAPTER I.

INTRODUCTORY.—THE PRINCIPAL FACTS OF ANIMAL
COLORATION.

%

We must clearly distinguish at the outset between ‘“ Colour’
and “ Coloration” : the two terms are frequently confused, but
they are obviously by no means synonymous. By colours we
understand the actual tints (blue, green, red, etc.) which are
found in animals ; by coloration, the arrangement or pattern
of these tints. In certain cases the two expressions colour
and coloration may be practically synonymous, may coincide :
in a perfectly green caterpillar it is only necessary to mention
the colour ; but in the vast majority of cases the colours are
more than one, and have therefore a certain arrangement :
there is thus a coloration.
The Colours of Animals.

The colours of animals are due either solely to the presence
of definite pigments in the skin, or, in the case of trans-
parent animals to pigment in the tissues lying beneath the
skin; or they are partly caused by optical effects due to the
scattering, diffraction or unequal refraction of the light rays.

Colours of the latter kind are often spoken of as, structural

colours ; they are caused by the structure of the coloured
1

2 ANIMAL COLORATION.

surfaces. The metallic lustre of the feathers of many birds,
such as the humming birds, is due to the presence of
excessively fine striee upon the surface of the feathers. Dr.
Gadow has recently gone into the question of the colours of
birds’ feathers as determined by their structure in great detail,”
and to his paper the reader is referred; in every case the
colour needs for its display a background of dark pigment ;
that this is so is shown very well in the case of the albino
forms of many birds: the structure of the feathers is perfectly
normal, but the pigment needed as a background to show up
the effect of the feather structure is wanting.

Colours caused by Absorption of Light due to the Presence

of Pigments.

By far the commonest source of colour in invertebrate
animals is the presence in the skin of definite pigments which
absorb all the rays of light except those of a particular wave-
length, thus giving the effect of a particular colour. Pigments
are found also in the hair and skin of mammals, in the feathers
of birds, and in the horny integument of reptiles. A great
variety of pigments have been approximately isolated and their
chemical nature studied ; but it would be beyond the scope of
the present work to attempt any general account of animal
pigments. Those interested in the subject may refer to Krii-
kenberg’s “ Vergleichend physiologische Studien,” to papers by
Dr. Sorby, Dr. Macmunn and others in the Proceedings of the
Royal Society, the Quarterly Journal of Microscopical Science
and elsewhere.

There are a few facts, however, which may be noticed here.

The same colour even in allied forms is not always due to
the presence of an identical pigment. Thus the brown colour of.

* Proc. Zool. Soc. 1882.

INTRODUCTORY. 3

birds is chiefly due not to one pigment, but to two apparently
distinct pigments, which give different chemical reactions; to
these two pigments their discoverer, Kriikenberg, has given
the name of Zoorubin and Pseudozoorubin respectively. An
inspection of the feathers would not enable one to tell with
certainty which of the two substances was the cause of the
colour ; but an extract of zoorubin can always be detected by its
change to a beautiful cherry red on the addition of the minutest
trace of blue sulphate of copper. The green colour of the
feathers of the turacou is due to a pigment, turacoverdin,
which is quite different from that which causes the green colour
of the parrot.* Again, the crimson colour of the same bird is
produced by a very different pigment from those which cause
the crimson colour of any other birds the colouring-matter of
whose feathers has been studied.

This being the case, it is not surprising to find that animals
only remotely allied are often coloured by quite different pig-
ments, which yet produce the same effect.

But on the other hand there are some pigments which have
a very wide distribution among animals. Zoonerythrin, or
tetronerythrin, as it has been also called, is found in both
vertebrates and invertebrates. The blood of the common
earthworm owes its red colour to hemoglobin, as does also the
blood of all vertebrate animals, including man.

Pigments may be even common to plants and animals: apart
from chlorophyll (see p. 6), it has been stated that carotin (a
vegetable pigment) is found in certain crustacea.

Sometimes differently coloured animals have in reality the
same skin pigments. The attention of the reader will be
directed in a later chapter to the remarkable difference in
colour between the males and females of certain parrots. In

* The actual pigment here is yellow.

4 ANIMAL COLORATION.

Eclectus polychlorus this sexual dimorphism is extremely
marked. It would be an exceedingly anomalous fact if the
same species of bird were to possess different pigments in the
two sexes; and as a matter of fact it is not so in this parrot,
different in colour though the two sexes are. The same
pigments are present, but the structure of the feathers is
different, and thus the resulting colour as seen by the eye is
different.

Different colours may be also produced by a variation in
the amount of the pigment present: the colours are darker
if a great deal of pigment is present ; and if there is but little,
the colour of the internal organs may show through the
comparatively transparent skin, and by their admixture with
the proper pigment of the skin produce a totally different
effect. The varying colours of many earthworms, leeches, and
other invertebrates, are instances of this.

It is commonly said that there is no white pigment in
animals : this statement appears to be erroneous. Mr. Gaskell
finds that the pineal eye of the lamprey has white pigment. This
is also the case with the butterfly Arge galathea. The white
patches on the wings of this insect* turn yellow when ammonia
is applied to them; as the ammonia evaporates the normal
white colour gradually returns. With fixed alkalies such as
sodium hydrate the primrose yellow colour was permanent,
but the white could be restored by means of acids.

Pigment is present in other organs of the body besides the
skin: in the blood, for example, of red-(vertebrates, many worms)
and green- (certain worms—e.g. Sadelia) blooded animals, and
in the liver. The colour of an animal is sometimes entirely due
to these internal pigments seen through the transparent and
colourless skin (¢.g., pelagic ascidians, very small worms).

* Nature, 1884, vol. xxx., p. 571.

INTRODUCTORY. >

Many of these pigments appear to have no special use in the
animal economy, except in so far as they may be utilised in
order to produce a protective resemblance to the surroundings,. :
and in other ways treated of in the succeeding chapters. They
are often merely waste products which are temporarily stored
up in the skin (see p. 126).

On the other hand, there are certain coloured substances
which have been proved to have a functional importance.

Colours associated with Substances of Physiological Importance

to the Animal.

Some animals owe their colour to substances embedded in
the skin, or existing in the tissues beneath, which play an
important part in the processes of respiration, digestion, and in
other physiological functions. The coloration of such animals
may be advantageous or disadvantageous as a means of con-
cealment ; if disadvantageous, we must assume that the direct
advantages of the processes accompanying life which the
coloured substances give outweigh the disadvantages in ren-
dering the animal conspicuous, etc. If they happen to be
advantageous in the latter way, it must be looked upon as a
fortunate accident. The substances themselves which give the
colour cannot probably be changed without destroying or
altering their useful physiological purposes ; nor, in some cases
at least, can they be concealed without rendering them useless
for their particular purpose.

Hemoglobin.

For example, most rivers and lakes abound with minute
worms of half an inch to two inches or so in length, which are
frequently of a bright red colour. These worms belong to
several genera of the Oligochceta—a group which also includes
the common earthworm.

6 ANIMAL COLORATION,

A particularly abundant form is Tubifex rivulorum, which
lives associated in great numbers and partially embedded in
mud at the bottom of streams, etc. ; the head end is fixed in
the mud, while the tail waves about freely in the water ; these
worms form exceedingly conspicuous red patches, which must
attract ground-feeding fish. The colour is due to a substance
termed hemoglobin dissolved in the blood; this substance is
also found in the blood of the higher animals, and it plays the
chief part in respiration ; it is able to absorb from the air, and
readily give up to the tissues, oxygen.

A thickening of the body walls of the worm, or an extensive
deposition of pigment, would no doubt render them less visible,
but would probably at the same time interfere with the efficacy
of the respiratory processes.

This substance hemoglobin is a very widely spread respira-
tory pigment, but it is not of much importance as giving a
colour to the animal except in the group of the Annelids.

Chlorophyll.

Another pigment which is of physiological import is chloro-
phyll. The colour of all green plants is due to this substance,
which is found in the cells of the more superficial tissues. The
importance of chlorophyll to the plant is enormous. The actual
physiological processes which occur are not yet thoroughly
understood, but the result is that in some way or other the
living matter—the protoplasm—of the plant is able with the
help of the green colouring-matter to split up the carbonic
acid of the air into its constituent elements, carbon and oxygen.
The carbon combines with the water in the plant to form starch.
This process can only go on in the presence of sunlight : if
some fragments of a plant that has been exposed to the sun
for some time be teazed up with needles, and stained with a

INTRODUCTORY. 7

solution of iodine, the blue colour of the starch, which com-
bines with the iodine, can be seen under the microscope.
The plant thus gets a large proportion of its food by the help of
this green chlorophyll.

It is a fact of very great interest that chlorophyll also occurs
in animals : it is a proof of the fundamental identity between
animals and plants ; the living matter or protoplasm of both is
capable of manufacturing an identical product. As might be
expected, chlorophyll in animals performs a perfectly similar
function to that which it performs in plants ; this is particularly
the case with certain lowly organised worms in which it occurs.
There is a small worm belonging to the Turbellaria, which is
entirely without an alimentary canal ; it has neither mouth nor
stomach. This creature—Convoluta Schultzei—lives in sandy
pools left by the sea, associated together in masses, which
freely expose themselves to the sunlight. Professor Geddes
found some years ago that they give off, when thus exposed,
bubbles of oxygen gas, which is of course an indication that the
vreen substance is chlorophyll.

Other Pigments of Physiological Importance.

Certain sponges are coloured by a substance which was
originally described by Wurm under the name of Tetronery-
thrin.* This orange red colouring-matter is widely spread
in the animal kingdom ; it occurs, for instance, in two groups
so widely separated as birds and sponges ; it is very common
in sponges, and is believed by Kriikenberg capable of absorbing
oxygen and converting it into ozone ; hence it is clearly of
great importance as a respiratory pigment, and is analogous
in a way to chlorophyll, or perhaps rather to hemoglobin.
Like chlorophyll, it is very susceptible to light.

~ It was afterwards redescribed as Zoonerythrin.

8 ANIMAL COLORATION.

Another pigment, which seems to be of equal importance to
hemoglobin, is chlorocruorin, found in certain green marine
Annelids ; it colours their blood, and performs the office of an
oxygen carrier. :

It is very possible that the brightly coloured oil globules
which are found in the epidermis of certain Turbellarian worms,
and in the small fresh-water annelid olosoma, play a part
analogous to that of chlorophyll or tetronerythrin.

The Coloration of Animals.

It is important, as has already been said, to distinguish
between “Colour” and “ Coloration ”
the actual tints and their arrangement and distribution. It is no

doubt the fact, as Mr. Wallace states, that colour is “a normal

—that is to say, between

product of organisation,” entirely independent of utility; on the
other hand, it will be pointed out in the following pages that
there is a good deal of evidence to show that “ coloration ”
bears often a distinct relation to the needs of the animal ; it
may therefore have been modified by natural selection.

One example will suffice to render this matter clearer: the
common Peacock butterfly has wings adorned with the most
varied and beautiful colours, with which are associated duller
browns and black; if these different tints were scattered
generally over the surface of the wings, the insect would be
conspicuous to its enemies at all times,—the coloration might,
if it were palatable to birds, render its extinction a matter of a
very short time. But in the actual butterfly the most brilliant
colours are concentrated upon the upper surface of the wings,
and particularly to form four eyelike markings, one at the
corner of each wing; the under surface is entirely mottled with
dull shades; accordingly, when the insect is at rest and therefore
more accessible to its foes, the inconspicuous underside is alone

‘ INTRODUCTORY. 9

visible; while when flying about in the sunshine and tolerably
free from molestation, as it is strong on the wing, the brilliant
colours do no great harm ; or possibly, as has been suggested,
the highly conspicuous marks upon the corners of the wings
attract the attention of birds to a part which may be injured
without doing the butterfly much harm.

It is supposed, therefore, that in cases of this kind there has
been a gradual elimination of colour varieties less in harmony
than others with the peculiar needs of the insect.

Plan of Coloration not always Useful to the Animal.

Any one who has some knowledge of natural history will
at once remark that coloration is apparently not always in
harmony with the mode of life of the animal; not only are
colours and coloration which have no use that can be detected
present, but the general plan of coloration is occasionally
absolutely dangerous; so it at least seems. Mr. Romanes has
pointed out that the different patterns on the breasts of
woodpeckers can have no function; for these birds when in
their natural haunts do not show the spotted under surface.
The highly conspicuous larve of one of our rarer Hawk moths
(Deilephila galit) must fall an easy prey to creatures that feed
upon them, for it has been proved experimentally that they
are not, as gaudily-coloured insects often are, distasteful to
insect-eating animals; their colours cannot therefore have been
acquired “as an advertisement of their inedibility.”

The advocates of the theory of natural selection as applied
to coloration are apt to explain cases of this kind by falling back
upon our ignorance of so much of natural history: they main-
tain that, were we better acquainted with the life and habits
of those creatures, some explanation would be forthcoming ;

10 ANIMAL COLORATION.

there is, of course, no gainsaying such an argument. But
many instances of coloration are not believed by any one to be

> remarks

adaptive; “there can be no question of adaptation,’
Mr. Wallace, “ in the brilliant colours of red snow and other low
algee and fungi, or even in the universal mantle of green which
clothes so large a portion of the earth’s surface.” * Mr. Wallace
goes on to remark that “it is the wonderful individuality
of the colours of animals and plants that attracts our attention
—the fact that the colours are localised in definite patterns
sometimes in accordance with structural characters, sometimes
altogether independent of them, while often differing in the
most striking and fantastic manner in allied species. We are
thus compelled to look upon colour not merely as a physical but
also as a biological characteristic, which has been differentiated
and specialised by natural selection, and must therefore find its
explanation in the principle of adaptation or utility.” There
are some cases of internal coloration which show precisely
the same individuality, and would, were they external, be put
down as colour modifications requiring some explanation on the
principle of utility.

The body cavity of some lizards is deep black; the pig-
mentation does not affect the entire lining of the body cavity,
but only a part of it which is sharply differentiated from the
rest ; the palate of the orang-outan is black, that of the
chimpanzee, flesh-coloured, with no pigment at all. It is exactly
these specific or generic differences in coloration which are
sought to be explained by natural selection ; though it is clear
that in these instances no such explanation is possible. It
would not be, therefore, unreasonable to say that many forms
of external colour modifications may possibly be also without
any such explanation. It is at least too much to assume that

* © Darwinism,” p. 189.

INTRODUCTORY. 11

they must have some explanation, which may not have been
forthcoming.

A flagrant instance of non-adaptive coloration is the green
tint of the bones in the fishes Belone, Protopterus and
Lepidosiren, in the amphibian Pseudis and in a lizard. This
green colour is due to the presence of vivianite.

These apparent anomalies can, however, be regarded from
another point of view: it cannot be too often or too strongly
urged that we are living now among changes in the organic
(and inorganic) world just as marked as they were formerly;
perhaps even more marked, for the number of species’ must
be greater now than in the very early periods of the world’s
history; hence competition is keener. It is therefore not
surprising to find, among forms that appear to be “in harmony
with the environment,” others that have not been able to move
with the times, or that are actually in process of moving.

Constancy of Coloration.

It has been urged that the constancy of animal colour
indicates utility; domestic animals, it is said, are subject to
great variability, which is vot seen in their wild relatives; the
reason for this is supposed to be the elimination of such
varieties among the wild animals. They occur in them just
as much as in the domesticated forms, but these varying indi-
viduals do not reach maturity, since they are not so suited to
cope with the conditions of their natural existence.

There are, however, a number of facts that must be considered
in relation to this question. Firstly, most of our domestic
animals have been domesticated for a long time; so long is
this time that in many cases their origin is lost in the obscurity
of the past. Who can say, for example, when the dog was first

12 ANIMAL COLORATION.

domesticated, and what was the original stock, or probably
stocks, from which an infinite variety of dogs have been bred
and selected? During this period they have been subjected
to every variety of treatment, have been fed with all kinds
of food, and have been repeatedly crossed with other breeds.
These facts alone give an opportunity for variation such as is
not possessed by most wild animals. Secondly, variations in
colour do of course occur among animals under natural con-
ditions; the pages of our entomological journals constantly
contain records of “varieties”; any one who will take the
trouble to consult the beautiful plates illustrating Mr. Buckler’s
“ History of British Lepidopterous Larve,” now being published
by the Ray Society, will find that in several of them (e.g.
Lophopteryx cimelina—four varieties figured) the colour is by
no means constant.

The Ruff is, of course, the classical instance ; it is said that
no two specimens of this bird are alike. One of the plates
illustrating Dr. McCook’s work * upon “ American Orb-weaving
Spiders ” is devoted to the illustration of eight or nine colour
varieties of the female of Epeira trifolium. In fact, if colouring
were really constant for a given species, there would be no
chance for natural selection.

Supposing that a marked variety occurs in a wild species,
there is, first of all, a considerable chance against its reach-
ing maturity; secondly, there is a considerable chance
against its finding a mate ; thirdly, the hereditary influences
on both sides are against the perpetuation of the variety. These
appear to be more potent causes of the comparative fixity of
colours in wild animals than the unfitness of the varieties
to live.

In domestic animals the two first difficulties are removed.

* Vol. ii., Pl. I.

INTRODUCTORY. 13

Occasionally, a fortunate concurrence of circumstances must
have removed the difficulties in the case of wild animals.

It is recorded in the “Proceedings” of the Zoological
Society for 1860 (p. 206), that nine albino moles were captured
in a field near Beckenham, in Kent. These may have been, it
is suggested, the offspring of one pair ; but more probably this
was not the case, since moles usually produce only four or five
young ones. Here, be it observed, the white moles were in a
position to find a mate, and therefore the colour was handed on
to their progeny.

In the Zoologist * Mr. Stevenson recorded that a pair of
albino night-jars were shot in the year 1856. The night-
jar is a very invariable bird, and so the fact is of interest, if
only as a record of variation. Moreover, white is a particularly
unfavourable variation in a crepuscular bird, coloured, as the
night-jar is, with hues entirely suitable to the dusky sur-
roundings of late evening. The isolated occurrence of even a
pair is not by itself, perhaps, a very remarkable fact as bearing
upon the question at hand; what is more remarkable and
important is the fact that an adult bird, also albino, was shot
near the same place in 1858,f and another in 1859; this
suggests a case of heredity of a variation most unfavourable to
the well-being of the species.

In the same Journal the existence of sixteen or eighteen
yellow rabbits in several adjacent warrens is recorded. This is
clearly a very large number of individuals of an unfavourable
variation. They disappeared, however, after the winter.

It would be of great importance to collect statistics of
variation occurring in nature ; but it is unnecessary to point,
out the great difficulties that would attend this line of investi-

gation.
* xiv.,tp. 5278. tT p. 6779. } p. 6560.

14 ANIMAL COLORATION.

The Action of Natural Selection in producing Colour Changes must.
be strictly Limited.

Although it is reasonable to suppose that the elimination of
unfit varieties may in some cases have led to the perfecting
of say a colour resemblance between the underside of a butter-
fly’s wing and a decaying leaf, calculated to deceive its enemies,
such action must be limited in various ways. The material
with which natural selection has to work is often very
restricted. One kind of modification may be possible in one
group which is quite impossible in another. Certain genera
of “* Whites,” such as Leptalis, are believed to owe their
striking resemblance to certain species of another family of
butterflies—the Heliconide—to a need for protection : the
Heliconide are distasteful to insect-eating birds, monkeys,
and other animals ; in consequence, they enjoy an immunity
from the attacks of these animals.

This immunity is apparently shared by Leptal/s on account
of its being mistaken for a Heliconid. It has the same shaped
wings and the same pattern of coloration. Now, this shape
and pattern are unusual among the “ Whites,” but it must be
remembered that the actual colours are present: yellow, white,
black and red are found among members of the family Pieride
which bear no resemblance to the Heliconide ; the shape of
the wings, too, which is so characteristic of the Heliconide is
met with in at least one white butterfly—the Wood White. It
is, therefore, not so remarkable to find the striking resemblance
that exists between certain Pieride and certain Heliconide z
the impression that is given by some books dealing with such
subjects is that the mimicking Pierids have, so to speak, gone
a very long way out of their road in assuming the livery of the
Heliconide. A mimicry between one of the “Blues” and a

INTRODUCTORY. 15

Heliconid would, for instance, not appear to be possible..
Similarly, we find among the Vanesside (“Red Admiral,”
‘ Tortoiseshell,” etc.) a very general dusky coloration of the
underwings, which often bears a very perfect resemblance to a
withered leaf, and, being thus probably advantageous to the
insect, may have been produced by the survival of the best suited
varieties; but among those Vanesside where such aresemblance
is not by any means perfect—e.g., the Painted Lady—there is
still the same confused mottling, which might, with but a little

change, be improved in the required direction. There is, so far
as I am aware, no case known of a Vanessa with leaf-green
underwings, such as are occasionally met with in butterflies
that frequent trees. This plan of colour would probably be
equally advantageous to a Vunessa, for green leaves often
sprout out low down on the trunks of trees. There is here
apparently, if not an impossibility of modification, at least a
tendency for progression along the line of least resistance.

Comparative Constancy of Colour in Genera and Families.

The fact is that not only is coloration, with a few exceptions,
constant for a given species, but it is also, with, of course, a
wider range of variation, constant to genera and to families.
There are exceptions, as there are among species ; but some of
these exceptions are often correlated with anatomical differences
which indicate that the supposed genus or family should be
divided. For instance. the “laughing jackass” of Australia
differs much from other kingfishers in colour ; and so do the
rest among themselves ; but this family of birds presents a
considerable variety of anatomical structure which argues a
wider separation between some of the species than has been
vet allowed by systematic Ornithologists. We find green to
be a very. common colour among Parrots, Touracous, , and.

16 ANIMAL COLORATION.

other tree-frequenting birds, but this colour does not occar
in plenty of other genera and families which equally live
among trees.

Green appears to be an impossible colour among rodents and
marsupials, and, indeed, among mammals in general, to which
rule the “green” Cercopithecus and the sloth* are hardly
exceptions. The Echinoderms as a group are distinguished by
shades of a brown or red to a purple coloration ; but the
wide distribution of certain colours is, perhaps, most strikingly
shown in the Mammalia.

Among butterflies we meet with the same thing. The
Lycenide (“Blues”) are generally, as their name denotes,
blue ; but they are also characterised by the eye-spots on the
under surface of the wings. The mottling of the underwings
of the Vanesside is another example ; so, also, is the “ silver-
of the underwings of the fritillaries, and the tawny

ing”?
coloration of the upper surface.

Besides, constancy of colour occurs among animals where it
can hardly be of much use. It would be difficult to say in
what way one species of earthworm is profited by having
a bluish purple coloration, another in having a decidedly
greenish tinge, and a third in being bright red. And yet it
is perfectly possible to distinguish species by their coloration,
as any one who takes a walk after a rainy night may see for
himself. The earthworm has enemies above ground as well
as below: the colours could obviously not be seen below
ground ; and it has yet to be proved that the rook, as he follows
the plough, exercises a deliberate choice in the colour of the
worms which are selected as food. Moreover, the same colours
are met with in earthworms inhabiting different parts of the
world, and as unlike in structure as they can be ; this would

* See, for the real cause of the green colour of the Sloth, p. 96.

INTRODUCTORY. 17

be set down in the case of many animals to a similar need
which has produced a similar effect. We can find, in fact, in
this group, and for the matter of that in others, examples of
most of the remarkable phenomena of coloration believed to
owe their existence to natural selection, which yet cannot, at
least so far as we can see, have that significance.

The Same Plan of Coloration often found in Distantly Related
Animals.

Just as the same pigments may occur in animals that are
not nearly related, so the same plan of coloration distinguishes
animals that are occasionally quite distantly placed in the
scheme of classification. Green butterflies, moths, beetles,
birds, lizards and frogs are numerous ; the transverse stripes
of the tiger are seen in the zebras and in the marsupial wolf
Thylacinus ; a spotted coat distinguishes a considerable
number of mammals belonging to different orders. The raven,
the American Ani, the Molothrus, agree in having a uniform
black covering of feathers ; the colours and patterns upon the
wings of the butterflies belonging to the genus Leptalis are
exactly repeated in butterflies of the genus Heliconius—a re-
presentative of an entirely distinct family. Hye-like markings
are found in caterpillars, moths, butterflies and shrimps. In
fact, it is not too much to say that hardly any animal has a
general plan of coloration which is distinctly its own, and is
not even closely paralleled in some other animal or animals
belonging to a different group. The reasons for these resem-
blances will be discussed in the following chapters ; they may
be roughly classified under three principal heads, which are
however not trenchantly marked off from each other. Animals
which resemble each other in having a uniform green colora-
tion, such as the iguana, the tree frog, certain caterpillars and

&
~

18 ANIMAL COLORATION.

moths, are for the most part tree frequenters. Their colour
obviously assimilates to that of their surroundings ; they agree,
therefore, in conforming to the same environment ; hence their
similarity of colour, which is believed to be effective as a pro-
tection from their enemies or as a means of allowing them to
steal upon their prey unobserved.

The patterns of coloration of other animals may have a
similar meaning: the spots of the jaguar are believed to be
suggestive of round patches of sunlight such as are admitted
through a screen of leaves ; spotted deer may also perhaps be
partially concealed by a similar impression being created. The
transverse striping of the tiger is always said to enable the
animal to shun observation among tall grasses ; the Thylacine
may benefit by the same plan of coloration. This protectice
coloration is widely spread among animals.

The salamander, several species of British caterpillars, and
the Heloderm lizard agree with each other in the startling
contrast of their colours, which are black and yellow ; these
animals, as well as many others which are conspicuously
coloured, have been shown to possess some disagreeable quality,
rendering them either unfit for food or dangerous to meddle
with. It is believed that this warning coloration has been
acquired in order to prevent any other animal making the
mistake of attempting to kill and eat them. It is an advertise-
ment—a highly coloured advertisement one may say—of their
unsuitability as food.

Finally, the particular and minute resemblances, often perfect
down to the smallest detail, which animals belonging to quite
different genera or families show for each other, are believed
to be advantageous, in that one animal is mistaken for the
other. In these cases a perfectly eatable and helpless insect
mimics one that is nauseous or dangerous ; it is therefore let

INTRODUCTORY. 19

alone by other animals, which have got to know either by
painful personal experience or by hereditary experience that
the insect. mimicked had better not be touched. This branch
of the subject will be treated of at length in the chapter re-
lating to “ Protective Mimicry.”

The theory of Natural Selection is believed by most natural-
ists to furnish the key to all these problems. ‘Among the
numerous applications of the Darwinian theory,” remarks Mr.
Wallace, “in the interpretation of the complex phenomena
presented by the organic world, none have been more successful,
or are more interesting, than those which deal with the colours
of animals and plants.”

Nevertheless, there are certain colour changes, which can be
produced by the direct action of external conditions such as
light, heat, cold, etc., and seem to be altogether independent of
any selective process. It is very possible that colour is more
largely atfected by such causes than has hitherto been ad-
mitted. A few cases where these environmental effects appear
to have come into play will be discussed in the next chapter.

Relation between Coloration and Structure.

Among segmented animals we constantly find that the
pattern of coloration conforms to the segmentation. The
oblique stripes on the caterpillars of certain hawk moths are
repeated from segment to segment. Mr. Alfred Tylor* has
attempted to show that in the Mammalia there is an analogous
connection between deep-seated structures and superficial
markings. In the zebra, for instance, a dark longitudinal stripe
marks the whereabouts of the spinal column ; the striping on
the flanks roughly corresponds with the ribs. :

There is certainly evidence that coloration has some relation

* “ Coloration in Animals and Plants,’ London, 1886.

20 ANIMAL COLORATION.

to the distribution of the underlying nerves. Mr. Allen has
stated* that the while marks on the head of the tiger correspond
to the area of distribution of the infra-orbital nerves. The
nerves terminate in or near the skin; and it is clear that there
must be some connection between nerve supply and coloration,
from the fact that in a hedgehog whose spines were white, the
nerves in connection with the muscles for contraction of the skin
were greatly diseased.t There are plenty of other pathological
facts of a like nature.

Changes of Colour during Lifetime.

Many animals which are hatched from eggs deposited by
the parent undergo a more or less elaborate series of changes
before they acquire the adult form. The most familiar
instances of this are the life histories of beetles, butterflies,
and other insects in which the series of changes are most
pronounced ; other insects, on the contrary, leave the egg in a
condition which is not very dissimilar from that which they
ultimately acquire. Many crustaceans, molluscs and other
invertebrates are also liberated from the egg before acquiring
their definitive structure and outward form. Among the
Vertebrata the Amphibia constantly are hatched as “ tadpoles,”
which possess only the rudiments of limbs, and have gills likea
fish ; after a longer or shorter period under normal conditions,
the gills disappear, limbs grow out, and the adult frog or newt
is formed. Even among birds and mammals the young are
occasionally produced in a somewhat imperfect condition ;
though the differences between the newly-hatched bird and the
new-born mammal from their parents are not nearly so great
as in the case of the Amphibia.

* Science, vol. ix., p. 36. t Zoolugist, vol. ix., p. 3022.

INTRODUCTORY. 2]

Where the metamorphosis is considerable, as for example
among the Lepidoptera and Amphibia, the structural differ-
ences are so great between the “ larva” and the “ imago” that
they are not fitted to lead a precisely similar life. The food
may be perfectly different: thus, the larva or caterpillars of
Lepidoptera usually feed upon leaves, while the imago—the
butterfly or moth—can only suck juices through its long
proboscis. The tadpole of the common frog feeds upon decay-
ing vegetable and animal matter, while the frog itself is
insectivorous. Seeing that pigment has been proved in so
many cases to be alterable by changes in the food, it is not
surprising to find that as a rule the colours of larve are totally
different from those of the adult form. There is no indication
of the gorgeous coloration of the Peacock or Red Admiral
butterfly in the dusky greenish larvie of these insects ; here, of
course, the change of colour is related to active internal changes
combined with a cessation from feeding.

Indeed, other causes besides food may contribute to these
dlifferences of colour and coloration ; but it is sufficient for the
present purpose to mention the fact that the differences exist.
Curiously enough, the rule is not without exceptions. The
common Magpie moth has a coloration which is very similar
in both the larva condition and in the perfect state; even the
chrysalis is not unlike the caterpillar: spots and blotches of
black and yellow on a whitish ground characterise the moth
and the caterpillar; the pupa is dark brown with yellowish
rings.

Some green moths—such as, for example, Halias quercana
—have green larve. These cases are less striking than that
afforded by the Magpie moth, since green is so common a
colour in nature. But resemblances of the kind shown by the
caterpillar and imago of the Magpie moth are so very rare

22 ANIMAL COLORATION.

that they may be fairly set down to a coincidence having no
particular meaning.

While it is easily intelligible that different structure,
different surroundings, and different food may produce differ-
ences of colour between larvee and imagos, it is not so easy
to understand the colour changes which take place during the
caterpillar stage, or during the lifetime of an animal which
is born in a condition practically identical with that of its
parents.

In some cases it may be plausibly urged that the progressive
modifications in colour have a protective value ; but in other
cases this kind of argument cannot be used.

The leaf insect. (Phyllium) has, in the adult condition, a most
extraordinary resemblance to a leaf; the colour is green, and
the wing-cases are marked with lines which simulate the
veins of the leaf; some of the joints of the limbs are flattened
and expanded. Mr. Andrew Murray relates” how an Indian
species exhibited in the Botanical Gardens at Edinburgh
deceived every person by its resemblance to the plant upon
which it lived. The deception was ultimately the cause of its
death ; for the visitors, sceptical as to its animal nature, insisted
upon touching it before they would be convinced.

This insect when it is hatched from the egg has, as have the
Orthoptera (crickets, grasshoppers, cockroaches, etc.) generally,
a form but little different from that which it finally gets ; but
its colour is yellowish red, and not green. Directly it begins
to feed, its colour speedily changes to a light green; this
colour gets mixed with yellow later in the year, suggesting
autumnal foliage, or at least a decaying leaf.

The first change, from brown to green, looks very much as
if the food were alone responsible, and as if it were caused by

* “Notice of the Leaf-Insect,” Edinb. New Phil. Journal, Jan. 1856.

INTRODUCTORY. 23

the deposition in the tissues of the insect of but slightly
altered chlorophyll. The brown colour of the young insect is
probably suggestive of a withered leaf, so that the change of
colour here is immaterial as far as concerns the protection of
the insect ; brown or green might be supposed to be equally
useful tints for a leaf-feeding and leaf-resembling insect.

Many green caterpillars are of a faint green from the very
first, and the eggs from which they are hatched are also green;
this is the case with the Convolvulus and Privet Hawk moths ;
but the green of the larva becomes intensified directly it begins
to feed; the colour is largely due to the contents of the
alimentary tract seen through the semi-transparent walls; but
the blood also becomes rapidly green-coloured.

The larve of most Sphingide pass through a very varied
series of changes from the time when they first leave the egg
to the time when they assume the chrysalis state. These
colour-changes have been recently studied with great care by
Mr. Poulton, especially with regard to the Convolvulus and
Privet Hawk moths.

The earliest complete observations upon the subject were,
however, published by Weismann.* In this work, referred to
in the foot-note, the reader will find an abundance of detail in
addition to that selected for the present purpose.

The caterpillar of the Large Elephant Hawk moth
(Cherocampa elpenor) leaves the egg with a yellowish-white
coloration, quite uniform, except for the caudal horn, which is
black ; later on the skin, at first transparent, becomes green,
the coloration being here, too, perfectly uniform, with the
exception of the caudal horn, which retains its dark, black
colour.

After the first moult a fine white line on either side extended

* “Studies in the Theory of Descent,” Eng. trans. by Prof. Meldola.

24 ANIMAL COLORATION.

between the dorsal middle line and the spiracles, from the
horn to the head ; while the horn developed a patch of red at
the base. A little later a rndiment of the eye-spots appears
as a slight curved indentation of the subdorsal white line on
the fourth and fifth segments ; at this period a second white
line connecting the spiracles is evident.

After the second moult the concavities on the subdorsal line
are filled in by a deposition of black pigment, the spiracular
white line disappears, and the subdorsal line becomes indistinct.

After the third moult the eye-spots become extremely con-
spicuous, the general green coloration is no longer so uniform,
bat darker green sinuous striations are shown upon a lighter
ground.

The fourth moult ushers in some important changes. The
general colour has changed to dark brown, the striations
being yellowish ; the subdorsal line only persists on the three
front segments and on the eleventh ; the red at the base of the
horn has entirely vanished, and that appendage has acquired a
greenish colour. There are a series of stripes, first visible in
the last stage, arranged obliquely on the spiracles.

In the last stage the eye-spots of the fourth and fifth
segments repeat themselves on the subsequent segment ; they
are, however, merely black spots without the white and violet
“ pupil” ; a pair of small, light-coloured dots also make their
appearance on each of segments 5—11l. The remains of the
subdorsal line on the first three segments is very evident as a
white line edged with black.

We may thus distinguish a number of well-marked charac-
teristics occurring at different periods of life. The young
caterpillar is green, with no markings. In the next stage it is
furnished with longitudinal stripes. Finally it becomes brown,
and the longitudinal stripes have disappeared, except on the

INTRODUCTORY. 24

first few segments, where one of them has given rise to eye-
like markings ; a series of oblique stripes, quite unconnected
with the longitudinal ones, have appeared. An important
result of these observations, which were carried out with a
large number of species of Hawk moths. is that the same
markings are repeated in the same order in allied forms ; one
stage or other may be omitted, but the oblique stripes never
precede the longitudinal striping; nor does any caterpillar
commence life with one of the later developed characters and
recur to one of the earlier.

Dr. Weismann considers that this series of stages, which is
more complete in some forms than in others, is an indication
of former influences that have been at work ; originally, for
example, a longitudinal striping was advantageous to such
caterpillars, perhaps for the reason, as it has been ingeniously
suggested, that monocotyledonous plants were more abundant in
former epochs of the earth’s history. The ribs on the leaves
of these plants are arranged longitudinally, and therefore a
caterpillar with a similar striping would be less conspicu-
ous ; even now it is found that grass-feeding caterpillars are
very generally longitudinally marked; for instance, those of
such butterflies as the Meadow Browns and Gatekeeper.
When these markings ceased to be useful, others more in
accordance with the surroundings were developed; but a
residue of the original coloration, only preserved in the earlier
stages, is left to tell the history of the species ; this, at least,
is the case as to some species ; others have, on the contrary.
remained at a stage of coloration, which is, ex hypothes?, dis-
advantageous. Dr. Weismann mentions a remarkable Sphinr
larva preserved in the Berlin Museum, which appears to have
remained of a uniform colour throughout the greater part of
its life. Green was no doubt the earliest colour of these cater-

26 ANIMAL COLORATION.

pillars, caused simply by the slightly altered pigment (chloro-
phyll) derived from their food. Possibly the advent of birds,
which are after all the chief foes of caterpillars, caused a
necessity for some change of colour, to escape their keen sight.
Dr. Weismann has pointed ont that green, although thoroughly
protective as a colour to leaf-feeding caterpillars while they
are small, is not so advantageous later:* the large size of
the body alone would render them conspicuous ; but this is
remedied by longitudinal or oblique striping, which breaks
up the large surface into a number of small areas, and thus
renders the insect less conspicuous.

It may therefore be wondered why this particular caterpillar
has still retained the primitive coloration ; it is as Weismann
has said, “a living fossil.” It must always be remembered,
however, that animal life is not stationary ; modification must
be going on before our eyes ; and the very fact of the rarity
of this caterpillar is so far an argument either that it is
becoming extinct owing to its inadaptability, or that it is a
variety of some form which has really become modified in the
required direction. The fact that many Sphinx larvee just
before pupation become brown-coloured is considered by Dr.
Weismann to be an adaptation to a change in habit: they rest
by day, and descend to the ground for concealment ; a green
colour would be therefore not nearly so suitable as brown. But
we have to consider the fact that such larve are dimorphic ;
some remain green, others turn brown. This, however, is not
to be explained, as suggested by Mr. Poulton (p. 135), as a
halving of the risks ; some caterpillars resembling leaves and

* It will be noted that this suggestion applies with equal force to
tree snakes, frogs, etc., which are usually brought forward as excellent
examples of protective coloration (see p. 145) ; they are, of course, muck
larger, and so the need for breaking up the surface is greater.

INTRODUCTORY. 27

others stems or the bare surface of the earth ; it is simply a
new and better adaptation which has not yet thoroughly esta-
blished itself. The green caterpillars are to be looked upon
as individuals of a class that will ultimately disappear owing
to their retention of a less perfect form of adaptation.

One difficulty in the way of this view of the origin of the
marking of the Hawk moth caterpillars is that the markings
are not always adaptive. With regard to the persistent reten-
tion of the longitudinal striping in the Macroglossine (the
Humming-bird Hawk moth, Bee Hawk moth, ete.), Dr.
Weismann remarks that “it is not difficult to perceive how
a whole group could have made shift with this low grade
of marking [longitudinal striping] up to the present time.
Colour and marking are not the only means of offence and
defence possessed by these insects ; and it is Just such simply-
marked larve as those of the Macroglossine which have the
protective habit of feeding only at night, and of concealing
themselves by day. Moreover, under certain conditions of life
the longitudinal stripes may be a better means of protection,
even for a Sphinx larva, than any other marking ; and all
those species in which this pattern is retained at the present
time live either among grasses or on Conifere.”

This last statement is not absolutely true, since Wacroglossa
Juciformis feeds upon honeysuckle, which, though it may
occasionally trail among grasses at the bottom of a hedgerow,
also climbs to a considerable height. It has longitudinal
stripes until an “advanced age.” So fur as the habit of night-
Teeding is concerned, many of these larvie might have remained
in the first stage: for it would not matter what their colour was.

But it may be always said that we have here an indication
of a former state of affairs; such an argument can no more be
refuted than those of the believers in Special Creation.

28 ANIMAL COLORATION.

On the whole, however, it is clear that there is a great deal
to be said for many of the phenomena of progressive change in
coloration being advantageous, and therefore conceivably due
to the action of elimination of unfit varieties.

Mr. Poulton has studied the life history of a caterpillar
belonging to quite a different group of moths—the Geometre.*

The adult larva of Selenia illunaria (one of the “ thorn
moths”) has the usual twig-like appearance and coloration
found in the group to which it belongs.

When first hatched, the caterpillars are almost entirely black,
with four transverse white stripes; these stripes gradually
disappear, and the ground colour becomes browner. During
the early stages the attitude, as figured by Mr. Poulton, would
seem to render the caterpillar rather conspicuous ; the twig-
like attitude assumed during later stages would probably be
more advantageous in the earlier stages in spite of the colour.
In fact, it is difficult to see any adaptation of colour and colora-
tion in this first stage.

It is still harder to detect any meaning of this kind in the
colour changes of some birds and mammals. The Tapirs are
forthe most part of a greyish-brown colour, which is uniformly
distributed. The Indian species has, on the other hand, a
good deal of white on the under parts.

Now, the young Tapirs are invariably spotted with white
spots on a brownish ground colour; the brown is decidedly
different from that of the adult animal. In the same way the
young of many Carnivora differ from their parents ; the young
Lion is distinctly spotted, and traces of this are to be seen
in the adult—particularly in the female; in relation to this fact
it must be remembered that the female is less differentiated
than the male. The young Pama is even more darkly spotted

* Trans. Entomol. Suc., 1885, pp. 309 et seq.

INTRODUCTORY. 29

than the lion whelp. The young of deer that are uniformly
coloured when adult are also, in some species, distinctly
spotted when young.

On the theory that every colour change has a meaning in
relation to the needs of the individual, it is not easy to see why
animals that are of a uniform colour should commence life by
being spotted. It has been suggested that the spots on the
young—in the case of the Carnivora, at any rate—enable their
parents to recognise them in the semi-obscurity of the caverns
or dark places which they inhabit ; but it is not likely that an
explanation of this kind can apply to all the cases mentioned.

It might, however, with some reason, be urged that the defini-
tive coloration is soon acquired ; and that in consequence the
ex hypothesi) disadvantageous colours of the young would not.
have time to do their possessors much harm.

But even this way out of the difficulty is barred in the case
of Gulls.

The bluish and white colour of many gulls is generally
allowed to be of protective value ; in any case, they are not
unlike their usual surroundings. For three years several of the:
common species of gulls have a brownish speckled plumage,
which is totally unlike that of the old bird; if one colour
is advantageous, the other must be the reverse; and three
years is either a considerable period, or not long enough.

The fact of the matter is that the colours of the young in
these cases are to be probably explained as a recapitula-
tion of ancestral characters, as in the case of the cater-
pillars investigated by Weismann. It is agreed among all
Ornithologists, since Professor Huxley’s well-known paper
upon the “ Classification of Birds,’* that the gulls are
most nearly related to some of the Waders. Now, a brownish.

* Proc. Zool. Soc., 1867.

30 ANIMAL COLORATION.

speckled plumage is very common among these birds (e.g.
Golden-Plover, Thick Knee, etc.), and might therefore be
expected to occur in the nearly related group of the Gulls.

In the same way many Carnivora are spotted ; hence it is
not surprising to find a remembrance of this condition in those
species which are self-coloured.

Professor Eimer has lately published an elaborate memoir
upon the markings of the Carnivora in which he maintains
that there has been a gradual progression from longitudinal
striping to spots, and that these have later united to form
cross-bars, a uniform coloration being the last term in the
series. This order is invariably maintained—a uniform
coloration, for example, never preceding a longitudinal
striping. Accordingly, though we find the young of the self-
coloured Puma spotted, we do not find a uniform coloration
in the young of any spotted or barred species. It must be
mentioned, however, that this conclusion of Himer’s has been
disputed by another zoologist, Dr. Haacke, who has found
cross stripes in the young of a certain Australian fish, which
is longitudinally striped when adult.

The regularity in the development of the markings of
the Carnivora corresponds to the regularity which Prof.
Weismann found in the markings of his caterpillars ; and in
both cases Prof. Eimer sees a definite law of variation altogether
independent of natural selection.

Prof. Eimer does not quote in his “ Organic Evolution,”
as he might have done, an interesting observation to which
Mr. Wallace has referred on the authority of the late Mr.
Alfred Tylor. It is that the cross stripes in the young of
certain hogs are preceded by spots which actually do fuse
together to form the cross-bars.

‘Still, these examples, like those described by Prof. Weis-

INTRODUCTORY. 31

mann, are, many of them at any rate, capable of explanation
on the theory that the markings of the young are a sur-
vival of a form of coloration that was once useful, but has
ceased to be so; but this explanation is obviously much
strained if it be applied, for instance, to the gulls. Further-
more, while it is quite intelligible that the remains of traces of
longitudinal striping upon the very young, and therefore very
small, Sphinx larvee could do no harm, it is not obvious that
the persistence of analogous conditions in large mammals
would be equally harmless ; it might have been expected,
therefore, that the spots or stripes would have been entirely
lost in the young. There, again, it must be of course borne in
mind that evolution is not at a standstill; perhaps, if we
knew it, there is an elimination of the spotted cubs of Carnivora
going on. The whole matter, like the problems of animal
coloration in general, presents us with an involved and
complicated question, to which the answer is probably no more
simple.

Absence of Brilliant Coloration among Mammals.

In view of the theories which have been advanced with
regard to sexual selection, it is, as M. Stolzman has pointed
out, a remarkable fact that brilliant colours are wanting in the
Mammalia. To this rule there are no conspicuous exceptions ;
the sternal callosities and naked patches about the face of
monkeys are often red or blue, and some of the fruit bats have
as bright a coloration as can be got from a contrast of black,
orange, and white; but there is no mammal which can
compare in point of brilliancy and variety of colour with even
such a comparatively plain bird as the chaffinch. The colours
of mammals are generally confined to dull shades of black,
brown, orange, and white. Considering the supposed ad-

32 ANIMAL COLORATION.

vantage of a green colour to tree-frequenting animals, it is not
a little remarkable not to meet with green in some of the
smaller arboreal mammals. The sloth, it is true, has greyish
green hair, and there are monkeys in which the fur has a
greenish tinge; but there is nothing like the leaf-green colour
of the Iguana or Phyllornis. These facts show in a very
striking way the limitations of the action of natural selection.
The colours of the mammals are mainly due to the presence
or to the absence of pigment in the hair; the hair is white when
it contains air and no pigment, or very little pigment. There
are apparently rarely structural peculiarities in hair which can,
in conjunction with the contained pigment, give rise to brilliant
colours. The Cape Golden mole (Chrysochloris) appears to
be one of the few exceptions, and it is remarkable that this
exception should be found in an animal which passes the
greater part of its time underground.

The Colours of Deep-Sea Animals.

One of the most remarkable biological discoveries of the
last thirty years is the proof that animals can live in the deep
abysses of the ocean. The first actual demonstration of this
truth appears to have been made so long ago as the year 1818,
during the Arctic voyage of Sir John Ross ; from a depth of
800 to 1000 fathoms an Astrophyton was brought up on the
sounding line; but little attention, however, was paid to the
matter until the cruise of the Lightning and the Poreu-
pine, in the years 1861-70. Since that date the memorable
Challenger expedition, and numerous other expeditions fitted
out by foreign governments, have resulted in the acquirement
of a vast amount of knowledge about the inhabitants of the
deep waters.

Next in importance to the actual proof that animals, differing

ra

INTRODUCTORY. 33.

in no essential peculiarities from shore-haunting forms, can
live at a depth of more than five miles, is the fact that brilliant
coloration is so generally met with among them.

This discovery obviously disposes of the old idea that colour
always depends for its development upon sunlight. Experiments
with sensitised photographic plates—a most delicate test—
show that the sun’s rays can only penetrate for a few fathoms.
It is, however, believed by some naturalists that some rays of
light can reach even the greatest depths. Nevertheless there
seems to be one objection to this view, and that is the fact
that the sea-water contains too many opaque objects to permit
of any such passage of rays.

The surface fauna consist of creatures which are, for the
most part, transparent or but faintly coloured, such as Medusz
of all kinds, minute Crustacea, many worms, such as Sagitta,
and various species of ascidians and molluscs, besides radio-
larians and other Protozoa, and a few plants.

Some of these organisms are so transparent as to be invisible
when placed in a bowl of sea water ; but many of the more
highly developed, such as the Sapa, are to be easily detected
by the yellow “liver” or by the contents of the alimentary
canal.

The surface waters often swarm with those minute Alge
which have been termed Diatoms ; these are so abundant in
some oceans, and so far outnumber other pelagic organisms,
as to produce, by the constant raining down of their siliceous
skeletons, a characteristic deposit upon the sea bottom.
Diatoms are coloured yellow by a pigment belonging to the
chlorophyll series, which is somewhat opaque; the Salpw
and other surface animals feed upon Diatoms, and the yellow
colour of the alimentary canal is due to their presence in large

numbers. Now, the surface fauna are not confined to a thin
3

34 ANIMAL COLORATION.

layer of living organisms upon the actual surface of the sea,
but extend downwards to some depth ; hence it follows that
light coming from above must be greatly prevented from
passing through the surface water by the innumerable spots in
the otherwise transparent organisms.

Near to the shores of continents the opacity of the ocean
waters is increased by the presence of sediment washed down
by rivers or by rain and carried far out to sea by rivers and by
the movements of the sea water itself. Such sediment occurs
at as great a distance as two hundred miles from the shore ;
but it is, of course, more abundant as continental land is
approached. In any case, the total absence of chlorophyll-
bearing plants from abyssal depths seems to point to an
absence of light ; for chlorophyll, with a few exceptions, is
not produced in darkness.

It may be, therefore, admitted, in agreement with the
opinion of most persons, that the ocean abysses are profoundly
dark.

One of the most noteworthy discoveries in view of this fact
was the occasional, in some groups of deep-sea animals usual,
occurrence of eyes. This discovery led to the formulation of
the celebrated theory of abyssal light, which was first put
forward by the late Dr. W. B. Carpenter and strongly supported
by Sir Wyville Thomson. This theory accounted for the
presence of eyes, on the view that the phosphorescence of deep-
sea organisms furnished the requisite light to render the eyes
available. That phosphorescence is a common phenomenon
among deep-sea animals is an undoubted fact; it occurs
among representatives of the most <liverse classes : Crustaceans,
Alcyonarians, Hydroids, Fishes and other groups are often
phosphorescent. '

The light is sometimes remarkably intense: Professor

INTRODUCTORY. 35

Moseley stated that the brilliant illumination created by a large
Anthozoon enabled him to read print; even if it does not
generally attain to this degree of brilliancy, a large patch of
phophorescent Alcyonarians would give off a considerable
amount of light. Round such spots it is believed that the
eyed forms congregate. It is not, of course, supposed that the
light emanating from the sessile Gorgonie and the Anthozoa
has been produced by natural selection, acting on behalf of the
creatures to whom the light is considered useful ; that would
be an application of the theory too extended for even its most
extreme supporters; the phosphorescence, it is thought, protects
these Gorgonians from their enemies ; incidentally, it happens
to be useful to the crustaceans and fishes that hover round
these well-lighted areas.

In some cases, however, it is conceivable that the phos-
phorescence may have been increased by natural selection as
being useful to the animal emitting the light ; certain deep-sea
fishes and crustaceans have phosphorescent organs developed
on the head or along the sides of the body ; these may even
be furnished with lens-like transparent bodies serving to con-
centrate the rays of light ; an animal of this kind swims about
in the abyssal water, and is guided to its prey by a series of
“bull’s-eye ” lanterns.

Professor Moseley made, during the voyage of the Chal-
lenger, some very important observations upon the nature of
the light given out by phosphorescent organisms. Among
Alcyonarians, red, yellow and green rays only were detected ;
“Hence,” remarks Professor Moseley, “ were the light in the
deep sea derived from this source, in the absence of blue and
violet, only red, yellow and green colours could be effective.”
As a matter of fact, these colours do exist commonly among
deep-sea animals—particularly shades of red and purple

2

36 ANIMAL COLORATION.

(among crinoids, sea-urchins, etc.) ; blue, however, is not absent;
Professor Agassiz remarks that “no blue animals have been
noticed among the deep-sea types,” excepting only in the case
of a small sponge not uncommon in the neighbourhood of the
hundred-fathom line in the Gulf of Mexico. I am not aware
if Sir Wyville Thomson’s description of a star-fish, Porcellana-
ster, as being of a blue colour was at all exaggerated ; but the
late Dr. Von Willemoes-Suhm described a large species of the
Isopod genus Serolis as “ of a fine blue colour,” which colour is
partially visible even in the preserved specimens of that species.

So far, therefore, there appears to be nothing unreasonable in
this theory, which depends upon two apparently undoubted
facts: (1) light due to phosphorescence, (2) the general
presence of eyes.

But while eyes are apparently often present among deep-sea
animals, they are not unfrequently entirely absent ; this fact
would not fit in with the theory, if the eyeless forms belonged to
genera or families of which the shallow-water species invariably
have eyes. As to the blind gastropods and fishes of the deep
sea, many of them live in mud, where eyes would be useless to
them in any case.

Among the Crustacea, where the eyes are more conveniently
studied than in many other groups, eyes may be present or
absent ; but this does not necessarily offer an unsurmountable
obstacle to the theory cf abyssal light, because some shallow-
water species may also be without eyes ; among the Isopoda,*
for example, the genus Pleurogonium, confined to shallow
water, is totally blind ; so are the genera Munnopsis, Eurycope,
Ischnosoma, Typhlotanais and Cryptocope, whether they occur
in deep or shallow water.

* See my Report on the Isopoda collected by the Challenger (Zool. Chall.
Exped.,” Pts. xxxiii. and xlviii.)

INTRODUCTORY. 37

The real obstacle to the theory—to my mind a fatal objection
—is the fact that in many cases the eyes are evidently in course
of degeneration. This is not apparent on a mere inspection of
the eyes ; they require to be studied microscopically. It often
happens that the external part of the eye—the facetted
“cornea”—is the last part to vanish, and that even the
pigment may persist long after the visual elements have
become so degenerate as to be unrecognisable.

There are so many cases among the deep-sea animals of
degenerate eyes, that it seems reasonable to suppose that vision
is impossible ; the presence of well-developed eyes or the total
absence of these structures are, as has been explained, intelligible
on the theory of abyssal light ; not so the existence of eyes in
an intermediate condition. The inevitable conclusion, there-
fore, from these facts appears to be that the brilliant and varied
colorations of deep-sea animals, is totally devoid of meaning ;
they cannot be of advantage for protective purposes or as warn-
ing colours, for the single and sufficient reason that they are
invisible.

It might possibly be argued that the colours in question had
at one time a secondary use, and had in fact been produced for
such purposes,—at the time when the animals were restricted
to shallow waters, accessible to the sunlight. These have been
preserved, it would then be suggested, owing to the fact that
sufficent time had not elapsed since migration into deep water,
for their disappearance or modification.

In the case of some organisms this suggestion may be
allowed, as it is really not worth combating; but it is generally
admitted that a great part of the deep-sea fauna dates from
extreme antiquity. Professor Moseley fixes the Cretaceous
epoch as the commencement of the colonisation of the abysses ;
this period is quite remote enough, though others would put it

38 ANIMAL COLORATION.

farther back. It can be hardly disputed that, were pigment
simply distributed by means of natural selection, sufficient
time has elapsed for the effects of this action to have ceased
or been reversed. And yet the coloration of the deep-sea
animals is, on the whole, similar to that of their shallow-water
allies. If natural selection has been the cause in the one
case, it ought to be in the other ; but there are serious reasons
for disbelieving in the share taken by natural selection (that
is, of course, in relation to environment, etc.) in affecting the
coloration of deep-sea animals ; the question, therefore, is
pressing: need natural selection be responsible for the colora-
tion of the shallow-water forms ?

“ Protective resemblances ” are shown among deep-sea forms,
just as they are in the shallow water.

Professor Agassiz remarks upon “the many species of
Ophiurans attached to variously coloured Gorgonians, branching
corals, and stems of Pentacrinus, scarcely to be distin-
guished from the part to which they cling, so completely
has their pattern of coloration become identified with it.
There is a similar agreement in coloration in annelids when
commensal upon starfish, mollusca, actinia or sponges, and
with crustacea and actinia parasitic upon corals, gorgonians or
mollusks.”

In my own opinion these cases of resemblance are to be
explained by the parasite actually assimilating and depositing
in its own skin the pigments of its host ; but they are entirely
parallel to instances of protective resemblance among the
littoral creatures.

Since the conditions of life in the deep sea are so different
from those of shallower coast water, we might expect, bearing
in mind the primary meaning of pigment (see p. 5), to see some
differences in the colour.

INTRODUCTORY. 39

Apart from darkness, which we have already considered,
deep-sea animals are subjected to enormous pressure: at a
thousand fathoms this pressure is something like a ton to the
square inch.

The temperature, again, is low; the heat of the sun does not
apparently extend to a greater depth than a hundred and
fifty fathoms. The investigations of the Challenger have
shown that there is everywhere a progressive decrease in heat
from the surface water downwards in the great sea basins. In
the deep abysses the average temperature is about 34° ; it is
occasionally below freezing point.

These temperatures, it must be observed, do not fluctuate.
In the shallow waters there is of course fluctuation.

As to the colours of the deep-sea animals, the tints are
sometimes deeper. Crustaceans are often brilliant scarlet, the
pigment being much more abundant than in the pelagic
forms. Professor Agassiz states that “the echinoids dredged
beyond the hundred-fathom line are many of them dark-
coloured” ; black is a common colour in deep-sea fishes. In
examining the Challenger collection of the curious Isopod
genus Sevolis, which bears so striking a superficial resemblance
to the extinct Trilobites, I found that three out of the four
deep-sea species were much more darkly and uniformly
coloured than any of the shallow-water species ; I imagine
that the pigment is the same, only more abundant.

Change of Colour after Death.

It is, of course, well known that the colours of insects,
lizards and other animals frequently change after death ; the
change generally takes the form of a diminution in depth of
colour,—the colours fade: the delicate greens of many moths—
the Emerald moths, for example—become a pale straw colour.

AO ANIMAL COLORATION,

Sometimes, however, the changes are different, and there
may even be an increase in the darkness of the colour, due
possibly to chemical change in the pigments slowly taking
place. At a meeting of the Entomological Society of London,
a few years since, the well-known coleopterist, Mr. C. O.
Waterhouse, exhibited some phytophagous beetles, which had
been exposed for twenty-five years in the public galleries of
the Bristol Museum, in which the colour changes were most
remarkable.

Beetles whose natural colour was a brilliant red had not
diminished in brilliancy, but had changed to green; pale
yellow had deepened into brown, blue into black ; while the
green colour of some forms had become converted into purple.
If such changes take place after death, it is: quite conceivable
that they may take place during the life of the animal. The
pigment itself is no more alive in a living animal than it is in
a dead one.

Connection between Integumental Pigments and Excretory
Products.

An interesting case of the connection between an integu-
mental pigment and excreted matter has been recently
published by Mr. Hopkins, of Guy’s Hospital. This gentleman
found that the yellow pigment of a number of butterflies—
including the following: “ Brimstone,” ‘Clouded Yellow,”
“Common White,” “ Orange-tip,” and “ Swallow-tail ”»—could
be extracted by hot water, giving a solution with an acid
reaction ; the solution when evaporated gave the ‘“‘ murexide
reaction ”; it yielded crystals of Uric actd when treated with
hydrochloric acid, and, after a more prolonged treatment
with the same acid, Urea.

There is thus no question that the colouring-matter of these

INTRODUCTORY. 4]

butterflies is related to ordinary products of the metabolism of
the body.* fe

Mr. Poulton has recently found that the red fluid excreted
by the Tortoiseshell and other Vanesside, immediately after
they escape from the chrysalis, contains uric acid; the fact
that this substance is evacuated in these butterflies may
perhaps have something to do with the absence, or at least
the presence of only traces, of a yellow colouring in these
butterflies ; metabolism must be nearly at a standstill in the
butterfly.

Dr. Urech has also pointed out that there is a close con-
nection between the pigments found in the urine of butterflies
and the colour of their wings.

We might expect that caterpillars, which lead such extra-
ordinarily active lives, as far as devouring food is concerned,

would normally store up a quantity of integumental pigment.

* Journ. Chem. Soc., 1889, and Jahresb. f. Thier. Chemie, 1890.

CHAPTER II.

COLORATION AFFECTED BY THE ENVIRONMENT.

THERE are numerous cases where the coloration of an animal —
appears in part to be due directly to the influence of the
surroundings, and to have no possible relation to natural
selection. I shall reserve what is probably the most striking
instance of this—viz., the fauna of caves—to the last, and
commence with some other cases.

The Scarlet Ibis of South America is frequently exhibited
alive at the Zoological Society’s Gardens. It invariably
happens that the brilliant colour fades in captivity, and
becomes much duller as well as paler. Such a change does
not happen with all birds, and cannot therefore be set down
at once to insufficient food or neglect of any kind. It may
depend upon the nature of the food, or upon temperature ;
many other causes might be suggested, but the real cause is
not certainly known.

Such differences of colour, due to obscure causes, are also
frequent in nature ; they give rise to “local varieties,” which
are familiar enough to entomologists.

Local Colour Varieties.

The Isle of Man produces a small dark variety of the
common Tortoiseshell butterfly. Mr. J. Jenner Weir has
discovered that in the Shetland Islands the Ghost Swift
(Hepialus humuli) has a tendency to lose the secondary

COLORATION AFFECTED BY THE ENVIRONMENT. 43

characters which distinguish the two sexes. Normally the
male insect has the upper surface of the wings of a shining
white colour, while in the female they are brown. In the
Shetland Islands, but not in the Hebrides, a proportion of the
males captured were like the females.

The same naturalist noted a tendency in a number of species
of Geometrides * taken in the Hebrides towards a greyer colora-
tion than the normal; but it is suggested that this is due to
the prevalent grey gneiss; by natural selection only those
forms which approached the gneiss in colour were preserved.
A similar explanation has been given of the black Lizard
(Lacerta Simonyi) found on an island of the Canary group ; it
does not greatly differ, except in coloration, from Lacerta
ocellata ; it is said that the black colour renders it less con-
spicuous to predaceous birds, which are its only enemies, since
the rocks upon which the animal lives are very dark in colour.
On the other hand, this black colour may be referable to the
same causes—namely, moisture, which Eimer thinks have been
effectual in the case of certain melanic varieties of lizards in
the Mediterranean islands.

A large moth, Bombyzx trifolii, appears, from the observations
of Mr. Milford,t to have a distinct local variety in Romney
Marsh, Kent; it is paler than the normal insect. The larve
were first found by Mr. Milford, “in May 1866, feeding in the
tufts of a very wiry grass growing in the shingle above high-
water mark ; they were again found and bred in May 1876.
In August 1868 two dead moths, exactly similar, were
observed in the same locality ; and in August 1871 eighteen

* Entomologist, 1881, p. 220. The following are the species : Bourmiu
repandata, Dusydia obfuscata, Larentia didymata, L. cesiata, Cidaria
russata, Melanippe hastata, W. montanata.

+ Entomologist, vol. vi., p. 53.

44 ANIMAL COLORATION.

examples were bred.” These facts seem to indicate a marked
persistence of this form in the locality.

In Ireland a dove-coloured variety of Plerts rape, one
of the common white butterflies, is abundant, and has been
imported into America, where the variety is now the typical
form of the species. e

Local races are of course not confined to reptiles and insects;
there are plenty of instances among birds and mammals.
Dr. Gadow, in one of the British Museum Catalogues of Birds,
has recorded the interesting fact that specimens of Lanius
collaris from the Congo have a red under-surface ; south of
the Congo this colour is changed to orange, and in the
Cameroons to lemon-yellow.

Geographical Distribution of Colour.

Dr. L. Camerano has attempted a geographical distribution
of colour which may be thus briefly summarised.* The
Palearctic region—that is, Europe and Northern Asia—bas
as prevailing tints grey, white, yellow, and black ; in Africa
yellow and brown are most abundant; green and red are
the prevailing tints of the Neotropical region (Central and
South America), yellow and red of the Indian. Australia is to
' be distinguished from the rest by the great abundance of black
animals.

A closer scrutiny of many of the above instances and
of others which seem to indicate some connection between
locality and colour, will probably show that other causes are
probably responsible for the colour changes.

Additional Instances of an apparent Connection between Colour
and Locality.

A curious instance of what appears to be an association

* Zoologische Anzeiger, 1884, p. 341.

COLORATION AFFECTED BY. THE ENVIRONMENT. 45

between colour and locality is shown by the fauna of Ceylon;
there is a great prevalence of green* among the insects of that
island; Haeckel pointed out that this might be merely pro-
tective; in a forest country it is not surprising to meet with
green as a prevalent colour.

But green is not confined to the forest fauna; it is quite
common also among the marine animals; and though there are
abundant alge in those seas, green is not altogether so common
a colour among the inhabitants of the sea as it is among the
inhabitants of forests. Besides, animals which seldom show
any green in other localities are green here: for example, sea-
urchins, brittle-stars and star-fish, among which various
shades of brown, purple and red are as a general rule the pre-
vailing colours. Particularly is this the case with corals, which
are not often green. Ransonnet, in his work upon Ceylon, gives
two beautiful plates which represent life upon a coral reef, and
which were sketched by the author from a diving-bell ; green
is the only colour which is at all prominent in these plates, and
is not by any means confined to the Corals.

Professor Haeckel f himself, though inclined to put down the
green to the necessity for protection, admits that the pre-
valence of green among the corals is a very remarkable and
noteworthy fact. He speaks, in describing a coral reef, of
“a yellow-green Alcyonia growing with sea-green FHeferopora,
and malachite-like nthophylla side by side with olive-green
Millepora; Madre poraand Astrea, of emerald hue, with brown-
green Monticulopora and Meandrina.” Kyen a species of the
gigantic clam = Tridacna is green, and so are many other
marine creatures. Even if this particular instance may be

* Even the great four-feet-long earthworm of Ceylon, which is usually
spoken of as blue, appears from Mr. Bourne's sketch to be green
t “ Ceylon,” p. 155.

46 ANIMAL COLORATION,

explained as a need for protection, an explanation of that sort
cannot possibly be advanced to account for a still more remark-
able instance of a connection between colour and locality which
has been lately brought forward by Dr. Adalhbert Seitz.

In a forest of southern Brazil Dr. Seitz found a perfectly
circumscribed region in which the insects were almost entirely
blue ; a few miles away from this locality the insects were red,
yellow—any colour but blue; but in the particular locality
blue was so characteristic a tint, that out of twenty butterflies
ten were entirely blue and the remaining ten partially blue.
Nor was blue found to be confined to the lepidoptera: the
flies and hemiptera were also largely blue. We must therefore,
as Dr. Seitz remarks in commenting upon these facts, not at
once put down every colour phenomenon to mimicry, need
for protective resemblance, warning coloration and so forth;
there are plenty of phenomena which do not seem capable of
explanation on any of these theories.

The connection between colour, form and locality was dwelt
upon by Dr. Andrew Murray. Some of the examples quoted
by Murray have been since explained by mimicry; but others
cannot, at least in the present state of our knowledge, be so
explained.

The Clonded Yellow (Colas edusa), one of our handsomest
English butterflies, has a well-marked variety known as Helice.
Felice chiefly differs from Edusa in the paler colour. In the
Argentine Republic * there occurs an allied species of Colias,
C. lesbia, which has also a varietal form differing from it about
as much as Hedice differs from Edusa. But a more striking
instance still is also to be met with in the same part of South
America, showing that there is a tendency in the widely
separated localities, which presumably resemble each other

* Zoologische Jahrbiicher, vol. v.

COLORATION AFFECTED BY THE ENVIRONMENT. 47

in some climatic or other condition, to produce similar
forms.

There is a butterfly common in certain parts of the Ar-
gentine, which Dr. Seitz at first mistook for the European
Vanessa (Araschnia) levana, so closely does it resemble that
butterfly in colour, in the notching of the wings, and in other
ways. Moreover, there is a variety of this form which is in
the same way exceedingly like the form prorsa. A closer
examination of the insect showed that it did not belong to this
species at all, or even to the same genus ; it is a member of
another genus, Phyciodes. “If,” says Dr. Seitz, “these were
found in our country, no one would doubt that this was a case
of mimicry as perfect as any which exists.” It might be
suggested that it 7s a case of mimicry, but the mimicking and
mimicked forms have each gone their own way, one migrating
to one country and one to another; they might possibly at one
time have both lived in North America, and later on separated,
one going south, and the other east, crossing over into Asia
by way of Behring’s Strait. Such an explanation would be,
as Dr. Seitz points out, entirely contrary to what is known of
the distribution of these insects; for the genus Araschnia is
absolutely confined to the Old World, and Phyciodes to the
New World.

We see here a particular type recurring in regions widely
separated, which may be reasonably supposed to be due to
similar environmental conditions.

The resemblance between the Danaide, Acrewide, Heliconide,
and Pieride of South America may be mentioned here; they
will be treated of in the chapter relating to mimicry; there
is also a Satyrid in which the wings have partially lost their
scaling, and there are other examples among South American
lepidoptera of the same transparency in the wings.

48 ANIMAL COLORATION.

Effects of Food upon Colour.

Food has certainly an important effect upon the colours of
many animals. Semper, in his “ Animal Life,” although he
quotes a gumber of cases where food seems to have had in-
fluence in affecting colours, is indisposed to accept the
evidence.

If the nature of animal colours is borne in mind, it seems
impossible to doubt the modifying action of food; those that
are due to stractural peculiarities of the parts coloured (e.g.
feathers of many birds) may be altered just as much as those
that are caused by the deposition of pigment; for the
“ structural” colours depend largely upon pigment for their
manifestation.

The mere increase in the deposition of pigment may lead to
an alteration of colour, oftenest perhaps in the direction of
melanism ; and there is evidence that various substances when
taken into the body do influence the amount of excreted matter.
Where there is an obvious relation between waste matter and
the skin pigments, it cannot be doubted,* that variation in the
amount only of the food may lead to colour changes.

The most interesting case of a colour change produced by
different food, with which I am acquainted, is that of the
larvee of the large Tortoiseshell butterfly when fed upon
nettles. The large Tortoiseshell (Vanessa polychloros) nor-
mally feeds upon elm, while the small Tortoiseshell (V. urtice)
is addicted to nettles. Mr. J. Tawell submitted to the late
Mr. Edward Newman some imagos of the large Tortoiseshell

* In making some experiments upon the colours of earthworms I
confined a large individual in a flower-pot. After the lapse of a month,
during which the specimen had been overlooked and the earth allowed to
dry up, the worm was found in a cavity in a lump of dry earth, perfectly
healthy in appearance, but bleuched ; this I attribute to its not having fed
for a long period.

COLORATION AFFECTED BY THE ENVIRONMENT. 49

which he had bred from caterpillars found upon nettles ; these
showed, according to Mr. Newman,* “a wonderful similarity to
Urtice,” though the colour was “ nearer to that of Polychloros.”

Plenty of other instances of a similar kind have been re-
corded, and by entomologists of experience ; I do not under-
stand why Professor Semper should throw a doubt upon the
validity of their statements, especially as he sees no intrinsic.
improbability in the influence of food upon coloration. ;

Professor Eimer + has quoted the researches of Koch in
this department of entomology. Koch was able in the case of
Chelonia hebe (one of the Tiger moths) to alter the colour of
the underwings from a fiery to a dull red, and bring out more
strongly either the black markings or the white ground
by feeding the caterpillars upon different plants. Similar
experiments were made upon the common Tiger moth (CA.
caja), and Nemeophila plantaginis, also a British insect.

Mr. Goss found that the larva of one of our fritillaries (Melitea
artemis), when fed upon honeysuckle, which is not the usual
food plant of the caterpillar, became very dark-coloured imagos.t
One of the “Thorn moths” (Ennomos angularia) shows
variations in colour according as to whether the larva has been
fed upon oak, hawthorn, lime, or lilac.§

In the Zoologist, on p. 7903, Mr. Gregson has tabulated the
results of a careful series of experiments dealing with the effects
produced by different food plants upon a number of different
species of moths.

Pygera bucephala was finer and darker when fed upon sycamore.
NXylophasia polyodon was dark, sometimes black, when fed upon heather.
Hadena adusta was darker when fed upon heather.

Acronycta menyanthidis fed on sallow produces var. Salicis.

* Entomologist, vol. vi., p. 88.

+ “ Organic Evolution,” Eng. Trans. by J. T. Cunningham.

t Entomologist, vol. vii., p. 203. § Tbid., vol. ix., p. 263.
4

50 ANIMAL COLORATION.

Acronycta menyanthidis fed on heath produces light specimens.
Hybernia defoliata fed on birch produces beautifully marked specimens :
- 45 fed on elm produces dull-coloured specimens, almost
without markings.
Noctua festiva fed on thorn gives specimens of a rich red colour and well
marked :
Fr ,, fed upon grass, light yellowish, rarely well-marked specimens.
Abraxas grossulariata, fed upon red currant ; light specimens :
$5 ss fed upon blackthorn ; darker specimens :
5 45 fed upon bullace ; darker still, the white sometimes
becoming yellow.

Not only does the nature of the food, as shown in the above
instances, produce colour variations, but the quantity may .
have an important effect in the same direction. Mr. Ramsay
Cox,* in relation to this matter, writes as follows :—‘‘ We
captured in the New Forest a number of half-grown larve of
Vanessa Io (the Peacock butterfly), which were carefully fed
for a few days; but, owing to my boy’s neglect and to my
being busy with the net, they were left several days without
food ; all dead leaves and stalks had been devoured. They
were a very long time changing, and many fastened themselves
to the bottom of the cage, as if too weak to spin upon the
top or sides, in the ordinary manner. Very few died, either
in the larval or pupal state. Nearly all the imagos were, of
course, rather small; they varied much in the intensity of their
colouring, and two specimens are very singularly marked. In
one the yellow costal spot is only represented by a very small
white mark. There is scarcely any yellow in the ocellus, a large
part of which is filled up with black; the usual chocolate patch
in it is also black. The chocolate ground-colour is also darker
than usual. In the hind wing the ocellus contains only two
small, round, violet spots. The other specimen is similarly
marked, except in the hind wings, in which there is no ocellus

* Entomologist, vol. ix., p. 58.

COLORATION AFFECTED BY THE ENVIRONMENT. 51

at all of the ordinary character, but merely an irregularly
shaped, dull whitish blotch, containing a very indistinct small
brown mark. Vanessa urtice and polychloros were similarly
treated : the latter produced no peculiar-looking specimens,
excepting that the ground colour was darker than in ordinary
bred specimens. The urtice, in spite of their starving, came out
nearly the natural size. Many have a thick black nervure in
the centre of the wing, also a brownish patch between the
middle costal spot and that in the inner margin ; and the dark
margin round the wings is wider than usual. The effects of
starving these three species would therefore appear to be
similar, as far as the causing of dark spots, patches, etc., goes.”

The change of colour in canaries when given red pepper,
and in certain parrots when provided with the fat of particular
fishes, are instances that are quoted in every book dealing with
these effects. There are even dealers in animals who have got
the reputation of being able to “ colour up” birds such as the
flamingo by judicious feeding.

Another remarkable instance of the apparently direct effects
of food in producing colour change was originally put forward
by Darwin, who obtained the information from Moritz Wagner.
It has been referred to by Prof. Mivart,* and also by Mr.
Lloyd Morgan.t ‘A number of pupe were brought’ in 1870
to Switzerland from Texas of a species of Saturnia widely
different from European species. In May 1871 the moths
developed out of the cocoons (which had spent the winter in
Switzerland), and resembled entirely the Texan species. Their
young were fed on leaves of Juglans regia (the Texan form
feeding on Juglans nigra), and they changed into moths so
different, not only in colour, but also in form, from their
parents, that they were reckoned by entomologists as a distinct

* “On Truth,” p. 378. + “ Animal Life and Intelligence,” p. 163.

52 ANIMAL COLORATION.

species.” It looks very much as if this change, which is one
of the most remarkable among those, which have been recorded,
were due to food; but it is possibly a question of climate.
In any case it seems evident that the action of the environment
is the cause.

The common garden snail (Helix aspersa) is said to become
darker when fed upon lettuce.

The “Tiger moth” (Chelonia caja) whose caterpillar is the

?

familiar “ Woolly-bear,” is almost ¢he classical instance of
the effects of food upon colour. It appears to be in any case a
most variable species; the pages of the Entomologist and other
journals devoted to entomology contain numerous records of
varieties, some of which have been traced to food while others
have not a known history. The orange red of the hind wings
may be replaced by yellow, and the proportions of brown and
white in the fore wings are subject to immense fluctuation.
Eimer * quotes from Koch a number of colour changes which
accompany and are probably caused by a change of diet.
Thus, if fed upon lettuce, the white ground of the fore wings
predominates over the brown ; the precise contrary is produced
by feeding the larvee upon the leaves of the deadly nightshade ;
in moths bred from larvee which have been fed upon the
leaves of this plant the white becomes almost obliterated,
while the bluish marks upon the hind wings fuse together and
displace the orange yellow ground colour. Koch concludes
the account of his observations with the following remarks :
“ Must not similar processes occur equally, and even on a
larger scale, in the natural life of the countless forms of the
class in question ? When a great number of individuals
perish through an occasional scarcity of their proper food
plant, must not, nevertheless, considerable numbers survive by
* “ Organic Evolution,” p. 150.

COLORATION AFFECTED BY THE ENVIRONMENT. 53

contenting themselves with other allied food materials, and so
give rise to varieties whose origin we do not dream of, and
which therefore we are led to regard as new species ? ”

The effects of food upon the colour of the imago or perfect
insect do not in these cases, curiously enough, affect the larva ;
it would seem to be the larva which ought to be altered before
the imago. There are, however, exanrples of a connection
between the coloration of the larva and the imago.

Mr. Jordan* observed that whitish larve of Sphinx populi
(the Poplar Hawk moth) gave rise to albino moths; on the
other hand, melanic caterpillars of the Magpie moth resulted
in imagos which were not specially black.

That the yellow colour of canaries can be altered to an orange
red by mixing cayenne pepper with their food, has been known
for a long time. This curious fact was first discovered in
England, as was also the fact that the different races of canaries
vary in their susceptibility to the action of the pepper ; some
kinds are more, others less, affected, while one race is absolutely
without any power of having its coloration altered by these
means. The colour change is produced by feeding the newly
hatched young with the pepper conveyed in their food or the
old birds while sitting upon the nest are furnished with food
containing the cayenne, with which they in turn feed their off-
spring. The colour change can, in fact, be only brought about
in very young birds whose feathers are not completely matured;
it is quite impossible to produce any alteration upon the fall-
grown canary. Clearly, therefore, here is an instance of the
direct effect of food upon colour. An interesting paper upon
the subject, which has also furnished me with the facts already
mentioned, has lately appeared,t and it will be of interest to

* Ent. Monthly Mag., vol. i., p. 63.
+ “ Archiv. Anatomie und Physiol.” 1889: Physiol., Abtheil. 543.

54 ANIMAL COLORATION.

give some account of the author’s (Dr. Sauermann’s) experi-
ments, for reasons which will appear. Cayenne pepper, of
course, is a composite substance, from which a number of
distinct chemical substances can be extracted: the red colour
is caused by a pigment termed capsicin, which can be separated
from the pepper; and it might easily be supposed that the
change from yellow to red in the feathers of the canary was
simply caused by a transference of the pigment, as in the cases
mentioned on p. 127; but Dr. Sauermann has shown that it is
not so. Yellow-coloured canaries were not in the very slightest
degree affected by the pigment alone; but, curiously enough,
parti-coloured birds did react,—the brown parts of the feathers
became distinctly lighter in hue. It is a fatty substance
(triolein) which appears to convey the pigment, and produce
thus a changing of the colour from yellow to red; and further
experiments were made with other birds, showing that it is
not only canaries which are influenced by their food in this
way. Some white fowls, belonging to a special breed, showed
traces of yellow among the feathers after feeding with cayenne ;
but in this case there were not racial but individual differences
in susceptibility, for all the specimens of the birds experi-
mented with did not react to the stimulus.

A similar series of experiments was made with some other
colours: it was found with carmine that the yellow colour was
destroyed and the birds became white. This unexpected effect
is explained by the fact that a mixture of violet and yellow
produces white. The proof that the fatty constituent, triolein,
plays the chief part in the colouring of the feathers may
perhaps help to explain the very singular fact that the Amazon
parrots change from green to yellow when fed upon the fat of
certain fishes.

With regard to the white fowls referred to, the experiments

COLORATION AFFECTED BY THE ENVIRONMENT. 5d

made by Dr. Sauermann were particularly interesting. The
interest lies in the fact that the pigment was not absorbed
equally by all the feathers ; only special tracts were affected;
the breast feathers, for instance, became red, while the head
remained white. It is therefore quite credible that in a state
of nature partial alteration of colour may be produced by a
change of diet.

In the chapter relating to protective resemblances will be
found an account of several examples of animals which have
apparently acquired a resemblance to their surroundings by the
transference of pigment to their bodies in their food.

Effects of Temperature and Moisture.

A common colour phenomenon in animals is that known as
melanism: by melanism I understand not necessarily a pre-
dominance of black, but a general darkening of the coloration.

Dr. Scudder, in his magnificent work upon New England
butterflies, remarks that melanism is confined to the districts
south of New York ; while the reverse condition (viz. albi-
nism) is hardly ever found, except north of that city ; this
is obviously suggestive of a climatal cause for the colour
modifications in question. ‘As we go north,” says Dr.
Scudder, “the colours become less sharply defined, then
gradually fade away or become blended with surrounding tints;
the red first disappears, the blue follows, the yellow longest
maintaining its hold.”

Furthermore, according to the same writer, loss of purity of
colour and suffusion of markings characterise northern and

‘Alpine forms of butterflies. Varieties of similar species are
commonly met with which exhibit the same suffusion ; these
’ varieties almost exclusively occur in temperate regions, and
they have also been artificially produced by cold.

26 ANIMAL COLORATION.

All these facts are clearly in harmony, and indicate a direct
variation of colour in correspondeuce with changes in tem-
perature, which would be very difficult to be proved useful to
the insects, and therefore perpetuated by natural selection.

Professor Leydig (quoted by Eimer*) gives an interesting
account of certain colour changes which are apparently pro-
duced by greater abundance of moisture in the atmosphere.
“The influence of light and warmth,” he says, “is very
distinctly evident in the colouring of Helix nemoralis in this
region. The fine citron yellow exhibited by the shell of this
snail at Mainz, and in the sunny vineyards of the Main valley,
is wanting on the banks of the Lower Rhine. .... On the
other hand, it is interesting to notice how in the neighbourhood
of Bonn and lower down the Rhine the red of this snail deepens
into chocolate brown, and thus forms the beautiful variety
above mentioned, which must attract the attention of every
collector. It is, perhaps, too much to say that the moisture of
the plain of the Lower Rhine determines this change of colour,
but we must keep in view the possibility that the moisture
coming up the valley from the sea, which certainly here at
Bonn has a distinct effect on the vegetation, has something to
do with the matter.” The colours of snail-shells, so varied as
they are and frequently so brilliant, can hardly have any other
signification, if we seck to attribute them to natural selection,
than “ warning colours ” or sexual. With regard to the latter
possibility sexual selection in hermaphrodite animals is a little
difficult to believe in; and Eimer has stated that a number
of snails in his garden, which he kept under observation for
some years, did not appear to exercise any choice whatever in
pairing. So far as concerns warning colours, the above instance
would have to be explained by the greater abundance of”

*“ Organic Evolution,” p. 137.

COLORATION AFFECTED BY THE ENVIRONMENT. aa

thrushes and other snail-eating birds on the Lower Rhine than
at Bonn, or evee corsa if the “citron vellow ™ variety is the
more conspicuous.

The suffusion of the markings and the duller colour which is
said to occur among Alpine butterflies is in striking contrast
with the unusual brillianey of colour which is noticeable in
Alpine plants.

The latter change is said to be owing to the less numbers of
inseets Which cross-fertilise the flowers; and hence the need for
a greater effort, so to speak, on the part of the plant to attract
them and thus secure the desirable effects of their visitations.

This might be urged as an objection to the climatic
influence, on the grounds of unlike effects in the two cases.
But it is perhaps hardly necessary to point out that the
pigments of the buttertlies’ wings are different from those of
the Howers, and that the physiological processes which take
place in the bodies of animals without chlorophyll are in the
first place different from those of chlorophyll-bearing plants.
and in the second place the same conditions may produce
ditterent effects.

Examples of Melanic Varieties found upon Islands.

There are a good many other examples of a tendeney towards
melanism—more or less realised—among the inhabitants of
islands.

The Galapagos Islands cousist of a group of islands, of
various areas, situated some tive hundred miles to the west
of the South American continent. One of the most charac-
teristic inhabitants of these islands is the curious marine
Iguanoid lizard, Oreocephalus. It is thus described by
Darwin: “It is a hideous-looking creature, of a dirty black
colour, stupid and sluggish in its movements. The usual

58 ANIMAL COLURATION.

length of a full-grown one is about a yard, but there are some
even four feet long. I have seen a large one which weighed
twenty pounds. These lizards are occasionally seen some
hundred yards from the shore, swimming about; and Captain
Collnett, in his “Voyage,” says that they go out to sea in shoals
to catch fish. With respect to the object, I believe he is
mistaken, but the facts stated on such good authority cannot
be doubted. When in the water the animal swims with
perfect ease and quickness, by a serpentine movement of its
body and flattened tail, the legs during this time being per-
fectly motionless and collapsed on its sides. A seaman aboard
sank one with a heavy weight attached to it, thinking thus to
kill it directly; but when, an hour afterwards, he drew up the
line, the lizard was quite active. Their limbs and strong claws
are admirably adapted for crawling over the rugged and fissured
masses of lava which everywhere form the coast. In such
situations, a group of six or seven of these hideous reptiles may
often be seen on the black rocks, a few feet above the surf,
basking in the sun with outstretched legs.” These powerful
beasts would hardly need protection; and as they feed upon
vegetable substances, they do not need to resemble their
surroundings for aggressive purposes.

There are other examples among the inhabitants of the
Galapagos archipelago of a darker coloration than that of
their allies upon the neighbouring mainland.

Mr. Salvin, in his exhaustive account of the avifauna of this
group of islands,* mentions several instances of birds which are
hardly to be distinguished as peculiar in the species except by
their darker coloration. An owl (Asio galapagoensis) closely
resembles the world-wide Short-eared ow] (Asio brachyotus), and
is only to be distinguished by its darker hues. Similarly a

* Trans. Zool. Soe., vol. ix., 1876.

COLORATION AFFECTED BY THE ENVIRONMENT. 59

night-heron (Vycticorar pauper) is, according to Mr. Salvin’s
diagnosis of the species, “similis .V. riolaceus sed multo
obseurior.” Larus fuliginosus is 2 gull which might be con-
founded with the Chilian Z. modestus. were it not for its black
hood.

Coronella phocarum. of Robben Island, is nearly allied to the
South African (. cana, a variable snake, but generally paler
in colour.

Further Examples of the Effects of Temperature and Moisture.

The English fritillary (Argynnis paphia) is known to occur
as a dark variety, which has been called “valerina” : this
variety appears to be almost confined to wooded countries,
and the question is whether the moisture of such localities is
responsible for the darker coloration.

The dark coloration of lizards in oceanic islands has been
already mentioned; such situations are, of course, pre-eminently
moist.

There are other facts which show that moisture, rather than
temperature, is the cause of a darkening. Dr. Eimer has
commented upon the prevalence of a dark colour in the slug
(Arion empiricorum) during wet summers in the neighbour-
hood of Tiibingen; but the same naturalist found dark-coloured
slugs on the summits of hills where there was but little
moisture; and there are other cases of darker-coloured varieties
of animals found in elevated localities. Dr. Eimer considers
that in all probability elevation, as well as moisture, is
effective in producing such colour changes.

There is no reason whatever against accepting this sugges-
tion ; seeing that there are constitutional differences among
individuals of one species, it may easily be believed that there
are such differences between different species and genera ;

60 ANIMAL COLORATION.

moisture may affect the formation and deposition of pigment
in one animal, temperature in another, while a third may be
entirely uninfluenced by either cause, but will yield to some other
environmental influence. Until all these matters have been
more thoroughly investigated than they have at present, the
theories of modification of colour by selection or elimination
rest upon a basis which is manifestly insecure.

The colour of the wings of the beautiful Indian Moon moth
(dctias selene) is very susceptible to dryness and moisture; the
normal colour is a delicate pale green; pieces of the wing of
a specimen chloroformed for the purpose of this experiment,
became very soon straw-coloured in dry air of a temperature of
a little under 60° centigrade ; when the same fragments were
floated in a saucer containing cold water they rapidly recovered
their green colour, which was even intensified. I am not at
present concerned with the chemical or physical reasons for
their change; it is sufficient that it occurs. On the other hand,
the green colour of an Emerald moth (Hemithea thymiaria),
though bleached when heated and dried, was not restored by
moisture.

It is at least possible that the tawny colours of desert animals,
which have been so often brought forward as an instance of
adaptation to the hues of their environment, may be due to a
similar cause.

Mr. Wallace has justly pointed out that the older theory,
that colour was dependent for its development upon light and
heat, is upset by the colour characteristics of the inhabitants of
sandy and dry localities; on this theory colour should be most
intense and varied where light and heat are at a maximum.

But any one who will take the trouble to inspect a most
interesting case of stuffed animals in the central hall of the
Natural History Museum, will be convinced that the contrary

COLORATION AFFECTED BY THE ENVIRONMENT. 61

is true. These animals comprise representatives of all the
principal classes; and they are without exception of a uniform
sandy or “isabelline” hue. There are rats, birds, lizards and
snakes in this collection; plenty of instances will occur to any
one at once which might have been exhibited, as well as those
that actually are.

Tn relation to this matter Mr. W. W. Smith has remarked
that the prolonged drought recently experienced in New
Zealand produced pale-coloured varieties; and that the
Lepidoptera of that country are generally paler on the plains
than on the hills; “the higher we ascend the Alps,” he
remarks, “the more humidity we meet with, and the greater
the darkening of the Lepidoptera, until we reach the summit,
when they become perfectly black.”

Influence of Light.

At one time light and heat were regarded as indispensable
for the development of colour, and the gorgeous hues of
tropical birds and butterflies were instanced as proving this
view. Mr. Wallace has, however, abundantly shown that
there is not necessarily an intimate connection between light
and colour. It is true, he admits, that there are more brilliantly
coloured animals in the tropics than elsewhere; but then
there are more animals of all kinds ; animal life is at its
maximum in the tropics. Besides, there are plenty of dull-.
coloured insects and birds. The temperate regions, too, pro-
duce some of the most brilliantly and diversely coloured
animals that are known.

The metallic blue of our “ Clifden Blue” rivals in brilliancy
of hue that of the “ Morphos” of South America; there are
no insects in the tropics belonging to the same group more.
brilliant in their coloration than the “ Red Admiral.” ,

62 ANIMAL COLORATION.

The Gold pheasant, which is always well represented in the
Zoological Gardens, and is undoubtedly, as are the pheasant
tribe generally, one of the most beautifully and strikingly
coloured of birds, is found in the temperate regions of China ;
many brightly coloured pheasants: have a similar range into
temperate climates. Mr. Wallace has instanced the Gold
pheasant and also the tiger, which, although found in the
tropics, ranges into the Amir, to the extreme north of China;
we have also the deep-sea fauna (see p. 32), which are
brilliantly coloured and yet live in absolute darkness. It is,
therefore, impossible to trace any general connection between
prilliancy of coloration and light.

Nevertheless, in certain cases there appears to be a con-
nection between light and colour; the connection is, however,
rather between absence or paleness of colour and absence of
light, than between brilliancy of colour and abundance of
light.

Colour sometimes dependent upon Light.

It is perfectly true that there is not always an intimate
connection between light and colour ; the instances already
given show that this is the case in a sufficiently striking way.
Nevertheless, there are some instances which point exactly in
the opposite direction, showing how difficult it is to generalise.

Werneburg* has given a number of examples of Lepidoptera
which go to show that light has an important effect during
the formation of the pigment—that is, in the pupal state.

As a general rule, those insects whose pupx are exposed are
brighter in colour than those insects whose pupe are concealed,
either in the ground or in a dense cocoon. Contrast, for
instance, the bright colours of the Vanesside—the “Red

* Quoted by Seitz Zoolog. Jahrbiicher, vol. v.

COLORATION AFFECTED BY THE ENVIRONMENT. 63

Admiral,” the “ Peacock,” and others—whose chrysalids are
naked and freely suspended, with the dull colours of most
Satyrids, which undergo their transformation in the ground.
Similarly, the “Tiger moths ” and the “Crimson Underwings ”
contrast with the Cosside and Agrotide and most other
Noctuz; and among the Geometers the bright yellow Swallow-
tail moth, Urapteryx sambucaria, Angerona prunaria, etc.,
may be compared with the sombrely-coloured species of the
genera Boarmia and Biston.

Absence of Colour in Animals which live in Darkness not always
due to Absence of Light.

It has often been pointed out that internal feeders among
caterpillars are usually devoid of integumental pigment; the
caterpillars of the clear-wing moths—Sesiide—are thus dis-
tinguished, and they all feed in the interior of stems. But
Professor Meldola has suggested, in a note appended to
his translation of Professor Weismann’s ‘Studies in the
Doctrine of Descent,” that this is really due to the absence
of chlorophyll in their food, which is so frequently, directly
or indirectly, the cause of coloration in caterpillars. This
suggestion is supported by the existence of certain small
leaf-mining caterpillars, which are green ; in the thickness of
the leaves in which their tunnels are made, colour would be
neither advantageous nor disadvantageous ; and, as it is present,
it seems fair to attribute it to the chlorophyll which occurs,
though less abundantly, in the deeper tissues of the leaf.

An instance rather different from the above is afforded by
the “ larva of one of our Tiger beetles (Cicindela campestris),
which lives in a hole, from which its head and thorax alone
protrude; and these are of the same green as the perfect
insect, while the rest of the body is of the usual whitish yellow

64 ANIMAL COLORATION.

of a grub” (Andrew Murray, “ Disguises of Nature,” p- 9).
Here light may have been influential in distinguishing the two
halves of the body.

Bright Colours in Subterranean Animals.

Absence of light seems to have had no effect in the case of
mammalia which habitually live below the surface of the soil,
nor in earthworms or snakes which live underground.

Uropeltid snakes (Rhinophis oxyrhynchus), which live “deep
in the ground,” and have degenerate eyes, are nevertheless

often marked with brilliant red and yellow colours.
e

Influence of Light upon Colours of Flat Fish.

It has been supposed that flat fish, which habitually rest
upon one side, are examples of the modifications of colour
which have been caused by natural selection; the exposed side
is coloured,—protectively coloured and variable (see p. 140),
while the underside is white. In the young of these fishes,
which are symmetrical and swim in the position of a roach or
perch, both sides are coloured alike. When the asymmetry
has been acquired, and the fish has come to lie upon one side,
it is believed that the pigment has disappeared from that side,
on account of its uselessness. This explanation has an air of
reasonableness, which might lead to the inference that it had
been amply tested by actual experiment.

Mr. Cunningham, naturalist to the Marine Biological
Association, has made an interesting series of experiments with
a view to testing the validity of this explanation. The fish
used for their experiments were young flounders.* After
keeping the fish in tanks with a mirror at the bottom, the
usually white under-surface was found in several cases to
be largely pigmented, which seems to show that some environ-

* Zoologischer Anzriger, Feb. 1891.

COLORATION AFFECTED BY THE ENVIRONMENT. 65

mental cause—probably light—was responsible ; there is
obviously no room here for natural selection.

Absence of Colour in Cave Animals.

In certain parts of the world, notably in Kentucky and in
Jarolina, there are immense caves excavated by the agency of
water in limestone rock, and possessing a peculiar fauna and
flora of their own. The Mammoth Cave, in Kentucky, which
is one of the best known, consists of a complicated network of
ramifying passages, the total length of which is no less than
150 miles. Some parts of the cave are drier than others, as is
shown by the absence of stalagmitic deposits. Streams course
through some of the passages, and there are deep pools here
and there ; there is thus provision for both aquatic and terres-
trial animals and plants. These caves are, of course, quite
dark, and their temperature is remarkably uniform. Dr.
Packard * made a series of observations upon the temperature
of the Mammoth Cave, and found that it never rose above
56° Fahr., or fell below 52° 5’ Fahr.; the mean temperature for

the summer being 54° Fahr., that for the winter 53° Fahr.
These conclusions were confirmed by another observer ; and
it appears, therefore, that the variations of temperature through-
out the year are very small, and, small as they are, are no doubt
gradual. It would be expected that such remarkable physical
conditions, so different from those which obtain outside the
caverns, would produce some effect upon the animals and plants
permanently resident in those caves. There is a certain
analogy between life in these caves and life at the bottom of the
ocean ; the chief resemblance, of course, lies in the darkness of
both situations. As to temperature, there is a uniformity in

* See, for a detailed account of the North American caves and a general
summary of the facts known about the subject, Dr. Packard’s “‘ The Cave
Fauna of North America,” ete., Jem. Nat. Acad. Sci., vol. iv., 1°89.

5)

66 ANIMAL COLORATION.

the ocean abysses, no less than in the caves, but the temperature
is much lower in the ocean. Corresponding to these physical
environmental differences, we might expect to meet with
differences in the faunas of the two localities, coupled, how-
ever, with certain resemblances due to a certain similarity
between the localities.

And this is precisely what investigations into the fauna of
caves show to be the case.

The darkness of the caves has produced an effect upon the
cave animals, just as the darkness of the deep waters of the
ocean has upon the abyssal fauna. The structure of the eve
and.brain in many cave animals has been worked out by Dr.
Packard as well as by others; it would be out of place here to
do more than give the general results of these inquiries, which
show that there are various stages of degeneration to be met
with, culminating in a total disappearance of the organs of
vision. In the same way there is an absence of chlorophyll-
bearing plants in both places; the common Aydra and the fresh-
water sponge flourish in some caves, but they are entirely
without chlorophyll. As to plants, Dr. Packard finds that not
only are Alge and the higher green plants absent from the
caves, to which their spores and seeds must nevertheless have
easy access, but even Fungi, independent though they are of
light, do not flourish there; with a few exceptions, including
Oozonium auricomum and a colourless Agaric, there were no
fungi in the caves explored by Dr. Packard.

The animals of the cave fauna belong to all the orders of terres-
trial and fresh-water animals; there is no restriction, any more
than there is in the case of the abyssal fauna, of particular
groups to the caves.

A very important difference between cave animals and
abyssal marine animals is in their colour, and this is, of course,

COLORATION AFFECTED BY THE ENVIRONMENT. 67

_the point to which I wish to direct special attention. Deep-
sea animals are by no means bleached; on the contrary, their
colours are occasionally even darker than are those of their
shallow-water allies ; the brilliancy of the coloration of abyssal
animals is one of their most marked characteristics, because it
seems at first sight to be opposed to what would have been
expected.

The cave animals are, without exception, “ either colourless,
or nearly white, or, as in the case of Arachnida and Insects,
much paler than their out-of-door relatives ”—“lucicolous ” as
opposed to “ cavernicolous” forms Dr. Packard calls them.
The bleaching seems to be more marked in the Myriapods
(centipedes, millipedes) than in any other group; our British
centipedes vary in colour from a golden yellow to dark amber-
brown, as do those of the United States ; the colour of the
cavernicolous species is white, “ like a freshly-moulded myria-
pod of normal habitat.” It should be explained, perhaps, that
this change of colour is not due to any bleaching of the
integuments, or to their replacement by a white pigment which
is so rare in the animal kingdom ; it is simply caused by the
white fat body showing through the transparent pigmentless
“ skin.”

The Planarian worms and earthworms living in caves are
not entirely bleached, but are distinctly paler in colour than
those living beneath the open sky; but, as Dr. Packard remarks,
the normal environment of these creatures is not very different.

There do not seem to bea great number of observations upon
the capacity of cave animals for regaining their coloration
when exposed to light and ordinary temperatures. Mr.
Poulton* has, however, recorded one instance of great interest;
a Proteus (a blind, whitish amphibian, living in caves at

* “The Colours of Animals,” p. 91.

68 ANIMAL COLORATION.

Adelsberg) in his possession became gradually darker since its
removal from the cave; this, however, may only show that the
degeneration of the pigment was not complete, and that a few
pigment cells still remained which were liable to the influence
of light, having been previously in a state of paralysed
activity. This explanation, however, is not altogether satis-
factory, for light would contract the pigment cells, and so
cause, if anything, a more marked bleaching. As has been
already pointed out, a frog, or a sole, or any animal with
chromatophores supplied by nerves, becomes darker in darkness,
owing to the expansion of the chromatophores, and paler when
the light is strong and causes their contraction. It seems
very likely that Mr. Poulton’s Proteus is another example of
the production of pigment under the influence of light, such
as that which Mr. Cunningham has recently described in the
case of flat fish.*

The colour, or rather the absence of colour, in cave animals
has been made use of as an argument for the purposeful-
ness of colour in the animal kingdom. It is urged that the
colour has disappeared because it is useless; the cave dwellers
have no eyes, or imperfect eyes; and besides, they live in
darkness. Hence, there could be no use for warning colours,
for protective colours, and so forth. In my opinion these facts
not only do not lend such negative support to those theories,
but they are to a certain extent opposed to them.

It has been explained over and over again that the theory
of natural selection, as applied to the elucidation of colour
phenomena among animals, is concerned only with the dis-
tribution and arrangement of colour—with coloration, in
fact, and not with the pigments themselves, though it is of
course claimed that if pigment is hurtful (e.g. in the Pelagic

* See p. 64.

COLORATION AFFECTED BY THE ENVIRONMENT. 69

fauna), it may be made to disappear. Mr. Poulton, indeed,
says, “‘ Just as the useless eye has become rudimentary in these
animals, so has the useless colour gradually disappeared from
the skin. The energy necessary for the production and
maintenance of such structures has been diverted, either wholly
or in part, to other and more useful ends.” It is trae that
these remarks are specially applied to the Proteus, where the
pigment corpuscles may be regarded as definite “ structures.”
But as the section which contains these remarks is headed
“ Loss of Colour in Cave-dwelling Animals,” the observation is
probably intended to apply to insects, crustacea, etc., also.

Now, in these animals, however much it may be modified in
arrangement by natural selection, we must regard the pig-
ment asa normal product of their organisation ; this is Mr.
Wallace’s view of pigment, and it is the only reasonable one.
Accordingly, we should expect to find in animals, which, like
the cave dwellers, can reap no advantage from protective colora-
tion and other such modifications, an irregularly arranged,
but not diminished deposition of pigment, perhaps even an
increased brilliancy on account of the absence of any check.
What we do find is a uniform absence of pigment, which is
highly suggestive of a direct action of the environment—and
an environment obviously different from that which has caused
or permittel the bright and varied coloration of deep-sea
animals.

Nor can it be urged that the cave-dwelling animals have
lost their colour through what Professor Weismann terms
“ Panmixis” or the “Cessation of natural selection” alone ;
for this would also imply that the pigment itself had been
called into existence by natural selection.

If the pigment were to gradually diminish to the very verge
of disappearance. because, its presence having become useless,

70 ANIMAL COLORATION.

natural selection had, so to speak, ceased to encourage its
production, this would necessarily imply the first formation of
pigment under the influence of natural selection ; whereas
those who advocate the important effects which natural
selection has caused in the patterns of coloration admit that
they do not explain by this theory the origin of the pigment.
It must be there before it can be acted upon, and modified in
this or that direction according to the needs of the animal.

Seasonal Change in Colour.

A change to white at the approach of winter is well known
to occur commonly among Arctic animals. But it is not so
well known—or, at least, so much stress has not been laid upon
the fact—that many animals which inhabit more temperate
climates have a winter and a summer dress.

It wili be well to commence with a few instances of the
latter, before proceeding to discuss the nature and meaning of
the complete change to white which occurs in certain Arctic
mammalia. In the Manchurian deer (Cereus mantchuricus)
the summer dress is a yellowish-brown with white spots; in
the winter the colour of the hair becomes much darker, and
the white spots are barely visible at all, except just on the back
above the shoulders. A quite similar change takes place in
the Japanese deer, but a conspicuous white patch by the tail is
nearly as evident in winter as in summer.

In other species of deer there is no such alternation between
a spotted and an unspotted condition. In Cerrus duraucelli
for example, Mr. Sclater* describes the winter coat as of “a
dullish brown, which, however, changes in summer into a

* In a monograph of the Deer in the Zoological Society's Gardens
(Lrans. Zovl. Soc., vol. vii.), from which paper the other facts about deer
are drawn.

COLORATION AFFECTED BY THE ENVIRONMENT. 71

brilliant golden yellow, glossed over in the male with purplish
black in front.”

In many birds there is a corresponding difference in ‘the
summer and winter plumage, which may be more or less
marked. Any ornithological work will furnish abundant
instances of such colour changes, which are, in many cases at
least, not of such a nature as to suggest any advantage in the
way of protection, etc. Indeed, the change of colour is some-
times a merely incidental result ; part of the feathers break
off in the spring, and the colours of the deeper parts of the
feather are thus brought into view, which frequently brings
about a marked alteration in the tints and patterns of the bird;
this change is of course comparable to the change from a
thicker winter to a thinner summer coat in many mammals.

The snow bunting is whiter at one season of the year than
at the other ; but curiously enough the change is precisely the
reverse of what one would expect. It is whiter in summer
instead of in winter.

The grey phalarope undergoes as marked a change from
season to season as is shown in any animal ; im the winter it
has a grey-and-white plumage which closely resembles that of
a gull. In the summer it is coloured with various shades of
brown.

Some of these and similar colour changes, which appear to
correspond to the seasons, may have some connection with the
renewal and decadence of sexual activity.

Seasonal Change in Orthoptera.

Leydig has called attention to the change of colour exhibited
by the green grasshopper: in the autumn it becomes yellowish
red. A change of this kind might be set down to natural
selection; as the foliage becomes yellow a corresponding

72 ANIMAL COLORATION.

alteration in the insect would preserve its harmony in colour
with the environment. It has even been suggested that the
colour change is the same as that which occurs in leaves,—that
the insect owes its coloration to chlorophyll,—but this has
been disproved by Kriikenberg.

The colour of the grasshopper is caused by several different
substances in the skin, which can be separated by treatment
with different reagents. Ifa green or brownish individual be
treated with ether, the fluid is stained yellow, and the insect
remains of a cochineal red. This effect is produced by the
removal of the green pigment, a red colouring matter being left
behind.

In Locusta viridissima the green colour is relieved here and
there by reddish spots; these alone remain when the green
pigment is dissolved away by ether or alcohol.

Dr. Kriikenberg was able to prove that the green colouring
matter is affected by light: a piece of paper was thoroughly
soaked in, until it became dyed by, the green extract; one half
of this was exposed to the light, and the other half covered by
a slip of metal; the light was found to partially destroy the
colour. It is concluded, therefore, that light may effect a
change under ordinary conditions during the life of the insect.

Seasonal Change in a Beetle.

Besides these Orthoptera, something like a seasonal change
of colour occurs in beetles. The green colour of some of these
insects changes in the autumn to a brownish tint ; here again
we have what appears at first sight to be an excellent instance
of adaptability to environmental colour. This case, however,
is a little different from that of the grasshoppers ; in those
insects the colours are due to pigments; but in the Beetle
(Carabus auratus) the structure of the chitinous wing-cases

COLORATION AFFECTED BY ‘THE ENVIRONMENT. 73

is, as in the feathers of many birds, the proximate cause
of the colour. The green of this beetle changes late in the
year to a dusky colour ; but the same effect is produced
by ‘unusually frosty spring weather,’ and is seen in insects
captured in high altitudes.

Though the actual nature of the change does not appear to
be thoroughly understood, it is clearly to be set down to direct
effects of weather, and not to a regularly recurrent change
which has been fixed by natural selection.

Experimentally the same change can be produced, according
to Dr. Kriikenberg, in the wing-cases of Cantharides by
boiling them in water, or soda, or hydrochloric acid.

This cannot of course be compared with the effects produced
by natural temperatures, but it shows that even colours which
are not due to pigments can be affected by similar processes,
which possibly cause an alteration in the structure of the parts
coloured (see the reference to the “ Moon Moth,” on p. 60).

Change of Colour in Arctic Animals.

But the most remarkable changes of colour which have a
definite relation to environmental changes are shown by those
Arctic animals which become white at the approach of winter,
and regain their darker colour in the summer.

Such a change, however, is not universally found among the
inhabitants of the polar regions. Among those in which no
such change occurs, some are white all the year round, while
others are-not white, but some other colour. The polar bear
is white all the year round, and so are the snowy owl, the
American polar hare, and the Greenland falcon. On the other
hand, the raven, the musk ox, and the glutton, undergo prac-
tically no change at the beginning of the Arctic winter. The
reindeer is somewhat intermediate between such extremes as

74 ANIMAL COLORATION.

are offered by the raven on the one hand and the Arctic fox
on the other ; it does undergo a certain amount of change at
the beginning of winter, becoming not white, but greyer.
Sometimes closely allied forms show a difference in their
susceptibility to these climatic changes. One species of hare
turns white in the winter, another does not.
The Hudson’s Bay lemming (Cuniculus torquatus) under-

goes the change of colour, but its near relation the Sean-

dinavian lemming (JJyodes lemmus) does not undergo this

an
Fig. 1. -Arctic Pox,

change. The principal animals which change to white in
winter, in addition to those already referred to, are the
ptarmigan, the American hare (Lepus americanus), the ermine
aid stoat. With regard to the Arctic fox (Canis lagopus) it
has been stated* that this animal does not alter its colour
according to the season, and that the change is merely a
question of age and sex; only the old males are white, and

* Trouessart,“‘ La Géographie Zovlogique,” Paris, 1890, jos 2H)

COLORATION AFFECTED BY THE ENVIRONMENT. vis)

intermediate stages are found. This view is not the one
generally accepted. It is, however, certain that this animal
does not invariably undergo a seasonal colour change ; and
there is a highly interesting connection between the capa-
bility of undergoing this change, and the habitat of the
individual. In its extreme northerly habitat,the Arctic fox
almost always, if not always, changes its bluish brown

summer dress for a pure white in the winter. The aspect of

2.—Ermine.

the animal in the summer and winter dress may be gathered
from the woodcut on opposite page, and specimens may be
usually seen at the Zoological Gardens.

In Iceland, which is the most southerly area of the animal’s
range, a change to white is the exception.*

The Alpine hare illustrates the same principle: in Scandi-
navia it always becomes white in the winter; in Scotland
this change generally occurs, but seldom in Ireland. So, too,
the stoat: it always becomes white in the Alpine districts of

* Proc. Zool. Soc., 1869, p. 228.

76 ANIMAL COLORATION.

Scotland ; occasionally the change occurs in the Midlands, —
and white stoats have been recorded from Cornwall, and from
Gloucestershire even during a mild winter. The accompany-
ing woodcuts (figs. 1, 2) illustrate the winter dress of some
of the animals referred to in the text ; the Arctic fox (fig. 1)
is shown both in summer and winter dress.

The actual mode of the change in the colour of the fur has
been carefully worked out by Mr. Welch* for Lepus americanus.
The change in the summer coat is accomplished without the
shedding of hair ; but there is a new growth of white hair.
Naturally the winter coat is thicker than the summer coat.
Besides the increase in the thickness of the fur produced by
the growth of new hairs, the coloured hairs change their colour
and become blanched. This blanching usually commences at
the tip, and does not always involve the whole of the shaft.
‘The entire change occupies three months; it begins about
the first week in October, and is completed by the last week
of December.

The change is more rapid in other animals. In a lemming
Sir John Ross found the change to take place in a week.

It is thought that it is the change of temperature which
produces the change in the hair; but it would be very im-
portant to ascertain whether this is really the case, and, if so,
what are the limits of cold within which the change will or
will not occur.

The experiment of Sir John Ross upon the lemming appears
almost to settle the point. The animal was kept in the cabin
through the winter, and first exposed on deck on February
Ist; on the next day it had several white patches, and, as
already stated, became white in a week, but the creature died
a few days afterwards. On the other hand, the whitening of

* Proc. Zool. Soc., 1869.

COLORATION AFFECTED BY THE ENVIRONMENT. 77

the fur in an Arctic fox (one of several) in the Zoological
Gardens, seems rather to indicate the persistence of an
acquired habit than the direct effect of environment; but
it may, perhaps, be explained on the assumption that the
stimulus (2.e. the cold) was not sufficiently great to affect one
individual, but was sufficient to affect another of (presumably)
a slightly different constitution. Moreover, the experiment of
Sir John Ross was so far inconclusive that the cold was
administered in a sudden dose, which may have produced an
effect analogous to a nervous shock: we know that in human
beings the hair may turn white from the effects of a sudden
shock.

The fact that the change to white at the approach of winter
is not seen in all the inhabitants of the polar regions, appears
to be an objection to the view that the change is a direct effect,
of the environment. It is not, however, a fatal objection,
for it is a reasonable assumption that different animals are
differently affected ; if individuals differ in their susceptibility,
we need not be surprised to find that different species vary
in the same way. Another view of the matter is that the
change is one which has been brought about by natural
selection ; the white coat being useful for concealment in
the winter, and useless or rather harmful when the snow has
largely melted, we get the need for such a change. Here the
exceptions seem to prove the rule. The sable, the musk-ox,
and the raven retain their summer colouring throughout the
winter; but the sable and the raven are strong and active
animals, which have no enemies to fear; the agility of the
sable in pursuing birds among the boughs of trees, and
perhaps also the dark colour of the boughs, renders un-
necessary the adoption of any concealment ; while, as regards
the raven, it is mainly a carrion feeder.

78 ANIMAL COLORATION.

The musk-ox being a comparatively defenceless animal, it
is perhaps a little surprising to find that it does not assume
a white colour in the winter. But here union is strength ;
it is more important that a straggler should be able to regain
his companions, which would be difficult if they were less
conspicuous. One is inclined, however, to suggest in the case
of this animal that its scent may serve for recognition purposes
perhaps more efficiently than even its conspicuous appearance
against the white snow. It is difficult to decide offhand in
every’ case how far the white coloration is useful, whether
for protective or aggressive purposes. The polar bear, for
example, always quoted as an instance of an animal that has
reaped advantages from its protective coloration, according to
Nordenskiéld, hunts rather by smell than sight ; its colora-
tion, therefore, can hardly be for aggressive purposes. It is
important to remember in this particular case that, although
the hairs are largely depigmented, they are not entirely so ;
at any rate the colour, except in very young bears, is of a
creamy tint rather than white. So pronounced is this some-
times that the Scotch whalers know the animal by the name
of “ Brownie.” *

Even the Arctic fox does not always change colour in the
winter in its native country, any more than it does with us ;
Mr. Brown states ¢ that white and blue foxes are met with in
the winter, that the colour is not dependent on the season. Both
these facts look more like the direct effect of cold and dryness
than of natural selection.

Professor Semper has pointed out another difficulty in the
way of accepting the theory that the change of coloration
in Arctic animals is due to natural selection. Even supposing
the usefulness of the change, which is not entirely obvious,.

* Proc. Zool. Soc., “Mammals of Greenland,” 1868. t Loe. cit.

COLORATION AFFECTED BY THE ENVIRONMENT. 79

the intermediate stages must be useless: a piebald animal
would be just as conspicuous as a black one—perhaps even
more so, by the unusualness of its appearance ; even if we
postulate a gradual whitening of the fur the difficulties are
hardly removed.

It may be replied, however, to this that albinism, complete
or incomplete, occurs in many animals, and it has been known to
be hereditary ; for the most part such albinos or partial albinos
are weeded out on account of their conspicuousness, but in
the Arctic regions the albinos would be just the ones to be
preserved, the others dying out. In this way we may possibly
account for the origin of the white coloration in the polar
bear and in other animals which are white the whole year
round. But this line of argument will hardly apply to those
creatures which only change in the winter. It is difficult to
avoid the conclusion that here the depigmentation of the hair
is directly due to cold, or dryness, or whatever the true environ-
mental cause may be. Nor, on the other hand, can it be
urged that the delicacy of constitution which allows of this
yearly recurring change has been produced by natural selec-
tion. It must have occurred suddenly, to be of any use; but
when it was once established it may have been perpetuated by
natural selection.

Seasonal Dimorphism.*
The classical instance of this remarkable phenomenon is of
course afforded by the spring and summer broods of the conti-
nental Vanessid (Vanessa prorsa levana).

* I confess myself unable to understand the necessity for Dr. Weismann’s
apologies for making use of the above—Mr. Wallace’s—term ; nor can I see
why Professor Eimer should stigmatise it as “in every respect monstrous.”
They are true English words—an adjective and substantive ; we might as
well object to such expressions as “ complete metamorphosis ” and “ mimetic:
resemblance.”

80 ANIMAL COLORATION.

Formerly it was held that 1. prorsa and A. levana were two
different though closely allied species: but as long ago as
1830 it was shown that they were merely the spring and
summer broods of one species, and produced from identical
caterpillars which feed upon the same plant (the nettle).
A. lerana is the spring form, A. prorsa the summer form ;
the first-mentioned passes the winter in the chrysalis stage.

Professor Weismann tried by raising the temperature in
winter to rear prorsa directly from the offspring of prorsa, and
conversely by lowering the temperature in summer to rear
levana from the offspring of levana. By lowering the tempera-
ture three levana were produced out of twenty, and twelve
porima, an intermediate form, the rest remained prorsa; by
raising the temperature only three out of forty chrysalids
produced the form prorsa. Professor Weismann remarks, in
his concluding chapter, “that differences of specific value can
originate through the direct action of the external conditions
of life only,”—a conclusion which appears to be justified in
spite of the comparative failure to make the influence of
artificial warmth felt. Eimer has suggested that it is possibly
easier to imitate by artificial means the conditions of winter
than those of summer; and this may account for the failure
to convert the winter into the summer form.

But it should be borne in mind that Professor Weismann’s
experiments were made upon the chrysalids only, not the
caterpillars ; besides, Dorfmeister, who made the same series
of experiments, failed just where Weismann succeeded, and
succeeded where he failed; that is to say, he found the
influence of warmth more potent than that of cold.

In spite of the sentence quoted above, Dr. Weismann is
inclined to consider the problem of seasonal change more
complex. Apropos of some important investigations upon

COLORATION AFFECTED BY THE ENVIRONMENT. 81

American species by Mr. Edwards, Professor Weismann has
contributed, in an appendix to the English edition of his
“Studies in the Theory of Descent,” some further remarks
upon the subject. Mr. Edwards experimented upon several
American butterflies, including Grapta interrogationis, a
species allied to our “Comma.” The summer form of this
butterfly is known as G. wmbrosa, the winter form is G.
Fabricti ; put there are intermediate generations which are
mixed, that is, they consist of both forms in varying propor-
tions. Some eggs laid by a female wmbrosa of the second
brood were hatched under natural conditions, confined by a
muslin bag upon a branch of the food plant. As the pupe
formed, they were removed at intervals to an ice box, in
order to find out if it were essential that exposure to cold
should take place immediately after pupation for an effect
to be produced. If left to nature, it would be expected
that the resulting butterflies, belonging as they do to an
intermediate brood, would be of both forms. The result was
that every specimen belonged to the form wmbrosa, but they
were darker-coloured in parts. Professor Weismann points
out that as two out of the four annual generations are mixed—
that is, consist of summer and winter forms—“ the conclusion
is inevitable that these forms were not produced by the
gradual action of heat and cold.” When the same conditions
produce two different results, neither can be said to be due
to those conditions. So says Professor Weismann; but is
this conclusion certain ?

It seems quite conceivable that the same condition may
produce different results upon different individuals, if we bear
in mind that one result is merely a maintenance of the status
quo, while the other is a change: individuals must, indeed do,

vary in susceptibility to external influence, as I point out
6

82 ANIMAL COLORATION.

(p. 77) with reference to the Arctic foxes at the Zoological
Gardens. Professor Weismann goes on to show reasons why
aumbrosa and not Fabricii was really the winter form (they
neither of them pass the winter in the pupa form) ; hence
the effects of cold upon the pupz are more intelligible.

It is not only butterflies which exhibit a seasonal dimor-
phism ; the same phenomenon is exhibited by certain moths.
One of the “thorn” moths (Selenia illustraria) is an example;
Mr. Merrifield has published in a recent part of the Transac-
tions of the Entomological Society a good account, accompanied
by a plate, of his experiments with this insect and with
Ennomos autumnaria-tiliaria,

By icing (a temperature of 33°) pup of ¢dlustraria of the
summer brood, a darker colour was produced upon the resulting
imagos ; on the other hand, by forcing (at a temperature of 80°)
pupe of the summer brood, moths emerged which were inter-
mediate in colour between the summer and spring broods, %.e.,
paler than they would normally have been.

There are various interesting questions concerning seasonal
dimorphism, the discussion of which would be beyond the
limits of this book: I am only desirous of pointing out here
that colour change may be directly caused by environmental
causes ; that this is so with seasonal dimorphic Lepidoptera
there can be no doubt.

CHAPTER III.
PROTECTIVE COLORATION.

Tux resemblances in colour and in shape, often perfect to the
most minute detail, which many animals bear to their in-
animate surroundings, is a fact familiar to most persons.

Tree-frequenting animals are often green in colour. Among
vertebrates numerous species of parrots, iguanas, tree-frogs,
and the green tree-snake are examples. There are several
green moths, such as the Oak Tortorix, and the Emeralds.
Green butterflies are not common, but there is one species in
this country—the green Hairstreak (Lhecla rubi). This is
a particularly good example, since the green colour is only
developed on the underside of the wings. Now, this butterfly
when at rest folds the wings over the back, so that it is
precisely the green underside which is alone visible. On
the other hand, the moths, if not entirely green, have the
upper wings only of that colour. This is equally advanta-
geous, for the upper wings alone are displayed when the insect
is sitting upon a leaf. Among beetles and other insects are
numerous species which frequent plants, and are green in
colour ; and of course innumerable caterpillars are green.

The very general tawny colour which animals that frequent
arid deserts exhibit, is equally striking, and is to be seen in
many groups of the animal kingdom. A beautiful case of
stuffed animals illustrating this varticular class of “ protective

84 ANIMAL COLORATION.

colours” has been placed in the central hall of the Natural
History Museum at South Kensington.

Mr. Wallace includes all these instances under the heading
of “General Protective Resemblance,” to distinguish them
from other instances, to be treated of immediately, in which
the animal shows a special resemblance to some particular
object, such as a leaf or twig.

Perhaps the “autumn tints,” so remarkably shown in
certain moths which emerge from the chrysalis during the
latter months of the year, are to be referred to the same
category. Several species of British moths belonging to the
genus anthia have the upper wings of a yellowish brown
colour, like dead leaves, often mottled with darker colours in
a way highly suggestive of more thoroughly decayed portions
of the leaf; and these moths are found in the perfect state in
the autumn months.

The white colour of many Arctic animals has been treated
of in Chap. II., as they come into the class of colours which
change in correspondence with changes in the environment.

The dusky colours of nocturnal animals—particularly of lepi-
doptera and birds—have been used as an instance of a similar
compliance with environmental conditions ; dusky colours and.
darkness seem to suit. It is true that there are no brilliantly
coloured nocturnal birds; but there are brightly coloured
nocturnal moths. Any lepidopterist who has “sugared” in
the New Forest knows the brilliancy of the tints exhibited by
the Crimson Underwing, the broad-bordered Yellow Under-
wing, and the more delicate but equally beautiful and con-
spicuous colours which adorn the upper wings of the “ Peach
Blossom” and “ Merveil du Jour.” One would, in fact, expect
that brilliant coloration would be the rule rather than the
exception among nocturnal inseets, for, however bright and

PROTECTIVE COLORATION. 85

varied, the colours would be invisible at night, and could do
their possessors no harm or good. During the daytime most
of the nocturnal insects hide themselves among herbage, or in
nooks and crannies. A few brilliantly coloured. species, like
the Red and Crimson Underwings, have these brilliant colours
confined to the second pair of wings, which are covered over
when the insect is at rest by the dull-coloured upper wings.
The dull colours of moths, which habitually fly at night, ought
rather, perhaps, if we accept the influence of natural selection
upon coloration, to be regarded as useful for protection
during the daytime.

Special Colour Resemblances.

These are so numerous that it will be impossible to give
more than a few examples, which will be selected from as
many groups of the animal kingdom as possible.

Most persons who had only seen these animals in the
Zoological Gardens would be inclined to look upon the giraffe,
the zebra, and the jaguar as among the most conspicuously
coloured of the Mammalia; and yet we are assured, by those
who have seen them in their native countries, that they are
most difficult to detect. The spots upon the jaguar harmonise
with the oval patches of sunlight which penetrate between the
leaves of the trees upon which it lives.

Sir Samuel Baker, in a very interesting work recently
published, and entitled “Wild Beasts and their Ways,”
remarks (vol. i, p. 191) of the tiger:—‘The striped skin
of the tiger harmonizes in a peculiar manner with dry sticks,
yellowish tufts of grass, and the remains of burnt stumps,
which are so frequently the family of colours that form the
surroundings of the animal.” With regard to the giraffe,
another apparently conspicuous animal, the same author

86 ANIMAL COLORATION.

remarks (vol. ii, p. 151):—“It may be readily imagined
that, owing to the great height of this animal, it can be
distinguished from a distance, and does not require an
elaborate search ; nevertheless it is exceedingly deceptive in
appearance when found among its native forests. The red-
barked mimosa, which is its favourite food, seldom grows
higher than fourteen or fifteen feet. Many woods are almost
entirely composed of these trees, upon the flat heads of which
the giraffe can feed when looking downwards. I have fre-
quently been mistaken when remarking some particular dead
tree stem at a distance, that appeared like a decayed relic of
the ferest, until, upon nearer approach, I have been struck by
tke peculiar inclination of the trunk: suddenly it has started
into movement and disappeared.”

The sloth, when suspended from the branch of a tree, has
been compared to a broken stump clothed with long, tangled
lichens, and an oval mark upon the back is said to produce the
impression of the broken end of the stump.

Mr. W. H. Hudson has described a Sonth American bittern,
which affords an excellent instance of the advantages which
result from a protective coloration. This bittern, when dis-
turbed, flies among the reeds, and suddenly disappears from
view by clinging to a tall reed, which its colour, and even
shape, cause it to resemble very closely—so closely that Mr.
Hudson was frequently deceived, and passed by.

The curious resemblance which flowers, particularly those
of orchids, bear to insects is possibly of no more importance
to the flower than is its fanciful resemblance to a lamb to the
plant Aspidium Barometz; legends state that wolves have a
peculiar liking for this plant.

The Butterfly Orchis and the Bee Orchis are well-known
examples of what is probably a mere “freak of nature.” On

PROTECTIVE COLORATION. 87

the other hand, the resemblance of insects to flowers may
conceivably be of use to them in various ways. The flower-
like Mantis—Hymenopus bicornis—has been referred to on
p- 187 as an example of what has been termed alluring
coloration. Mr. T. W. Wood has figured, in the Intellectual
Observer, the Orange-tip butterfly when at rest on an
umbelliferous plant, its favourite resort. The scattered green
spots upon the under surface of the wings (see fig. 3) might

Fig. 3.—Orange-tip.

have been intended for a rough sketch of the small flowerets
of the plant, so close is their mutual resemblance. An
American entomologist, Mr. C. M. Weed, has called attention
to a small white Geometrid moth (Tetracis lorata), which he
found adhering to the stamens of the ‘‘ May Apple,” its wings
giving the impression of petals ; two were found in the same
position. The Lappet moth (fig. 4) looks like a bunch of dry
leaves, owing to the peculiar way in which it carries its wings.

It is among insects, indeed, in correlation with their im-
mense numbers and diversity of form, that we meet with the

88 ANIMAL COLORATION.

most numerous as well as the best examples of special
protective resemblances.

A most instructive case of butterflies has just been added to
the Natural History Museum at South Kensington, ulus-
trating the colour resemblances of a species of Kallima.
This butterfly is a native of the East ; itis of large size, and
adorned with blue and orange patches upon the upper surface
of both fore and hind wings. It is therefore one of the most

Fig. 4.—Lappet Moth.

conspicuous of insects. But this is at once changed when the
insect settles upon a twig. The under side of the wings is
brownish, and marked with a median line, from which
branches are regularly given off. The contour of the wings in
this position is oval, terminating in a sharp point anteriorly,
while the tails of the hind wings touch the stem of the plant
and perfect the remarkable resemblance to a decayed leaf.
Furthermore, just as the processes of decay in the leaf are
not absolutely alike in any two leaves—that is to say, the spots

PROTECTIVE COLORATION. 89

and patches of mildew are varied in extent and position—so the
under sides of the wings of the Kallima show a considerable
range of diversity. This instance is perhaps the most
striking case of resemblance to the environment that has
been yet described and illustrated (see plate).

Protection afforded by Resemblances of this kind chiefly efficacious
against Vertebrate Animals.

As a matter of a fact, are animals concealed by their
“‘ protective resemblances ” from their foes? This is a question
which really cannot be answered in many cases ; sufficient data
upon which to found a reply are not forthcoming. <A few
points, however, bearing upon the matter may be noted. No
doubt Mr. Poulton is quite right when he says that no species,
however perfectly it is concealed by these means, can wholly
escape. If this means of protection and that afforded by
warning colours were entirely successful, insect-eating birds
would disappear altogether for lack of food. And besides,
caterpillars—to limit ourselves to that class for the present—
have other enemies besides birds. They are eaten by monkeys,
lizards, frogs and toads, and by other insects, such as wasps;
Ichneumon flies deposit their eggs in them, and thus ultimately
dlestroy them. It is just as important for a caterpillar to be
protected from these Hymenoptera as from birds, which are
perhaps the chief enemies among Vertebrates—in this country
at any rate.

In discussing these and similar questions, there ix always too
great a tendency to endow animals with senses exactly similar
to those possessed by ourselves. This tendency is, of course,
more dangerous when we are dealing with the lower animals.
Mr. Platean’s experiments in the vision of Arthropods* are thus

* Dr. Sharp’s most useful abstract is in Trans. Eutom. Socivty, London,
for 1889.

90 ANIMAL COLORATION.

summarised by Dr. Sharp. “ There is at present no evidence
at all that the light perceptions are sufficiently complex to be
entitled to be called seeing ; but that, as the large develop-
ment of the compound eye permits the simultaneous perception
of movement, its direction, and of lights and shades over a
certain area, a dragon-fly may pursue and capture another
insect without seeing it at all, in our sense of the word seeing.”

Nor is it quite certain that the colour vision even of birds is
precisely the same as ours: their sight in general seems to be
much keener, and possibly therefore they can see through an
insect disguise far more readily than we can, particularly when
keenness of vision is aided by hunger. It is said that when
a photograph of a green tree-frog or snake is examined the
animal is quite easily seen. The deceptive colour being
removed, the difference in form is at once apparent.

It is clearly, therefore, premature to assert that colour
protection is in any way a means of defence against insect
enemies. It has been observed that animals which simulate
their surroundings constantly remain without movement ; this
is specially well seen in the case of various twig-like Geo-
meter larvee, which, clasping a branch firmly by the posterior
legs, stand out rigidly at an angle with the branch ; this
attitude, which of course increases their resemblance to a twig,
is maintained for hours. Indeed, absence of movement is
absolutely essential for protectively coloured animals, whether
they make use of their coloration for defensive purposes as
in the case of the caterpillars, or for offensive purposes like the
Mantis or spider.

The power and the will to remain motionless is in itself
a most advantageous possession for an animal subject to the
attacks of carnivorous foes. Many insects will “ feign death ”
when pursued; toads and frogs, as well as many reptiles, will

PROTECTIVE COLORATION. 91

as a rule only seize their prey when moving; in these instances
a protective coloration would be no additional advantage ; it
would be simply superfluous.

These arguments do not, however, apply to birds, which
admittedly search for insects assiduously on the ground and
among trees. Insectivorous birds are mostly small and very
keen-sighted; I have frequently observed that they will readily
detect. the smallest insect or particle of food when thrown
amongst gravel ; and the observation is by no means new.

Judging of birds by our own standard—which is the way in
which nearly all the problems relating to colour have been ap-
proached—does it seem likely that we should fail to see a cater-
pillar, perhaps as long or longer than the arm, of an obviously
different texture from the branches, and displaying in many cases
through its semi-transparent skin the pulsations of the heart,
for which we were particularly searching? In the elaborate
“ Report upon the English Sparrow ” lately issued by the U.S.
Department of Agriculture, it is asserted (on p. 109), on the
authority of Dr. Leconte, that a Geometer larva (/nnomos
subsignaria) abundant on the trees growing in the streets of
Philadelphia had been exterminated by European sparrows ;
although this statement is demurred to by the editors of the
volume, on the ground that other causes besides the sparrows
had probably contributed to this end, it is admitted that “from
different parts of New England unimpeachable testimony has
come as to the good work done by the sparrow” * in feeding
on another Geometer larva (Paleocrita rernata). While it is
not pretended that this evidence settles the question as against
those who hold that Geometer larvee are protected by their
colour and form resemblances, it is contended that it Hes with

* The Sparrow, moreover, unfortunately for the agriculturist, does
not confine his depredations to insects.

12 ANIMAL COLORATION,

these naturalists to produce conclusive evidence that birds do
constantly pass over these larve before the theory can be
regarded as firmly established.

In the meantime the excessive fertility of the parent moths
appears to be a sufficient guarantee against extinction, apart
from any subsidiary advantage to be gained by colour pro-
tection.

Some Evidence showing that Caterpillars are concealed by
Protective Coloration from Enemies.

Mr. Poulton gives a few instances which tend to prove that
lizards do pass over and leave unnoticed protectively coloured
caterpillars. I may quote here an observation to the same
effect made by myself and Mr. Finn. A small green cater-
pillar (of one of the “ Whites”) upon a nasturtium leaf was
put into a case with Lacerta viridis. The caterpillar was, so
far as could be judged by similar experiments, quite suitable
in point of size as food for the lizard, but it was certainly
entirely ignored. It must be mentioned, however, that the
caterpillar was absolutely motionless.

Protective Coloration of the Iguana.

Each instance of apparent colour resemblance must be dis-
cussed on its merits ; it is quite unphilosophical to assume
without further inquiry the general action of natural selection
in producing, or at least intensifying, the similarity of colour
between an animal and its usual environment. The onus
probandi lies with those who advocate the action of. natural
selection. The usefulness of each case of colour resemblance
must be demonstrated ; and any facts which tend to prove
that it is of no particular use have tar greater weight against
the theory than suggestions, merely based upon human ideas
of resemblance and difference, have in its favour. The green

PROTECTIVE COLORATION. 93:

iguana, resting motionless upon the branch of a tree, seems to.
be a perfect case of protective coloration. We learn, however,
that a species in the island of Sta. Lucia is easily captured in
spite of its colour; the iguana in question is highly esteemed
as an article of food, and is hunted by means of dogs; it is not
pretended that the dogs can see their quarry, but they detect
its presence by the sense of smell. The iguanas of South
America, some of which have the same coloration, may fall
an easy prey to jaguars and ocelots guided by the same sense.
It is true that the cat tribe do not appear to have quite so
keen a nose as dogs; but they belong to those Mammalia which
have been termed, on account of the large development of that
part of the brain which is concerned with smelling, “ osmatic ”
as distinguished from the Primates and aquatic mammals.
which have at most a very slightly marked “rhinencephalon.”

Protective Coloration occasionally appears to be Superfluous.

It is not, of course, fatal to the theory that various colour
modifications have gradually arisen through elimination, to be
able to show that disguises are sometimes seen through, and
warning colours occasionally disregarded. Any quality which
gives to its possessor the smallest advantage in the struggle
for existence may be seized upon and perpetuated by natural
selection. At the same time we must carefully avoid assuming
that a given disguise is effective, without abundant experi-
mental proof. Nor does it necessarily follow that a gaudily
coloured caterpillar rejected with signs of disgust by one
lizard will be refused by another. Animals have their likes
and dislikes, just as we have. Experimental evidence that
this is so is given on pages 164,165. All these matters must
be carefully considered before framing hypotheses ; the diffi-
culties arising chiefly from our imperfect knowledge, and

G4 ANIMAL COLORATION.

partly also from the contradictory results of experiments, are
so great that it does not appear to the present writer that we
are anywhere near a real ‘understanding even of the problems
that have to be solved—let alone their solution. Dr. Seitz
has pointed out * that certain insects, for the most part pro-
tectively coloured, often select for their resting-places “ quite
circumscribed situations on trees.” Biston pilosarius, for
example, is constantly found, according to that writer, at a
height of 2 to 1 metre on tree trunks. The male of Hibernia
progemmaria sits for the most part at the foot of a tree, while
the female rests higher up—from 14 to 2 metres. The same
regularity is observable among caterpillars : those of Saturnia
car pint frequent only the lowest boughs, while Stauropus fag?
selects the loftiest branches of oaks.

Since many birds habitually seek their prey upon different
parts of the tree,t and have, as has been pointed out already,
their likes and dislikes, we may often account for the preva-
lence of a well-disguised species not by the efficiency of its
disguise, but by its choice of a feeding-ground or a resting-
place.

Protective Resemblance in an Annelid.

In examining water from fresh-water pools and streams, it
is common to meet with examples of a little worm belonging
to the Annelida Oligocheta, a group which also contains the
Earthworm. These worms, of which there are five species
known to occur in Great Britain, have received, on account of

* Zool. Juhrb., Abth. f. Syst., 1888, p. 63.

+ This fact may account for the rarity of the Lobster moth caterpillar
in England. I only saw, during five years’ active collecting of Lepidoptera,
a single specimen of this larva.

t Sita searches for insects at the very foot of a tree, and in the herbage
round about. Dendrecopus investigates only the upper branches, etc., etc.

PROTECTIVE COLORATION. 95

the bright-coloured spots on the body, the name of #olosoma.
In two species these spots are bright green in colour, often
with a bluish tinge ; in a third species the spots are yellow-
green, sometimes almost brown ; while in the remaining two
they are orange-brown. I have already suggested the possi-
bility of this pigment having a physiological importance ; but
it also bears a most striking superficial resemblance to chloro-
phyll and to some other plant pigments. The bluish-green
colour of the oil globules in 4. Headleyi recall the bluish
green pigments of certain Alge, and the other colours recall
pigments of an almost identical hue in other plants, though
apparently they have no chemical relationship to them what-
ever. As the bodies of these small worms are transparent,
they present no small resemblance to a living or dead (with the
chlorophyll altered) filament of an Alga. But we can hardly
suppose that this resemblance is of much use to the worm
which is preyed upon by animals that cannot have the least
appreciation of its colours.

Protective Coloration in Man.

It is even said that man himself may assimilate in colour to
his surroundings. The traveller Schweinfurth remarks that
“the Bongos have a reddish-brown skin similar in colour to
the soil of their country; the Dinhas (a neighbouring race), on
the other hand, are as black as the alluvium of their native
soil.” It should be added, however, that Dr. Schweinfurth
instances this fact rather as a curious accident than as an
example tending to prove the truth of any theory respecting
protective resemblance.

Green Colour of the Sloth.
The greenish colour of the hair of the sloth is very sug-
gestive of a lichen-covered branch ; and, considering the

96 ANIMAL COLORATION.

sluggishness of the animal, this colour may have a protective
value. The colour, however, curiously enough, is purely ad-
ventitious, and is the only example of the kind among the
Mammalia.

In captivity the sloth gradually loses this green colour, and
becomes greyer; this is not a change comparable to the
gradual fading of the brilliant red of the scarlet Ibis, but is
simply due to the disappearance of certain minute Alege,

Fig. 5.—The Sloth.

which, as Mr. Sorby first discovered, are the cause of the
peculiar coloration ; doubtless it is the absence of a damp
and warm climate that is fatal to the Algz, and is the cause,
therefore, of what appears to be an actual change in the colour
of the hair-itself. It would be difficult, therefore, to set down
this case of what appears to be an adaptive coloration to the
action of natural selection ; though it must be admitted that
we still have to explain why this animal alone should be
subject to the intrusion of the Alge: possibly its sluggish

PROTECTIVE COLORATION. 97

mode of life may encourage the growth of these vegetable
parasites, which could not gain a footing upon the bodies of
more active animals.

Protective Coloration the Prevailing Device among
Leaf-feeding Caterpillars.

The majority of the caterpillars of the Lepidoptera are pro-
tectively coloured ; it is the rule, for instance, with the extensive
families of the Noctuae, the Geometric and the Tortrices ; there
are exceptions to this rule, as to every rule: for example, the
larvae of the Acronyctides, the Dagger moth and its allies,
including the “ Merveil du Jour ™; these larvie are usually hairy
and brightly coloured; this exception, however, may possibly
be explained as due to affinity : the larvee closely resemble the
brightly or at least conspicuously coloured and hairy larve of
the Bombyces: and this group of Noctuae are sometimes classed
apart from the rest as Bombycoidea, a term which gives ex-
pression to this view. On the whole, it scems more profitable
to a caterpillar to adopt protective resemblance to its sur-
roundings as a means of escaping its foes ; at any rate, this
is what actually occurs. “The main purpose in life of a
caterpillar,” says Mr. Sendder, “ next to feeding, is not to be
seen” Eyen some larvie which are commonly regarded as
exhibiting warning colours are by no means conspicuous,
particularly if they feed among flowers, or upon low-growing
plants in situations where there is a varied vegetation and
abundance of flowers. Larvie, as well as other animals which
have not a very marked protective resemblance to any special
object, or have not a colour which is in general harmony with
the environment, are nevertheless by no means invariably

conspicuous.

98 ANIMAL COLORATION.

Longitudinal Striping of Caterpillars.

Sir John Lubbock, in a very interesting survey of the colours
of Caterpillars,* comments upon the connection that exists
between longitudinal stripes upon caterpillars and a habit of
feeding either upon grass or low-growing plants among grass.
The green or brownish colours of these caterpillars, of course,
heightens the resemblance to grass leaves, the longitudinal
stripes representing the veins upon these leaves. The bulk of
the caterpillars (found in Great Britain) that frequent such
situations exhibit these characters. They are also for the
most part motionless during the day—an absolute necessity for
protective coloration to confer any benefit. Without any
further statement it might be at once inferred that this must
be a case of protective resemblance brought about for purposes
of concealment. But, before accepting this conclusion, it will
be desirable to examine the facts a little more critically.

Grass-feeding caterpillars are not confined to any one group
or order: they are confined neither to butterflies nor moths ;
plenty of instances occur in both these two divisions of the
Lepidoptera. The striped caterpillars particularly referred to
by Sir John Lubbock are those of the Satyride, a family of
butterflies typified by the abundant ‘“ Meadow Browns.” The
Galium-feeding larva of the Humming-bird Hawk moth has
also these longitudinal stripes; the Bedstraw or Galium,
however, often grows in patches where there is no grass. The
Skippers or Hesperide, a family which seems to be a con-
necting link between the butterflies and moths, feed upon
small plants, and are longitudinally striped. So, too, are the
larvee of the genera Leucania, Nonayria, Caradrina, lpamea,
and Jana, among the Noctue. The caterpillar of the “ Duke

* “ Scientific Lectures,’ London, 1879.

PROTECTIVE COLORATION. 99

of Burgundy” fritillary (Nemeodius lucina) shows a similar
relation between markings and habitat, and there are other
instances, some of which will be referred to later.

The striping is not, as a rule, to be found during the hole
life of the caterpillars; when just hatched they often show no
markings at. all, and are uniformly green. But a minute green
caterpillar is sufficiently protected; it is only when it becomes
larger that the striping becomes necessary as an aid to con-
cealment: this, at any rate, is the usual view.

Longitudinal Striping found in all the Species of the Butterfly
family Satyride.

Now, the Satyrids ad/ possess striped larvee. There does not
appear to be a single known exception to the rule ; this is the
case not merely with the European forms, but with the genera
and species from other continents. It must be remembered,
however, that a very large number of these butterflies are only
known in the perfect state. The statement “Larva unknown”
is of constant occurrence in the descriptions of species—even
Kuropean. Furthermore, they all, with one doubtful exception,
feed upon grasses, sedges, and such plants. The doubtful
exception is a North American species of Gineis (a genus
which occurs in Europe, but not in England); Mr. Scudder
relates that he found a larva of this butterfly in such a position
with reference to a partially-eaten patch of lichen, as to suggest
that it was a lichen feeder. On other occasions, however, it
was always found on sedges; so that its feeding upon lichens
is doubtful. Here, again, it must be remembered that excep-
tions may be met with as our knowledge increases. We find,
therefore, that all the members of a large and widely dis-
tributed family of butterflies are, so far as we know, striped in
the caterpillar stage and met with upon grasses and other low

100 ANIMAL COLORATION.

plants occurring among grasses. This very fact does not look
like selection; it looks much more like a family characteristic.
Still there is the coincidence of colour and habit. It has been
mentioned that the very young caterpillars are not striped; but
among tufts of bright green and luxuriantly-growing grass is
there any need for even the adult caterpillars to be striped ?
One does not notice the striping produced by the venation of
the grass leaves in many cases. As a matter of fact, some of
the Satyrid larve are greener than others, and the striping is
reduced to the minimum of visibility. These species are
equally well, if not better, provided for in the way of protective
coloration than the brown ones with strongly marked lines.

These Larve usually feed by night, and often conceal themselves
by day.

The larvee of these butterflies feed chiefly by night ; under
these circumstances striping or no striping would be quite
immaterial,—they would run an equal risk of discovery with the
most brilliantly coloured of caterpillars. But although these
caterpillars usually, if not always, feed by night, they often
rest during the day freely exposed upon grass stems, so that
their protective coloration would stand them in good stead.
Immobility, as has already been remarked, is an absolutely
necessary concomitant of protective coloration. If the matter
ended here, there would be considerable grounds—almost
perfectly convincing indeed—for regarding the coloration of the
caterpillars as due to adaptation. But this is not all.

Several species hide themselves by day ; Newman * relates
that this is the case with the “Grayling” butterfly, Hipparchia
semele. A number of these larve were observed not only to
feed during the night, but to hide themselves during the day

* “British Butterflies and Moths.”

PROTECTIVE COLORATION. 101

by burrowing into the sandy soil upon which their food-plant
was placed. Scudder also says that the larva of the Gneis,
already referred to as being possibly a lichen-feeder, feeds by
night and hides itself by day under stones. Mr. Scudder never
succeeded in finding these caterpillars during the day except
under stones. Now, in these cases the colour obviously does not
matter; if, therefore, the longitudinal striping is kept up by
constant selection on account of its utility, and has no other
signification, we might expect that in these two species, and in
others with similar habits, the cessation of natural selection
would have permitted the high standard required in the other
cases to be lowered,—perhaps, even, as has been suggested in
the case of the cave-animals, the colours being useless to their
possessors, might have disappeared altogether,—but they have
not ; the caterpillar of the ‘“ Grayling” is a typical Satyrid
caterpillar.

As an alternative suggestion to modification of coloration to
suit environment, may not we suppose sometimes a change of
environment to fit in with colour? This is, perhaps, a crude
way of stating it, as it suggests a deliberate picking and
choosing on the part of the caterpillar of a plant or locality
best adapted to the concealment of its otherwise conspicuous
livery. (See, however, the case of the black moth quoted on
p- 113.) Prof. Drummond” suggests how easy itis to produce
changes of structure, which free the animal so changed from
any need of alteration of habit. ‘A few daubs of colour, a
little modelling of thorax and abdomen, a deft turn of antenna
and limb, and the thing is done,” he says. If natural selection
chooses the easier path, which we must obviously assume to be
the case, a change of habit will be often much easier. There
are plenty of examples of change of habit in the animal

*“ Tropical Africa.”

102 ANIMAL COLORATION,.

world. I need only refer to the classical instance of the New
Zealand Parrot, which has, in the last fifty years, taken to a
purely carnivorous living. Caterpillars often feed upon many
different plants; the Gooseberry caterpillar will eat almost any
shrub, including laurel; and I have “ beaten” the larve of
Notodonta trepida from both oak and beech in the New
Forest. A change from shrubs to grasses may therefore have
been found necessary by the larve of these Satyride ; those
that remained upon the shrubs were decimated by birds, while
those that dropped on to the grass underneath and stayed there,
survived in greater numbers; thus the habit might be in-
herited. Among the thick-bodied night-flying moths—the
Noctuee—there are many genera in which the larve are
invariably striped, and as invariably feed upon the tissues of
reeds, grasses, and other low-growing plants. I have already
mentioned the genera, the larve of ald the species of which in
this country are striped. This again looks like a race character,
independent of selection, but there is still the coincidence
between colour and surroundings. It must be remembered,
however, that there is nothing peculiar in longitudinal striping;
the patterns of coloration among animals are limited to very
few, types; we have spots, cross stripes, and longitudinal stripes
turning up in all orders. There are longitudinally-striped

quirrels, just as there are longitudinally-striped caterpillars.
If there were something unique and remarkable in the colora-
tion, more stress might be laid upon the resemblance to
grasses. Most of these caterpillars, however, are night-feeders,
and a large number hide themselves during the day; it may be
suggested that they begin to feed early in the evening, when
their colours, if conspicuous, would be readily seen. If this is
so, it does not much matter, for the birds would, the bulk of
them at any rate, have gone to roost.

PROTECTIVE COLORATION. 103

Internal-feeding Larve sometimes Striped.

But many of these larve have a far more efficient means of
protection than that afforded by longitudinal striping. They are
internal feeders, devouring the pith of reeds and other stems;
and yet they retain the longitudinal striping in a situation
which insures immunity from the attacks of all but entomo-
logists! I am not aware whether birds ever do extract.
such caterpillars from their galleries, but it is quite immaterial
to the present argument if they do.

Striping sometimes occurs in certain Species only of a Genus.

The caterpillars that have been hitherto dealt with belong to
genera in which all the species are striped. There are other
genera, among British insects, in which some of the species.
are striped and some not striped; though all feed upon low-
growing shrubs. Of the genus \y/op/asia the species rurev,
hepatica and scolopacins are striped, while Uthoxylea and
polyodon are not. X. polyodon is one of the commonest of
British moths; it is often quite a pest at “sugar,” and turns up:
everywhere; it is the commonest species of the genus, and does.
not therefore seem to have lost much by its (hypothetically)
less perfect adaptation in the larval stage. Still these instances.
sugeest ‘selection’ more than the others.

Striped Larve do not always feed on or among Grasses.

It is perhaps not a very strong argument against the view
that longitudinal striping is protective in origin to point to-
caterpillars which frequent situations where the striping does.
not appear to be of so much value; but in a discussion of the
subject these instances must be mentioned. Many of the
“ Prominents ”—all of them apparently that have not larva:
with excrescences and humps upon some of the pigments—

104 ANIMAL COLORATION.

have longitudinal stripes; for instance Notodonta chaoma,
NN. dodonea upon oak, Ptilophora plumigera, which feeds upon
oak and poplar; Lophopteryx carmelita, which feeds upon
birch. <Acronycta megacephala and ligustri are also striped,
and so is the genus Cymatophora. Curiously enough, most of
these larvee are day feeders, and so their coloration is less
useful still. It has been urged that stripes are useful in
breaking up the large area of a caterpillar’s body, and so
rendering it less conspicuous than it would be if all of one
colour. But on an oak leaf a different method would be more
advantageous, one might suppose. The longitudinal striping
is very suggestive in these cases of some more deep-seated cause
of coloration. We must therefore conclude, after considering
the examples brought forward in the last pages, that the
Jongitudinal striping of caterpillars is a phenomenon the
explanation of which must be still regarded as sud judice.
There are many facts which favour the view that it is to
be explained on the very simple hypothesis of a need for
resemblance to the environment; but there are other facts
which do not altogether suit this hypothesis.

The Resemblance of the Larve of Geometers to Twigs.

A very large percentage of lepidopterous caterpillars are
green ; the colour is due not only to the contents of the ali-
mentary canal, but also to the presence of a pigment known as
metachlorophyll in the blood; metachlorophyll is a slightly
altered derivative of the chlorophyll of the food plant. Where
the integument is but little pigmented, the caterpillar under
these circumstances appears green. If more pigment is present
it is brown. In other cases the integumental pigment is so
abundant and varied as to entirely conceal the green colour.
The colour alone, apart altogether from the form of the cater-

PROTECTIVE COLORATION. 105

pillar, renders it inconspicuous. There is one group of cater-
pillars which, in addition to a prevailing green or brown colour,
has a most striking resemblance in form to twigs or buds.
This resemblance has been long noticed. Messrs. Kirby and
Spence, in a chapter dealing with the “Means of Defence of
Insects,” in their “ Entomology,” remarked upon these cater-
pillars as follows :—“ There is a certain tribe of caterpillars,
called surveyors (Geometre), that will sometimes support
themselves for whole hours, by means of their posterior legs,
solely upon their anal extremity, forming an angle of various
‘degrees with the branch on which they are standing, and looking
like one of its twigs. Many concurring circumstances promote
this deception. The body is kept stiff and immovable, with the
separations of the segments scarcely visible ; it terminates in a
knob, the legs being applied close, so as to resemble the bud at
the end of a twig; besides which it often exhibits intermediate
tubercles, which increase the resemblance. Its colour, too, is
usually obscure, and similar to that of the bark of a tree.
So that, doubtless, the sparrows and other birds are frequently
deceived by this manceuvre, and thus baulked of their prey.
Résel’s gardener, mistaking one of these caterpillars for a dead
twig, started back in great alarm when, on attempting to break
it off, he found it was a living animal.”

The protective colour and form of some of these geometrid
larvee have been carefully studied and described by Mr. Poulton
in an admirable series of papers,* the results being summed
up in his book “The Colours of Animals.” The caterpillars
are generally long and cylindrical in form, of the same or
nearly the same diameter throughout: the greater part of the
body lies between the anterior and posterior legs, and this
structural fact is largely responsible for the twig-like appear-

* In Trans. Entom. Noc., 1885—%.

106 ANIMAL COLORATION.

ance, which would be considerably diminished did the middle
segments have legs. The anterior legs are often directed
forwards when the larvais resting outstretched from a branch,
and suggest buds at the extremity of a branchlet. The two pairs
of posterior legs, with which the larva grasps the branch,
in the Brimstone moth (Ruma crategata), and the tract of
body lying between them has numerous minute fleshy tuber-
cles, which soften the contrast between the caterpillar and the
branch, and thus heighten its resemblance to a twig. These
Geometer caterpillars are very plentiful; and any one can
observe them for himself even in a London garden.

A resemblance to a twig shown by a tree-feeding caterpillar
seems to be so obviously useful, that it might be assumed,
without any further discussion, that the need for protection
was the cause of the whole likeness which these caterpillars
bear to twigs. The Geometre form a large group of moths
spread over the whole world, and feeding in the larval con-
dition upon every variety of tree, shrub, and plant. They have,
therefore, to cope with most varied conditions, and with enemies
of all kinds.

Although the prevailing device for protective purposes which
they exhibit is a likeness to a twig, there are some specics
which appear to imitate bits of curled-up and withered leaf;
or even empty snail-shells ; while others lose their resemblance
to a twig by their strikingly untwig-like coloration (e.g. Magpie
moths), or by their habit of extending themselves along leaves
instead of resting stretched ont from a branch. And vet, in
spite of these varied resemblances, the same general form is
found in all Geometer larvee, and in no others excepting in
some genera which are nearly allied to these moths.

We must, therefore, not too hastily assume that the chief
features of resemblance which the caterpillars of the Pepper-

PROTECTIVE COLORATION. 107

and-Salt moth and of others bear to a branch of their food-
plant are due to natural selection acting in this particular
direction. All that we are justified in saying is that these
resemblances may have been perfected by that cause. The
very fact that the majority of the Geometer caterpillars simulate
twigs seems an indication that natural selection has taken
advantage of a considerable initial resemblance ; otherwise we
might have expected to meet with more numerous examples
of warning coloration, and of resemblance to other objects,
coupled with and heightened by structural as well as colour
modifications.

Occasional Absence of Coloration in Internal-Feeding Caterpillars.

The fact that internal-feeding caterpillars are white or
yellowish has been used as an argument in favour of the
effects of reversed natural selection—or Panmixis as it is termed
by Weismann. The green colour of the leaf feeders is pro-
tective ; and this form of protection is not needed by internal
feeders, protected as they are by their position ; hence the
green colour tended to disappear and finally did disappear in
these caterpillars, because it was useless and no longer pre-
served by natural selection ; a green colour came to be not
disadvantageous, but simply unnecessary. The caterpillars
being no longer selected for their greenness, gradually lost it.
Prof. Meldola, however, pointed out that the explanation was
in reality the simple one that there was no chlorophyll in
their food, and none, therefore, to colour their tissues. Leaf
miners, which feed upon the internal tissues of leaves, are often
green because these tissues contain chlorophyll. The larva of
Nonagria sparganii is green, although it feeds in the interior
of Iris stems, and needs no protection by colour. It is pro-
hable, though it has, I believe, to be proved, that this green

108 ANIMAL COLORATION.

colour will be found to be due to chlorophyll existing in the
internal tissues of the stems of that plant.

I have already referred to this subject in connection with
the direct influence of light upon colour.

Comparative Rarity of Green tree-frequenting Animals an Argument
in favour of Selection,

It is not a little surprising to find how few green animals
there are: this assertion may appear to be rather bold ; but if
we consider the great prevalence of sandy coloured animals in
arid and sandy localities, the absence of a correspondingly large
number of green animals among trees is striking. As regards
birds, we cannot fairly take this country as an example, be-
cause, as Mr. Wallace has pointed out, the deciduous foliage
would expose green-coloured birds in the winter and in the
early spring, when they most need protection; but insects,
which only survive for a summer, may be fairly taken as a
crucial test. There is only one butterfly—the green Hair-
streak (Thecla +ubi)—which is distinctly green; the mottling
or veining of green on the under surface of the wings in the
Pieridae is supposed to be a special adaptation to a particular
plant.* Among moths the number of green species is not
proportionately much greater, there are eight species of Emerald
moths, which are all of a nearly uniform green colour; four or
five Tortrices with the upper wings green ; and a few Noctue
in which green forms a large component part of the coloration in
the upper wings at least; finally, we have the two “ Forester”
moths. Green Lepidoptera do not appear to be relatively
more abundant in tropical countries. There are plenty of
green beetles ; but on turning over the plates which illustrate

* Mr. T. W. Wood has figured (‘‘Student,” vol. ii.) the orange. tip at rest
upon an umbelliferous plant, to which its speckled green under-wings
bear a striking resemblance. See Woodcut, fig. 3, p. 87.

PROTECTIVE COLORATION. 109

Mr. Jacoby’s papers in the Proceedings of the Zoological Society
one cannot help being struck by the large absence of green
among the phytophagous Coleoptera. There are plenty of
green tree-frogs, but, as has been already mentioned, there are
more that are not so uniformly coloured. Even about birds
living in tropical countries, and especially arboreal in their
habits, the most that can be said is that there are a good many
green species.

Now, the reader must not assume that these few facts hare
been brought together for the purpose of throwing discredit
upon the theory that a green coloration has been gradually
produced for protective purposes. Any one convinced of
the truth of this theory would at once triumphantly point
out a large number of omissions from the above very scanty
list; it seems to me, however, that a prevalence of green
among arboreal animals cannot be proved; and thus there
might appear to be a certain weakness in the theory of
protective coloration as applied to these instances.

In my own opinion the apparent weakness of the arguments
constitutes the real strength of the theory; it is precisely
because the sandy colour of desert animals and the trans-
parency of pelagic organisms is so universal, that some general
environmental cause appears to be necessary for the explanation
of the facts; on the other hand, the picking and choosing among
arboreal animals savours distinctly of natural selection. There
are quite enough examples of green tree-frequenting creatures
to call for some theory to explain the facts, but there are not
too many to render a selection improbable. When a whole
group of animals shows a similar modification, adaptation
seems less likely.

Deceptively-coloured African Mantids.
Every naturalist traveller appears to have some instance to.

110 ANIMAL COLORATION.

relate of how he was taken in by a protectively-coloured insect.
These stories are told with a curiously exaggerated delight at
the deception, and often with a framework of details tending
to throw the deception into still greater prominence. Professor
Drummond, in his most fresh and interesting little book,
‘Tropical Africa,” tells us that he went to that country
resolved to be proof against the frauds of insects, and sus-
picious that “the descriptions of Wallace and the others were
somewhat highly coloured.” The insect which succeeded in
deceiving Professor Drummond was one of the Mantids.
Professor Drummond, however, relates with somewhat of an
imprudent (and, I am disposed to think, unintentional) candour,
that his black companion recognised the animal nature of the
supposed wisp of hay at once. It seems to me that that part
of the story is the most important. Ihave not been to Central
Africa, but I have seen twenty people pass a “ Tiger moth ”’—a
conspicuous insect anywhere, and particularly so when it was
sitting, and not one of them noticed it, and yet it was probably
new, in spite of its being a common insect, to most of them.
The fact is that we must get out of the way of judging
instances of this kind from the human standpoint. The most
acute observers among us are dull compared with uncivilised
man and many animals. Any one who will take the trouble
to inspect the plate of Prof. Westwood’s recently published
monograph upon the Mantids can see how all the members of
this group resemble sticks and bits of straw. This resemblance,
as we think it, is a race character.
Protective Coloration in Spiders.

Mr. H. 0. Forbes, Proc. Zool. Soc., 1883, p. 586, relates how
he was taken in by the coloration of a spider :—

“On June 25th, 1881, in the forest near the village of
Lempar, on the banks of the Moesi river, in Sumatra, while my

PROTECTIVE COLORATION. 111

‘boys’ were procuring for me some botanical specimens from
a high tree, I was rather dreamily looking on the shrubs
before me, when I became conscious of my eyes resting on a
bird-excreta-marked leaf. How strange, I thought, it is that
I have never got another specimen of that curious spider
I found in Java which simulated a patch just like this! I
plucked the leaf by the petiole while so cogitating, and
looked at it half listlessly for some moments, mentally re-
marking how closely that other spider had copied nature ;
when, to my delighted surprise, I discovered I had actually
secured a second specimen, but the imitation was so exquisite
that I really did not perceive how matters stood for some
moments. The spider never moved while I was plucking or
twirling the leaf, and it was only when I placed the tip of my
little finger on it, that I observed that it was a spider, when
it, without any displacement of itself, flashed its falces into
my flesh.

“The first specimen I got was in West Java. While hunting
one day for lepidoptera, I observed a specimen of one of the
Hesperide sitting, as is often a custom of theirs, on the
excreta of a bird on a leaf; I crept near it, intending to
examine what they find in what one is inclined to consider
incongruous food for a butterfly. I approached nearer and
nearer, and at last caught it between my fingers, when I
found. that it had, as I thought, become glued by its feet to
the mass ; but on pulling gently, the spider, to my amazement,
disclosed itself by letting go its hold. Only then did I
discover that I was not looking on a veritable bird’s excreta.”

There arenumerous other examples of protective resemblances
in spiders.

Prof. Edouard Heckel has described and illustrated * with

* Bulletin Scient. France et Bely., t. xxiii. (1891).

112 ANIMAL COLORATION.

two coloured plates the colour variations of Zhomisus onustus
—a species abundant in the south of France. This spider
frequents the flowers of Conrolvulus arvensis, and is so
abundant during the months of August and September that
nearly every plant has its spider ; it is evident, therefore, that,
in spite of the numerous insect visitors to these flowers, there
must be a certain amount of competition for food among the
spiders ; this is especially the case if it be true that the spider
limits itself almost exclusively to two Diptera, ignoring the
other insects. The flowers of this convolvulus show three
varieties : one is pure white ; another pink, with traces of a
vinous red externally ; while the third is a paler pink tinged
with green externally. These three varieties of the convolvulus
are inhabited by three varieties of the Thomdsus, which corre-
spond exactly in their hues with the flower, with the exception
of the one which lives in the white flowers ; this variety of
spider has a blue cross on the abdomen, and the extremities of
its legs are likewise bluish. Blue, however, may be suggestive
of shadow, and not render the animal very conspicuous. These
three varieties do not embrace all the colour modifications.
of which the spider is susceptible; it becomes a dark red
when upon the flowers of Dahlia versicolor, which has a similar
colour, and yellow when upon the flowers of the yellow
Antirrhinum majus.

The term “ variety” has been made use of in referring to
these spiders ; but the use of the term is misleading in so far
as it implies a fixed colour form, for Prof. Heckel found that
the spiders were capable of changing their colour when trans- -
ferred from one flower to another, but that the change took
three or four days for its accomplishment.

It is only just to mention that the experiments, as described,
were not absolutely conclusive. Three spiders were taken

PROTECTIVE COLORATION. 118

and placed in a box, where, after the lapse of some days
they became bleached. One of them was placed upon a red
Dahlia, another upon a yellow Antirrhinum, the third upon a
white convolvulus. They were all marked with an ink spot to
ensure recognition ; but a storm of rain washed out the marks,
so itis possible that the individuals found upon the flowers
and coloured like them were not really those originally placed
there.

The distinguished British Arachnologist, the Rev. O. P.
Cambridge, has already referred to the same spider as imitating
the colours of flowers.* He found it pink when upon heather
blossom, and quotes the Rev. C. W. Penny to the effect that it is
yellow when upon yellow blossoms. Mr. Cambridge is, however,
inclined to doubt this, since he found more mature examples,
which are generally devoid of colouring, also upon the pink
heather blossoms ; the yellow colour, therefore, is not adaptive,
but simply due to age. The two series of observations must
be set against each other.

Do Animals select Resting-places which are in Harmony with their
Colour?

It is not generally believed that insects and other animals
that are protectively coloured deliberately select for a temporary
restine-place a situation—whether it be a trunk or a leaf,
that harmonises with their own colour. The theory is that their
colours have been modified in accordance with their usual
environment ; those that habitually settle among trees being
green, and so forth. It has, however, been stated that a small
black moth (Phiycis carbonariella) is constantly met with in
patches of underwood that have been burnt ; its dusky hues
approximate to the colour of charred wood. The Snowy Owl,

* “Spiders of Dorset.”

Tt

114 ANIMAL COLORATION.

too, appears to select a snowy patch of ground to rest upon,
in preference to rocks and stones which are not covered with
snow; so at least says Bishop Stanley, in his “History of British
Birds” (p. 149) of a pair of these birds shot in the severe
winter of 1823, in Northumberland. These birds had, we are
told, “been noticed in the wild and rocky parts of an open
moor, either perched upon the snow, or on some large solitary
stone projecting from it, from whence, without attracting
notice by any contrasting colour, they could look out for their
prey.”
Indifferent Colours.

There are numerous examples of coloration the reverse of
protective, which nevertheless cannot be regarded as “warning,”
inasmuch as they are not accompanied by disagreeable qualities.
The most prominent instances are animals which are entirely
white or largely marked by white. Mr. Wallace has pointed
out that the defenceless inhabitants of islands* often show
such conspicuous colours; the butterflies of some of the
islands of the Eastern Archipelago have more white upon their
wings than their relations upon the mainland; this he
attributes very ingeniously to the smaller need for protection
owing to the less numerous Insectivorous animals. The
struggle for existence is, in this particular, less keen ; hence the
elimination of unfavourable varieties proceeds with diminished
severity. Among British Lepidoptera there are a number of
white species—butterflies as well as moths. As to the butter-
flies—the Cabbage White and its allies—it may reasonably be
urged that they have not so great a need for protection as
many other insects : as a rule, butterflies do not appear to be so
favourite an article of food with birds and lizards,as do moths:

* Sir Walter Buller has remarked upon the abundance of albinos
among New Zealand birds.

Ketinde®

PROTECTIVE COLORATION. 115

but this is a fact which may be made use of in several ways.
If Mr. Poulton* is right in assigning a protective value to the
bright-coloured wings of butterflies “as a conspicuous mark
easily seized by an enemy, and yet readily tearing without
much injury to the insect,” it seems tmnecessary to pay much
attention to the supposed utility of protective colours, such as
are shown by the Aadd‘ma or the Green Hairstreak.

The conspicuousness of the white butterflies is, however,
diminished by their fondness for settling upon the yellow and
white flowers of cruciferous plants; but they cannot be regarded
as good examples of protective coloration, as they fly much and
are, of course, conspicuous during flight. Both Mr. Wallace

Fig. 6.—Delphinus delphis.

and Mr. Poulton have dwelt upon the protective value of
white under certain circumstances. White cggs laid in an
open nest such as the pigeon builds, and the white under-side,
of many pelagic fish, of whales and dolphins (fig. 6), and even of
aquatic birds such as the penguin (fig. 7), are stated by these
writers to be inconspicuous when seen, as they would naturally
be, from below, and against a bright sky. It appears, however,
that this is really not the case. If snowflakes, which are of
a purer and brighter white than any egg, are watched as they
fall from the sky, which is naturally overcast and dull, they
appear almost black. If we can imagine for a moment the

* “ Colours of Animals,” p. 205.

116 ANIMAL COLORATION.

possibility of snow falling from a cloudless sky, the darkness
of the flakes seen against the bright sky would be more
marked still. This difficulty in the way of accounting for the
above-mentioned facts was suggested to me by Prof. Weldon.

There are several species of white birds which, not being
inhabitants of the polar regions, can get no advantage from

Fig. 7.--Aptenodyles patagonica (from Brehm),

their coloration. Some of them, like the pelican, are strong
birds, which can defend themselves without the help of any such
adventitious aids ; but others are distinctively not so. Mr. W.
H. Hudson has called attention to the way in which the White
Egret of South America is singled out from a flock by pre-
daceous birds, and wonders how it can be so common in the
face of this obvious persecution. Here again we may emphasise

PROTECTIVE COLORATION. 117

the remarks already made, that a few unreconcilable instances
do not of themselves overthrow a theory like this which we are
discussing ; but they do not lend much support to Prof.
Drummond’s contention that “mimicry is not merely an
occasional or exceptional phenomenon, but an integral part of
the economy of nature”; that “it is not a chance relation
between a few objects, but a system so widely authorised that
probably the whole animal kingdom is more or less involved in
it.” On the contrary, the instances of mimicry, using that term
in the earlier and wider sense that Prof. Drummond uses it,
do not appear to be by any means so numerous as he would

lead us to infer.

Certain apparently protectively Coloured Animals probably do not
owe their Coloration to the Action of Natural Selection.

One of the commonest of British Moths—the “ Garden
Carpet” (Melanippe fluctuaria), abundant everywhere in the
early summer, and again later on, is an insect which would be
regarded by most people as an instance of protective coloration.
It is met with under the copings of walls, and upon tree
trunks, and in fact in nearly every kind of place ; the varied
browns and white of the wings are not unsuggestive of a
lichen ; and lichens are often found where the moth is found.
Several of the allies of the moth—which are distinguished
from each other by the varying amount of brown (sometimes
black) and white, and its distribution, are found in similar
localities. On the other hand the moth is as commonly found
upon the leaves of trees—both the under and the upper surface;
in fact, it will select any handy resting-place. When upon a
leaf, with the wings more or less extended, it resembles, as
Mr. Poulton thinks the Goose Egg—Cilia spinula—does, a
patch of birds dropping flattened out, through having fallen

118 ANIMAL COLORATION.

from a considerable height. Which of these two models does
the insect most resemble ? Perhaps it will be said that the
summit of a chalk cutting, where the white chalk is beginning to
commingle with the brown earth lying above it, is a still more
likely model. Now, if we accept “natural selection,” it is
quite evident that the main principle upon which Nature works
is economy: a new organ is not made for the performance of a
new function when an old one a little altered will do as well.
Accepting the analogy, we might be led into forgetting the
«difference between this kind of economy and the more human;
and into believing that the colour of the insect was brought
about in order that it might resemble as many ‘“ environments”
as possible. It might be urged that only one of these different
models was successfully imitated by the moth, the likeness to
the others being accidental ; in fact, this is the only possible
view that could be taken. But if the resemblance is accidental
in the one case, why not in the other? The fact is, that with
a varied environment—such as a wood for instance—we may
easily get a large number of examples of coloration among its
insect inhabitants that are purely accidental. After all, the
same colours occur among animals as among plants, even
amounting in a few cases to an identity in the pigments
(e.g. chlorophyll, and carotin—which has been found by Prof.
Blanchard in a crustacean). Among moths, for instance, yellow,
browns, greys and white, are the prevailing colours ; and these
are just the colours which predominate upon the tree trunks
and decaying vegetation at roots of trees, where moths
chiefly pass the day. To assume that the second is the reason
for the first is to assume too much. It is not the pigments
themselves which are supposed to be produced by the action
of natural selection, but their distribution; it is not the colour,
but the coloration of animals, which forms the subject of

PROTECTIVE COLORATION. 119

investigation by those who wish to collect evidence in favour of
modification due to natural selection.

Specific Characters retained even in Insects which imitate the same
Environment,

In referring to the changes of colour undergone by flat fishes
in order to assimilate to the ground upon which they happen
to be resting, Mr. Cunningham remarks: * “A large number
of different species belonging to different genera lies within the
same area or ground of uniform colour ; to this colour they
all have to assimilate their general tint, but each species has
its own permanent characteristic marking. As these markings
are all different, they cannot all aid equally in the protective
resemblance; some of them, at least, must either be indifferent
or disadvantageous to the attainment of the useful result. As
far as we can judge, all the specific markings are indifferent.”
This is equally true of other animals besides fishes. There are
a large number of moths which habitually settle upon lichen-
covered trees: for instance, Biston betularia, Cleora glabraria,
Epunda lichenariv, ete.; all these insects have white or brownish
wings dusted or marked with black. But not even the veriest
tyro among entomologists would fail to recognise the specific
adlistinctness. It may be (I am not aware if it is so) that
one species resembles more closely a particular lichen than
another does, which is more like a second species; but in this
there is not much advantage, for I can say from personal
experience that the insects are found upon different tree trunks
and among various kinds of lichen, to most of which they have
a certain likeness.

Protective resemblance, therefore, even if due entirely to
natural selection, has its limits; and we must regaril as an

* Preface to his Translation of Eimer’s work, p. xiii.

120 ANIMAL COLORATION.

exceptionally fortunate (for the insect) result the wonderful
‘“mimicry ” of the Kallima butterfly. Indeed, such cases are ex-
ceedingly rare. On the other hand, there are a few insects which
are absolutely alike in the imago stage, only known to be differ-
ent species by the differences in their caterpillars. One of our
leading entomologists, Mr. Stainton says—or rather said (I
do not know whether he has changed his opinion)—that it is
quite impossible to discriminate between the two Dagger
moths, Acronycta Ps, and A. tridens : if the pattern has been
produced for purposes of concealment, which is rather difficult
to believe, as there is no object in nature which they resemble
exactly, Mr. Cunningham’s objection will have to be recon-
sidered.

Protection often due to Multiplicity of surrounding Objects.

When a conjurer intends to surprise his audience by the
production of an object from some unsuspected quarter, he
places it beforehand, with no attempt at concealment, upon the
table, which is generally covered with various mysterious
objects not meant in the least for use. It is concealed until
the right moment among a multitude of objects, some more,
some less like it. Every one knows from experience how
difficult it is to tind an object which has fallen upon a carpet
with a complicated pattern. We find exactly the same
principle in Nature.

Prof. Drummond gives a good instance of this.* “ One of
the most beautiful and ornate of all the tropical reptiles is the
puff-adder. This animal, the bite of which is certain death.
is from three to five feet long, and disproportionately thick,
being in some parts almost as thick as the lower part of the
thigh. The whole body is ornamented with strange devices

* “Tropical Africa,” p. 175.

PROTECTIVE COLORATION. 121

in green, yellow, and black; and lying in a museum its glitter-
ing coils certainly form a most striking object. But in nature
the puff-adder has a very different background. It is essen-
tially a forest animal, its true habitat being among the fallen
leaves in the deep shade of the trees by the banks of streams.
Now, in such a position, at the distance of a foot or two, its
appearance so exactly resembles the forest bed as to be almost
indistinguishable from it.”

The puff-adder does not specially resemble fallen leaves, but
among the variety of objects in the situations which it affects
it escapes notice. The colours cannot be exactly protective,
because the reptile does not talways conceal itself in such
situations as Mr. Drummond describes. It often lies half
buried in sand, and would not probably be very conspicnous
then.

I refer later (p. 257) to the sexual differcnces in this reptile,
which are not consistent with a theory of protective resem-
blance, but are thoroughly consistent with the view that
concealment is effected by frequenting situations where the
ground is broken and varied in colour by living and decaying
vegetation of all kinds.

Colours of Pelagic Organisms.*

The surface of the sea, whether near to shore or in mid
ocean, appears to any one looking down from a boat almost
devoid of animal life ; from time to time a solitary medusa or
a shoal of these animals will be seen, and less frequently
some of the rarer surface organisms will break the monotony ;
but with these exceptions the water appears to be absolutely
free from living creatures.

* A general account of the pelagic fauna may be found in Moseley’s
“Naturalist on the Challenger,’ and in Agassiz, Three Cruises of the
Blake.”

122 ANIMAL COLORATION.

If, however, a quantity of sea-water be strained through a
muslin bag, a gelatinous mass will be left behind. On a closer
examination this proves to consist entirely of the bodies of
innumerable animals, so perfectly transparent as to be prac-
tically invisible when floating singly. So abundant in every
latitude is life in the surface waters, it has been calculated
that there are eight hundred tons of organisms to every
square mile on our coasts. At night the phosphorescence
of these organisms renders their presence obvious.

The surface fauna of the oceans comprises representatives of
all the groups of invertebrate animals—chiefly, perhaps, larvee,
but also numerous adult forms; and these all agree in the
entire absence of pigment, or in having but a small amount;
and when colour is present it seems to suit their special cir-
cumstances. The Salpv, for example, are colourless and
transparent, with the exception of a small portion of the
alimentary canal; this has a brownish-yellow colour, and
suggests a fragment of floating seaweed. The ultramarine
blue of the floating eled/a has been compared to the blue of
the sea. Among pelagic fish it is common to find the upper
surface dark-coloured and the lower surface white, so that the
animal is inconspicuous when seen either from above or below.

The transparency of the greater part of the pelagic fauna is,
so far as our senses are concerned, an undoubted protection to
them, rendering them, of course, invisible. Inasmuch as many
of these organisms have close relations which are brightly and
variously coloured, it is believed that natural selection has
effected the change from a coloured to a colourless condition ;
the supposed advantage is naturally the concealment afforded
by this change. The Ascidians that live attached to stones or
weed are generally brilliantly coloured, while the pelagic forms
such as the Sa/y@ are nearly perfectly transparent.

PROTECTIVE COLORATION. 123

I have already referred on another page to the gor-
geous and diverse coloration of the littoral and deep-sea
nudibranchs. This group of molluscs has one representative
among the pelagic fauna; the animal was named by its dis-
coverer, Forster, the companion of Captain Cook, G/aucus; it is
of a dark blue colour. 1 have never myself had the opportunity
of seeing Glaucus in a living condition, but I have seen Ve/el/a
on the south coast of Spain ; in the shallow water it was a
tiny but extremely conspicuous object; perhaps this is not the
case when it is floating in waters far removed from the shore.

Perhaps the most remarkable case of apparent adaptation
in accordance with a pelagic life is afforded by the transparent
fish Leptocephalus ; this long and narrow, perfectly trans-
lucent fish received the name Lvptocephalus in the belief
that it was an adult form ; it is now known to be merely the
young of the Conger. It is not only perfectly colourless as
regards the skin, but the blood, which should be red as in all
other vertebrates, is also colourless ; this instance, upon which
stress is generally laid by those who are convinced of the
effects of natural selection in rendering pelagic organisms
transparent, certainly offers to that view strong support. This
is not. the place to attempt any comprehensive account of
the characteristics of pelagic life ; those who desire further
information upon the topic are referred to the books mentioned
in the footnote to page 121. Enough has been said in illustra-
tion of the fact that pelagic organisms, if not perfectly pellucid,
are coloured in such a way as to render them inconspicuous to
our eyes at least.

The members of the surface fauna—the more highly organ-
ised members, at any rate—possess, however, every facility for
seeing each other, Their eyes are, as arule, very well developed.
The amphipod crustacean Phronima (fig. 8) is “not satisfied,”

124 ANIMAL COLORATION.

says Prof. Agassiz, “ with a set of eyes enabling it to see both
laterally and downward,—it has also an immense pair facing
dorsally, so that the animal has a free field of vision in all
directions.” The eyes of many Zoe (the larve of decapod
crustaceans), as well as of many young fishes, are entirely out
of proportion, so large are they, to the eyes of the adult. If
we are to assume that eves are meant to see with (which is.

however, by no means clear, in our sense of seeing, in some of

Tig, 8.—Phronime sedentaria.

the lower forms) these pelagic creatures must be endowed
with unusual clearness of perception. If this be so, are they
deceived by the transparency of the animals upon which they
prey? The great marauders of the pelagic fauna are, accord-
ing to Prof. Agassiz, the copepod crustaceans and Jfysis
(fig. 9), both well off in the matter of eves, the latter especially.
A large part of the pelagic fauna is formed by fishes in various
stages of development, from the egg to the adult; and these,
although pellucid and invisible to our eves, unless a minute

PROTECTIVE COLORATION. 125

and prolonged attention be given to them, are dotted over with
pigment spots varying in number and position. If the reader
will take the trouble to refer to any work in which such pelagic
larve are figured,* he will at once see that the general trans-
parency is interfered with by these spots. The accompanying
figure of J/ysis shows the ramified pigment patches; they (the
spots) are, ‘it is true, not very evident to our eyes; but if we

ii
ge
Fig. 9.—Mysis.

imagine ourselves of the same size as the minute members of
the pelagic fauna, or imagine them of the same size as our-
selves, it is difficult to believe in invisibility.

An animal floating about in the sea, perfectly transparent but
decked with dense black patches, of the size of saucers, would

* For example, the elaborate and well-illustrated Memoir of Prof.
Macintosh and Mr. Prince, Trans. Roy. Soc., Edinburgh, vol.

126 ANIMAL COLORATION.

betray its whereabouts even to the least observant ; if the
observer were stimulated by hunger or by fear, the conspicuous-
ness would not be lessened. It is not necessary to apologise
here for viewing these matters from the human standpoint; it
would be, perhaps, if those who have advanced the theories
of protective coloration had been able to take up a line of
argument a little different from the one which they have taken.

Besides the internecine warfare which is continually going
on amongst the smaller surface organisms, they are devoured
wholesale by the larger pelagic fish and by whales and other
Cetacea. A whale, rushing through the water with open
mouth and gulping down all before him, is not in the least
inconvenienced by the invisibility of the organisms devoured
in such enormous quantities; nor do a solid phalanx of herring
or mackerel stop to look carefully for their food: they take
what comes in their way, and get plenty in spite of “ pro-
tective absence of coloration.”

If the transparency of the pelagic organisms be due entirely
to natural selection, it is remarkable that there is so little
modification in this direction among the species inhabiting the
bottom at such depths as are accessible to the sun’s rays;
the advantage gained by this transparency and consequent
invisibility would be equally great. And yet this is not the case:
the bulk of the bottom fauna of the coasts are brilliantly
coloured animals, and those that show any protective coloration
at all appear to be coloured so as to resemble stones or sea-
weeds.

Protective Resemblances due to Causes other than Natural
Selection.

The currently received opinion about these resemblances
between animals and their usual surroundings is that they

PROTECTIVE COLORATION. 127

have been produced through natural selection. It is supposed
that variations in the direction of a» more perfect resemblance
have survived, and that by a cumulative effect, which may
have taken generations to produce, the wonderfully faithful
likenesses between many caterpillars and the twigs of their
food-plants, ete., have been arrived at.

There are, however, certain cases to which this line of
reasoning cannot well apply.

Dr. Hisig* found an annelid of the genus Luxiee living
parasitically upon a marine sponge in the Bay of Naples.
The sponge is of a yellow colour, caused by the presence in its
tissues of small particles of a colouring-matter in all proba-
bility belonging to that class which I have referred to in
Chapter I. as of physiological importance. The annelid is
similarly coloured, its body being decked with numerous
orange spots. This resemblance is not comparable to that
between Arolosoma and various filamentous plants; for the
pigment is identical, and has been simply transferred from the
tissues of the sponge to the skin of the worm, having first
traversed a portion of the alimentary canal of the latter.

It ix possible that this explanation of protective resem-
blances may be applicable to many other cases, and do away
with the necessity of assuming any special action of natural
selection.

In an interesting series of articles upon protective colours in
the Nudibranchiate Mollusca,+ Prof. Herdman has described in
some detail the habits of these creatures. Many nudibranchs
are furnished with simple or branched processes upon the
back ; these forms are chiefly carnivorous, feeding upon bydroid
polyps, among the colonies of which they may be frequently

* « Fauna und Flora des Golfes von Neapel: Die Capitelliden.’
+ Life-Lore for 1890.

128 ANIMAL COLORATION.

discovered. T'ritonia plebeia is, according to Prof. Herdman,
generally found creeping over the surface of colonies of
Aleyonium digitatum—“ Dead men’s fingers” ; its colours, like
those of the polyp, are various shades of yellow, brown,
and grey. Dendronotus (see fig. 10) is marked with purple,
brown, and yellow tints, and it is to be met with among
masses of brown and yellow zoophytes. It is true that the

Fig. 10.—Eolis and Dendronotus.

similarity between these molluscs and their living environment
is heightened by the dorsal processes already referred to ;
these processes simulate the polyps in various degrees of ex-
pansion and retraction ; but this resemblance would not be of
much advantage, were the colours in striking contrast. That.
the resemblance in coloration is due to the action of natural
selection, and not to the direct transference of pigment from
the polyps upon which the nudibranchs browse, cannot be for

PROTECTIVE COLORATION. 129

one moment admitted until the pigments themselves nave
been studied. There is no inherent improbability in the view
that this cause of protective coloration is very widely spread ;
many colouring substances, as has been already mentioned,
are extremely resistant to chemical action. Carmine is used
in every physiological laboratory as a means of detecting the
paths traversed by substances taken into the body by the
alimentary canal, or injected into the blood; the particles of
carmine can be readily traced from one tissue to another,
because of their chemical stability. It is at least possible that
this may be the case with other substances. From this point of
view the variability in the tints and patterns of many animals
can be more easily understood; it will depend upon the
variability of the pigments in their food, and upon the amount
absorbed and transferred to the skin.

The fixity of the markings of animals has frequently been
made use of as an argument in favour of their secondary
meaning ; but there are also plenty of instances where there
is an infinite diversity of markings and tints, which can be
more readily explained in the way that has been suggested.

An interesting suggestion to the same effect is made by
Kirby and Spence in their “ Introduction to Entomology.” On
p- 405 (of the 7th edition), in commenting upon the many
insects which escape destruction by simulating the lichens
upon which they live, it is remarked that “the caterpillar of
Bryophila alge, when it feeds on the yellow Lichen juntper-
‘nus, is always yellow; but when upon the grey Lichen
saxatilis, its hue becomes grey. This change is probably
produced by the colour of its food.”

Another instance which may be very possibly explained in
the same way has been recently made known in America.*

* Science, vol vi. (1885), p. 9.
9

130 ANIMAL COLORATION.

Ovulum uniplicatum is a shell-fish which lives wpon the sea fan
(Leptogorgia virgulata). The latter has a stem of an orange
yellow colour, and is frequently found to exhibit swellings
caused by the presence of a barnacle which has been covered
over by the yellow tissue of the sea fan. Now, the Oruwlum has
a yellow shell, and its soft mantle, which is protruded from the
shell during life, is of a darker orange. With another species
of Leptogorgia, of a deep rose colour mottled with white lines,
is found an Ovulum of a perfectly similar coloration.

Another example of the same phenomenon is given by Prof.
J. Brown-Goode : “ On certain ledges along the New England
coast are rocks covered with dense growths of scarlet and crim-
son seaweeds. The codfish, the cunner, the sea raven, the rock
eel, and the wrymouth, which inhabit these brilliant groves,
are all coloured to match their surroundings; the cod, which
has naturally the lightest colour, being most brilliant in its
scarlet hues, while others whose skins have a large and original
supply of black have deeper tints of dark red and brown.”

Mr. Brown-Goode suggests that the pigment is derived
directly from the red algze; directly in one sense, but indirectly
in another, for the fish in question are animal feeders; the
same reefs, however, swarm with crustaceans and other marine
organisms which are vegetable feeders, and whose stomachs,
therefore, are fall of the alge and their pigment: it is from
these crustaceans that the fishes probably derive their colour;
just as, according to Dr. Giinther, the red flesh of the salmon
is coloured by a pigment derived from the crustacea upon
which it feeds. There is, it is true, no positive proof offered
that this is really the case; no analysis of the pigment in
the fishes was made for the purpose of comparison with the
pigment of the alge. But in the first place it is exceedingly

* Science, vol xv. (1890), p. 211.

PROTECTIVE COLORATION. 131

probable that the pigment is directly transferred to the skin,
just as the skin of a man is discoloured by nitrate of silver
taken as medicine; in the second place it is very significant
that the red pigment is apparently present in addition to the
normal pigments. If natural selection had in the course of
long ages brought about the colour resemblance between the
fish and their surroundings, it would be, one might fairly
imagine, rather by an alteration of the existing pigment than
by the formation of a fresh pigment red in colour, deposited
side by side with the original pigments. It is too remarkable
‘a coincidence that the fish normally with but little pigment
should be when among these weeds dvight red, and that the
fish normally possessing black pigment should be dark red,
to permit of a settlement of the question offhand by the easy
help of the theory of natural selection—without at least some
further inquiry.

Possibly the Gulf-weed fauna is an example of something of
the kind. Prof. Moseley, in his work “ Notes by a Naturalist
on the Challenger,” comments, as have many other writers,
upon the extraordinary colour resemblances which exist
‘between the animals living upon and among the weed, and
the weed itself. The Gulf weed is of an olive yellow colour,
and “the crabs and shrimps which swarm in the weeds are
of exactly the same shade of yellow as the weed, and have
white markings upon their bodies to represent the patches of
Membranipora. The small fish Antennarius * is in the same

* The Lntennarius referred to is really Pterophryne histrio—an apt
specific name. It is suggested by a writer in Proc. Acad. Nut. Sei.
((Philadelphia,1889, p. 344), that the white patches on the Gulf-weed animals
imitate the shells of a minute worm Spirorbis. The writer also relates
that this little fish was first mentioned by Osbeck in 1757, who remarked :
“Probably Providence has clothed it in this leaflike manner, in order that
the predaceous fishes might confound it with the seaweed, and therefore
mot exterminate it.”

132 ANIMAL COLORATION.

way weed-colour with white spots. Even a Planarian wornr

which lives in the weed is similarly yellow-coloured, and also.

a molluse, Scyllea pelagica.” Mr. Wallace * quotes the above
passage to exemplify protective resemblance among marine
animals presumably brought about by the action of natural
selection. It would be highly desirable to ascertain whether
the colour of the animals is not simply due to the pigment of
the algze, just as the colour of caterpillars is sometimes due
to chlorophyll absorbed directly from their food. Here again
we should have to suppose that the pigment passes unaltered
through the bodies of two animals, for the carnivorous forms
could only get it from those that fed upon the alge. This
explanation obviously does not include the ‘‘ white patches,”
which look much more like natural selection.

Considering the resistant nature of many pigmentary sub-
stances, vegetable as well as animal, it is at least probable that
a large number of cases of colour resemblance, often set down
to the action of natural selection, may be due, as in the case of
Eunice, to the simple excretion by the skin of these pigments
which have been taken in as food. Until more is known about
the chemical composition of animal pigments it would be rash
to adopt an elaborate explanation when the more simple one
would possibly be sufficient.

That the green colour of many caterpillars is directly due
to their food has been shown by Mr. Poulton in some of his
highly important contributions to the colour question. This
green colour may be partly due to the food contained in the
alimentary canal, but it is also in many cases caused by the
green colour of the blood and of the epidermal layer. But this
green pigment is chlorophyll in a slightly altered condition.

There remain, however, numerous cases which cannot in

* “Darwinism,” p. 208.

PROTECTIVE COLORATION. 1338

the present state of our knowledge be explained in this way.
There is no obvious relation, for example, between the green
colour of the Iguana or Tree Snake and its food. And it is
still less easy to explain the wonderfully close likeness between
the larvee of certain Geometers and the twigs of their food
plant, and between the spider discovered by Mr. Forbes and
the droppings of a bird.

To explain these phenomena by natural selection demands,
of course, as an essential preliminary, that the resemblances
should be useful. Admitting for the moment that this is
proved, we have still the apparent objection that comparatively
few creatures have succeeded in availing themselves of this
means of protection. Mr. Poulton has grappled with this
difficulty, and has suggested * that “the antagonistic principle
would be found in the too complete success of the method
itself.’ If all animals acquired a perfect resemblance to their
surroundings, the senses of their enemies would have to be
proportionately sharpened, or they would get no food.

Combination of Many Methods of Defence.

Mr. Poulton quotes the Puss Moth caterpillar as being well
defended from its enemies in more than one way. This cater-
pillar (fig. 11), being green, is inconspicuous ; but when it is
discovered it retracts the head, the effect being “an intensely
exaggerated caricature of a vertebrate face, which is probably

?

alarming to the vertebrate enemies of the caterpillar.” Besides
this, it can eject, from glands near the mouth, a liquid which
has been shown to be a mixture of formic acid and water, and
is therefore naturally irritant; it is also stated by De Geer
(quoted by Kirby and Spence) that this insect can bite very

* Mr. Poulton has used this argument in relation to warning colours,
but it must hold good in the present case if it does in the other.

134 ANIMAL COLORATION.

sharply. But we have not yet done with the defensive weapons
of the Puss Moth: two pink lashes can be protruded from
the bifurcate tail which the creature lashes about ; these are
believed by Messrs Kirby and Spence to be rather a protection
against ichneumon flies ; but they terrified Résel, who, when
he first saw the caterpillar darting forth these menacing cata-
pults, in addition to its grim attitude, was afraid to touch it.
Mr. Poulton found that a marmoset was evidently terrified ;
but Weismann found that Lacerta viridis would eat it.

An interesting case of a combination of several modes

SS

il >
@ \ ; yp

ASN

Fig, 11.—Puss Moth and Caterpillar.

4

of defence is given by Dr. Adalbert Seitz in his very read-
able paper already referred to. The “Eyed Hawk” moth,
common enough in some districts where willows abound,
appears, from the red eve-like markings upon the blue under
wings, to be a conspicuous insect. Such, at least, would pro-
bably be the opinion of a person who had only seen the insect
in the cabinet with its wings “ set.”

Under natural circumstances it rests with the brightly
coloured lower wings covered by the brown upper wings ; in
this attitude it comes to resemble a withered leaf. When not
too roughly disturbed, or when abont to take flight, it elevates

PROTECTIVE COLORATION. 135

the upper wings, and produces, according to Dr. Seitz, a re-
semblance to a terrible-looking creature with red, fiery eyes
and vibrating ears ; the abdomen plays the part of a pointed
snout projecting between the eyes. This, it is supposed, is
sufficient to appal the most courageous and stout-hearted of
birds.

In many of these cases the infinite resources believed to be
possessed by an insect for evading or terrifying or actually
injuring its enemies, are only paralleled by those of the
White Knight in “ Alice, through the Looking Glass.”

Dimorphism in Coloration.

If it is useful to an animal to resemble its surroundings,
either for aggressive or protective purposes, the advantages
must be greater when the colour can be changed in response
to changes in the environment, or differs in accordance with
different environments. <A green caterpillar is safe so long as
it remains upon a green leaf; but upon a twig or upon the
trunk of the tree the conspicuous green colour betrays it. It
is quite common for caterpillars to exhibit a colour dimor-
phism ; some individuals of the same species being green,
others brown; this ix the most usual form of colour dimor-
phism, and it will be observed that both colours assimilate to
tints found in Nature.

So far as is known, this difference of colour among individuals
of the same brood has no relation to any feature in the perfect
insect ; it is not, for instance, a mark of sex.

Mr. Poulton has justly pointed out the advantage which a
larva such as that of the Large Emerald moth ((reometra
papilionaria) would have over other species, in being dimor-
phic: the larva itself is not unlike the catkins of the birch ;
there are green and brown larvee just as there are green and

136 ANIMAL COLORATION.

brown catkins ; thus a larger number would have a chance of
escaping the attention of insect-eating birds than if the cater-

pillars were all green ov brown.

Variable Protective Resemblance in Chrysalids.

The chrysalids of most moths which lie in the ground
at the foot of the tree upon which the larva has fed
are brown in colour, and therefore assimilate more or less
closely to the colour of the soil. Such pupe are, however,
commonly enclosed in a slight cocoon. Probably the-immo-
bility of the pupa (unless it be touched) has more to do with
their escaping enemies than the colour; the colour is due
chiefly to the thickness of the chitinous layer; this substance
(chitin) forms the ‘‘shells” of crustacea and insects, and is
transparent when in thin layers; as the thickness of the chitin
is increased, it becomes golden yellow, and finally brown.
The resemblance of pupe to the soil can, therefore, hardly be
regarded as an adaptive colour; fortunately for the insects
it happens that the colour of the pupa coincides with that of
the usual environment. If there has been adaptation any-
where in this case, it is probably in the assumption of the
habit of pupating underground. Many insects, however, par-
ticularly butterflies, form themselves into a chrysalis in an
exposed situation ; in these cases the chrysalis is either naked
or wrapped in a cocoon formed by the caterpillar. Sometimes,
as in the case of the Puss Moth, particles of the surrounding
surface are woven into the cocoon, which in this way very
perfectly protects the enclosed chrysalis.*

The pup of butterflies which have no cocoon possess a
remarkable power of adapting themselves to the hue of the

* In this particular case the cocoon is not only like the trunk of the
tree against which it is placed, and from fragments of which it is con-
structed, but exceedingly hard : thisis, of course, an additional protection.

PROTECTIVE COLORATION. 137

surface upon which they rest. Apparently Mr. T. W. Wood
was the first to call the attention of naturalists to this fact.
He exhibited a series of chrysalids of the Swallow-tailed
Butterfly and of the Garden Whites, which were darker or
lighter in colour in correspondence with the situations where
they were found. The subject has been recently studied in
ereat detail by Mr. Poulton, who has published an important
and beautifully illustrated memoir,* describing his experiments.
These experiments dealt with several species ; among others
with the common Tortoiseshell Butterfly.

When the caterpillars were compelled to “spin up” upon a
dark ground they were extremely dark in colour, with, at
most, only a trace of gold spots. With white surroundings
the pupe were light-coloured,t and the’ gold spots were often so
greatly developed that “the whole surface of the pupa glittered
with an apparent metallic lustre.”

A point to be noticed is that colours were produced which
are “very rarely [the italics Mr. Poulton’s] seen in nature.”
Prof. Eimer speaks { of the production of red-coloured chry-

-salids, when the larva was enveloped by a red cloth at the
time of change; but he does not mention the species of butter-
fly in which these effects were artificially produced. Clearly,
therefore, the pupa is highly susceptible to the colours of sur-
rounding objects, and to an extent which is not limited by the
colours of its usual surroundings. Mr. Morris succeeded § in
producing white, red, salmon, black, and blue pupe of Danais
chrysippus ; they are only green or pink in nature.

The metallic colour of the pupa, which is so often met with

* © Philosophical Transactions,” 1889.

+ By an ingenious arrangement the pupa was also made to assume a
light colour upon one half and a dark colour upon the other.

¢ Loe. eit., p. 144.
§ Journ. Bombay Nat. [Hist. Soc., 1890.

1388 ANIMAL COLORATION.

in that family of butterflies (Vanesside) to which the Tortoise-
shell belongs, is puzzling. The very name “chrysalis” or
‘“aurelia,” as some of the older entomologists termed it, is
derived from the golden colour which is so distinctive a feature
of many pupe. Mr. Poulton has most ingeniously suggested
that the angular shape of these pupw combined with their
gilding might be protective when the pupa was attached to
surfaces of rocks containing glittering particles of mica.

It has been suggested that natural selection has played no
part in the production of this sensibility to colour,—that it is
purely a question of the direct influence of light. Prof. Eimer
suggests * that “The substance composing the envelope of the
pupa possesses, as a fact, the property of being changed by
light, like a photographic plate; and the relation of this pro-
perty to the outer world may be useful, but it does not neces-
sarily owe its origin to selection. That this substance is so
constituted as to exhibit in action a process of colour photo-
graphy, the goal of so much human longing and striving, leads
to another consideration. Since the discovery of visual red
in the retina of the eye, a substance which quickly bleaches
under the action of light after death, and which is situated
in the very cells of the retina on which the light falls, we
are brought near to the conception that sight, especially the
perception of colours by the eyes of the higher animals and of
man, is likewise a chemical process, a kind of photography. A
short step farther in the specialisation of nervous stimulation
or nervous conductivity might well render comprehensible
the wonderful fact above referred to, that the colours of the
environment of an animal may be reflected in the colours of its
skin. For it is self-evident that the path of action of the
coloured light is principally through the eyes. Experiments

* Kimer, doc. cit., p. 145.

PROTECTIVE COLORATION. 139

prove this: after the eyes have been removed, the ‘action of
the colour of the environment on the colour of the skin ceases.
Thus, in many cases, chemical action and stimulation of the
optic nerves may be closely connected in the process by which
the colours of animals are affected by light.” The use of the
term “ photograph ” is apt to prejudice the question ; nothing
of the kind occurs in the soft tissues of a caterpillar about
to change into a chrysalis. Furthermore, Mr. Poulton has
shown that the eyes have no share in the production of a
harmony in colour with the environment : he covered the eyes
with a varnish, so as to entirely exclude the light, and yet
there was no failure in the adaptability of the larva.

The case is not to be compared with the change of colour in
frogs and fishes, where the pigment is contained in chromato-
phores connected with nerves, and subject, therefore, to reflex
action—the stimulus coming through the eye. Nevertheless,
Mr. Poulton considers it probable that the change of colour is
due to nervous influence exercised upon the nerve terminations
in the skin. This influence can, however, be hardly exactly the
same as that exercised upon the contractile chromatophores
in the skin of the frog : an actual bleaching possibly occurs in
a bright light, which probably also favours the production of
the gold colour ; this colour, it should be remarked, is not due
to gold-coloured particles deposited in the skin of the larva or
in the pupa case,—it is a structural colour caused by unequal
refraction of the light through thin films of air (or some gas)
and chitin. Possibly, therefore, intense light may cause some
gas to be given off in greater abundance.

In any case, the action of natural selection here must be
quite different from the action of natural selection in producing
fixed resemblances to the environment—snch as is seen, for
example, in the butterfly illustrated on Plate II. In Av/lima

140 ANIMAL COLORATION.

we may suppose that there was originally no particular like-
ness to a dead leaf, except that the colours corresponded more
or less ; those individuals which were most like a withered leaf
were passed over for those which were less like ; and thus the
protective resemblance was heightened, until it attained to the
wonderful perfection which we now see. On the other hand,
the variable pupa may be supposed to have been, as many
pup still are, originally uninfluenced by light ; the acquire-
ment of such a susceptibility, being of manifest use, was favoured
by natural selection. In fact, we assume in this case not a
positive change of any kind, but the acquirement of the
capability of change when necessary.

The whole matter, however, is very difficult of comprehension.
An investigation of the colouring substances which give the
colour to the pupa may show that they are sensitive to light
directly--that is, without the intervention of the nervous
system. In this case natural selection would hardly be
required, or would have had so roundabout an action as to
be incapable of being followed. At every step, in fact, in the
study of animal coloration we are met with closed doors, which
can only be unlocked by keys furnished by an intimate chemical
and physiological knowledge such as we do not at present
possess.

Variable Protective Coloration in Vertebrates.

Another kind of variable coloration is seen in certain animals
which possess the power of rapidly adjusting their colour to
that of the environment.

The changes of colour in the Sole forms the subject of one
of the most interesting chapters in Mr. J. T. Cunningham's
work upon that fish,* lately published by the Marine Biological
‘Association. Altogether, five species of sole are found upon

* “A Treatise on the Common Sole ” (Plymouth, 1890).

“ah

TANS I

Peter Srrut del. et lith. Mintern Bros. Chromo

Kalama butte fly .

PROTECTIVE COLORATION. 14]

our shores, but one of these is as yet only known from a single
specimen. So far as is known, all these species show a change
of colour in response to changes in the environment ; it is only
in Solea vulgaris that they have been carefully studied by
Mr. Cunningham.

A series of beautiful plates illustrate the changes of colour.
The colour of the living fish is yellowish-grey with large,
irregular, dark blotches and small white spots ; this colour is
confined to one side of the body ; the opposite side, which rests
upon the ground, is, as in other flat fishes, white.

When the fish was lying upon a “coarse, bright, clean
gravel,” consisting of yellow and orange-coloured pebbles
mixed with others black and white, its colours were very
conspicuous, though nothing approaching an exact similarity
to the ground could be seen ; on the whole it is inconspicuous,
though the white streak along the edge of the fins was very
evident.

When a sole was placed in a white porcelain dish and ex-
posed to strong daylight, the colours became much paler ; the
blotches, instead of being brown or black, were pale orange:
but, curiously enough, the white marks, which might have been
expected to increase in size, or at least to persist, disappeared.

A sole placed in a tub containing some washed coal and
removed from the light became very dark in colour; but the
result of this was to render the white band along the fins
extremely conspicuous. The changes of colour depend not on
the nature of the ground, but on the amount of light ; for the
blackest ground did not produce the darkest coloration in the.
fish until the amount of light was diminished. The sole does
not become uniformly coloured ona uniformly coloured ground.
The fact that it does become, on the whole, lighter on light-
coloured ground and darker on dark-coloured ground, is to be:

COLORATION.

ANIMAL

142

e lieht is reflected in the former

explained by the fact that mor

case than in the latter.

VS

Mancini

aN

iy
VR
p

of,

Fig. 12.—Chameleon,

This is a simpler explanation than that which Semper offers.*

OT.

* “ Animal Life” (Internat. Scientific Series), p. {

PROTECTIVE COLORATION. 143

Semper’s explanation is based upon certain researches into the
different effects upon the eyes of different colours. The eye
is stimulated most by pure white light, and least by black,
the intermediate colours having an intermediate effect : thus,
yellow causes a stronger stimulation than violet. If, therefore,
the animal is surrounded by a black environment, the stimu-
lation of the eye will be slight, and not enough to affect the
chromatophores. “If the light is reflected from a red or blue
object, the somewhat stronger stimulation causes the black or
brown chromatophores to contract, wile it does not affect the
red or yellow ones; the animal then exhibits a reddish or
bluish tint. The light reflected from green or yellow bodies
produces a still stronger effect on the chromatophores, till a
pure white light makes all the inmost layer of the chromato-
phores contract, and the animal is almost colourless.” The
chameleon * is naturally the most familiar example vf power
of colour change ; the physiology of this change has been
investigated by several naturalists, including the late Dr.
Kriikenberg of Jena. It appears that contractions of the
chromatophores can take place through stimuli, not only
to the eye, but to the skin; other effects, therefore, besides
those of light, may produce a change of colour.j Various
emotions are well known to do so: if the chameleon be
somewhat roughly handled, it shows its anger, not only by

* Mr. Poulton, as well as others, has remarked that the chameleon
becomes very dark-coloured before death ; this is not invariably the case

for I have had in my hands a dead chameleon of a bright but Myhtish
green.

+ Practically, however, a change of colour seems always due to stimu-
lation through the eye and optic nerve: blinded frogs, etc., have been
shown to have lost the power of colour change ; and there are instances
on record of individual fish having been noticed whose colours did not
correspond to that of their fellows, and to the ground from which they
were taken. These individuals proved tu be blind.

144 ANIMAL COLORATION.

movements common to most infuriated beasts, but by changes
of colour. So, too, does the cuttlefish.

The power of changing its colour to suit the environment is
not confined to the chameleon, but is found in other lizards.
According to Drs. Elliott Coues and Yarrow, species of the
genus Phrynosoma (the ‘‘ Horned Toads”), Uta and Sceleporus
have a like power. With regard to Uta symmetrica Dr. Coues

Fig. 13..—The Horned Toad (Phrynosoma).

writes (loc. cit., p. 597) : “ Out of great numbers of specimens
procured in one locality ... and unquestionably the same
species, almost the only colour mark common to all was the
pale yellow throat. Some were plain silvery white below,
others were bright greenish-olive on the belly. Above, the
colour ranges from a deep greyish-black to a dull greyish-
brown with dark lateral streak. I satisfied myself that the
same individual assumed these different colours according to
the kind of rocks it happened to be upon. The blackish

i

Su
fps

)
(
:

i.
i

tit
Mf in

:

A

If
:
ty

Lan
LN ul le ZZ

PROTECTIVE COLORATION. 145

specimens were invariably found upon dark lava rocks, the
lighter ones upon yellowish sandstone.”

Although it has been stated that no insect has the power of
rapidly changing its colour in correspondence with the changing
environment, certain Crustacea can. The little swimming
crab Nautilograpsus shows temporary changes of colour ; so,
too, does a shrimp, Atyoida, recently described by Fritz

P.\\ iL.

Hh

Hi
HH

HIN
in

ty
.

Fig. 14.—Tree Frogs.

_Miiller ; this crustacean is dark green when among weeds, but
becomes pale brown when placed in a glass vessel; a dark
brown individy.al was placed with a number of others which had
a greenish hue ; it assumed their colour directly.

Frogs also have this power of colour change ; it is well seen
in the little tree frog (Hyla arborea) of Europe, which is
green when among leaves, and browner when upon stems ;
this colour change appears to have an obvious bearing upon

the habits of the creature. Mr. Poulton surmises that the
10

146 ANIMAL COLORATION.

faculty of colour change may here have a twofold value ; it
may be both defensive and aggressive.

The European tree frog has not, perhaps, so many enemies
as those of some tropical countries which occasionally fall
victims to tree-frequenting snakes. There are green tree
frogs in many parts of the world, just as there are here and
there green tree snakes. In Guatemala there is a green tree
viper which, according to an illustration accompanying a paper
by Mr. Salvin* on some of the reptiles of this region, preys
upon green tree frogs; and there are non-poisonous green
and greenish-brown tree snakes, which are probably quite as
destructive to the tree frogs ; so also, no doubt, are many other
snakes. It cannot, of course, be urged against the advantage of
this coloration to the species, that there are tree frogs in which
the colour is not so thoroughly protective : in Hyla Cerulea,
for example—a large Australian species—the green colour is
just as bright as in the European Hyla, but its value for
defensive or aggressive purposes is to some extent interfered
with by a number of white spots and patches along the side.
At the moment of writing there are several of these frogs in
the reptile house at the Zoological Gardens.

Assuming that snakes are the principal enemies of tree
frogs, it is necessary to make observations upon the habits
of the snakes before admitting the defensive value of the
coloration in the frogs. Generally speaking, snakes only
strike at a moving object ; if this is the case with the tree
species, no amount of protective coloration will avail the
frogs.

As to the aggressive value of the colour, it does not seem

at all clear how far insects are affected by the circumstance ;

* Proc. Zool. Soc., 1860.
+ Snakes will, however, Dr. Stradling informs me, eat pieces of meat
n captivity.

PROTECTIVE COLORATION. 147

there is a tendency to assume their gullibility without bringing
forward any proofs. As a matter of probability, it seems
likely that most insects would be indifferent to the appearance
of an object, provided that it remained motionless; the frog,
of course, does remain motionless. The European tree frog
has been stated to have an inordinate appetite for wasps,
which surpasses that of other frogs ; there are enough wasps
and other brightly coloured Hymenoptera about trees to afford
sufficient food for the tree frogs, and it would be opposed to
the theory of warning colours to imagine that a gaily coloured
wasp, trusting to its formidable weapon, would be especially
wary.

CHAPTER IV

WARNING COLORATION.

In the preceding chapter attention has been directed to
numerous instances of colour and arrangement of colour
which appear to have the result of rendering the animal
similar to its surroundings.

The colours known as “ warning” have a precisely opposite
tendency—viz., to render their possessor conspicuous.

As the explanation of warning colours was first devised by
Mr. Wallace to account for the brilliancy in the tints of certain
caterpillars, and as the whole subject has been principally
studied by experiments upon these animals, we shall commence
here, and afterwards pass on to other groups.

The Magpie Moth Caterpillar as an Instance of Warning
Colours.

One of the most abundant caterpillars in any garden is that
of the “ Magpie”? moth (Abraxas grossulariata) ; it belongs
to the Geometers, but has not the habit, which most of its
allies have, of remaining during the day stretched out rigidly
from a twig. Nor does it approximate in colour, as do nearly
all other Geometers, to the plants upon which it feeds. The
colour of the Magpie caterpillar is white, with black stripes
and dots, and some reddish marks below.

Mr. Jenner Weir, Mr. A. G. Butler, and Mr. Poulton, found
that several birds, lizards, frogs and spiders, almost invariably

WARNING COLORATION. 149

refused to touch this caterpillar when offered to them ; occa-
sionally it was tasted by the tree frog, and once “ chewed
for some time,” but finally rejected, by a hungry Lacerta
muralis. Mr. Weir once found that a specimen was eaten
by Lacerta viridis. Some experiments made by myself at
the Zoological Gardens partly confirm and partly contradict
the conclusion to which the above observations appear to
point—viz., that the larva is regarded by birds as inedible.

Several birds, including the Kagu, Psophia, and one or two
species of Curassows, pecked several times at caterpillars which
I gave them. Two species of Tanager and a White-eye
(Zosterops), took a caterpillar in their bill and masticated it
for a long time ; the White-eye, I am inclined to think, ended
by swallowing the insect. In any case a large ground cuckoo
(Carpococcyx radiatus) undoubtedly did swallow a caterpillar
after one or two preliminary pecks. Several other birds made
more than one ineffectual attempt to conquer their dislike for
what was evidently a disagreeable morsel ; but only one bird
(a small finch) absolutely declined to have anything to do
with it. It should be mentioned, however, that this individual
had observed a neighbour industriously pecking at the cater-
pillar, but evidently disinclined to swallow it.

I also experimented with four monkeys, which are well
known to be great eaters of insects. A marmoset (Jfdas
rufimanus) ate one up quite greedily, to the very last bit ; two
Cebus monkeys and a Cercopithecus callitrichus sucked at the
caterpillar and threw away the skin after the contents had
been entirely extracted ; they paused every now and again to
sniff suspiciously at the caterpillar, but nevertheless they
steadily persevered in munching it. These experiments show
that, with a few exceptions, the caterpillar of the Magpie moth
is distasteful to animals.

150 ANIMAL COLORATION.

Earlier Experiments with Warningly Coloured Insects.

Now, before these experiments had been made, the brilliant
hues of caterpillars—which were useless for protective pur-
poses, and could obviously have no sexual meaning—had
puzzled Darwin; he drew the attention of Wallace to the
subject, who ventured to predict that gaudily-coloured cater-
pillars would prove to possess some unpleasant qualities ren-
dering them unfit for food.

The purpose of the conspicuous coloration is to advertise
their inedible qualities. “They require some signal or danger
flag which shall serve as a warning to would-be enemies not
to attack them, and they have usually obtained this in the
form of conspicuous or brilliant coloration, very distinct from
the protective tints of the defenceless animals allied to them ”
(Wallace). This 1s shown in the case of the Magpie cater-
pillar: it has been proved to be uneatable, and it is about as
conspicuously-coloured as any caterpillar.

Experiments have been also made with other caterpillars by
the above-named gentlemen and by others, which are carefully
tabulated by Mr. Poulton,* so that the results of the inquiries
can be seen at a glance.

The larva of the Cinnabar moth (Euchelia Jacobee) is
banded with alternate rings of black and yellow; it feeds
during the day upon ragwort, and is extremely conspicuous. Its
conspicuous appearance is largely increased by the fact that it
lives in companies.

Many gregarious caterpillars (eg., the “Lackey” and the
“Buft-tip”) possess warning colours, and it has been supposed—
the suggestion was originally put forward by Fritz Miiller—that
the advantages which accrue to them by the advertisement of

their colour are rendered greater by this habit. The mass
* Proc. Zool. So., 1887, p. 191 et seq.

WARNING COLORATION,. 15]

of colour thus produced must obviously stand out in greater
contrast to the surroundings. This suggestion is particularly
applicable to the larve of many of the Vanesside; several
species of these butterflies lay their eggs upon nettles, and the
larvee remain associated together in herds, sometimes entirely
defoliating the plants. Now, the caterpillars of the Tortoise-
shell and others are greenish-black ; seen singly, their appear-
ance is not very striking: indeed, it is almost a case of pro-
tective resemblance : the caterpillar, with its hairy or rather
spiny coat and greenish-black colour, is not unlike a half-

Fig. 15.—Butt-tip Moth and Caterpillar.

withered and rolled-wp leaf of nettle. But a whole battalion
of these caterpillars could hardly be passed over by any insect-
eating bird; and, like the other instances mentioned, they have
been proved to beusually unacceptableto birds, lizards, and frogs.

Some of the experiments made may be fairly criticised,
notably those upon the larva of the Elephant Hawk moth.
This insect when disturbed retracts the head and distends the
anterior end of the body. Two pairs of large eye-like markings
are thus brought into great prominence, and suggest the head
of a serpent. Dr. Weismann found that a tame jay ate the
larva at once, but that wild sparrows and chaftinches were
frightened by it, and would not even approach the trough in

152 ANIMAL COLORATION.

which it was placed. Fowls were evidently afraid of it, but
finally cautiously attacked it and ate it. Lady Verney made
some experiments with the same caterpillar: it was placed on
a tray with some crumbs, and no small birds would approach
the tray; they were evidently frightened by the snake-like
appearance of the caterpillar. So far, the experiments do not
strike one as very conclusive : small birds would have possibly
shown just as much hesitation or alarm at an equally large
caterpillar of any kind; and the jay, which was of a suitable
size, ate it. The behaviour of the fowls was not so intelligible.

Mr. Poulton’s experiment was better: he found that a
Lacerta viridis, which had often devoured large Hawk moth
caterpillars of other species “without any ceremony,” evinced
some suspicion at the sight of this terrifying larva of Chero-
campa elpenor; ultimately, however, it must be noticed, the
caterpillar was eaten. And that appears to be rather the
important fact. The question is, whether in a wild state the
lizard’s attention might have been drawn off by the sight of
some less alarming-looking prey, or whether it would have
overcome its fears in the same way that the captive lizard did.
If the eye-like markings of the caterpillar are of the very least
use in frightening away enemies, we can understand that they
may have originated, or at least become perfected, to this end.
But if they only temporarily disconcert a lizard who has possibly
not seen the insect or anything like it before, and who finishes
by eating it, it is not intelligible that they can have arisen
tor so useless a purpose.

It is to be noted, however, that warning coloration of the
kind referred to in the foregoing pages does not always seem
to be effective.

I have already mentioned my own experiments with regard
to A. grossulariata ; this same caterpillar, as well as many

WARNING COLORATION. 153

others, has been tested from this point of view by Mr.
Poulton. These experiments show a very complete series of
transitions between conspicuously-coloured caterpillars that are
disregarded by all foes, and conspicuously-coloured caterpillars
that are always eaten with avidity.

Some Experiments upon the Palatability of Various Animals.

The following experiments were conducted during last
summer at the Zoological Society’s Gardens by Mr. Frank
Finn and myself. The larva of Acronycta psi—the common
Dagger moth—a brightly-coloured larva, was left untouched
by a rose-coloured Pastor, but immediately afterwards seized
and struggled for by two common thrushes ; the issue of the
struggle was not witnessed, but it must have gone hard with
the caterpillar. A specimen was eaten by a green lizard.
A wasp-like fly (Syrphus) was eaten, though with no great
relish, by a Bramble finch. A drone of Bombus lapidarius
was refused by a Golden plover, but tried at, though missed,
by a Troupial. A drone-fly (/:ristalis tenax), which presents
so remarkable a likeness to a bee, was seized and dropped by
a thrush ; and then was tried and refused, as if unpalatable, by
an Australian plover; a third was entirely disregarded by a
rose-coloured Pastor. An Australian crow was offered one,
which it took and carefully pinched with the tip of the bill
before eating. Marmosets seemed afraid of it ; but in some
cases they soon found out the deception, and ate the insect
greedily. A blue jay (Cyanocittu cyanopogon) ate an Eristalis
without making any fuss about it; and this bee-like fly was
taken without hesitation and eaten with relish by a chameleon,
green lizard, and sand skink. The sand skink, indeed,
snatched one from a specimen of Zonurus cordylus, which had
already commenced to eat it. Toads, of course, will eat this fly;

154 ANIMAL COLORATION.

but they will eat wasps, bees, and the most gaudy of cater-
pillars. A specimen of Fristalis was offered to a Great
Spotted woodpecker, which seized it and flicked it away at
once. Some smallish larve of the large White Butterfly,
found upon nasturtium, were placed in a glass case containing
a ereen lizard and Amphibolurus muricatus, an Australian
lizard ; both these species ate them readily. An African
Zonurus (Z. cordylus) ate one, but refused a second ; and
another individual of the same species would not touch the
larva at all. A small sand skink in the same case ate two.
A chameleon looked suspiciously at the caterpillar, but was
not to be tempted. The Greater Spotted woodpecker ate
several, but pinched them carefully first ; the woodpecker ate
larvee of this species on two consecutive days. Two rose-
coloured Pastors also took these caterpillars after rabbing them
carefully on the ground. They were readily eaten by marmosets.
The conspicuous larva of the “ Buff-tip’ moth was eaten by
marmosets, though they evidently found it to be very tough.
One was offered to a Great Spotted woodpecker, and partially
eaten, though after some time and much pecking. Its skin
appears to be very tough. A great tit ate a little of the
protruding viscera, but did not seem to care very much about
finishing it. The insect was well tasted, and curiously enough
rejected unhurt, by a duck ; they were not noticed by fowls.
The hairy larva of Sp/losoma lubricipedu was eaten by a green
lizard, which had previously snatched it away from an Amphi-
bolurus ; the lizard rubbed its jaws afterwards and declined
another specimen. The marmosets smelt and rejected this
caterpillar, but they had been recently fed. The Great Spotted
woodpecker tried to get a specimen of this caterpillar, thrown
into its cage, but was anticipated by a great tit, who was
busy with the insect for a long time, and rubbed it on the

WARNING COLORATION. 155

ground. A magpie ate two caterpillars after it had carefully
rubbed off the hairs.

It is quite clear from these experiments that insects which
exhibit warning colours are by no means always exempt from
attack. The opinions of insect-eating mammals, birds and
reptiles, appear to vary as tothe edibility of this or that insect.

It may be said, of course, that these experiments, having
been conducted upon foreign animals, are of less importance
than those upon British animals; this, however, cannot be
allowed, because the theory of warning colours implies—not:
a special recollection of any particular type of imsect—but a
general association of bright colour with poisonous or dangerous
qualities.

But these experiments do appear to show that very generally,
though not always, a disagreeable taste is associated with a
conspicuous and varied coloration.

On the other hand, precisely the same deductions can be
drawn by watching the behaviour of animals when offered in-
conspicnonsly-coloured insects.

Mr. Poulton has directed attention to the apparent inedibility
of the cockroach ; this insect is, however, eaten by various
animals, though not by all to which it has been offered. As
will be now mentioned, a protectively-coloured caterpillar is
distasteful to some insect-eating species.

Mr. Finn found that the larva of one of our common Noctue
—Mamestra persicarie—was not a universal favourite. This
caterpillar is inconspicuously coloured, and might fairly be
adduced as an example of protective coloration. There are two
varieties which occur together on the same plant ; one is brown,
the other green. These caterpillars were eaten, after being
well pinched, by a Glossy starling, and by the Greater Spotted
woodpecker ; if the caterpillar had been one of those which

156 ANIMAL COLORATION.

are distinguished by brilliant colour, this experiment would
have been surely quoted as an instance of the hesitation and
reluctance with which a bird, probably compelled by hunger,
satisfied its appetite. The instance shows the pitfalls
which surround the path of those who wish to deduce
theories from experiments of this kind, which are necessarily
made in very great ignorance of bird psychology or even
physiology. The same larva was readily eaten by marmosets,
but treated very doubtfully by a large American monkey (the
marmosets and monkeys had been recently fed). The larve
were also readily eaten, without any preparatory pinching, by
the rose-coloured Pastor. On the contrary, the Australian
plover pinched the larva carefully before swallowing it.
Another kind of larva, with which I am not acquainted, of a
brown colour with black marks ranged segmentally along the
sides, were eaten by the Great Spotted woodpecker, after a
very little pinching. These larvee were well pinched, but finally
rejected, by a Toucan ; a small individual was taken by one of
the “ Hang Nests ” in the parrot house (Icter'us chrysocephalus);
it was pinched to a pulp and held in the bill for a long time ;
occasionally the bird put it down and pecked at it; it was
finally swallowed. The same species was eaten after pinching
well by the Motmot and by Hypocolius. A number of other
birds took the caterpillars with varying degree of pinching and
pecking before swallowing them.

The common wood-louse was rejected by the woodpecker :
this seems to be a very remarkable fact, because wood-lice must
be almost the commonest creatures met with by the wood-
pecker under normal circumstances. That they are not dis-
tasteful to many birds has been shown by other observers ;
and we found that they were eaten at once by magpies, and
after a few pinches by a piping crow.

WARNING COLORATION. 157

Earthworms are creatures that are generally acceptable to
insectivorous birds ; but there are three exceptions, which are
remarkable for different reasons. A gigantic species, reaching
to a length of six feet or more, which I described some years
ago,* from the Cape Colony, appears to be free from the attacks
of many animals. Mr. De Witt Meulen informed me that no
domestic animal whatever, including fowls, will touch them.
This instance may be used by those who are disposed to believe
in the theory of warning coloration, for the worm is very
conspicuous—dark green above and reddish-yellow below.
Another exception is an equally large species from Australia,
whose habits and structure have been recently well described
by Prof. Baldwin Spencer: + this species is not conspicuously
coloured, but it has a powerful odour resembling that of creosote.
Fowls refuse to touch this worm living ordead. There is little
doubt that in this case the powerful smell acts as a deterrent.
More remarkable still is the fact that our common earthwormst
are refused by the Guinea fowl (Numida mitrata) and by the
blue tit and Great Spotted woodpecker ; no less than three
Guinea fowls declined to taste the worms, which are certainly
eaten by the common fowl. The comparatively large size may
perhaps have deterred the blue tit. The woodpecker seemed
afraid of it, only pecking at it once and rapidly recoiling when
it wriggled.

The Tiger moth and the Leopard moth are particularly
referred to by Mr. Poulton § as being inedible forms. They

* Trans. Zool. Soc., vol xii. (1886), p. 63.

+ Trans. Roy. Soc. Victoria, vol. i., Pt. I.

+ One of the most conspicuous of our British worms is the Brandling
(Allolobophora fatida), found upon dunghills ; it is conspicuously ringed
with dark brown and yellow. Dr. Stradling has told me that it was eaten
by several lizards kept by him, but that it caused them ‘“ epileptiform fits.”

§ “Colours of Animals,” p. 175.

158 ANIMAL COLORATION.

are both highly conspicuous and easily captured, particularly
the second insect, which is frequently met with on the ground,
under trees, where the larva has no doubt fed up. Neverthe-
less both these moths were greedily eaten by Lacerta ocellata,
the large South European “ Eyed Lizard” ; this lizard, it may
be observed, would be quite likely under natural conditions
to meet with the two moths ; they live where the lizard lives,
and they are constantly met with on the ground. But even if
this were not so, no use could be made of the fact. The

Fig. 16,—Leopard Moth.

theory of “ warning coloration” is not based upon particular
cases of recognition ; the broad principle which is believed in
by the supporters of this theory is that a gaudy and striking
coloration is associated with a nasty taste and with a corre-
sponding impression in the minds of animals that these two
facts go together. Reference has been already made to the
inedibility of the larva of the Cinnabar moth (Luchelia
Jacobee) ; a caterpillar was offered to a lizard, Lacerta galloti,
which had not been fed for some time previously, and was
therefore probably hungry ; it took one without any hesitation,
but refused, or rather declined to notice at all, a second.

WARNING COLORATION. 159

Another specimen of the lizard licked, but did not take the
caterpillar, A Lacerta viridis licked, tasted, and finally
refused another caterpillar. A sand skink (Chaleides viri-
danus) licked and refused the same caterpillar. Uromustix
spinipes went rather farther: it chewed up one, but did not
swallow it in the end.

The most remarkable results were obtained by experiment
with two toads—one a common toad, the other a green one (Bufo
viridis). The common toad is a creature which will apparently
eat anything in the shape of an insect; nothing seems to come
amiss: the largest humble bee and the most irritable of
wasps are swallowed without the least indication on the part
of the toad that they are capable of using their stings. A
common toad seized and swallowed a Cinnabar moth cater-
pillar directly it began to move, but almost immediately threw
it up, and the caterpillar did not appear to have suffered the
very least inconvenience from the events.

Another toad in the same case ate a caterpillar, but neither
of these seemed disposed to try another. But these toads had
been fed, and were not particularly hungry. A green toad,
which was hungry, eagerly swallowed a caterpillar, and as
eagerly took a second. In experiments of this kind it is
always important to give an animal more than one of the
insects experimented with, in order to see how far experience
may tell in influencing its behaviour.

Another caterpillar was offered to a brown Capuchin
monkey, who ate it, though perhaps rather slowly and reflec-
tively.

The larva of the Vapourer moth (Orgyia uwntiqua) is con-
spicuously coloured and armed with tufts of hairs. One was
offered to a green lizard, which seized it, and seemed at the
same time both anxious and unwilling to eat it. The lizard

160 ANIMAL COLORATION.

appeared to intimate that it would eat the caterpillar if it were
not for its hairy covering. No such hesitation was exhibited
by another lizard, Uraniscodon plica, which captured and ate
one with the greatest rapidity.

The large ground beetle (Carabus violaceus) was eaten by
Lacerta ocellata. Lacerta viridis ate at once a Doristichus
niger. Another example of the same insect was placed in a
small cage containing a number of British finches: the birds

Fig, 17.~Vapourer Moth : male, female, and larva.

gave one the impression of being rather afraid ; but neverthe-
less they attacked it, and ultimately it was eaten.

The wasp is one of the best examples of a conspicuous
appearance associated with a dangerous quality, and yet it has
many enemies; toads and bee-eaters eat wasps readily. On
October 16th of last year two queen wasps were offered to -
and taken by the lizard Amphibolurus muricatus. The lizard
certainly seized them by the head and thorax first and crushed
these parts before proceeding farther; but there was not the
least appearance of hesitation in the attack, nor did the lizard

WARNING COLORATION. 161

appear to get stung, though the wasps had every chance of
stinging. The second wasp was eaten much more slowly than
the first, the lizard holding it for some time in its mouth with-
out chewing it. This experiment recalls that made with the
drone fly and recorded above. They show how difficult it is to
interpret experiments, apart altogether from the formulating of
wide-reaching generalisations. The wasp presumably advertises
its sting by its bright colours, while the drone fly is supposed
to delude its would-be enemies into the belief that it could
produce a sting if it liked. There is not supposed to be any
question of unpalatability, and yet the hesitation of the lizard
Jooks more like the recognition of a disagreeable taste
than the fear of a sting. Another queen wasp was eaten by
a Laughing Jackass, but was well crushed first, and the bead
bitten off.

Lithobius forficatus is instanced by Mr. Poulton as an
example of a protectively-coloured animal; it is like the soil in
‘which it lives, and is inodorous. Its mandibles would be hardly
‘formidable to a bird or to a lizard which does not care for the
‘sting of a wasp.

Prof. Weismann found that it was greedily eaten by Lacerta
wiridis. Mr. Finn and I found, on the contrary, that the same
‘species of lizard bit and refused one with what are generally
termed, by those who make such experiments as these, “signs
of disgust.” The lizard rubbed its mouth on the ground as if
trying to get rid of some disagreeable substance. A larger
‘specimen then attacked and bit it several times, wiping its
mouth afterwards in the same way. The centipede ended by
getting away in safety.

Another centipede was offered to a green woodpecker: the
woodpecker picked up the centipede, but immediately flicked

,it away as if it were unpalatable.
1]

162 ANIMAL COLORATION.

An earwig was given to the same woodpecker, which made
a great deal of fuss over it, but ended by swallowing it.

The wireworm is not a conspicuous larva; it is no doubt.
tough, but should be, on account of its colour and habits,
eatable. And yet one was flicked away by the woodpecker,.
just in the same way that it treats a decidedly unpalatable
insect.

The woodpecker was clearly hungry, for it ate a house fly
immediately’ after declining the wireworm. A _ great tit
subsequently declined the same wireworm.

The small garden slug is an animal which cannot be said to:
be conspicuous; it is eaten greedily by ducks, but fowls will
not touch it.

We made some experiments with the large brown slug, an
animal which has been instanced as an example of warning
coloration (perhaps, however, the black variety alone is meant).
Two of these slugs were eaten readily by the Kagu. Another
was eaten with equal readiness by the Thick-knee (Qdicnemus
grallarius). A curlew refused both brown and pale specimens.
Oyster-catchers ate them, but not very readily after they had
been fed. The South American Trumpeter (Psophia) refused
them. A blackbird ate one after a long and diligent rubbing
of it on the ground. The Laughing Jackass ate two large
brown ones and two pale ones. The Great Spotted wood-.
pecker seized and swallowed at once a small slug, but de-
clined the large ones. A dark brown slug was offered to the
Sun bittern, which did not touch it; a song thrush in the
next cage, who was greatly interested in the proceedings, took
it, and, after much rubbing on the ground, devoured first of all
the viscera, which had protruded owing to the rough treatment
the slug had received, and then the body. During the time
which the thrush was occupied with the slug, a rose-coloured

WARNING COLORATION. 163

Pastor took it away from it, but left it; the thrush (or perhaps
another one) then recovered it, and, as already mentioned,
swallowed it.

Three speckled brownish and whitish slugs were refused by
a magpie and jackdaw; another three were eaten without any
signs of hesitation by a woodhen.

A small black slug was eaten by a Glossy starling after
much rubbing on the ground.

On another day a brown slug was offered to a Laughing
Jackass and eaten, though after some time.

The larva of the small Ermine moth ( Ypomoneuta padella)
has been a great pest in London during the past summer,
disfiguring with its webs and defoliating the trees; it will feed
on almost any tree or shrub. Mr. Jenner Weir found that the
“ Jarvee only which ventured beyond the protection of the webs,
were devoured by birds, which “appear very much to dislike
the web sticking to their beaks.” Mr. Poulton considers that
this instance favours Mr. Wallace’s converse suggestion that
inconspicuous caterpillars which evade their enemies (in this
case bya web) will be found to be palatable. Mr. Finn and I
found that the caterpillars of this moth were not invariably
palatable. Lacerta galloti ate several readily, but Zonurus
cordylus, though it ate one, bit and refused others.

It may be convenient briefly to tabulate the results of these
experiments for purposes of comparison with the results
obtained by Weismann, Jenner, Weir, Poulton, and Butler.

The names of insects (and other animals) supposed, on
account of their colour, to be edible are printed in italics, with
the exception of those that have a sting, or mimic insects with
a sting.

The tables would clearly have more significance if a larger
number of larve had been experimented with.

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A great number of conspicuous larve belonging to the

Bombyces and Bombycoide are, on account of their rarity,
-omitted from this list. These experiments may perhaps be
made in the future. But it would need a very ardent disciple
of Mr. Poulton’s to sacrifice, for the purposes of philosophical
zoology, the larve of the rare and beautiful “Merveil du Jour”
(Diphthera orion) |

These experiments certainly bring out the fact that the “likes
and dislikes of insect-eating animals are purely relative.”
They are a further proof of the old saying that ‘‘one man’s
meat is another man’s poison.” They perhaps also show that
birds are more fastidious in their taste than either lizards or
monkeys. But none of these experiments are thoroughly satis-
factory : it is so difficult to interpret them, and they are often
contradictory, for a bird will eat one day what it has refused
before.* The experiments that have been made are like most
other statistics—they may be made to prove anything. A
careful series of observations upon the contents of the stomachs
in wild birds would be the nearest approach to a satisfactory
solution of the difficulty ; but there are obvious objections to
this mode of investigation.

Now tasting, especially of birds, would be quite as dangerous
to the caterpillar as swallowing it outright. If rejected by a
frog it might certainly be completely uninjured, and it appears
that even a very prolonged tasting by a duck may not result
in any injury.

Mr. Poulton has pointed out how very important it is that
an uneatable caterpillar should be at once recognised and
avoided; owing to the thinness of the body wall which contains
the blood under considerable pressure, the slightest injury may
prove fatal; for the blood will escape in considerable amount,

* Butler, in Ann. and Mug. Nat. Hist. 1890.

WARNING COLORATION. 167

‘quite incommensurate with the size of the wound, or the pres-
sure of the blood may force out the viscera ; hence the means
of protection are chiefly passive, depending upon concealment
or advertisement by warning colours.

I have myself noticed that a caterpillar twice bitten by a
large spider crawled away apparently unconcerned ; in these
cases, therefore, the disagreeable taste itself is the protection,
and not the brilliant colours. In many cases the supposed
protection afforded by the warning colour is reinforced by other
means of defence. Mr. Wallace accounts for the development
of warning colours by the need for advertisement of dangerous
or uneatable qualities. Ido not see the absolute necessity for
this, excepting only if various other causes should prevent the
caterpillar from having recourse to protective coloration.
Moreover, evidence has been got together by Mr. Poulton
which proves that one species of protectively-coloured larvee
at least is uneatable.

The instance which he brings forward is Mania typica, but
other examples are given from other orders of Arthropoda, and
I have referred to a few above.

Insects with Warning Colours often protected in Other Ways.

In the Magpie caterpillar the habit of feeding upon many
kinds of shrubs may be an adequate set-off against its con-
spicuous appearance; and the same remark will apply to
Acronycta psi (the Dagger moth), and to the Buff-tip caterpillar.
A considerable toll might be taken by many destroyers of insect
life (among them ichneumon flies, which do not avoid gaudily-
coloured caterpillars) without unduly diminishing the numbers
of these insects. With regard to the Magpie moth, I have
noticed that, like other Geometers, they do not begin to feed

168 ANIMAL COLORATION.

until evening. I have a quantity of these caterpillars on some
thick-leaved shrubs in my garden ; during the daytime none
are visible, but in the evening they commence to crawl about:
quite actively.

Again, a large number of conspicuously-coloured larvee are
also hairy ; with the exception of the cuckoo, birds dislike
hairy larvee ; it may be also difficult to pick them up, or they
may escape with the trifling loss of a few bunches of hairs.

Among the “ Tussock” moths, the localisation of the hairs
into tussocks (see figure of Vapourer Moth caterpillar on
p- 160), and the attitude assumed by the caterpillar, almost
compels the bird to peck at these thick bunches; other larve
produce odoriferous secretions, which are, probably, at least
as effective as their appearance in keeping off enemies. Still
there is no reason why a caterpillar should not have more
than one means of defence at its command; there are some
species, indeed, which undoubtedly have. For example, the
larva of the “ Puss” moth: its general green coloration may
be fairly considered protective ; if discovered it can adopt a
terrifying attitude and eject a quantity of formic acid ; the
flagella may perhaps be considered rather as a weapon for
warding off the attacks of ichneumons than for repelling

vertebrate foes.

Warning Colours can only be safely adopted by a comparatively
Small Number of Animals.

It has been pointed out by Mr. Poulton that warning colours
can only be safely adopted by a small proportion of the insects.
in any country. The means of defence is so simple that it is
remarkable not to find more examples of it; but this result
is prevented by reason of the fact that a too complete success
would frustrate its objects: if all insects became distasteful

WARNING COLORATION. 169

and exhibited warning colours, or exhibited warning colours.
without becoming distasteful, birds and other insect-eating
animals would be compelled to feed upon them; and it has
been proved by Mr. Poulton and by others that if pressed by
hunger animals will eat such distasteful insects.

It appears to me, however (ay I have already said on p. 133),
that the same objection might be applied to other characters :
protectively-coloured caterpillars are suffered to escape their
enemies by their powers of concealment; but if all, or the
majority of insects became thus difficult to find, some improve-
ment in their foes—additional keenness of sight or smell—
would tend to render these disguises easier to detect.

Objections to the Current Theory of Warning Coloration.

The larva of the Swallow-tail (Papilio Machaon) is coloured
with green, black, and orange ; it possesses, in Prof. Weismann’s.
opinion, “a striking appearance,” and when offered by this.
naturalist to Lacerta viridis, was untouched by the lizard.
This caterpillar becomes specially conspicuous when touched
or interfered with in any way ; it then everts from the neck a
glandular apparatus of a red colour.

When at rest upon its food plant the colours are by no
means conspicuous. These invisible glands referred to have
been termed “ osmateria ” or “stench throwers” ; they secrete
an offensive-smelling substance ; the caterpillars are no doubt
to some extent protected by them.

Mr. Wallace thinks that their function is chiefly to ward off
the attacks of ichneumons; but they may also, he considers,
frighten small birds.

We may consider, perhaps, that this larva is inconspicuous,
but when found it possesses a means of defence in the osma-

170 ANIMAL COLORATION.

teria. However, there are other Papilionid larvee which
are undoubtedly conspicuous. The North American Laertias
philenor, the “Blue Swallow-tail,” is ; and it has the same
osmateria as the European Papilio machaon.

These facts are hard to reconcile with the theory of warning
colours. Presumably, the bright colours of the larva of
Laertias philenor ave an advertisement of the osmateria ; and
yet these same weapons of offence are not advertised in

Fig. 18.—Swallowtail Butterfly and Larva,

Papilio machaon and in other species with a defensive or
at least a non-conspicuous coloration.

Mr. Scudder thinks that possibly the explanation is that
the larva of the American Swallow-tail conceals itself under
leaves, and is therefore less readily found. But this explana-
tion is not consistent with the theory of warning colours: the
very essence of the theory is that brightly-coloured larvee
display themselves in the most open way.

Another great difficulty in the way of accepting the theory
of warning colours is the actual change which must take

WARNING COLORATION. 171

place in many cases. The pigments themselves must be
altered, not only in their amount and distribution, but in
their nature and chemical composition. Assuming that there
is no change of habit (of diet, for instance), it is almost im-
possible to conceive of such important physiological changes
evoked by what is, after all, so small a need.

There are so many other easier ways of defence, and one
would imagine that the action of natural selection would
proceed along the line of least resistance. To take a par-
ticular instance,—Mr. Poulton suggests that the larva of the
Cinnabar Moth caterpillar was originally entirely orange-
coloured, like the flowers of the ragwort upon which it
feeds. In this case, what is the need for any change ?
Why should the insect, so to speak, tempt fortune when it
is well off? Mr. Poulton, however, partially disposes of this
difficulty by the suggestion that the black bands have been
only accentuated by natural selection; they stood in the
way, it may be assumed, of a perfect protective coloration,
and were increased so as to produce a warning coloration.
The suggestion is ingenious, but it is of course purely hypo-
thetical. It might be imagined with equal reason that the
caterpillar was originally almost black (like the Fox Moth
larva), and is now gradually acquiring a protective instead
of a warning coloration, by the increase of the yellow and the
diminution of the black. The most probable suggestion of all
(based, be it observed, like most theories of animal colour,
upon absolute ignorance of the pigments) is that the cater-
pillar owes its yellow coloration to the yellow pigment of
the flowers of the ragwort—the black being possibly a denser
deposit of the same, or due to the chlorophyll in the leaves, or
formed anew. If the caterpillar took to the leaves more than
the flowers it might lead to the production of the black

172 ANIMAL COLORATION.

pigment or to its increase. The field of hypotheses has
no limits ; what we want is more study of the actual pigments
and their formation.

The Wings of some Inedible Butterflies resist Injury.

The immunity of gaudily-coloured, slow-flying butterflies
is not always due entirely to their uneatable qualities.
Mr. Trimen has pointed out that the wings of these insects
have often a very elastic structure, and can endure very
rough treatment without serious injury; in this way they
can frequently recover from the mistaken attacks of inex-
perienced foes. Looked at from this point of view, the
strength of the wings is merely an additional protection,
like the nocturnal habits of many protectively-coloured cater-
pillars. It may also have another meaning, which is not
suggested by Mr. Poulton.

The wings call attention to the distastefulness of the insect ;
they are the danger signal, and it is highly important that
they should be kept intact if possible: a large piece bitten
out of the wing by a lizard or a bird in the hastiness of youth,
would not ouly impair the wings as organs of flight, but would
diminish their efficacy as danger flags by reducing their size:
the next animal that passed by would be less Impressed by the
warning coloration, and might kill the insect. Mr. Skertehly
considers that nauseous insects are often yery strong and
less easily injured; the experiments with the caterpillars of
the Magpie moth and Buff-tip caterpillars (pp. 164, 165), qnite
bear out this opinion.

Dr. Eisig’s Theory of Warning Colours.

The suggestions of Dr. Hisig* seem to afford a more reliable
clue to the phenomena of warning colours; his suggestions
* Die Capitelliden, “ Naples Monographs.”

TRILL

Peter Smit delet lith : , Mintern Bros . Chromo
Group of aniinals eahibiting warning coloration.

we a ee

WARNING COLORATION. Lis

have been largely neglected by those who have thought and
Written upon the subject ; but it may be reasonably urged that
one would not expect to meet with valuable physiological
observations in a work devoted to a small group of Annelids.

Dr. Eisig points out, as has been already mentioned in this
book (p. 127), that pigment in the skin has been actually
proved in some cases to be excreted matter; and it mav be so
in other cases where no direct evidence is forthcoming.

In earlier times, when there were no birds—and after all,
the chief enemies of caterpillars are birds—brilliant colora-
tion, due to abundant and varied pigment, would be the rule.
Dr. Eisig is of opinion that this pigment is itself largely the
cause of the distastefulness.* If so, we arrive at an interesting
conclusion—that the brilliant colours (i.e. the abundant secretion
of pigment) have caused the inedibility of the species, rather
than that the tnedibility has necessitated the production of bright

This is an important alteration in the usual view of warning
colours ; but it is obviously not entirely antithetical to the
views of Wallace, Poulton, and others ; for we may still sap-
pose that the bright colours are actually ** warning ~ colours,
although they have not been evolved for this express purpose.

On the view advocated here brilliant coloration is the
normal condition of caterpillars : the advent of bird-life
proved a disastrous event for these animals, and compelled
them to undergo various modifications, except in the caxe of
those forms which combine brilliant coloration with uneatable-
ness,

Dr. Eisig’s ingenious suggestion may possibly apply to

* I may remark that a C2bus monkey sucked a Magpie caterpillar, and

threw away the skin, as a boy sucks an orange and disposes of the peel.
This is so far evidence that the pigmented skin is the distasteful part.

174 ANIMAL COLORATION.

other animals besides lepidoptera—to many invertebrates,
for instance.

Warning Colours of Nudibranchs.

Some interesting experiments have been carried out by
Prof. Herdman and one of his pupils* upon the palatability
of nudibranchs ; these animals form a group of the Mollusca,
and are usually marked by a very varied and brilliant colora-
tion. Sometimes this coloration is such as to conceal the
molluscs when feeding amid their usual surroundings; in
other species the colours are so disposed as to render them
conspicuous anywhere. Experiments were tried with both
kinds of nudibranchs—7.e., those that resemble their usual
environment, and are therefore, as it is termed, ‘“ protectively
coloured,” and those that exhibit “ warning colours.”

Doris lamellata, an instance of the first kind, was eaten by
no fish, but “ seized and rejected ” by a number.

Ancula cristata, a species conspicuously ornamented with
bright yellow, was “seized and rejected” by thirty-eight
fish, “touched aud rejected” by a few, and eaten by three
individuals.

Dendronotus arborescens, a protectively-coloured species, was
eaten by some fish and rejected by others.

Folis, another nudibranch exhibiting warning colours, was
taken into the mouth but never eaten.

These experiments cértainly prove that the nudibranchs
used are, on the whole, distasteful to the fishes which were
attempted to be fed with them; this even applies to the
protectively-coloured forms. Mr. Bateson has moreover shown
that certain fishes do not seek their food by sight at all, and
therefore no amount of colour protection or warning would

* Trans. Biol. Soc., Liverpool, vol. iv., p. 131, ete,

~

WARNING COLORATION. 175.

delude or dissuade them from eating, or at least trying to.
eat, these nudibranchs. It is true that the majority of fishes
do use their eyes in hunting, but the list of those that do not.
comprises a good many forms that must often fall in with
nudibranchs, and possibly devour them.

It cannot, therefore, be admitted that the experiments with

Fig. 19.—Eolis and Dendronotus,

nudibranchs offer any support to the theory of warning colours
as generally understood ; but they do support the suggestion
that unpalatability is associated with brilliant colour, even if

that colour is protective.

Warning Coloration in Wasps.
Many stinging Hymenoptera are brightly coloured, and even
those that are not are frequently conspicuous. The striking
colours of the wasp and the hornet and some of the humble.

176 ANIMAL COLORATION.

‘bees are believed to have been acquired for the purpose of
reminding their foes that there is a sting in the background,
and thus warning them off.

But the males of these Hymenoptera are not armed with
a sting, though, being sometimes weaker and more slightly
built than the females, they would appear to have, if anything,
a greater need of one.

The male hornets, however, when captured, move their body
as if about to sting, and against human assailants who do not
happen at the same time to be naturalists, this pretence is no
doubt very effective. The sting of the worker bee or wasp
is simply the somewhat altered ovipositor ; the workers are
neuter in sex, or rather imperfect females. The yellow band-
ing which characterises our British wasps is not confined to
them ; many exotic species have the same colours, which, as
I have already mentioned, are often met with in insects that
are, for one reason or another, undesirable as food. The
bright colours of the male Hymenoptera must be looked upon
‘as a sort of mimiery, due to “arrested divergence.”

The matter, however, is not quite so simple as it might
appear. Originally, it may be presumed, communities of
wasps, hornets, etc., consisted of males and females only ; later
‘on, the stunted workers were produced, perhaps, by defective
nutrition. Seeing that the females and workers are the main-
‘stay of the wasp colony, it is intelligible that useful variations
which happened to occur might be perpetuated. The males
principally stay at home and perform the duties of scavengers
‘in the wasp city ; and as they have no sting, it could hardly
ibe supposed that gaudy colours were first produced in them
cand then handed on by inheritance to the female. There is
another fact, however, which should be taken into considera-
tion. Many Hymenoptera have a strong odour: thus Pelopeus

WARNING COLORATION. 177

madraspatanus * has both sting and odour. This particular
Hymenopteron is not so conspicuous as many others ; its body
is black, though the legs are ringed with black and yellow.
Is it the odour and the consequent disagreeableness of flavour
which is advertised, or the sting? We know that the sting
is by no mears always a protection ; perhaps the odour may
be effective in other cases, where the sting is disregarded. I
mention later the curious fact that certain Sesiide (Clear-wing
moths) have not only the look but the sme? of hornets.

These facts lead one to believe that odours as well as colours
may he protective. It is just possible that the Clear-wing
may escape by its resemblance in smell to a hornet quite as
often as by its resemblance in colour.

Speaking broadly, it is safe to say that the sense of smell
is much more highly developed in animals than the sense of
sight. Odour has usually been supposed to have a sexual
meaning, to enable the sexes to find each other, or perhaps,
as in the case of the musk ox, to enable a strayed individual
to regain its companions. Particular odours, like particular
plans of coloration, are sometimes found in animals which
are so far from each other in zoological position that they
have no special resemblances at all.

The odour of musk characterises the musk deer and certain
species of crocodile, as well as other mammals. The odour of
the crocodile may perhaps be a lure to entice musk-flavoured
mammals, who fancy that they are approaching one of their
mates—a case of aggressive mimicry in smell. This subject,
however, is rather out of place in the present work.

The fact that I desire to emphasize is the association of a
disagreeable, or at least a characteristic, odour with a con-
spicuous coloration in animals, supposed to be protected in

* Messrs. Horne and Smith, Zrans. Zool. Soc., vol. vii.
12

178 ANIMAL COLORATION.

another way (sting), no less than in the weak-flying Heli-
conide, which are believed to be entirely protected by the
said disagreeable smell and taste. As has been seen, the
explanation of warning coloration would be greatly facilitated
if this could be proved in all cases.

Dr. Eisig’s View not Universally Applicable.

Dr. Eisig’s suggestion, however, will not apply to many
cases : for instance, to the bright colours of birds which owe
their colours largely to structural modifications of the feathers
themselves.

There is, however, only indirect evidence (furnished by
mimicry) that any bird is distasteful. Nor are there many
cases of warning colours in which the disagreeable quality
advertised can be definitely proved not to reside in the skin
itself ; but there are some.

The Warning Coloration of the Skunk.

The skunk has been instanced by Mr. Wallace as illus-
trating the accompaniment of a conspicuous coloration by
some disagreeable quality. Neither one fact nor the other
can be doubted in this case. But the skunk has its enemies,
and is not so unmolested as has been stated. In Patagonia the
skunk is one of the most abundant animals. The traveller
D’Orbigny wrote that in that country the skunk formed the
chief food of the Crowned Harpy eagle; but although
D’Orbigny’s statement is, according to Mr. Hudson, “pure
conjecture,” Mr. Hudson* admits that most of the eagles shot
by himself in Patagonia, including a dozen Chilian eagles
and one Crowned Harpy, smelt of skunk. Pumas also some-
times evidently commit the same mistake, for their fur in
some cases smells strongly of skunk.

* “ Argentine Ornithology,” vol. ii.. p. 66.

~

WARNING COLORATION. 179

Mr. Hudson, however, thinks that this does not necessarily
mean that the birds of prey and the pumas feed upon skunks
habitually ; for the smell of the skunk “is so marvellously
persistent, that one or two such attacks a year on the part of
each eagle would be enough to account for the smell on so
many birds.” But it clearly does show that their lives are
not passed in absolute peace.

There are a considerable number of species of skunks (a
dozen or so), and they are all white, or yellowish and
black.

Mr. Wallace has pointed out the slow, leisurely movements
of the large skunk (VWepAitis mephitiea), which are the result,
he thinks, of its freedom from persecution ; armed with its
offensive secretion, the presence of which is so strikingly
advertised, it has no need for unduly hurrying itself. Some
of the smaller skunks, however, which have been placed in
a separate genus—Spilogale—are spoken of by Dr. Merriam
as being “active” and “agile”; they are also arboreal in
habit, and would therefore perhaps have fewer enemies than
the ground skunks. Nevertheless the coloration of Sprlogale
is similar in principle to that of Mephitis. With regard to the
colour of these animals, it is stated that in the young the
colours are intense black and pure white; as age advances
the black becomes browner and the white creamier. This
fact, however, is quite in accord with the application of the
theory of warning colours to the skunk; they might be
reasonably supposed to need more protection when young
than when older and better able to fight.

Warning Coloration in Other Mammals.
There are other mammals coloured black and white, and
therefore highly conspicuous in their usnal surroundings ;

180 ANIMAL COLORATION.

these, however, are by no means always animals that it
would be obviously dangerous to meddle with.

Mr. Salvin described and figured some years ago* a con-
spicnous black and white squirrel from the Arru Islands.
An arboreal mammal of this colour would under most circum-
stances be conspicuous ; it would be intere: ting to ascertain
if there were any objectionable qualities such as to render it
distasteful.

The curious little marsupial, Myrmecobius is as conspicuously
coloured as any other mammal, except perhaps such as are
black and white. It possesses a complicated glandular
apparatus situated upon the under surface of the thorax,t
which may possible secrete an offensive fluid ; but this is
simple guessing, as nothing is known of the nature of the
secretion and its uses. Such glands are very common among
the Mammalia, and it is quite likely that in certain cases
they may, as in the skunk, secrete a nauseous fluid. It cannot
be said that a conspicuous coloration is always associated
with the presence of these glands ; but they may even possess
one function in one animal and a different one in another.
I have referred to them in another connection on p. 177.

Warning Coloration in Reptiles.

In the hotter parts of North America a large lizard (Helo-.
derma) is met with, coloured in the way that is so common
among animals which possess some dangerous or distasteful
quality. The body is blotched with black and pinkish-yellow,
the colours being thus much the same as those of the wasp:
and the caterpillar of the Cinnabar moth.

A plan of coloration of this kind might lead to the sup--

* Proc. Zool. Soc., 1858, Plate Lxiii. t Ibid., 1887, p. 527.

WARNING COLORATION. 181

position that the reptile was for some reason or other to be
avoided by its foes. Now, Heloderma is the only certainly
known case of a poisonous lizard: it has grooved teeth, which
conduct the poison from the glands which secrete it, con-
structed on a plan similar to that of many poisonons serpents ;
and it has been proved, by actual experiment upon some
specimens exhibited in the Zoological Society’s Gardens, that

the bite of this creature is fatal to many small animals.

SEA BROGKHAUS AA
ae

It is sluggish in its habits until thoroughly roused and

Fig. 20.—Coral Snake.

infuriated. For a creature of this kind some advertisement
of its deadly qualities is most useful. The poisonous snakes
are, perhaps, not as a rule brilliantly coloured, but there are
plenty of exceptions to this rule: the deadly Elaps of Central
and South America (fig. 20) is ringed with black and red,
and thus furnishes another example of the common plan of
coloration and the often similar colours which are utilised for
warning purposes. This has been emphasised by Mr. Poulton.

182 ANIMAL COLORATION.

One of the pelagic sea snakes belonging to the genus
Hydrophis* is similarly ringed with black and yellow ; these
slender serpents, which often grow to a considerable length,
are extremely poisonous, but not generally so conspicuously
coloured. On the other hand, the common English viper,
the Puff adder, the Fer de lance, and the Rattlesnake are
rather protectively coloured, if anything ; and the accounts of
travellers abound with instances of the narrow escapes they
have had from the invisibility of these reptiles. Mr. Salvin
has described a green tree-viper from Guatemala.f Warning
colours in snakes, as in other animals, have not been brought
about to assist them in impressing human beings with their
venomous nature; they have to contend with much more
important foes than our own species, but these cannot be said
to be very numerous.

There are a few snake-eating birds, such as the Secretary
bird and that large Australian kingfisher called the Laughing:
Jackass. The Ground hornbill of Africa will also eat serpents.
Among mammals the mongoose is an enemy to snakes, and
Swine are said to be impervious to the poison of the rattle-
snake and other venomous serpents, which they will kill and
devour ; but their immunity from the effects of the venom has
been denied. In India the formidable Ophiophagus lives, as
its name denotes, upon snakes; and it will kill and eat a
cobra with perfect indifference.

There does not, therefore, seem to be so much need for
warning colours among poisonous snakes as in other groups :
snake-eating animals seem to disregard the bite of the snake,
either because it produces little or no effect upon them, or
because they possess special means of defence against the bite;

* See Trans. Zool. Soc., vol. II., Plate 56.
t Proc. Zool. Soc., 1860, p. 457.

WARNING COLORATION. 183

the thick coating of fat of the hog, and the feathers of the
Secretary bird, protect these animals from the serious conse-
quences of meddling with a poisonous serpent. A protective
coloration would be much more useful to the snake, and the
very fact that poisonous serpents are generally not unlike their
environment is in accord with this opinion.

Warning Coloration in Amphibia.

Warning colours are also known among the Amphibia. The
brightly coloured frog discovered by Mr. Belt in Nicaragua,
was avoided by ducks and other creatures that habitually or
occasionally devour frogs. A singular combination of warning
and protective coloration has been believed to be shown by
the little European Fire-bellied toad (Bombinator igneus) ;
it is small and inconspicuous, being of a dusky greenish-grey
colour upon the back, like many other toads, but the under
surface is bright orange red, whence the name of the animal.
If annoyed or interfered with in any way the Bombinator turns
upon its back, displaying its brilliantly coloured under parts to
the reputed discomfiture of the assailant ; it has, at any rate,
been figured in this position.

Mr. Poulton draws attention to the contrasting colours of
the salamander (Salumandra maculosa), and suggests that it
probably possesses some disagreeable attribute. It may be
remarked incidentally that both this and the last-mentioned
amphibians may be usually seen in the reptile house at the
Zoological Gardens.

The salamander is black and yellow—a combination of
colours so often seen in distasteful or poisonous animals.*

* In wasps, hornets, certain flies which resemble wasps, the larva of

the Cinnabar moth, the Heloderm lizard, a species of sea snake, Magpie
moth, etc.

184 ANIMAL COLORATION.

Mr. Poulton thinks that the frequent recurrence of this type
of coloration may be particularly advantageous, as it assists
enemies of the animals so coloured in learning easily to avoid
them. This is a very interesting suggestion, and seems highly
probable.

Mr. Howes * relates an experience in keeping certain am-
phibians, which is decidedly confirmatory of the poisonous
nature of the salamander. A small frog (Xenovus levis),

Fig. 21.—Salamander.

which is interesting as being in some points a connecting
link between the tailed and tailless amphibians (frogs and
newts in the broad sense), was kept in a vessel with a
salamander ; one morning both creatures were found appar-
ently dead, the frog covered with a quantity of its own
secretion and the salamander showing evidence that it had
been trying to swallow the former; the frog ultimately
recovered, but the salamander was quite dead.

This tragical history seems to show that both creatures

* Zoologist, Aug. 1891.

WARNING COLORATION. 185

can secrete a poisonous substance, but it points to the more
deadly properties of the frog’s skin. It is well known that
the skin of the common toad prodnces a secretion which will,
if injected into the body of a fowl, cause death. This was
proved by the late M. Paul Bert ;* it is probably common
among Amphibia, but does not necessarily lead to their being
refused as food. Even toads are taken by certain birds, as
I have myself proved, though the toads were not perhaps
relished so much as frogs are. -Yevopus is not a more con-
spicnous animal than the common toad ; they are apparently
both instances of a disagreeable quality being concealed by
a well-protected exterior. The small newt is also eaten by
several birds, but with no particular signs of enjoyment.

Bright Colours not always used as a Warning.

Although it has been proved, particularly among cater-
pillars, that a conspicuous coloration is often a mark of
inedibility, this is thought to be not always the case; 1 do
not now refer to brilliant colours, distinction of sex, or what
has been thought to be the result of sexual selection,—this
part of the subject will be gone into later.

Mr. Savile Kent, in a very interesting presidential address
to the Royal Society t of Queensland, relates an instance of
commensalism between a fish and a sea anemone. Com-
mensalism, it should be said, is a term used to express a
kind of parasitism where the parasite recompenses its host
for favours received by material benefits rendered in return.
Among the coral reefs in the neighbourhood of Thursday
Island an enormous sea anemone occurs; it is at least two

* Prof. Howes informs me that he has repeated-the experiment, and
verified Paul Bert’s results.

+ Nov. 22nd, 1891. For the loan of this pamphlet I am indebted to
Prof. Howes.

186 ANIMAL COLORATION.

feet. across the disc when fully expanded. In the interior—
in the gastral cavity, that is to say—of this gigantic polyp
there is often a small fish belonging to the species Amphiprion.
percula.

When this fact was first observed it was thought that the
occurrence of the fish in the interior of the polyp was simply
a preliminary to its being digested by the latter. Mr. Kent,
however, found that the fish when dislodged by a stick
invariably returned to its singular dwelling-place, apparently
oblivious of the danger likely to result from a contact with
the stinging arms of the anemone. The fish is very brightly
coloured, being “of a brilliant vermilion hue, with three broad
white crossbands.” Mr. Kent suggests—and the idea is very
plausible—that benefits are mutually conferred by this habit.
The fish, being conspicuous, is liable to attacks, which it
escapes by a rapid retreat into the sea anemone; its enemies.
in hot pursuit blunder against the outspread tentacles of the
anemone, and are at once narcotised by the “thread cells,”
shot out in innumerable showers from the tentacles, and
afterwards drawn into the stomach of the anemone and
digested.

The plausibility of this very interesting suggestion is in--
creased by the fact that there is a similar association between
an allied species of anemone and a prawn. Singularly
enough, the prawn has a plan of coloration similar to that
of the fish. The reason for this is not at all apparent, and
Mr. Kent is unable to offer any explanation of the similarity
of the colours and coloration of the two animals. He
believes, however, that in both instances the active animals
play the part of a lure to attract prey within reach of the
motionless anemone, and in return get protection.

This suggestion is of course quite at variance with any

WARNING COLORATION. 187

theory of warning colour in the fish or prawn ; and, though
the matter clearly requires further investigation, it is at least
probable.

It is likely that other cases of brilliant coloration may
have a similar signification.

The remarkable Mantis, first described by Mr. Wood Mason
and figured by Mr. Poulton, may be an instance to the point.
Both Mr. Wallace and Mr. Poulton * dwell upon the form re-
semblances of this insect to an orchid, as well as its colour
resemblances. These are, it must be admitted, not a little
striking. The proximal joints of the limbs are flattened and
radiate out from the body like the petals of a flower, which
they also simulate in their pink coloration. It has, however,
yet to be proved that insects have any definite perceptions of
form. A white butterfly will, as Messrs. Geddes and Thomson
remark,f “ fly naively to a piece of white paper on the ground,”
evidently influenced by its colour alone.

In the vegetable world bright colours appear to me to have
an attractive rather than a repellent function. The red berries
of the service tree and other shrubs are much sought after,
as any one can prove, by birds. The advantage of this to
the plant is supposed to be the dissemination of the seed ; it
has been proved experimentally that the seeds of many plants
will pass uninjured through the alimentary tract of a bird,
being still perfectly capable of germination. It was Mr.
Grant Allen, I think, who made the ingenious suggestion
that poisonous berries secured a twofold advantage by their
bright colours: the seeds are disseminated, and the death
of the bird provides abundant manure for the plant when it
pushes its way out of the seed coats.

* “The Colour of Animals,” p. 7+.
+ “The Evolution of Sex,” p. 28.

188 ANIMAL COLORATION,

Mr. Poulton admits the attraction of bright spots and
patches upon animals, which may serve two purposes: they
may either ure on insects to their destruction, or may direct
attention to less vital parts, and so serve as a protection.

Instance of Alluring Coloration in a Lizard.

As an instance of the former may be cited a lizard which
is to be seen at the College of Surgeons Museum. This
creature is protectively coloured, being like the sand in which
it lives; but a fold of skin at each corner of the mouth is
“produced into a flower-like shape, exactly resembling a little
red flower which grows in the sand.”

Both Mr. Stewart and Mr. Poulton believe that insects are
deceived by what they think is a flower, and approach the
lizard only to fall victims to their lack of intelligence.

While agrecing with these naturalists as to the probability
of such events happening (they have got to be proved, how-
ever), I would lay stress rather upon the bright colour than
the likeness to a flower, which I should not venture to describe
as “exact.”

Other Examples of Alluring Colours.

It is said unat the brightly coloured crests of many birds
act’ in the same way as a lure: here, of course, there can
be no question of any special resemblance to a flower. It
is well known that many insects are attracted by the droppings
of animals. Mr. Forbes discovered in Java a spider which
showed the mest marvellously detailed resemblance to the
excreta of a bird ; this will be admitted by any person who will
refer to the figure of the insect in the paper quoted on p. 110.

The supposition is that the spider profits by this resem-
blance and secures an ample harvest of insects. ‘The whole
combination of habits, form, and colouring,” says Mr. Poulton,

WARNING COLORATION. 189

“affords a wonderful example of what natural selection can
accomplish.” The very same resemblance, though serving a
different purpose, is shown by several greyish white moths,
such as the common Carpet moth, so abundant in gardens ;
these insects rest with their wings expanded and pressed against
the leaf, and are by no means unlike the excrement of a bird
which has fallen from a height and been therefore flattened

Fig. 22.—Fishing Frog.

out. Mr. J. P. Barrett * has also compared the young cater-
pillar of the rare Alder moth (lcvonycta alnz) to the dropping
of a bird. In these cases the theory is that the resemblance
protects the insects from birds.

To return to the subject of the attraction of special markings.
Mr. Poulton includes among his instances of “ Alluring Colora-
tion” which have been quoted above the waving tentacles of
the Fishing frog (see woodcut, fig. 22); the fish is provided

* Entomologist, vol. x., p. 238.

190 ANIMAL COLORATION.

with a number of tentacles on the head, which wave about
and attract little fishes into the neighbourhood of the
creature’s immense mouth. It has been suggested that a
little vibratile tag in the mouth of the Terrapin Macro-
clemmys Temminki serves a similar purpose: but these in-
stances do not strictly come within the scope of a book
devoted to Animal Colours.

Bright-coloured patches may also, it is thought, play an
important part in diverting the attention of an enemy to the
less vital parts of its prey.

Of such use are the eye-like markings on the wings of
the Peacock butterfly, and, Mr. Poulton thinks, the bright-
coloured under wings of certain moths like the Red and Yellow
Underwings.

The last-mentioned insects are often captured showing
mutilations of the hind wings, implying that they have only
just escaped at the expense of these wings. It may be
remarked, however, that the reason for this may be not
necessarily the bright colour of the hind wings first attracting
the attention of the bird.

The Yellow Underwing when disturbed flies rapidly, and
more or less in a straight line. I have observed one of these
moths hotly pursued by a band of sparrows, who joined in the
chase after the moth had got a little start : it must have been
a little time before they came up with it; if the bird made
a peck at the moth flying just in front of it, there would
be a considerable chance of its touching the hind wings first,
whatever their colour might be.

It is, moreover, not at all safe to make any such generalisa-
tions with regard.to eye-like markings, even if it be admitted
that those upon the wings of the “ Peacock ” have the useful
function which has been assigned to them. The John Dory

WARNING COLORATION. 191

has a pair of curious marks—the thumb-marks of St. Peter,
according to the legend—on each side of the body; these can
hardly be seen in the fish when exposed for sale in a fish-
monger’s window, but are very conspicuous during life. An
enemy, whose attention was drawn to these spots, would
inflict a very serious injury upon the fish if it attempted to
take a bite at this place. So, also, with regard to the bright
eye-like markings upon a species of shrimp figured * a good
many years ago by the late Mr. Spence Bate.

It will be noticed that some of these instances of attractive
coloration are absolutely opposed to the theory of warning
colours; this is, of course, especially so with the Yellow Under-
wings. In these moths the black bands upon the yellow
ground-colour present us with precisely that contrast of colours
which is believed to be so efficacious in protecting the wasp
and the Cinnabar Moth caterpillar from being interfered with.
This is a serious dilemma. Any one ignorant of the fact that
the Yellow Underwing is quite palatable to, or at any rate
pursued by, birds, would regard the insect as affording a
remarkable combination of protective and warning coloration;
the warning colours, it might be argued, are displayed only
after the protective colours have failed to play their part with
enough success.

Bright Colours and Large Size of the Fins in Certain Fish may
have a Protective Value.

At the moment of writing there are a number of specimens
of one of the most beautiful of British fishes—the grayling—
in the fish house at the Zoological Gardens. The beauty is
chiefly in the fins, which are of large size and shot with iri-
descent green and red. They remind one, in a very striking

* Proc. Zool. Soc., 1863, Pi. XL, fig, 1.

192 ANIMAL COLORATION.

way, of a butterfly’s wing, and it is just possible that they
may play an analogous part in protecting the fish from its
foes. It has been already mentioned that the butterflies’
wings may be in some cases an actual defence, on account of
their very conspicuousness; they may divert attention from the

Fig. 23.—Flying Gurnard.

more vital parts. So, in the case of the grayling, a young and
inexperienced pike may make a futile attack upon the con-
spicuous waving fins, and thus give the grayling time to escape
before the attack can be renewed.

The large and brightly coloured fins of other fishes, for
example of the species depicted in the woodcut (fig. 28), may
be very possibly used for a similar purpose.

CHAPTER V.
PROTECTIVE MIMICRY,

Mr. Bates’ Theory.
Tur theory of warning colours is believed to obtain very
strong support from a series of remarkable facts of which
an adequate explanation was first offered by Mr. Bates.*

This naturalist spent many years in South America, being
principally engaged in studying the Lepidoptera of that
country. Among the most abundant butterflies in the
Amazonian region are those of the family Heliconide ; the
prevailing pattern of these insects’ wings is shown in the ac-
companying woodeut (fig. 24). The contrast between yellow
and black suggests at once that they belong to that group
which are protected from attack through being distasteful :
this suggestion is, to a certain extent, borne out by Mr. Bates’
observations. He found in the first place that they could
secrete from certain glands in the abdomen a disagreeably
smelling fluid ; it does not, however, follow from this fact
alone that the buttertlies would prove disagreeable to the
palate of a lizard or a bird: many animals are attracted by
odours which to us appear in the highest degree objectionable.
An attentive observation of the butterflies convinced both
Mr. Bates and Mr. Wallace that they were avoided, or at

* Transactions of the Linnean Society, Vol. xxiii.

13

194 ANIMAL COLORATION.

any rate not pursued, by birds and other creatures. The
late Mr. Belt found that a tame Cebus monkey invariably
rejected these insects when they were offered to him; occa-
sionally he went so far as to smell them, but they were never
tasted.

On the other hand Mr. Belt also discovered that the
Heliconias were hunted by a wasp, and that they exhibited
in the presence of their enemy a greater alertness than at

any other times.*

Fig. 24.—«, Leptatis Theonoe, var. Leuconoé (Pieris). 6, Ithomia Ierdine (the
mimicked Heliconius). (After Bates.)

Although the three naturalists whose observations have just
been quoted believed themselves justified in stating that the
Heliconide were not captured by birds, Fritz Miiller has
brought forward evidence which points to the opposite con-
clusion. He captured several Heliconide with pieces torn

* ‘Wasps appear, according to M. Plateau (Le Naturuliste, xii. p. 188),
to be exceedingly stupid and dull of sight. It is possible, therefore,
that their attacks upon the butterfly are simply caused by an incapacity
for comprehending the significance of its coloration.

PROTECTIVE MIMICRY. 195

out of their wings: sometimes the lacerations were symmetrical
on both wings thus indicating that the insect had been seized
when at rest with the wings folded together over the back.
Mr. Poulton has admitted that “there is, unfortunately, too
little direct experimental proof of the unpalatability of the
specially protected groups which are the chief models of
Mimicry.”

The observations of Fritz Miller must be set against those
of Bates, Wallace, and Belt ; they do not, of course, prove that
the species is eaten by birds, but they do prove that the
insect is occasionally pursued by birds. It is suggested by
Mr. Wallace that the injuries were produced by the attacks
of young and inexperienced fledglings ; this must obviously
for the present remain a suggestion.

In the same situations as those in which the Heliconias are
found there also occur, more rarely, specimens of butterflies
minutely resembling the Heliconias, but belonging to a per-
fectly distinct family—the Pieride. They belong to the two
genera Leptalis and Euterp., consisting of numerous species,
each of which shows a striking likeness to some one particular
species of //eliconia. This likeness is not a mark of near
affinity ;* it affects no important character, but only the
shape and coloration of the wings.

Now the Pieride, as a group, differ in these last-mentioned
characters from the Heliconidee; there is not, excepting in the
genera Leptalis and Luter, this remarkable superficial imita-
tion of the Heliconid type. These facts, therefore, evidently
require some explanation.

Mr. Bates suggested that the resemblance had been brought
about for the protection of the Pierids. It is obvious that
if a species which is perfectly eatable, and therefore yreatly

* This has, however, been denied.

196 ANIMAL COLORATION,

sought after by birds, should come to resemble an uneatable
butterfly, it might often be mistaken for it and so escape
destruction. Natural selection, it is thought, has acted upon,
the originally slight variations of certain Pieride, and produced
the often wonderfully close similitude to the Heliconidee which
we now sce.

Mimicry often found only in Females.

There are plenty of examples of this phenomenon, which is
occasionally confined to the female sex. It is more important
for the continuance of the species that the female insect
should be preserved; and, just as among birds we often
meet (see p. 258) with examples of protectively coloured
females and brightly coloured males, there are instances among
butterflies where the female alone shows a protective mimicry.
Mr. Trimen has described and figured an African “ Swallow-
Tail” in which the female is entirely without the “tails”
which are usually so conspicuous a feature of the group.
There are three distinct varieties of the female insect, each
of which mimics a particular form of Dancis occurring in the
same district. Danais is said to be an unpalatable butterfly,
and avoided on that account.

Are the Danaide strongly scented, like the Heliconide ?

It is not reasonable to lay much stress upon the fact of
insects possessing qualities which are disagreeable to our-
selves ; for it by no means follows that these same qualities
affect the enemies of the insects ; indeed, there is experimental
evidence that the reverse is the case. With respect to the
Danaide, Acraeide, and Heliconidie,—the typical families
which are models for mimicry,—Mr. Poulton says that “a
peculiar and frequently unpleasant smell has been noticed by

~

PROTECTIVE MIMICRY. 197

all observers who have studied these groups.” In view of this
statement, which certainly expresses the general opinion, it is
surprising to learn from Dr. Seitz that this is by no means the
case invariably—even with the species referred to by previous
writers. Dr. Seitz tested as many as fifty species of Danaids,
both African and American, but could not recognise the least
odour, disagreeable or otherwise: and a number of these
species were models for mimicry. It is clear, therefore, that
every one interested in the subject must test this matter for
himself and form his own opinion.

Distastefulness sometimes limited to a Few Individuals.

In some, but not in all, Heliconids Dr. Seitz found an
odour decidedly objectionable to human nostrils, which he
compares to that of naphthalin. In /feliconius beshit, a
species with a particularly evil odour, it was found that only
a few individuals were odoriferous, as is also the case with
our common lacewing fly, Chrysopy. If the odour is as
objectionable to birds and lizards as it is to us, it looks as
if the majority traded on the unpleasant reputation of the
few ; and that the odour is not persistent, but depends upon
some variable circumstance, such as food.

Resistent Structure of the Wings in Danaids an Additional
Defence.

The elastic structure of the wings in conspicuous butterflies
which Mr. Trimen first noticed, is a highly interesting fact.
The wings are often so flexible that they can be bent without
breaking.

Dr. Seitz has remarked in Tropical America that a species
of .lcer@u is constantly found with its wings much rubbed,
with the scales largely removed. He attributes this to the

198 ANIMAL COLORATION.

clumsy flight of the insect, which causes it to come against
obstacles instead of neatly avoiding them, as other butterflies
do who thread their flight among the most confused network
of branches of a tropical forest. It is a more obvious sugges-
tion that the wings of this insect have been rubbed through
contact with birds’ beaks—their elastic structure saving them
from breaking.

Dr. Seitz, however, particularly says that birds do not
attack this Acr@a ; he never saw a bird attack one of these
insects, nor observed their wings lying about on the ground,
as one sometimes (rarely, however, be it remarked) sees the
wings of lepidoptera in this country.

Another suggestion may be made to account for this rubbing
of the wings; and that is that they have been produced by
ineffectual attempts on the part of bats and nocturnal birds
to seize the insect. Now, butterflies are for the most part
diurnal in their habits, as the name “ Dzurni,” sometimes
applied to the group, attests; but they are not exclusively
so. I have myself seen butterflies on trees “sugared” for
the purpose of attracting moths, and I believe that this
experience is not uncommon. These instances are probably
due to exceptional circumstances, such as the proximity of the
resting-place of the insect to the sugared tree. But in Central
America Heliconids have been found lured into the towns by
the electric light ; and there seems to be some evidence for
the partially nocturnal habits of certain Heliconids.

If these Acrwas are not nocturnal, it is possible that they
pass the night on a leaf or tree trunk, and might often be
snapped at by a passing bat or goat-sucker. The particular
species of Aer@a which is referred to is normally covered with
scales, but there are other species whose wings are normally
nearly transparent.

PROTECTIVE MIMICRY. 199

This opens up an interesting question, which may be referred.
to parenthetically, as it does not strictly bear upon the matter
at hand. Dr. Seitz calls attention to the coincidence, but
does not pursue the matter farther. The question whether
mutilations are ever inherited has been hotly discussed ; the
inheritance has been affirmed and denied. A South American
bird, the Motmot, has the curious habit of plucking off the
barbs of some of the tail feathers, leaving only the tip un-
injured ; this produces a racket-shaped feather, which is very
characteristic of the bird. It is said that the young birds
have the tail feathers narrower in the middle where the barbs
are plucked out. It is difficult, however, to understand how
any alteration of a dead structure, as a feather is at the
extremity, could affect the living tissues and so produce in
course of time a modification. The same difficulty also occurs
in the butterfly, though it is perhaps not so great: the wing
is permeated with air-channels, and by blood vessels also,
which may possibly send minute branches to the “roots” of
the scales.

To return to the flexibility of the wings of Acrewids and
Danaids: this peculiarity is less important to distastefal
insects than it would be to protectively-coloured insects. It
would be undoubtedly a useful form of protection ; but if the
attacks of insect-eating creatures are so frequent as to haye
led to this modification, one is disposed to question the advan-
tage of the warning coloration.

Mimicry between Protected Forms.

The case of Leptalis Theonoe and Ithomia élerdinu, ilus-
trated by the woodcuts on page 14, is a typical case of
mimicry ; a sweet-tasting Lepfalis gains protection by imitat-
ing a disagreeably flavoured Ithomia. The mimicry is not,

200 ANIMAL COLORATION.

however, always limited to cases of this kind. Heliconias
belonging to different species or genera, often show such minute
resemblances as to suggest a mimicry ; and such facts, which
are numerous, do not appear at first to fit in with the theory
of mimicry. On the principle of utility it is easily intelligible
that an edible Leptalis would score a point or two in the battle
of life by being mistaken for an inedible Jthomia. But one
would have thonght that the inedible and highly conspicuous
Heliconide might each have traded on their own peculiarities,
without needing a mutual resemblance in coloration. The
method is one which should perhaps have been treated of in
the chapter devoted to “ Warning Colours” ; but itis impossible
really, to draw a hard-and-fast line between these two classes
of phenomena.

For instance, attention has been called to the fact that there
is a tendency among animals, which are believed to be pro-
tected by warning colours, to develop only a few patterns, and a
simple, striking coloration. The larve of the Fox moth, the
Cinnabar-moth, the adult wasp, and the wasp-like beetle
Clytus, agree in being marked with alternating rings of black
and yellow. Are we to call this mimicry ?

It is believed that the simplification of the colours and
patterns is brought about to diminish the difficulties which
insect-eating animals must experience in distinguishing eatable
from uneatable insects. The fewer the patterns and colours,
the more easily will the lesson be learnt. The amount of
“experimental tasting” will be reduced, and thus the insects
will profit. In the same way may perhaps be explained the
similarities among the Heliconide. But there is another
explanation : it is certain that no form of protection—neither
resemblance to surroundings nor warning colours—is absolutely
safe. (It is no objection to the theory that such colours have

PROTECTIVE MIMICRY. 201

originated by natural selection to be able to show this ; at the
same time the amount of protection given must be carefully
inquired into. There is too great haste in assuming that
because an insect is like a leaf or a twig it must be greatly
protected by this resemblance ; and that another is nauseous,
and let alone on account of its warning coloration ; and where
experiments have been made, they have been very few.)
Hence insect-eating birds and reptiles must take a certain toll
of even the most warningly-coloured butterflies, before they
learn, by unpleasant experience, to associate bright colours and
a bitter taste.

Now, if this be the case, it is clearly advantageous to the
insects that these depredations should not be confined to a
singl.. species ; one species might be entirely obliterated, par-
ticularly if it was rare to begin with, by these experiments.

On the other hand, if the necessary amount of destruction
were divided between, say half a dozen different species, the
loss to each species would be comparatively trifling. The
need for co-operation is quite evident. It will be noticed, how-
ever, that this explanation presupposes, not so much a general
association between warning colours and disagreeable taste
in the minds of birds, as a particular recognition of certain
patterns and colours, which have to be learnt by vach bird, and
are not hereditary impressions.

This is not altogether in accord with some of the experiments
given on page 164. If the reader will turn to that page, he
will find there recorded that certain birds objected strongly to
certain caterpillars, which they could not possibly have seen
before.

Mr. Scudder has suggested a third way of explaining this
mimicry among mimicked species. There are, no doubt,
various degrees of distastefulness among disagreeably-flavoured

202 ANIMAL COLORATION.

animals. More birds and reptiles, for example, will eat the
caterpillar of the large Garden White Butterfly than will eat
the larva of the Cinnabar-moth ; and this latter, in spite of its
more conspicuous colours, is apparently, if there is any difference,
less objectionable on the whole than the Gooseberry caterpillar
(Abraxas grossulariata). Tf there are these differences we
might be justified in putting down the mimicry of the dis-
tasteful Heliconius eucrate by the also distasteful Mechanitis
lysimnia, as a case of mimicry between a highly disagreeably-
flavoured insect and a relatively palatable one.

Mimicry between Insects belonging to Different Orders.

Mimicry among insects is not, however, confined to a more
or less close resemblance betweeu individual species of allied
families, as in the examples already selected. Perhaps the
most striking facts concern the resemblances between insects
belonging to quite different orders.

In this country there are a number of moths—popularly
termed Clearwings—which would be taken by the uninitiated
for wasps and flies. The wings are but slightly covered with
scales, and the body is often banded with yellow. It has even
been stated that some of the species, when handled, writhe the
abdomen as if about to sting. It has been stated that some
species at any rate give off the characteristic odour of hornets.
In spite of this superficial resemblance to various species of the
orders Hymenoptera and Diptera, the Clearwings undoubtedly
belong to the Lepidoptera. Some instances of mimicry among
the Clearwings—in some respects even more striking than is
afforded by the British species—have been lately described
in the Transactions of the Entomological Society ;* one or

* In a paper by Col. Swinhoe, 7'rans. Ent. Soc., 1890.

PROTECTIVE MIMICRY. 203

two of these species cannot fail to impress the reader with
their bee-like form.

These resemblances, undoubtedly striking though they are,
must be discounted by the fact that the whole family of Clear-
wings have a general resemblance to Hymenoptera.*

Dr. Seitz has published from a diary kept in Brazil a number
of interesting cases of mimicry among Lepidoptera.

A species of Trichiura closely resembles an ichneumon fly ;
the ichneumon in question has brownish wings, with a yellow
spot on each ; the wings are kept folded against the body
when the insect is settling upon a leaf; the Lepidopteron gets
the same appearance by an altogether different method, which

Fig. 25.—-Hornet Clearwing.

is most remarkable, and exceedingly suggestive of purely
adaptive mimicry. The wings are nearly transparent, but while
they are kept closely pressed against the body they appear
brownish (the colour of the body), and a yellow spot upon the
abdomen is seen through the transparent wings, and thus pro-
duces a precisely similar effect to a spot wpon the wing, which
occurs in the mimicked ichneumon. The ichneumon has, of
course, its long ovipositor with two sheaths, or rather the two
halves of the sheath ; these are imitated by three processes in

* Mimicry has even been the cause of mistakes in entomology, the
mimicking species having been occasionally confounded with the mimicked.

204 ANIMAL COLORATION.

the other insect, which has given it its name of Z'richiura *
(Thread-tail).

Dr. Seitz also describes tf a Humming-bird Hawk moth,
which closely imitates a particular hnmming-bird. The re-
semblance, although clear cnough to our eyes, does not deceive
the insect ; for it makes no attempt to pair with the humming-
bird. And it is notorious that insects are sometimes deceived
into believing an insect of a different species to be a suitable
mate.

If the insect, with its hmited and imperfect vision (see p. 228)
is proof against a deception which is enough to strike an
observant naturalist, would birds be ?

A more remarkable case still is perhaps that of a Sesiid
belonging to the genus J/clitta. The singular resemblance
which the Sesiide, or Clearwing moths, bear to various Hymeno-
ptera and Diptera is a fact which almost every one can have
the opportunity of verifying, since one or two species are fairly
common—S. tipuliformis very common. But the Sesiida, as
a rule, are not active in their habits ; they have a fondness for
sunning themselves upon leaves. This J/eltta, which Dr. Seitz
observed, resembles an Anthophora, not only in colour, but in
habit. Contrary to what is generally found in the Sesiide, this
particular insect hovers in front of a flower just like the bee,
which it mimics, does.

Mr. H. O. Forbes, in his * A Naturalist’s Wanderings,”
notes the mimicry of a dragon-fly by a butterfly, Leptocircus
ciresccens 3 the butterfly was captured on the margin of a small

* It is suggested by Kirby and Spence (‘* An Introduction to Ento-
mology,” 7th edition, p. 473) that these processes serve as a kind of
rudder to assist them when flying. We get, therefore, a clue to their
origin quite apart from mimicry.

+ Stettiner Lint. Zeitschrift, 189), p. 28.

PROTECTIVE MIMICRY. 205

stream, among a crowd of dragon-flies. “It flits over the top
of the water, fluttering its tails, jerking up and down just as
dragon-flies do when flicking the water with the tip of their
abdomens. When it settles on the ground it is difficult to see
as it vibrates, in constant motion, its tail and wings, so that a
mere haze, as it were, exists where it rests.”

Unprotected Insects sometimes Mimicked by More than One
Species.

It is not invariably the case that a given insect which
possesses asting, or some other means of defence, has only one
mimicker. Very often quite a large number of insects have
sheltered themselves under the protection afforded by a re-
semblance to one particular insect ; thus, according to Dr. Seitz,
Apis mellijica, the common hive bee, is imitated by no less
than five species of harmless insects.

Mimicry of Vertebrates by Insects, and of Insects by Vertebrates.

A more fanciful case of mimicry, as it appears to me, is one
communicated to Nature by Mr. &. E. Peal. A caterpillar
found in Assam, when suddenly surprised, erects its head in
an attitude strongly suggestive of a shrew, probably the very
animal that preys upon it.

The resemblance is caused by two lateral prolongatious, and
a pointed tip to the head; these, when lifted in the peculiar
attitude assumed, simulate cars and a long muzzle, while the
mouth parts in profile look like the mouth of a vertebrate.

It seems very unlikely that a shrew, with a strong odour,
and power of perceiving it in other animals, would be taken m
in this ready fashion ; and even if it were, shrews are a pug-
nacious race, and the caterpillar might not gain much by the

deception.

206 ANIMAL COLORATION.

These instances, and many others which have been quoted,
savour of such fanciful resemblances as were detected by
naturalists of the sixteenth and seventeenth centuries between
animate and inanimate objects.

A flying lizard (Draco sp.) found in the island of Mindanao,
by Mr. J. B. Steere,* is compared by that naturalist to a
butterfly ; the wing membranes are coloured blue and red,
and it is suggested that this mimicry of a butterfly may aid
the lizard both in escaping its enemies, the hawks, and in
capturing its own food of insects.

Mr. Wallace’s Statement of the Conditions under which
Protecting Mimicry occurs.

All the examples of mimicry that have been given in the
preceding pages fall within the definition given by Mr. Wallace,
which is as follows :

(1) That the imitative species occur in the same area and
occupy the same station as the imitated.

(2) That the imitators are always the more defenceless.

(3) That the imitators are always less numerous in indi-
viduals.

(4) That the imitators differ from the bulk of their allies.

(5) That the imitation, however minute, is external and
visible only, never extending to internal characters or to such
as do not affect the external appearance.

Objections to the Theory of Mimicry.

Although the sufficiency of this ingenious theory appears at
‘first sight to be obvious, a number of objections suggest them-
selves on further reflection.

* “Six Weeks in Southern Mindanao,” American Nuturalist, April 1888.

PROTECTIVE MIMICRY. 207

An objection which strikes at the root of the whole matter
has been combated by Mr. Belt. I quote the passage which
relates to the matter in full :—

* The extraordinary perfection of these mimetic resemblances
is most wonderful. I have heard this urged as a reason for
believing that they could not have been produced by natural
selection, because a much less degree of resemblance would
have protected the mimetic species. To this it may he
answered that natural selection not only tends to pick ont
and preserve the forms that have protective resemblances,
but to increase the perceptions of the predatory species of
insects and birds, so that there is a continual progression
towards a perfectly mimetic form. This progressive improve-
ment in means of defence and attack may be illustrated in this
way. Suppose a number of not very swift hares anda number
of slow-running dogs were placed on an island where there
was plenty of food for the hares but none for the dogs, except
the hares they could catch, the slowest of the hares would be
first killed, the swifter preserved ; then the slowest-running
dogs would suffer, and, having less food than the fleeter ones,
would have least chance of living, and the swiftest dogs would
be preserved : thus the fleetness of both dogs and hares would
be gradually but surely perfected by natural selection, until
the greatest speed was reached that it was possible for them
to attain. I have in this supposed example limited myself to
the question of speed alone: but, in reality, other means of
pursuit and escape would come into play and be improved.
The dogs might increase in cunning, or combine together to
work in couples or in packs by the same selective process ;
and the hares, on their part, might acquire means of conceal-
ment or stratagem to elude their enemies; but, on both sides,
the improvement would be progressive until the highest form

208 ANIMAL COLORATION.

of excellence was reached. Viewed in this light, the wonderful
perfection of mimetic forms is a natural consequence of the
selection of the individuals that, on the one side, were more
and more mimetic, and, on the other (that of their enemies),
more and more able to penetrate through the assumed dis-
guises.”

If the few instances of mimicry given in the preceding
pages were typical of the colour and form resemblances that
exist between animals not showing any special affinity, no
other theory than that of Mr. Bates could be considered, and

its truth would be very convincingly shown.

Resemblances among more or less remotely Allied Animals which,
perhaps, cannot be put down to Mimicry.

But these instances are only a part of a much wider series
of resemblances between more or less remotely allied forms ;
they are only the extreme cases. Nuch resemblances have
been long familiar to naturalists, and they cannot be ex-
plained on the theory first suggested by Mr. Bates.

Many of the cases of mimicry, which fall within Mr. Wallace’s
definition, show a resemblance in form as well as colour and
markings between two otherwise <lissimilar creatures.

Resemblances in form alone may exist, and have given risc
to erroneous systems of classification on the supposition that
external form implied affinity. Belon and other naturalists
before and after, classified the Whales among fishes ; while
there are several Lizards, of which our common blindworm
is a familiar example, and the Amphisbaena, which have a
snake-like habit.

No doubt these animals, in departing from the form
characteristic of their nearest allies, and acquiring that of
more distantly related species, have simply yielded to the

PROTECTIVE MIMICRY. 209

influence of their surroundings: the fish-like form of the
whale is more suited to progression through the water ; it is
possible that the blindworm can more easily force its way
through the tangled stems of a hedge or through dense
herbage, owing to its snake-like form. Causes of this kind
may possibly have had a share in producing these form re-
semblances that are seen in true mimicry. The genus Leptalis,
for example, among the Pieridze, imitates the Heliconide not
only in its colour markings, but also in the form of its wings,
departing in both particulars from most of its immediate allies.
The similarity of flight between these butterflies, upon which
stress has also been laid, is of course a consequence of the similar
conformation of the wings.

If Leptalis and Euterpe were the only genera of “ Whites ”
which showed this deviation from the normal wing structure
in the direction of the Heliconide, the assertion that this
was due to causes other than natural selection producing a
resemblance for the sake of protection, could hardly be sub-
stantiated.

But we have in this country a white butterfly—the Wood
White (Leucophasia sirepis)—in which the male has the fore
wings terminating in a somewhat pointed outer extremity, but
in which the female has oval wings by no means unlike those

of various Heliconide.

Instances of Developing Mimicry in Butterflies.

In the genus Zeptalis and some allied genera, the bulk of
the species not only show a general resemblance to the pro-
tected Heliconid, but are like particular forms. But there
are other examples of mimicry in which one particular species
differs from its congeners, and is coloured after the same

14

210 ANIMAL COLORATION.

pattern as some poisonous or uneatable creature. A re-
markable instance of this is the genus Pasilarchia among
North American butterflies : with one exception the species
are dark-coloured with blue spots round the margins of the
wings ; the exception is B. hipparchus, which has a tawny
brown colour diversified by black bands and marks. This
butterfly almost exactly copies Anosta plerippus*; the re-
semblance is more striking in this and some other similar
instances from the very fact that it is only ove out of a number
of species which is coloured after the pattern of an insect
belonging to another family, and in acquiring this coloration
has departed widely from the plan of colour found in its
immediate relatives. On the theory of mimicry we interpret
this divergence as due to natural selection ; and if an insect
is found whose coloration is strikingly unlike that of its allies
we immediately assume that some other species will be found
which it imitates. This assumption, however, is not always
borne out ; and the existence of such forms constitutes to a
certain extent a difficulty in the way of accepting the currently
received theory of mimicry : if a divergence from the normal
style of colour and marking does not always go with the
existence of a prototype belonging to a different genus or
group, a certain amount of doubt is thrown upon the validity
of the explanation in other cases where there is a prototype.
This difficulty has been suggested, and has been grappled with,
by Mr. Scudder in his magnificent work upon American
Butterflies to which I have so often had, and shall have,
occasion to refer. He quotes two suggestions with reference
to the matter: the first is the obvious one that the prototype
which is imitated does exist, but has not been found ; this
explanation is easy to make and difficult to disprove. Another

* I follow Scudder'’s nomenclature of the species.

PROTECTIVE MIMICRY. 211

suggestion is that the prototype did exist—z.¢., that it has now
become extinct ; the mimicking form has established its
position by the help of its vanished model, and by its great
numbers is able to carry on the deceit, just as a dishonourable
firm may trade for a time under an old-established name no
longer represented in the firm. This again is a suggestion
which is easier to make than either to prove or refute.

The third explanation is the most satisfactory: Mr. Scudder
believes that in such cases we have a general mimicry in course
of formation into a special mimicry,—that is to say, the
mimicking insect has got so far as to bear a certain likeness to
the members of another family or genus, but as yet has not
acquired a particular resemblance to any one species of that
genus or family. The general resemblance might in the
meantime profit the insect. Arge galathea, a butterfly which
bears a certain likeness to the Whites, may be such a case ;
it is not particularly like any one species of White; but a
comparatively slight change in the relative amount of the
black and white in its wings would certainly cause a close
resemblance to any of the Whites. The “ Gate-Keeper” or
“ Wall Butterfly ” is possibly another example: it has the rapid,
strong flight of a Vanessa, and is not altogether unlike the
“ Small Tortoiseshell.”

In the earlier periods of the earth’s history reptiles were
no doubt the principal enemies with which butterflies had to
deal ; considering the obtuseness of modern lizards (see “ Ex-
periments on Warning Colours,” p. 153) to the most glaringly
obvious warning colours, and the possibility that the ancient
lizards were, if anything, still less discriminating, it is probable
that the butterflies of that time trusted more to protective
resemblance than to any other way of escaping their foes.
With the advent of birds, keen-sighted and apparently more

212 ANIMAL COLORATION.

delicate in their taste than lizards, came the necessity for
warning coloration and its concomitant mimicry. If we believe
that mimicry is a comparatively new phenomenon, it is reasonable
also to believe that it is still developing under our eyes.

A closer resemblance still is shown between the Common
Blues (Lycena argus and /. agestis—in the case of the former
species the female only)—and the type of coloration shown by
some of the “ Ringlets” (77. cassiope, for instance).

The “Merveil du Jour” (Agriopis aprilina) closely re-
sembles the “Scarce Merveil du Jour ” (Diphthera orion). It
is no doubt a matter of opinion, but I should be inclined to
regard this likeness as being quite as close as that between a
species of Papilio, and a species of Dangis figured by Mr.
Poulton.* The very names of these two moths imply a
likeness, and yet they appear in different months !

This particular case might be, doubtless, explained by sup-
posing that the two insects have been coloured after one
pattern, the model being afforded by a green lichen ; their
resemblances to each other would be thus due to their re-
semblance to a common object. Certain recognised cases of
mimicry may possibly be explicable in an analogous way.

Difficulty of distinguishing between Mimicry and Warning
Coloration.

It has been pointed out that the Danaide, themselves an
uneatable race of butterflies and models for mimicry, resemble
in South America the uneatable Heliconide ; some of the
Danaidz of that country are spoken of as Heliconoid Danaide
on that account. This, it is believed, is not a case of true
mimicry ; it would not fulfil any of the conditions (p. 206) of
true mimicry. The resemblance is supposed rather to be like

* “The Colours of Animals,” Plate I,

PROTECTIVE MIMICRY. 213

that which is seen between various other unpalatable animals.
Stress has been very justly laid upon the prevalence of such
strongly contrasted colours as yellow and black among un-
eatable caterpillars, which are, moreover, disposed in more than
one form in alternate rings. This tends to the advantage of
the insects, for their enemies have to learn fewer colours and
patterns, and thus are less likely to make mistakes, than if the
lesson to be learnt were an excessively complicated one.

It is just possible that this principle may be also applied to
the mimicking Pierids. The general belief appears to be that
these insects are sweet and palatable ; but I find in Scudder’s
“ Butterflies of New England ” the observation quoted that the
females of two genera of Pierids—viz., Melite and Callidryas
—have similar organs to those of the Heliconide which secrete
a strongly odorous substance. Even ZLepftal’s, one of the
mimicking genera of Pierids, gives off an odour which, ac-
cording to Miiller, ‘is disagreeable to human noses.” It may
be that the primary object of these to us disagreeably smelling
substances is to attract the opposite sex; but the same sugges-
tion might, of course, be offered as explanatory of the scent ot
the Heliconide. Mr. Poulton has expressed the opinion that
no hard-and-fast line can be drawn between sexual and warn-
ing colours: the same brilliancy which delights the female
insect or bird may, it is thought, warn off an enemy. Perhaps
the same idea may be extended to embrace sexual attraction
due to the secretion of strongly smelling substances; these may
also serve the same double purpose.

Butterflies more attacked by Birds in the Tropics than in
. Temperate Regions.
In this country butterflies are not greatly persecuted by
birds ; moths are—when they are to be found ; but a moth has

214 ANIMAL COLORATION.

generally a larger, softer, body than a butterfly, and is in con-
sequence more worth eating than a butterfly, which is chiefly
wing. It is stated that in the tropics butterflies are greatly
sought after by birds. But even in temperate regions they are by
no means entirely avoided. Prof. Eimer * relates the following
incident which bears upon the matter :—“ Some years ago...
on a hot summer’s day, I was on the high plateau of the
Swabian Alp; far and wide no water was visible, but at one
spot in the field path there ran over it the outflow of a
little spring, forming a shallow, clear pool in the track. Here
sat hundreds of butterflies, all whites and blues, closely crowded
together, drinking thirstily, On my approach a number of
birds (stone chats) flew from the spot, and when I came up I
found a number of maimed butterflies lying fluttering on the
ground ; pieces had been bitten from the wings of most of
them—indeed, the wings were often torn to pieces before the
birds succeeded in getting the bodies of the butterflies, although
hese were sitting quietly on the ground.”

Mimicry possibly Originated between Forms much alike to

start with.

If it be difficult to understand how the wonderfully perfect
copying of one insect by another—that “palpably intentional
likeness that is perfectly staggering,’ as Mr. Bates wrote in
an oft-quoted passage—has been brought about, it is harder
still to understand the first commencement and the early
stages of the development of the mimicry. Probably, however,
mimicry is always based upon a considerable initial resem-
blance.

To take, for example, the classical instance of mimicry, that
of the Heliconide by the Pieridae; the typical Pierid (our

* “Organic Evolution,” Fng. trans. by Cunningham, p. 118.

PROTECTIVE MIMICRY. 215

common Whites, Clouded Yellows, Brimstone, etc)., is totally
different from the Heliconide, not only in colour but in the
shape of the wings ; the Wood White, however (Leucophasia
sinapis), presents a certain likeness to the Heliconide in the
shape of the wings, and also in the comparative feebleness of
its flight—a circumstance which will perhaps cause its extinc-
tion in the future. The feeble flight is perhaps a necessary
concomitant of the shape of the wings ; it is not at all needful
to believe—the suggestion has been made—that the genus
Leptalis imitates the Heliconide in its wretched powers of
flight as well as in the form of the wings and their markings ;
it is much more likely the insect is a poor flyer on account of
the shape of its wings, and that this very circumstance rendered
the mimicry necessary as an alternative to extinction. But,
even starting with a form like the Wood White, there is a
very considerable distance to be traversed before the Leptalis
becomes at all like an IJthomia.

This difficulty has been met by Fritz Miiller*; a com-
parative study of a number of different species of Leptalis led
him to believe that the banded forms are the most archaic ;
comparatively little modification, therefore, was needed to pro-
duce the detailed resemblance between the several species of
Leptalis and the protected Meesanitis and Acrea.

If this is generally the case, it is far easier to believe in the
efficiency of natural selection in bringing about mimicry ; but
it raises the further question—How are we to account for the
initial likeness? The answer to this question may bring us
back to the neighbourhood of the theory of “like conditions ”
—to the view expounded by Murray, and the earlier opinion of
Mr. Wallace.

* Senaische Zeitschrift, 1876. This important paper is noticed in the
American Naturalist for 1876, p. 538.

216 ANIMAL COLORATION.

There remains, however, in the mimicking genera the re-
semblance of colour, which is superadded to that of form ; and
the colour resemblances in these cases of mimicry are perhaps
to be regarded as more striking than those of form.

In some instances, however, which have been used to
illustrate the phenomena termed mimicry, the form resem-
blances are as striking as, or even more striking than, the
colour resemblances.

Spiders mimicking Ants.

Mr. KE. C. Peckham has recorded several instances of
spiders which appear to mimic ants; these are possibly
examples of “ aggressive mimicry ” ; the imitation enables the
spider to approach the ants undetected. It has been suggested,
on the other hand, that a more probable explanation is to secure
the immunity of the spiders from the attacks of birds which
do not prey upon ants.

But neither of these hypotheses is thoroughly satisfactory.
In a conflict between an ant and a spider of about the same
size, the fortune of battle would be very uncertain ; this would
be no case of a wolf in sheep’s clothing. On the other hand,
ants are preyed upon by so many different animals—mammals
as well as birds—that the alvantage of another animal, so to
speak, going out of its way to mimic them is at least doubtful.

The resemblances between the spiders in question (¢.y.,
Synageles picata and Synemosyna formica) and ants is not
limited to shape, but is also shown in colour. In these cases,
however, unlike Zeptalis and the Heliconide, the colour
resemblances might well, if it were necessary, be left out of
consideration, for a blackish-brown or yellowish-brown is a
common hue of Arthropoda, covered as they are externally with
a shell of chitin. Other causes, therefore, perhaps comparable

PROTECTIVE MIMICRY. 217

to those which have converted a terrestrial quadruped into a
fish-like creature, may be responsible for the “mimicry” of
ants by certain spiders. To return to colour resemblances
between not nearly allied forms.

In various parts of the world there are spiders which mimic
ants. Mr. Pickard-Cambridge instances among British species
Mearia scintillus ; to be sure that the creature is really a
spider and not an ant “requires the second look of even a
practised eye.” Prof. Peckham has stated that he is ac-
quainted with at least seventy-five species from North America
which look like ants. Mimicking spiders also occur in South
Africa. The mimicry is supposed to have one meaning in one
case, and another meaning in another case; it may be aggressive
sometimes, protective at other times.

The late Mr. Belt believed that a spider which lived among
ants in Nicaragua also lived upon them; its resemblance to
the ants lulled them into security. Mr. Poulton suggests that
more probably the spiders avoid, by mimicking ants, the attacks
of insectivorous birds.

Neither suggestion seems to entirely suit the case: to begin
with, the ants are “bold and fearless,’ and therefore no
disguise is needful on the part of the spiders; besides, ants are
not as a rule either dull of comprehension or mild in their
behaviour towards intruders. Dr. McCook,* speaking of the
supposed mimicry between the spider S/monella americana and
the Texas leaf-cutting ant, is disinclined to believe that it
would be safe in the midst of a swarm of the predaceous ants.
Ants, moreover, are not by any means avoided ly birds ; Dr.
McCook quotes a number of birds which commonly feed upon
ants: the Formicariide, like the Bee-eaters, have perhaps had
their name conferred upon them on account of this habit. It

** American Spiders,” p. 357.

218 ANIMAL COLORATION.

is perfectly true that no animal, however perfect its protection,
can wholly escape ; and it is,as has been pointed out in another
case, no argument against mimicry to be able to show that one
group of birds has acquired the habit of feeding exclusively upon
ants. But when we learn that such different birds as domestic
fowls, sparrows, partridges, woodpeckers, etc., also eat them,
it seems rather doubtful whether the advantages gained by
the protection afforded would be sufficient to account for the
mimicry of the spiders on the theory of natural selection.

Dr. McCook also points out that the greatest destruction of
spiders takes place when they are very young—when, therefore,
the protective mimicry would be perhaps hardly established,
or, if sufficiently evident to a naturalist, not sufficiently so to
their enemies to serve any useful purpose. When excessively
minute the young spiders have many enemies besides birds,
which would take no account whatever of a slight resemblance
to an ant; again, all the young NSaltigrade spiders (the ones
which show the mimicry) float in the air by their parachutes,
and countless thousands must fall a prey to swallows. Excep-
tion may, perhaps, be taken to the objection that no spider
mimics a wasp.

But on the theory that variation is indefinite and on all sides,
it would seem on @ priori grounds probable that spiders would
be met with which do mimic wasps, the most deadly enemies
with which the spider tribe is confronted. Perhaps Dr.
McCook’s suggestion that the mimicry of ants by spiders
renders this unnecessary, because the spiders are thereby
protected against wasps, does away with any force that this
objection may have. Wasps do not appear to prey upon ants.
Dr. McCook, however, goes a little too far in implying that
various members of the same group, Hymenoptera, do not prey
upon each other ; they certainly do in some cases, for hornets

¢

PROTECTIVE MIMICRY. 219

will capture wasps. Although Dr. McCook makes the sugges-
tion referred to, he does not accept it as an explanation of the
mimicry, and for the following reason. ‘Those spiders,” he
says, “ which are most frequently found within the clay cells
of mud dauber wasps, and those which these insects most
frequently collect as food for their larve, are the Sedentary
groups, such as Orbweavers and Lineweavers. They do, indeed,
take the Thomisoids, especially those that lurk on flowers
in pursuit of prey, and which, in turn, sometimes capture the
wasps. The Saltigrades are also taken ; but, if I may judge
from my own observations, they are least numerously repre-
sented of all the tribes, except perhaps the Lycosids and the
Tunnelweavers. This seeming immunity is evidently not due
to any likeness of Attide in general features to wasps, but
simply to their manner of lite, which in large measure screens
them from assault and enables them to escape. Now, the
question must rise, in considering such a theory, “‘ Why does
not natural selection operate for the protection of those spiders
which obviously need protection the most?” The most in-
genious explanation of this mimicry, on the natural selection
theory—and it only apples to one instance—is the explanation
which has been advanced to explain the mimicry of a South
African species: the ant feeds upon honey-dew along with
quantities of other insects; as the ants are engaged in a peace-
ful occupation, they do not interfere with the other insects,
which therefore do not fearthem. The spider takes advantage
of this state of affairs to prosecute its own ends; but this
explanation reopens the debated question of insect vision.

Resemblances between Insects occurring in different Countries.
Mr. Herbert Druce has kindly allowed me access to his rich
collection of Neotropical Lepidoptera, which furnishes numerous

220 ANIMAL COLORATION.

illustrations of mimicry as defined by Mr. Wallace, and of less
marked resemblances.

In North America there are several species of moths belong-
ing to the genus Catocala (which includes the rare “ Clifden
Nonpareil,” as well as the Red and Crimson Underwings),
Catocala linelea is a species which has yellow under wings
with no second black bar, such as is common in the family ;
this species distinctly recalls the moths belonging to the genus
Triphena—the “ Yellow Underwings.” So also do Catocala
amica, from Florida, and other species. Some of them look like
the “ Narrow-bordered Yellow Underwings” (e.g., T. orbona),
and others like the Broad-bordered species (7. fimbvia, etc.).
It is evident, therefore, that among Lepidoptera we have a series
of resemblances closer and more distant between forms that are
apparently not very nearly allied. Some of these resemblances
—for instance, that between the “ Merveil du Jour” and the
“Scarce Merveil du Jour”—are fully as striking as those
between forms that are quoted as instances of true mimicry ;
but they have not been referred to by the advocates of Bates”
theory of mimicry. The fact that such colour resemblances do
occur between two forms, to neither of which can they be for
obvious reasons advantageous, must be borne in mind when
considering the theory of mimicry.

T have referred elsewhere (p. 46) to resemblances between
insects coming from different countries, as evidence in favour
of similar environments producing similar effects. Form and
colour resemblances of this kind are, however, not confined
to Lepidoptera or to insects.

These instances of close resemblances between animals that
do not inhabit the same country—so close that, did they in-
habit the same country, they would be put down as examples
of mimicry—are very numerous. Dr. Seitz mentions a Sestid

PROTECTIVE MIMICRY. 22]

belonging to the genus Gymnalia which imitates, as many
Sesiidee do, a humble bee. The only objection to regarding
this as a question of mimicry is the rather important one, that
no humble bees exist where the moth does. Dr. Seitz, how-
ever, suggests, not, as Mr. Scudder has, that the mimicked
form did exist, but has died out; but that the moth has mi-
grated from some country where humble bees are found. The
suggestion is, however, and naturally, put forward very doubt-
fully. There is clearly no « prio: objection to it, particularly if
the larva feeds in the interior of stems which are constantly
imported and exported, but it must as clearly remain a
suggestion for the present—an alternative suggestion to the
hypothesis that the mimicked form has died out.

Cases of Apparently Useless Mimicry.

I am indebted to Dr. David Sharp, F.R.S., for a curious
instance of resemblance between two British beetles, which
appears at first sight to conform to all the conditions of true
mimicry.

Caliodes didymus is a minate beetle, very common upon
nettles ; with it is occasionally found a rare species, Ceutho-
rhynchus urtice ; these two insects are so much alike, that it
needs a careful investigation to distinguish them. And yet,
what advantage is got by this resemblance? Supposing that
the common species is nauseous in taste,—it cannot well possess
any other adequate defence, and this has not been proved,—its
very minuteness would seem to render any detailed mimicry
more than necessary ; and yet this exists.

A Swedish naturalist, Dr. Carl Bovallius, has lately de-
scribed * a remarkable species of amphipod crustacean which

* Novu Acta Reg. Suc. Upsalu, 1885.

222 ANIMAL COLORATION.

he named Jfmonectes on account of its likeness to a Medusa.
The body of this animal is produced into a dome-like structure
transparent as glass, from the under side of which depend the
tninute legs, which give the impression of the tentacles of a
Medusa.

Here we have a case of mimicry which is the more
striking inasmuch as it exists between animals widely removed
from each other in zoological position. And the poisonous
character of the Medusa, armed as it is with innumerable
“lasso cells,” would seem to make it an excellent model for
the defenceless crustacean to copy. It is a pelagic animal—
that is, it lives in the surface waters, precisely where Medusze
live—and there are three or four different species belonging to
the genus, all of which have aimed at the same model for
imitation.

But in this instance it is equally doubtful how far the
Mimonectes profits by its departure from the usual amphipod
appearance: a school of whales or a shoal of pelagic fish,
rushing through the water and devouring all before them,
could hardly be supposed to stop and analyse carefully the
advantages or disadvantages of selecting or rejecting a given
animal as food. And these must be the chief enemies with
which small pelagic creatures have to deal. Nor does any
theory of aggressive mimicry afford much help.

Prof. Semper discovered a most remarkable instance which
he was at first inclined to regard as confirmatory of the theory
of mimicry. This is his description :—

“ During my last stay at Port Mahon, in the Balearic Islands,
I found among the polyps of Cladocora cespitosa—a coral
which is there very common—a species, as it seems to me
now, of the genus Myzxicola (Annelida). . . . The species of
this genus spread out the tentacles with which the head is

PROTECTIVE MIMICRY. 233

farnished—and which are often regarded as branchie—in the
form of a funnel ; the sides of this funnel are perfectly closed,
and are formed of the filaments of the branchiee which lie in
the closest contiguity ; the section of the funnel is circular.
Each branchial filament has on its inner surface a multitude
of fine and minute hairs, which, however, are rendered rigid
by having in their interior cartilaginous cells; these hairs
radiate towards the centre of the funnel, so that the space
enclosed within the funnel is divided perpendicularly, by a
great number of septa, into a corresponding number of
chambers.

“The new J/yzicola of Port Mahon I found, as I have said,
among the polyps of Cladocora ; they lived in long mucilagi-
nous tubes, which they had formed in the rifts of the coral,
and in which they could move about freely. As long as no
light was thrown upon them, they protruded themselves: just
so far as that the top rim of the corona of tentacles was on a
level with the tentacles of the polyp, so that when the worm
and the polyps were both extended, the coral itself presented a
perfectly level surface of cups. Moreover, the funnels of the
Jyxicola were of precisely the same chocolate-brown colour as
the polyps ; and when fully extended, the interior of the funnel
formed by the tentacles looked exactly like the oral disc of
one of the neighbouring polyps, for the radial pinnules were
in the same position as those lines which, on the oral dise of
the polyp, radiate towards the narrow central oral slit ; in the
Afyxicola, also, a small central slit was observable, and all the
parts which corresponded so exactly in size and position alsv
displayed exactly the same colouring of greenish grey, with
radial lines of a lighter hue, and a narrow white streak in
the middle. In short, the resemblance, in size, position, and
colouring, of every part of the two creatures, was so perfect.

224 ANIMAL COLORATION.

that for a long time I took the corona of the Annelid for a
polyp, until by an accidental blow I caused all the Jfy.ricole of
a large coral stock to shrink suddenly into their tubes, though
it was not severe enough to induce an equally rapid movement
in the polyps of the apathetic Cladocora.

At the first moment I must confess I felt an almost childish
delight at having detected so flagrant an instance of protective
mimicry: here was a defenceless tube worm, evidently most
effectually protected by its resemblance to a polyp, well defended
by powerful weapons. However, I soon found reason to doubt
this interpretation of the facts; why should the annelid re-
quire any such protection, since it could withdraw itself with
the swiftness of lightning into its tube embedded in coral,
where probably no enemy would be able to follow it? Still,
the wonderfully complete resemblance between the two creatures
could not be disputed, nor could the fact that this resemblance
was perfectly normal.

Among the hundreds of specimens of Iyxcicola, which I
found in various pieces of coral, procured from the most various
localities, I never found one that had not these same points of
resemblance to the polyps. One day, finally, I found a marine
sponge in which hundreds of this same MWyxicol were living,
and in every portion of it their funnels of tentacles extended
just to the level of the surface of the sponge; but the sponge
was coloured very differently from the annelid, so that these,
when protruded, were very easy to distinguish from the sponge.
I then sought for the J/yxivolu in other spots, and succeeded in
finding it almost everywhere: in the rifts in rocks, and in the
sand, between marine plants or the tubes of other worms—in
short, everywhere—and wherever I examined it closely, it was
exactly of the size and colour of the polyps of Cladocoru
ceespitosa. Mimicry, it is plain, is out of the question ; the

PROTECTIVE MIMICRY. 225

resemblance between the two creatures is simply and wholly
accidental.”

Mimicry of Hymenoptera by Volucella is Difficult to Account for.

One of the most singular cases of apparent mimicry among
British insects is that of the flies belonging to the genus Volu-
cella and humble bees or wasps. They were first studied by
Réaumur, who spoke of them as “Des mouches «i deux ailes qui
ont Vair @abeilles.” Mr. Lloyd Morgan, in his recently published
volume, “Animal Life and Intelligence,” gives illustrations of
the two insects side by side, which show this resemblance very
well. I have also had reproduced upon plate IV. a group of bees:
and Volucelle in the Natural History Museum. It is a long
time since this case of mimicry was first pointed out. Kirby
and Spence * remark upon the probable advantage which the
flies get by being able to deposit their eggs in the nest of the
humble bee without arousing the suspicions of their involuntary
hosts. ‘ Did these intruders venture themselves amongst the
humble bees in a less kindred form, their lives would probably
pay the forfeit of their presumption.”

The example of mimicry afforded by these Volucelle is one
of the strongest that has been put on record; it would be
more remarkable still were some others of the hive parasites
protected in a similar way. The two moths (ralleria cerella
and Aphomia sociella, which also lay their eggs in hives, are
not in the least degree like the insects which they attempt to
rob: but it may be urged, perhaps, that the disguise is not so
necessary in their case, because they enter under cover of the
twilight.

This moth is by no means confined to English bees ; Messrs.
Horne and Smith t describe the occurrence of a Galleria in

* “Tntroduction to Entomology.” + Trans. Zool. Soc., vol. ii.

15

226 ANIMAL COLORATION.

the nest of an Indian Apis, which is quite indistinguishable
from the European Galleria melolella.

The principal difficulty in adopting the theory of mimicry to
account for this special resemblance was pointed out long ago
by Mr. Andrew Murray,* though, naturally, not in connection
with that theory.

The objection is that bees would not be so easily deceived as
the theory demands: it is well known that they are averse to
permitting even individuals belonging to another hive from
entering their hive; indeed, the facility with which other
Hymenoptera besides bees recognise the inmates of neigh-
bouring hives and nests is one of the most remarkable facts
connected with the life histories of these insects. It is, of
course, abundantly clear that the Volucelle do get access to
the hives, for their larvee are found there ; but whether they
achieve their purpose by an occasional fortunate raid while no
bees are about, or are really passed over by the bees which
they meet, is at present a little doubtful. A necessary pre-
liminary to all speculations concerning mimicry, as well as
other theories about colour, is an inquiry into the powers of
vision of the animals concerned. This part of the subject is
apt to be passed over, or else the sense capacities of animals
sre deduced from the phenomena of mimicry—a most dangerous
reversal of the proper order ; thus, Mr. Grant Allen + suggests
that the degree of perfection of mimetic and other resemblances
is a gauge of the perceptive powers of the animals concerned ;
“disguise has been unconsciously acquired to deceive certain
creatures, and it is just sufficiently perfect to deceive them.”

Bees in Europe are attacked by bee-eaters and by Titmice ;
toads are said to sit by a wasps’ nest, and pick up the wasps

* “On the Disguises of Nature,” Edinburgh New Phil. Journ., 1859.
+ Art. “ Mimicry,” Encycl. Brit., 9th ed.

= ee ae
PEATE iy,

Peter Smit del.et ith

ad

PROTECTIVE MIMICRY. 227

as they settle on the ground before entering the tunnel that
leads to their nest. In India, the bee-eaters are equally fond
of bees ; but lizards are, according to Mr. Horne, “ still more
destructive”; they lie in wait at the entrance of the hives,
and have a disregard for the sting of their prey which is only
equalled by the common toad. This does not exhaust the list
of animals that prey upon bees: the Honey buzzard will eat
them, or at any rate the honey, and is therefore, of necessity,
regardless of their stings, as is also the bear; the grey horn-
bill also eats bees. This persecution of the stinging Hymeno-
ptera contrasts with the case of a black and red Australian
spider which Mr. Wallace mentions ; not even a predaceous
wasp will attempt to carry off the creature “whose bite will
kill a dog.”

While the resemblance shown by Volucella bombylans to a
bee is very striking, Volucellu inanis is not so much like a
wasp ; according to Mr. Poulton this Volucella only lays its
eggs in the evening, and at the entrance of the nest; the
danger, therefore, is reduced to a minimum—which is very de-
sirable, if it be true that wasps are more acute than humble
bees. M. Kiinckel d’Herculais* relates how the wasps de-
tected the Volucella entering their nests; he suggests that
the flies must lay their eggs at the entrance of the nest ; the
larvee enter the nests, as they naturally move away from the
light.

The difficulty of this instance of apparent mimicry is greatly
increased, by the occurrence of numerous other insects in wasps
nests. Mr. Newstead t has lately given a list of no less than
eighteen species of insects which he met with in wasps’ nests ;
and this list does not include Acar?, perhaps parasitic on the

* “Organisation des Volucelles.”’
t Ent. Monthly Mag., Feb. 1891, p. 39.

228 ANIMAL COLORATION.

wasps’ bodies, and a few Lepidoptera “too worn for identifica-
tion.” Among the eighteen species are four Diptera without
any protection such as is supposed to be enjoyed by Volucella
énanis ; and Kiinckel d’Herculais met with V. pellucida, not
a wasp-like species, in wasps’ nests. The two-winged flies
or Diptera are diurnal in their habits, and must deposit their
eggs during the day-time ; added to this difficulty, due to the
probability that the wasps would resent in a very conclusive
fashion the presence of any intruder, is the additional difficulty
that wasps especially feed upon Diptera. They are said to
visit ripe frnit mainly in quest of the flies which congregate
there. If wasps and bees have the same unintelligible liking
for keeping pets that another group of Hymenoptera—the
ants—have, the whole series of facts may prove to have a
very different meaning, but one which is not quite in accord
with the theory of mimicry on the part of the Volucella.

Vision of Insects.

The question of visual perception among animals is one upon
which different opinions have been held.

When an accurate observer like Sir John Lubbock says,*
“We know, as yet, very little with reference to the actual
power of vision possessed by insects,” it is surely premature
to build up theories which often demand a sense of vision in
invertebrated animals precisely similar to that possessed by
ourselves. Nevertheless, Sir John Lubbock himself is con-
vinced that bees distinguish between different colours. A drop
of honey was placed upon blue and orange slips of paper, and
though the position of thefpapers was alternately transposed,
the bee invariably selected the blue.

* « The Senses of Animals,” Int. Sci. Series.

PROTECTIVE MIMICRY. 229

The observations of M. Plateau, who has particularly de-
voted himself to elaborate experiments upon insect vision, have
an important bearing upon the matter now under discussion.*
As regards the compound eyes of Hymenoptera, he has written
as follows: “My first experiments on Hymenoptera, both
deprived of their wings and unmutilated, whether moving in
the maze or tested by means of the vertical obstacle at the
end of a stick, astonished me profoundly. These insects ap-
peared to guide themselves amongst the obstacles with remark-
able certainty, avoiding the barriers when these were at a
distance, and apparently behaving in every respect like
creatures possessing good powers of sight.

Certainly, if I had contented myself with a few superficial
observations, I should have been persuaded that Hymenoptera
are an exceptional group, possessed of definite vision. This
illusion—a very pardonable one—was due to the rapidity of
action of the creatures on which I made my first observations.
The strangeness of the results having induced me to make
fresh experiments, I discovered some species whose ambulatory
movements were less rapid. This enabled me to analyse the
details, and to detect the explanation, as simple as it was
certain, of the fact.

This explanation may be thus summarised: The Hymeno-
pteron directs its course, with but few exceptions, straight
towards the light—that is, towards the windows. In such
conditions the obstacles forming the maze, or those placed at
the end of a stick, give rise, according to their position, to a
shadow cast in front of them—a shadow which is, in fact, of
a double nature—a faint one, or penumbra, and a darker and
narrower shade.

* My information about these papers has been drawn from an excellent
review by Dr. David Sharp, in Truns. Ent. Soc., 1889, p. 393.

230 ANIMAL COLORATION.

If, in pursuing a straight course, the creature haps on @
gap between the obstacles, it naturally takes advantage of
this, as indeed a beetle would do ; but if across its road there
intervene an upright obstacle, the Hymenopteron continues to
direct itself towards it, evidently without perceiving it, or at
any rate without perceiving it distinctly, until the insect’s.
body, or a portion of its body, has penetrated into the shadow-
Instantly the insect receives a general, impression (impression.
that may be either dermatoptic or visual, possibly both) ; it
then hesitates for a very brief instant, then alters its course to
a right angle, makes literally a half-turn to the right or to the
left, proceeds parallel to the outline of the shadow, then again
resumes its course towards the source of light, making again
a similar change of direction when it again passes into the
shadow of a fresh obstacle.”

It should be explained that the “maze” referred to in his
description consists of a number of pieces of wood arranged in
a series of concentric circles, something after the fashion of
restorations of Stonehenge. In the circles, the pieces are in-
terrupted by intervals, and each interval is covered or nearly
covered by a piece belonging to the next circle ; there is thus
no possibility of an insect, placed in the centre of the maze,
seeing its way out at once.

The vertebrates experimented with found their way out by
the shortest route, making their way directly from one interval
to another, and avoiding the obstacles ; the way in which the
Hymenopteron proceeds indicates that it is largely euided by
the sensations from the distinctions between light and shade.
This does not look as if a clear appreciation of form re-
semblances were possible. Dr. Sharp, at the conclusion of his
review, remarks that “there is at present no evidence at all
that the light perceptions of insects are sufficiently complex to

PROTECTIVE MIMICRY. 231

be entitled to be called seeing ; but that, as the larger develop-
ment of the compound eye permits the simultaneous perception
of movement, its direction, and of light and shades over a.
certain area, a dragon-fly may pursue and capture another
insect without seeing it, in our sense of the word seeing.”

Cases of Mimicry in which the Mimicking Form is equally abundant.
with the Model.

One of the essentials of true mimicry is that the mimicking
form should be scarce as compared with the model which it.
imitates. The mimicking Pieridae comply with this requisite,
and so also do the Wasp and Hornet Clearwings. This very
fact has been used as an objection to the theory of mimicry, by
Mr. A. W. Bennett.* The whole object of mimicry is obviously
the perpetuation of the mimicking species. Defenceless insects
have found out this way of escaping annihilation ; and having
been directed into this safe path, we may fairly inquire, with
Mr. Bennett, how it is that the mimicking insects continue to
be rare in spite of their advantages.

Curators of museums, and other persons who purchase
butterflies, know perfectly well that the mimicking insect
often costs as many guineas as its. model does shillings ; the
obvious inference is that mimicry does not seem to be of much
use; but as a matter of fact the mimicking species are not
always so rare as has been supposed. Fritz Miiller states
that the mimicked species is not always more abundant than
its counterfeit ; the proportions between the two vary very
much in different localities; sometimes one and sometimes the
other preponderates.

There is one very striking example of a resemblance between.
two insects belonging to different orders, usually quoted as a

* American Naturalist, 1877, p. 3.

282 ANIMAL COLORATION.

case of mimicry, which does not fall in with this paragraph
in Mr. Wallace’s definition of mimicry. The insect in
question is the Bee-tly (Eristalis tenaa),* which, although a
Dipteron—possessing two wings—has a strong superficial
likeness to a bee. It frequents flowers just as bees do, but
has a more lethargic disposition than the active hive bee which
jit imitates. Now, this insect is extremely common, and has
even in recent times extended its range to many distant parts
of the world. Experiments, moreover (see p. 165), have shown
that it is not systematically rejected by insect-eating animals.

Criticism of an Apparent Case of Mimicry.

Dr. Seitz gives several interesting cases of mimicry among
Lepidoptera in Germany, some of which, however, appear to me
to be open to criticism. He calls attention, for example, to
a moth which mimics one of the day-flying Yellow Underwings
(Brephos nothum); or rather, he emphasises the resemblance
between B. nothum and Ploseria diversata without being in
a position to say which is ‘ original” and which “copy.” “If
it were strange,’ remarks Dr. Seitz, “that two not nearly
related species are found in March, an unusual month for
moths, so much so that on fine spring days these insects are
generally the only two met with—it would be carrying scepti-
cism too far to regard the agreement between the species as
merely the result of accident.” This is plausible, but not
entirely convincing, if we take other facts into account.
Mr. Poulton, in arguing for the efficacy of warning colours (and
of course this will include mimicry), points out “the entire

* It is an interesting fact, in connection with the resemblance between
this fly and a hive bee, that it feeds upon pollen and honey. This fact
may have some significance in relation to the effects of food upon form

and coloration (see p. 48). For a discussion of the food of this fly see
Entomologist, vol. vi., p. 336.

PROTECTIVE MIMICRY. 233

disappearance of all insects with warning colours during the
seasons when insect-life is scarce,” and therefore in great
requisition by insect-eating birds. During the earlier and
later months of the year, anything in the shape of an insect
would be eagerly snapped up, and warning colours would
become a danger signal, not to the bird, but to the insect
itself. In spite, therefore, of the similarity in colour and
habit between the two moths mentioned above, it seems to me
that the position taken up by Mr. Poulton is too strong a one
to be overthrown. The only alternative to supposing that
resemblance, however detailed and remarkable, to be a striking
coincidence, is to assume a recent change of time of emergence,
which has simultaneously affected both species ; but this is, if
possible, even more difficult of belief.

Mimicry in some Cases possibly only a Resemblance due to Affinity.

Another consideration must be kept in mind, in weighing
the arguments for and against the theory of Mimicry ; and
that is, how far the resemblances are due to affinity. Of
course, we may at once dismiss from this category such
examples as that afforded by Imonectes. But with regard
to different families or genera of butterflies and moths, which
display mimetic resemblances, these considerations demand
investigation. It is a fact quite familiar to every zoologist
that, in certain members of a group, characters now and then
are noted, which betray its relationship. to another group.
These characters may have been inherited from the common
stock whence both groups were derived, or they may possibly
be in some cases a reversion to that stock.

All existing birds, with the exception of one genus, Palamedea
(the Screamers), have bony outgrowths—the uncinate processes
—attached to their ribs, which serve for the more secure fixing

234 ANIMAL COLORATION.

of certain of the muscles used in respiration and in flight.
The absence of these in the Screamers allies those birds, which
in other respects do not occupy an especially low position in
their group, to the lower Reptilia, which are believed to
represent more nearly than any existing animals, the original
stock from which birds were evolved.

With one exception all earthworms at present known to us.
—and they comprise now a couple of hundred well-marked
species—possess sete, which serve as organs of locomotion,
of a peculiar form, curved like the letter § and terminating in
a free, pointed extremity. In a very large number—by far the
majority—of the fresh-water members of this group of annelids.
there are sete of the same general form, which terminate in a
distinctly bifid extremity. One genus only of earthworm,
Urocheta—a form which is widely distributed through the
tropics—possesses these bifid setee.

If colour markings have that importance which the advocates.
of the theory of mimicry believe them to have, it is quite
intelligible that resemblances due to relationship may have
survived in some members of a group and disappeared in
others. This would be analogous to arrested divergence in
unpalatable insects, to which reference has been made on a
former page; but it does not fit in with the defence of mimicry
by Mr. Belt, which I have quoted above.

Even in. cases of superficial resemblance between insects.
belonging to different groups, the question of a possible affinity
must not be left out of sight. The Caddis flies mentioned on
p- 242 resemble Lepidoptera in their brown-coloured and hairy
body and wings ; these hairs may actually take the form of
scales. Some entomologists are of opinion that this resemblance
is one of affinity.*

* See Comstock, ‘ An Introduction to Entomology,” Part I.

PROTECTIVE MIMICRY. 235

Mimicry among Mammals.

It is a remarkable fact that so extremely few cases of
mimicry among the Mammalia have been placed on record ;
I cannot help thinking also that it is a highly significant fact.
There can be no @ priori reason against the occurrence of
mimicry in this group ; on the contrary, many considerations
seem to point to the great advantages which would be secured,
by a defenceless quadruped mimicking one that, for some
reason or other, was little attacked by predatory enemies. The
chief foes of the herbivorous Mammalia are, perhaps, the
carnivorous members of their own order; but a good many
of the smaller species—rodents and insectivores—are devoured
by predaceous birds, not only hawks and eagles, but also
by the raven and other birds of the crow kind; many
mammals in tropical countries fall victims to alligators and
crocodiles.

Now, all these foes of the unprotected Mammalia are ad-
mittedly creatures which have a keen sight. Many of the
Carnivora, notably the Cats—using the term, of course, in a
wide sense, to include lions, tigers, panthers, and so forth—
appear to hunt their prey almost entirely by sight. Dr. Hill*
has come to the conclusion that “in the dog the sense of smell
is paramount, in the cat it is largely replaced by hearing and
sight, in the otter it is extremely deficient.” This conclusion,
based upon the varying development of certain parts of the
brain connected with those three senses, appears to be borne
out by actual observations upon the habits of the animals.

As to birds, it is generally agreed that the sense of sight is
far more perfectly developed than that of smell. In fact, if it
were not so, the theories of warning colours and mimicry

would at once fall to the ground, since it is especially birds
- “The Plan of the Central Nervous System.” Cambridge, 1885.

236 ANIMAL COLORATION.

which are supposed to be duped or warned by these colour
phenomena.

The only case of mimicry among the Mammalia advanced
by Mr. Wallace is that of the insectivore Cladobates, which
has a bushy tail like a squirrel. This instance of mimicry is
believed to be for aggressive rather than protective purposes.
The view taken by Wallace is that the squirrels, being veget-

Fig. 26.—Cladobates.

able feeders, do not disturb the insects among which they live,
and that, in consequence of its resemblance to a squirrel,
the insectivore can steal upon its prey without causing any
alarm.

The validity of this example is disputed by Semper, who
maintains, in the first place, that at any rate the European
squirrel is omnivorous, like many other rodents—notably the
rat ; in the second place it is pointed out that the shaking of
the branches, caused by the squirrelias he leaps from bough
to bough, would be probably in itself somewhat alarming to

PROTECTIVE MIMICRY. 237

the insects. This particular instance involves a high degree
of perceptive power and of reasoning intelligence among the
insects, which is difficult of acceptation.

An excellent model for mimicry would be the skunk, which
is, according to Mr. Wallace, an example of warning coloration;
and there is a black and white squirrel, but not in the same
country. The paucity of examples of close resemblances be-
tween remotely allied mammals appears to me to have some
relation to the fact that the total numbers of the Mammalia
are so small as compared with insects.

Some notion of the vast number of species of insects may
be formed by mentioning that in the year 1889 (according to:
the Zoological Record), there were nearly fifteen hundred new
species and varieties of Lepidoptera alone described. Out
of the vast assemblage of insects, with their varied colours
and patterns, it would be strange if there were not many cases.
of accidental resemblance; and there are many sueh.

Mimicry among Birds.

Among birds there are plenty of instances of resemblance:
between members of different families, which may or may not
be advantageous. It is not easy to say whether some of these
may not be really due to generic affinity ; closely allied forms
of animals, showing their near relationship in numerous points
of structure, are often widely dissimilar in external character-
istics ; on the other hand, identical peculiarities of external
form and colour often crop up in animals which are apparently
some way removed from each other, and serve as an index of
their real affinity.

The singular likeness between the goatsuckers and the owls
has frequently been remarked upon; the mottled grey and
brown plumage has, in many cases, a closely similar pattern in

238 ANIMAL COLORATION.

both groups; among the goatsuckers there are ‘“ horned”
forms, such as Lyncornis macrotis, which suggest of course
the horned owls. So long as the owls remain associated with
the eagles and vultures in our systems of ornithological
classifications, these resemblances must be set down either
to accidental resemblances, or to mimicry, or to resemblances
brought about by similarity of habit: goatsuckers and owls
are both of them predaceous, and are crepuscular or nocturnal
birds.

But the opinion has been lately gaining ground* that the
owls are not so nearly akin to the Accipitrine birds as they
have been thought to be, and that their association with the
goatsuckers would not be entirely contrary to the facts of
anatomy ; in this case the superficial resemblances spoken of
may be an expression of real affinity.

The cuckoos are a group of birds which show resemblance
to a number of quite different families.

The Sumatran ground cuckoo (Carpococcyx radiatus), of
which a specimen may be seen in the insect house at the
Zoological Society’s Gardens, is curiously like a gallinaceous
bird in its gait and appearance. Centropus phasianus, which
may be also inspected at the Zoological Gardens, has received
its specific name in accordance with its striking resemblance
to a pheasant.

The late Prof. Garrod f attempted to show that the cuckoos,
in many structural features, come near to the gallinaceous
birds, though his views have not, perhaps, met with general
acceptance among ornithologists. If, however, further research

* See Prof. Newton's article “Ornithology” in the 9th edition of the
Encyclopedia Britannica.

t Collected papers of A. H. Garrod, edited by W. A. Forbes. London,
R. H. Porter, 1881.

PROTECTIVE MIMICRY. 239

show that Garrod’s suppositions are tenable, we shall have
here a resemblance which may be in reality based upon affinity.
It is difficult to see what particular advantage a cuckoo could
secure for itself, by having become like a pheasant, unless
the spurs of the cock bird are known to their enemies, and
associated in their minds with the gallinaceous build and
coloration.

But the cuckoos do not only present resemblances to the
pheasant tribe. The cuckoos themselves form a very hetero-
geneous group of birds ; their internal structure is not by any
means so uniform as in other restricted groups. Coupled with
these internal differences are many external differences, which
are not merely those of colour. No one would suspect that
the Ani of America, with its glossy black plumage and its
beak “resembling an immense Roman nose,” was a member
of the same group as our somewhat hawk-like Cuculus
canorus.

Messrs. Sclater and Hudson quote Azara to the effect that
this cuckoo (Crotophaga ani) “ follows the cattle about in
the pastures like the cowbird.” The cowbird (Jolothrus
bonariensis) has a black plumage like that of the Ani, and
is of about the same size; they are both common, otherwise
it would be tempting to adduce this as an example of true
mimicry.

Mr. Frank Finn has, at my suggestion, collected together
a number of cases where birds belonging to different orders,
and often living in different countries, show superficial re-
semblances. He has kindly furnished me with the following
instances.

Sir Walter Buller, in the new edition of his “ Birds of New
Zealand,” speaks of the striking resemblance between the
cuckoo, Hudynamis taitensis,and an American hawk, Accipiter

240 ANIMAL COLORATION.

coopert. Our own cuckoo, Cuculus canorus, is by no means
unlike a sparrow-hawk, and there are various rustic legends
based upon this likeness ; but the New Zealand cuckoo shows
a far more detailed similarity to the American hawk. Sir W.
Buller says, ‘‘ Not only has our cuckoo the general contour of
Cooper’s sparrow-hawk, but the tear-shaped markings on the
under parts and the arrow-head bars on the femoral plumes
are exactly similar in both. The resemblance is carried still
further, in the beautifully banded tail and marginal wing
coverts, and likewise in the distribution of colours and mark-
ings on the sides of the neck. On turning to Mr. Sharpe’s
description of the young male of this species in his
catalogue of the Accipitres in the British Museum (p. 137).
it will be seen how many of the terms employed apply equally
to our Hudynamis, even to the general words “deep brown
above with a chocolate gloss, all the feathers of the upper
surface broadly edged with rufous.” It might perhaps be
imagined that this resemblance, which is as striking as it is.
useless to either bird, separated as they are by half the globe,
was exceeded in the case of some New Zealand bird of prey.
Sir Walter, however, says: “ Beyond the general grouping of
the colours, there is nothing to remind us of our own Bush
hawk ; and that there is no great protective resemblance is
sufficiently manifested, from the fact that our cuckoo is perse-
cuted on everypossible occasion by the tits, which are timorous
enough in the presence of a hawk.

The Cat Birds (Aeluredus) have a singular resemblance to the
green Barbets, and one species is actually called “ duccoides” ;
but this resemblance is clearly not referable to mimicry, for the

distribution of the two groups does not coincide. Gould has
remarked upon the close similarity between Melicophila picata

and Petroica bicolor, which are figured and described, in one of

PROTECTIVE MIMICRY. 241

that magnificent series of illustrated volumes upon Ornithology
associated with Gould’s name. Both birds are black and white,
and the sexes differ in both species. As the honey-eater is
totally unlike in colour to other honey-eaters, this bird should
be the mimicking form.

Curiously enough, it is the male, and not the female, which
has adopted the mimetic livery. Attention has been already
directed to the fact that, among butterflies, mimicry, if not
shown in both sexes, is restricted to the female; this is,
of course, explained by the greater need for protection of the
females, upon whom devolve the most serious cares connected
with the continuance of the life of the species. It is, in fact,
most likely that the resemblances between the Melicophila and
the Petroica are purely accidental, or related to circumstances
of which we have at present no knowledge whatever.

There are numerous other examples which might, did space
allow, have been brought forward. Mr. Wallace himself has
instanced the mimicry of the aggressive Friar birds by the
weak Orioles. Here some advantage would appear to accrue
to the mimicking species.

The foregoing pages contain a number of instances, which
could easily have been multiplied, of resemblances in colour
and form of varying degree, between animals more or less
remotely allied, which seem to confer no particular advantage
upon either.

There are other instances where such resemblances occur,
and are positively disadvantageous to the mimicker.

Mimicry may be in Certain Cases even Disadvantageous.

Attention has been directed to the singular mimicry of
hymenopterous insects afforded by certain species of moths
16

242 ANIMAL COLORATION.

belonging to the genus Ses7a. Not only are their wings
nearly bare of scales, which are so characteristic a feature of
the Lepidoptera, and from which indeed their very name has
been derived, but the colours of the body resemble those of
wasps, bees, and hornets. These stinging Hymenoptera are
not, however, the only insects which the Sesiide superficially
imitate. Several of the smaller species—for example, VN. tipudi-
Jormis *—are by no means unlike flies. When basking in
the sun upon the leaf of a currant bush, S. tipuléformis, might.
easily be passed over, even by a collector of little experience,
as a fly. This would seem decidedly disadvantageous to the:
moth, or, at least, not positively advantageous.

The curious likeness which certain “water flies” show to
moths is, if anything, probably disadvantageous to them,
though it is of course difficult to decide these matters offhand.
In any case, the brown opaque wings of the water fly must
render it more conspicuous than if the wings were transparent,
and the conspicuousness is not quite marked enough to allow
of the use of a theory of warning coloration.

Mimicry not always Deceptive.

Mr. Poulton found that the bee-like appearance of Sesia
Juciformis and 8. bombyliformis did not in the least impose
upon a lizard, to which he offered one of these insects. It
was eaten “ without hesitation or caution.” These two insects
are sometimes removed from the other Clearwings and placed

“ Mr. Wallace has, however, pointed out that the resemblances of
Sesia tipuliformis are rather with a wasp, belonging to the genus
Odynerus. Rogenhofer has, however, lately (Verhandl. Zool. Bot:
Gesellschaft, Wien, Bd. xxv.) stated that Sesiu tabaniformis mimics a
fly, Ceria conopoides, which is found about the same time on trunks of
poplar.

PROTECTIVE MIMICRY. 243

in the same genus with the Humming-bird Hawk moth.
Mr. Poulton evidently does not take this view of their
relationship, which seems to be mainly founded upon the
characters of the larvee.

But when we bear in mind the totally different habits of the
larvee of those two insects, which feed upon leaves, from those
of other Clearwings which bore in the interior of stems, this
difference is not surprising. The Clearwings, therefore, form
a group of Lepidoptera, a// of which are distinguished by the
peculiarity of the defective scaling of the wings. It seems less
likely, therefore, that the loss of the scales was due to a need
for protection, than if only a few were thus modified ; it is a
family character. But even if it were not so, and if only a few
Sesiids resembled Hymenoptera, the modification would not
be so remarkable as many other divergences from the normal
structure of the genus or family that occur ; for in many quite
different families of Lepidoptera we have the same tendency to:
lose the scales: in the Zygenidie, for instance, and in the
Heliconide.

It might be supposed that the absence of scales had some-
thing to do with the origin of the Lepidoptera from insects
without scale-covered wings—the Neuroptera, for instance—to
which they are believed to be most nearly allied ; but embryo-
logy shows that the loss of scales is a modification, and that
the parent form was a lepidopterous insect. Mr. Poulton
mentions that the Bee hawk, even when just emerged from
the chrysalis, has the wings thinly clad with scales, which fall
off directly it begins to fly. In the Currant Clearwing (Sesza
tipuliformis), and in Sesia apiformis the insect is hatched
from the chrysalis free from scales: these are partially formed
during the pupal stages, but arrested in development.*

* Ann. and Mag. Nat. Hist., Ser. 6th, vol. vi., p. 185.

244 ANIMAL COLORATION,

The study of the development of animals always shows,
with more or less clearness, an epitome of the history of
the development of the race: every animal, as it has been
put, “is compelled to climb up its own genealogical tree.”
The facts that have been mentioned about the Clearwings can
hardly be explained, except on the hypothesis that they have
taken their origin from moths with fully scaled wings; and the
farther inference is probable that the Bee Clearwings have
more recently lost their scales than some of the others. This
probability is perbaps increased by the resemblance which the
larva of S. bombyliformis bears to a Sphinx larva, while the
larva of 8. tipuliformis is different ; but, after all, we do not
know positively whether the internal feeding-larva might not
be the older.

The advocates for explaining the facts of mimicry by a need
for protection experienced by the mimicking insects could
point to Mr. Poulton’s experiment with S. dombyliformis and
S, bembecifor'mis as being more conclusive than they at. first
appear. The fact that S. bomdbyliformis was eaten without
hesitation, and that S. bembeciform/s created a suspicion in the
lizard’s mind, seem to indicate a considerable imperfection in
the resemblance. In the detailed record of his experiments,*
Mr. Poulton suggested that the resemblance to a bee or other
stinging Hymenopteron shown by 8. fuciformis is possibly to
be regarded as “a remnant of a former more perfect mimicry,
reliance being now placed on powerful flight and concealment
during rest.” He admits that the instance is a difficulty in
the way of the theory. However, remembering the facts of de-
velopment, this particular difficulty almost disappears. Seeing
that the loss of the scales in the Bee Hawk moth is more
recent than the loss of scales in the Hornet Clearwing, it is

* Proc. Zool. Soc., 1887.

PROVECTIVE MIMICRY. 245

not surprising to find the mimicry less perfect in the one
case than in the other. The Bee Hawk moth may not have had
time to acquire so close a likeness to its model.

Mr. Poulton regards the beetle Clytus arietis as offering a
case of mimicry to some of the smaller wasps: it is banded with
bright yellow, and has long, slender, wasp-like legs. “ When
walking,” says Mr. Poulton, “the slender, wasp-like legs are
moved in a rapid, somewhat jerky manner, very different from
the usual stolid coleopterous stride, but remarkably like the
active movements of a wasp.” The resemblance is heightened
if the beetle be made to sprawl upon its back; when this

Fig. 27,--Bee Hawk Moth.

happens, the legs have a distinctly wasp-like appearance, from
their thinness and length.

Mr. Poulton records no experiments with this beetle ; un-
fortunately, I have been only able to experiment with one
individual. This was put into a case containing two green
lizards: the beetle began to move rapidly in the direction of one
of the lizards ; when it got near enough, it was, without any
symptom of hesitation on the part of the lizard, snapped up
and swallowed; this lizard had a few moments previously eaten
a large ground beetle, and had unsuccessfully chased a cock-
roach. It was, therefore, presumably in an average state—
not dainty through repletion, nor ravenous.

246 ANIMAL COLORATION.

The Occasional Limitation of Mimicry to the Female Insect.

When the two sexes differ in butterflies, the female appears,
according to Dr. Scudder, to diverge more from the typical
coloration of the genus or family thanthe male. This opinion,
it should be remarked, is not universally shared; more generally,
it is held that the male is the most specialised sex. However,
it may not be so in butterflies.

Among the “ Blues,” for instance, the normal coloration is,
as their popular name denotes, blue ; in some of the species
both sexes are blué and closely similar; where there is a
divergence, it is the female which differs; the females of many
species are brown. This is not the place to discuss how far
these differences are due to the greater need for protection by
the female; the fact remains that among the butterflies of
North America, treated of by Dr. Scudder in his great work
upon this group, only one butterfly which is sexually dimorphic
has a male which departs from the usual coloration of the
family to which it belongs. This butterfly is Cyaniris pseud-
argiolus, a member of the very family which has just been
referred to—the “ Blues.” In this species it is the male, and
not the female, which is somewhat dusky in its hues. If the
organisation of the female is really more plastic than that
of the male, we can understand how in cases of mimicry it
is, net unfrequently, the female only which resembles some
other distasteful butterfly ; instances of this have been already
mentioned (on p. 169). It is quite easy, that is to say, to
understand this from one point of view—but from one only.
Why are not the males also modified? They may not require
protection quite so much as the females; but it is obvious
that they have their importance in the continuance of the race.
The question of heredity may perhaps be set aside ; but even

PROTECTIVE MIMICRY. 247

that introduces some difficulties. It would be supposed that
mimetic females pairing with non-mimetic males would pro-
duce a progeny of a mixed kind—not so perfectly mimetic as
the female parent; in this way the effectiveness of the mimicry
would tend at once to disappear, and finally would disappear.

When the Eyed Hawk moth produces a hybrid with the
Poplar Hawk moth, the offspring unites the characters of both
parents.

As to the results of breeding from dissimilar parents a few
other instances may be mentioned. Near Manchester the
common Pepper-and-Salt moth (Biston detularia) shows a
well-marked melanic variety, which is gradually getting more
abundant. This instance of an apparent connection between
local conditions and a colour variety may be added to those
mentioned in Chapter I]. A male of the melanic variety was
crossed with a female of the common form. The offspring
were intermediate in coloration, and showed very beautiful
markings. The same insect was experimented with under the
same conditions (7..a melanic male with a normal female), and
produced a different result : the offspring consisted of eleven
individuals, eight males and three females ; six of these were
melanic and five normal. It is clear, therefore, that the colour
varieties do xot coincide with the sex.

Another supposition—also based upon facts—is that the
progeny would be divided, one portion having a preponderance
of characters derived from the male parent, the other portion
agreeing more closely with the female. This, again, would
teud in the course of time to destroy the mimetic resemblance,
unless the female offspring were always like the female
parent.

But there is another ditfticulty to be faced.

If the females escape destruction by virtue of their likeness

248 ANIMAL COLORATION.

to protected forms, it follows as a matter of course that the
males do not. Hence a gradual dwindling of the male insect
nust take place, which, if it does not result in extinction, must
materially interfere with the chances of a given female securing
a mate; thus, in any case there would be a diminution in the
number of the species. This difficulty is partly met by Mr.
Wallace’s suggestion that the females need an additional
protection because their flight is slower, owing to their being
laden with eggs, and they are exposed to attack when actually
depositing their eggs. Presumably, therefore, at other times
they are as well able to take care of themselves as the males.
But this suggestion does not altogether remove the difficulty :
it has to be definitely proved that a butterfly with eggs is
markedly slower in its flight than one without; as to the
exposure to enemies while actually depositing the eggs, this,
no doubt, constitutes a real danger; but the time so occupied
is not long, and it might be urged that the pairing was equally
dangerous ; and the danger incurred here is shared by both
sexes alike.

Mr. Belt has made an additional suggestion, which, although
very ingenious, no doubt needs confirmation, as Mr. Poulton
says, by a careful observation of the habits displayed during
courtship.

The suggestion is that the females exert a selective influence
upon the males, not in the direction in which sexual selection
is generally supposed to proceed (see p. 263): instead of prefer-
ring the more brilliantly coloured males they are believed by
Mr. Belt to exhibit ‘“‘a deep-seated preference for the normal
colour of the order to which these mimetic forms belong.”
This explanation docs not satisfy Dr. Scudder, in spite of his
opinion that the female butterfly—if the two sexes differ—is
farther from the normal coloration than the male. If the con-

PROTECTIVE MIMICRY. 249

verse is proved to be the case, this explanation of Mr. Belt’s
will obviously at once fall to the ground.

A curious disadvantage in the restriction of mimicry to the
female insect is quoted from Dr. Fritz Miller by Mr. Wallace.*
“One of the most interesting of our mimicking butterflies is
Leptalis melite. The female alone of this species imitates one
of our common white Pieride, which she copies so well that
even her own male is often deceived; for I have repeatedly
seen the male pursuing the mimicked species, till, after closely
approaching and becoming aware of his error, he suddenly
returned.” It is quite possible that, in this and other cases,
actual pairing may take place, which would be clearly dis-
advantageous to both species concerned. This instance proves
that it is not always the female insect which shows mimetic
resemblances ; the female of Leptalis melite is perhaps more
normal in coloration than the male.

Mimicry between Unprotected Forms.

This last instance leads to the consideration of apparently
mimetic resemblances letween genera and species which are
perfectly eatable, and are not protected from attack by a dis-
agreeable taste or any other unpleasant attribute.

Instances of this kind, Dr. Scudder? thinks, are probably
much more numerous than the other classes of mimicry, though
they are less conspicuous. What advantage can this confer ?
Probably the advantages are the same as those enjoyed by
distasteful species that mimic each other, and which I have
gone into more fully on page 199. The whole theory of mimicry
would of course collapse, if no usefulness could be shown to
exist in any of the mimetic resemblances: other explanations

* “ Darwinism,” p. 245.
+ “ Butterflies of the Eastern United States.”

250 ANIMAL COLORATION.

of the phenomena would have to be sought for. The theory 1s
mainly supported by instances among Lepidoptera, which is,
no doubt, due to the fact that it was in this group that the
phenomena were first studied. From certain points of view it
is unfortunate for the theory that this is the case: Lepidoptera
are, as a rale, very short-lived in the imago state.

If cases of undoubted mimicry could be shown to be more
uumerous among the higher and longer-lived animals than they
have yet been, they would furnish much stronger evidence for
the truth of the theory. A mammal which may have to exist
for some years before it can reproduce its kind needs protection
much more than an insect, which sometimes pairs the moment
it leaves the cocoon. There are even cases on record of male
moths waiting by the unopened cocoon in expectation of the
emergence of the female.

Relative Unimportance of the Imago Stage in Butterflies.

It may seem paradoxical to say that the perfect butterfly,
which has passed through so many preparatory stages, is the
least important stage of all. In a certain sense also it would
be manifestly untrue, for the butterfly lays the eggs, and upon
the life of one female insect depends the future existence of
perhaps a large number of butterflies. There is no doubt that
a single butterfly deposits, under favourable circumstances, a
great quantity of eg¢s,—from two to five hundred, according to
the species, is one estimate,—but. it is also calculated that out
of these eggs only 1 per cent. reach maturity : if that is so,
the life of an average female butterfly is only worth three or
four times that of a caterpillar.

As long as the perfect insect is able to pair and lay its eggs,
that is all that is necessary ; after this its life is of no value,
and it is immaterial whether it is destroyed or lives on for a

PROTECTIVE MIMICRY. 251

time. The pairing and egg-laying takes a very short time,
even among those insects which do not lay all their eggs at
once ; the risk run by the insect before it has accomplished its
purpose is therefore very slight, compared with the dangers
incurred by a caterpillar, which has sometimes two seasons
to pass through in preparation for the chrysalis stage, and is
constantly exposed all this time to numerous enemies, belonging
to almost every group of the animal kingdom. This is perhaps a
reason why we see such numerous and varied devices, whereby
caterpillars delude, warn, or frighten their enemies ; and it
is perhaps also a reason which explains the great dearth of
such devices among butterflies and—though apparently to a
less extent—among moths. It is therefore surprising to find
so many examples of apparently useful mimicry among butter-
flies. It has already been pointed out that protective colora-
tion is not very useful in these insects ; warning coloration
and mimicry are therefore the only colour modifications of a
protective value which they could advantageously assume ;
and, it must be admitted, it is precisely these modifications
which are met with.

Summary.

All these facts, which are of course only a selection from
more numerous instances that might be brought together,
show ‘that very close superticial resemblances frequently exist
between animals more or less remotely allied. These resem-
blances may be in form (e.y., snake and blindworm), or colour
(e.g., various Lepidoptera), or form and colour combined (e.g,
Leptalis and Heliconide). Resemblances between animals of
widely different groups (ég., caterpillar and shrew) are so
very rare as to be probably regarded as purely accidental ;
resemblances between more nearly allied forms (.g., Lepido-

262 ANIMAL COLORATION.

ptera and Hymenoptera) are less rare, but not common ; re-
semblances between species, belonging to different families or
genera of the same order (e.y., among Lepidoptera), are very
common: their number bears a certain proportion to the variety
of forms in the order; thus, they are most common among
insects, less common among birds and reptiles, rare among
mammals. This fact is against the hypothesis that the re-
semblances have been produced by the action of natural
selection, since protection of this kind would be just as effica-
cious in the higher group as in the lower ; and we find among
mammals, as among insects, a large number of cases of pro-
tective coloration.

Nevertheless, cases of mimicry that do occur—particularly
among Lepidoptera—are often so striking that no other explana-
tion than that offered by Mr. Bates seems to account for the
finishing touches, at least, of the resemblance. A considerable
initial resemblance may be fairly set down to other causes ;
because it is impossible to believe that a slight move in the
required direction would be of sufficient importance to serve as
material for the action of natural elimination. At the same
time, instances of mimicry, which are to be appreciated only
by insects (e.g., Volucedia and bee), must, in the present state
of our knowledge of insect vision, be removed from the
category ; so also are certain other cases such as Brephos
nothum and Ploseria diversata, and the annelid mentioned by
Semper. Seeing, then, that resemblances may occur between
animals which either cannot be, or are probably not, advan-
tageous to either, it is at least necessary to wait for more
convincing proofs before it can be more than provisionally
assumed that natural selection is responsible for these re-
semblances in other cases where they appear to us to be
useful.

CHAPTER VI.
SEXUAL COLORATION.

Sexual Dimorphism in Colour.

Is many animals where the sexes are separated, the males
and females are to be distinguished by certain “ secondary
sexual characters,” as they have been termed. Familiar in-
stances of such are the antlers of the stag, the spurs of the
cock and other gallinaccous birds, and the gorgeous plumes
found in the males of the birds of paradise.

The secondary sexual characters are sometimes confined to
differences of colour alone, as is the case with the chaftinch
and many other birds. The reasons for these differences in
the sexes have been much discussed, and the fact that at
least five theories have been put forward at different times
is an index of the difficulty of the questions involved.

An attempt will be made here to give some notion of the
arguments for and against the several theories which profess
to explain sexual dimorphism. Some notion must, however,
be first given of the facts which have to be dealt with.
Among the invertebrates, insects furnish the most abundant
examples, chiefly because they are the largest group of
animals in which the two sexes are distinct.

In many species of butterflies and moths, the sex cannot
be distinguished by the colour; the Vanesside in general

254 ANIMAL COLORATION.

(Red Admiral, Peacock, Tortoiseshell, etc.) present identical
tints in both sexes. In others, on the contrary, the colours
are so different that they might be taken for different species.
The Ghost Swift has white shining wings in the male sex,
and brown with orange markings in the female ; the males
of the “ Blues,” for the most part, alone deserve their name,
for the females have a prevailing brown colour. Among
moths the difference is sometimes reduced to little more than
a difference in size—as, for example, the Leopard moth. The
female of the Vapourer, Winter moth, and some others (fig. 28)

Fig. 28.—c, Female of Psyche helix. b, Male. ec, Case of the male; d, of the female
caterpillar.

have almost completely lost those characteristic organs of the
Lepidoptera—the wings. The colours of dragon-flies some-
times differ in the two sexes, and there are plenty of other
examples among other insects of the same phenomenon.
Among the Isopod Crustaceans (of which the commou
woodlouse is a familiar example), there are secondary
sexual differences which seem to be unnecessary, that is to
say, they have, or appear to have, no relation to pairing ; they
are merely evidence of maleness or femaleness as the case
may be. In certain species of Spheromide the males have
a long spine upon the back—a structure which is entirely
wanting in the female. In Ceratocephalus grayanus, a large

SEXUAL COLORATION. 255

species found off the coasts of Southern Australia, the males
have three long horns projecting from the head ; if the males
of this species were proved to fight for the possession of the
females, there would be a wonderful analogy in these horns
to the antlers of deer.

More striking still is the sexual dimorphism of the Echino-
derms. This group includes the sea-urchins, sea-cucumbers,
starfish, brittle-stars, and sea-lilies, which’ are characterised
by their radial symmetry, and by the presence of a calcareous
skeleton, more or less perfect, beneath the true skin; they
are not active animals as a group, though the Comatiula can
swim as well as crawl, and some of the starfish and brittle-
stars can move about with a certain degree of rapidity ; many
of them have eyes. Some of these echinoderms are among
the most brilliantly coloured of marine invertebrates, but the
colours can hardly have much significance, for the reasons
stated in considering the fauna of the deep sea.

Sexual differences have been discovered to exist in a good
many specics.* These differences may be seen extended to
the colour of the sexes, for Oscar Schmidt.in “ Brehm’s
Thierleben,” p. 981, remarks that the males of Strongylo-
centrotus lividus (a common sea-urchin) are darker coloured,
while the violet tint of the females tends more towards red.
Prof. Camerano,t while disinclined to admit any constant
differences in colour, abundantly confirms Prof. Schinidt’s
description of other sexual differences in form and _ size.
There can here be no question of preference in either sex,
for the ova and sperm are, as in the case of worms, simply
shed into the surrounding water. It should perhaps be re-
marked that secondary sexual characters, other than colour,

* Zool. Anzeiger., vol. iii., a paper by Prof. Studer of Berne.
+ Boll. Mus. Zool. Torino, Nov. 1890.

256 ANIMAL COLORATION.

are supposed also to have been produced by the esthetic
preferences of the female, not of course such characters as
the accessory grasping limbs of male Crustacea—for these
have an obvious use in seizing the female,—but structural
characters, such as the presence of wattles and plumes among
birds, which have no such use.

Among the Crustacea sexual diversity of coloration is
not very common. Darwin* only mentions two examples—
Squilla stylifera and a fiddler crab belonging to the genus
Gelasimus.

Another example of this phenomenon is a common American
edible crab—Neptunus hastata ; but the difference of colour is
limited to the large claws—the “ chelee” as they are technically
termed: these appendages are much bluer in the male than
in the female. This rather small difference is, according to
Prof. Conn,t quite constant.

Among vertebrates, we have sexual differences in coloration
even so low down in the scale as fishes. Mr. Cunningham t
has lately shown that the two species Avnoglossus lanterna and
A.Cophotes (plaice) are in reality males and females respectively
of but one species. Sexual differences of this kind are met
with in the Amphibia—for instance, in the notched crests and
lurid colouring of the large newt. The blackened index
finger of the male edible frog is associated with a structural
modification which enables him to seize the female at pairing
time ; this character, like the stag’s antlers, only reaches its
full development at the actual breeding season.

Sexual differences are not common among reptiles ; it is a
curious fact that in tortoises the colour of the iris sometimes
differs in the two sexes, as it does commonly among birds.

* “Descent of Man,” chap. ix.
t+ Johns Hopkins Univ. Circulurs, iii, p. 5,
} Proc. Zool. Soc., 1890, p. 540.

SEXUAL COLORATION, 257

Among lizards and snakes sexual differences in coloration
-exist, though instances of this dimorphism are not plentifal.
Lacerta galloti, of which there are at present a number of
specimens in the reptile house at the Zoological Gardens,
shows a dimorphism in colour, the throat of the male being of
a beautiful blue colour. The common British lizard (Zootoca
vicipara) shows a somewhat similar variation in the two

Fig. 29.—Bird of Paradise.

sexes: the under side is of a crimson tint in the male, and
pale buff in the female.

Among snakes the Puff Adder (Vipera arietans) is an
instance in point. So different in colour are the two sexes
that they might readily be mistaken for two different kinds
of snakes. In the male the prevailing tint is a rich yellow-
brown, in the female the prevailing tint is grey. It would, how-

ever, be difficult to decide which of the two sexes has the more
7

258 ANIMAL COLORATION.

beautiful or the more obtrusive coloration. Probably they are
equal: on a sandy ground the female would be more obvious than.
the male; on greyish soil, or among decayed-leaves, perhaps.
the male reptile would be more visible than his mate.

The great variety of sexual diversity which is found among:
birds has furnished most arguments for the theories of

Fig. 30.—Humming bird. Fig. 31.—Argus Pheasant,

sexual coloration. Every gradation is found, from perfect
resemblance, such as is afforded by the goldfinch, to. the
extreme differences exhibited in the case of the birds of
paradise. As a general rule the male is distinguished by
greater brilliancy of tints, and by the exclusive possession
of crests and wattles and other appendages; or by their
greater development if they are found in both sexes. But
it would be difficult to point to either sex among certain

SEXUAL COLORATION. 259.

species of curassows* as the more brilliant in colour. So,
too, the parrots formerly referred to different species of the
genus Eclectus, which have been shown by Dr. A. B. Meyer to
be merely the males and females respectively.

The Upland goose (Bernicla magellanica) is coloured in

Fig. 32.—Cincinnurus regivs (male and female),

both sexes by equally conspicuous tints; it would be inter-
esting to ascertain the proportion of persons who declared
a preference for each sex. The female is a rich brown diver-
sified by white marks, while the male is black and white ;
both sexes are extremely beautiful, though the colours cannot
be said to be brilliant.

* See Mr. Sclater’s beautiful monograph of this group, Trans. Zool. Suc.,
vol. ix., p. 273, and vol. x., p. 43.

260 ANIMAL COLORATION.

Where the two sexes resemble each other in coloration the
tints may be brilliant (e.g., the toucans) or dull (e.g., the robin).

It is among the humming birds (fig. 30), birds of paradise,
and many gallinaceous birds (fig. 31), that the most marked
differences of colour occur, associated very frequently with the
presence of accessory plumes or specially elongated feathers.
Compare, for instance, in the accompanying figure (fig. 32),
the male of the paradise bird (Cincinnurus regius), possessing
the extraordinary tail feathers, with the very ordinary-looking

female.

Sexual Dimorphism of Colour most marked in Birds and Butterflies.

It is a very suggestive fact that sexual dimorphism in colour
is most marked in birds and butterflies; in both of these
groups, particularly in birds, the colours are largely “ struc-
tural ”—zi.e., they are chiefly determined by the actual minute
structure of the part coloured—though, as I have already
mentioned, a background of pigment is required to show off
the colours. Furthermore, in both these groups, as Mr. Wallace
has pointed out, the extent of the coloured surface is much
larger in proportion to the body than in many others. Hence
sexual differences in colour are much exaggerated, as a neces-
sary consequence: three or four bits of glass coloured in a very
slightly different way from three or four other bits, will, when
multiplied and arranged by a kaleidoscope, produce an effect
greatly diversified in the two cases. It is perfectly clear that
sexual differences of colour may exist in animals, where
nothing like sexual selection can come into play; there is
therefore a groundwork for the production of the complicated
patterns we see in the feathers of birds. We presume that
birds have been evolved out of a lizard-like ancestor. Now,
lizards present us, occasionally, with sexual differences in

SEXUAL COLORATION. 268

colour of the scales which are not conspicuous ; convert every
scale into a feather, and the differences will be much more
striking, even without any complication of the pigment. In
fact, what seems to require an explanation is not so much the
diversity of coloration in the two sexes, but the occasional
similarity.

Slight Development of Colour Dimorphism in Mammals.

It is a remarkable fact that there is but little sexual diversity
among mammals, except such as is directly connected with
pairing and reproduction. It may be as well to explain here
that secondary sexual characters may be referred to two classes,
which are perhaps not very sharply marked off ; first, those
which have an obvious relation to the habits of the sex which
possesses them; secondly, those characters which have not
such an obvious relation. To the first category I would refer
the antlers of deer and the spurs of gallinaceous birds ; the
males of these animals are pugnacious, and use the weapons
in question in their combats with each other; the accessory
grasping organ possessed by the males of the Isopod genus,
Serolis, and the great development of olfactory hairs in the
genus Tanais* are of evident use to the crustacean in
seizing or finding the female. To the second category belong
colour differences, and perhaps such structural differences as
are exhibited in the male of the lemur, Hapalemur griseus.
In this animal I pointed out some years ago f the existence of
a peculiar patch of spine-like structures, upon the arm of the
male, which, as I was informed by Prof. Milne Edwards, are
not so highly developed in the female ; but this organ may
possibly be used by the male as a grasping organ at the time

* Fritz Miller, “ Facts for Darwin.”
t Proc. Zool. Soc., 1884.

262 ANIMAL COLORATION.

of pairing. The mane of the lion and the beard of man belong
to the same series. Sexual differences in colour among the
Mammalia are not common ; the most striking instance, per-
haps, is one referred to by Mr. Wallace*—Lemur macaco ;
the male of this lemur is black, and the female brown.
Dr. Dobson f has brought together some interesting examples
of sexual dimorphism among bats. There are, in addition to
various remarkable structural differences between the two
sexes, occasionally colour differences. These colour differences
are frequently developed only at the breeding season. In a
common Calcutta bat, Nycticeius temmincki, the under parts
are usually of a pale straw colour; but in females captured
during the months of March and April the prevailing hues
were arich saffron. It is important to notice, however, from
the point of view of sexual selection, that colour differences
are more common among the frugivorous bats, and they have
a better sense of sight.

Dependence of Sexual Dimorphism upon the Generative Organs.

The dependence of colour and other secondary sexual
characters upon the essential organs of reproduction is almost
too well known to need illustrating by examples. I shall,
however, refer to two recent instances which have been
carefully described. Prof. Max Weber of Amsterdam { has
examined a chaffinch, in which the left side of the body has
the coloration of a hen bird, the right that of a cock, which
are sharply marked off from each other in the middle line.
An examination of the viscera showed that the bird was a
hermaphrodite, with a well-developed ovary on that side of the
body which was clad with the plumage of the female, and a

* “ Darwinism,” p. 282.

t+ Proc. Zool. Soc., 1873, p. 241.
t Zool. Anzeiger, 1890, p. 508.

SEXUAL COLORATION. 263

male gland on the opposite side. The same kind of herma-
phroditism has been noticed in other birds. In cases where a
female bird has assumed the plumage of the cock, it has been
found that the ovary was diseased or atrophied.*

The second instance which I shall bring forward is that of a
moth—the common Oak Eggar. Dr. Bertkaut has figured
and described a hermaphrodite specimen of ‘this insect in
which the wings of one side of the body showed the colora-
tion, form and size of those of a male, while the opposite
couple of wings had the coloration of the female, and were,
as in the female moth, larger than the wings coloured after
the male pattern. On a dissection, the insect proved to be not
hermaphrodite, like the chaffinch, but a female with degenerate
organs, some of the parts typically present being absent. It
cannot, therefore, be called a hermaphrodite; it should be
remarked that the ovary was more degenerate upon the side
of the body on which the wings were those of a male, than
upon the other.

The Theory of Sexual Selection.

The classical theory to account for these sexual differences
is of course Darwin’s theory of “sexual selection.”

According to this theory the females, when courted by the
males, exercise a decided choice, and are not simply the prey
of the most persevering or the most powerful male. Hence
there is a tendency to an increase in the beauty of the colora-
tion of the males, and to an increased development in such
special appendages of that sex as crests, wattles, etc. The
gorgeous tail of the peacock, and the curious crests and other

* See Mr. Bland Sutton’s “ An Introduction to Pathology,” for further

instances. Also J. H. Gurney (jun.), “ Ibis,” 1888, p. 226.
+ Arch. f. Naturgeschichte, lv., p. 75.

264 ANIMAL COLORATION.

appendages of the birds of paradise, are among the more
striking effects which Darwin believed to have been produced
by this selection on the part of the female birds. Obviously
this theory must be limited to such animals as have an acute
sight and an esthetic appreciation ; accordingly, most inverte-
brate groups which show sexual differences, whether in colour:
or in the form of special appendages, must be set aside..
The vision of these animals, as has been already remarked,
does not appear to come up to the requisite standard of
efficiency.

On the other hand, it may be admitted that at least birds.
and mammals do possess a sufficiently developed sense of sight..
So far there is nothing to render the theory untenable. It is,
however, a remarkable fact that the Mammalia show, relatively
speaking, very little sexual divergence. The stags have their
antlers ; blue and red patches are developed upon the skin ina
few monkeys; and there are actual differences of colour in some.
species, such as the red kangaroo. In the male of this animal
the colour is brown, aud the throat is coloured pink by a sub-
stance of the colour of carmine which is secreted by the skin
in this region ; the female, on the contrary, is grey, and does
not show this peculiar efflorescence. On @ priori grounds one
would expect the most intelligent of the Vertebrata to show
the most strongly marked differences of colour; particularly
since there are well-founded instances of preferences exhibited.
by the female of certain mammals. Mr. Darwin, in a note
prefixed to a paper by Prof. Van Dyck,* calls attention to an
instance of this kind exhibited by the dog.

Among birds, it is remarkable that gorgeousness of colora--
tion is not always limited to the male sex; very often both
sexes have an identical coloration, which is as brilliant as in

* Proc. Zool. Soc., 1882.

SEXUAL COLORATION. 265

the males of other dimorphic species. This fact, however, is
not necessarily an objection to the theory of sexual selection.
It is explained by Darwin as being due to heredity ; the
brilliant colours were first of all, it is supposed, acquired by,
and limited to, the males, in response to a choice on the part
of the female bird. Gradually the effects were handed down to
the offspring of both sexes.

Difficulty of believing in a highly-developed Zsthetic Sense.

Viewed as a matter of probability or improbability, it is
difficult to conceive of so exalted an esthetic sense in birds.

It is necessary to assume that the females of many species
have a sense of beauty not only equal to, but far surpassing
that of the average human being. Merely brightness or un-
usual gaudiness in the male bird one could understand, as being
in part at least due to “ preferential mating,” but to put down
the delicate browns and greys of the feathers of the Argus
pheasant, which is almost the most beautiful of birds, to sexual
selection, is to assume a most refined sense of beauty in the
bird. Moreover, as Mr. Stolzmann has pointed out in discussing
another theory of sexual differences, which will be referred to
later, the taste of closely allied birds must differ in an immense
degree, if this theory be accepted.

He gives, among other instances, that of two species of the
American genus Basileuterus. In B. castanetceps the coloration
is dull; in B. coronatus the under parts are, in both sexes, a.
bright yellow; this bright colour would be, on Darwin’s theory,
first developed in the male and then handed down to the off-
spring of both sexes. We must therefore assume that the
females of B. coronatus have greatly surpassed the females of
the other species, in the development of their esthetic sense.
As the areas of the two species are contiguous, this difference

266 ANIMAL COLORATION.

‘cannot be set down to isolation, and the females of the sombre
species have every opportunity, did they desire it, of selecting
the brightly coloured males and abandoning their lawful
spouses.

The question, however, cannot either stand or fall upon its
probability or improbability. Actual observation can alone
settle the matter.

Z’sthetic Sense of Butterflies.

The case is clearly put by Mr. Scudder :—

“That butterflies have some perception of colour in mass
is unquestionable. It has often been remarked that a white
butterfly alights by preference upon white flowers, yellow
butterflies upon yellow flowers. Direct observations have
shown that this vague opinion is founded clearly upon fact, and
several instances which show this, and at the same time show
the lack of power of perception of form have been published.
Thus, Christy observed in Manitoba one of the Swallow-tails
‘fluttering over the bushes, evidently in search of flowers.
As I watched it,’ he says, ‘it settled momentarily, and exactly
as if it had mistaken it for a yellow flower, on a twig of Betula
glandulosa bearing withered leaves of a light-yellow colour.’
Albert Miiller records seeing the blue Alexis of Europe fly
rapidly towards a very small bit of pale blue paper lying upon
the grass, and stop within an inch or two as if to settle, doubt-
less mistaking it for another of its own kind. Plateau has
observed Agloe urtice [the small Tortoiseshell] of Europe fly
rapidly towards a white Calla, which could offer it no sweets.
And Jenner Weir has noticed how the white butterflies settled
on the variegated leaves in his garden.”

These facts are a long way from proving so highly developed
an esthetic sense as sexual selection renders necessary ; they

SHXUAL COLORATION. 267

are not even enough to prove the “recognition mark ” view of
coloration ; they simply show that insects can recognise colour,
and perhaps prefer certain hues to others. The facts of
hybridisation may be also quoted as possible errors of recog-
nition on the part of Lepidoptera.

Objections to the Theory of Sexual Selection.

It is quite common to see the peacock expand his tail and go
through all the performances incidental to courtship, while the
hen peacefully searches for food, quite uninfluenced by this
amatory display. It may be, however, that this is to be
explained simply by the fact that the hen is not in a mood to
respond to these advances.

Excitability at Breeding Season of Animals among which there is
no Pairing.

It is not only animals which pair that show a departure from
their usual habits at the breeding season. The Palolo worm,
greatly esteemed as an article of food by the Pacific islanders,
is an instance to the point. This worm, which is ofa greenish
colour, appears at certain seasons upon the surface of the sea ;
these times coincide with the maturity of the sexual products.

Another instance of the same phenomenon has been recorded
by Mr. Savile Kent. A marine worm belonging to the same
family as the Palolo appears in vast numbers in October ; after
.a few hours of active movement on the surface, they entirely
disappear from view. ‘‘By a close examination of these worms,”
says Mr. Kent, “ disporting upon the surface of the water, and
also isolated in suitable receptacles, and with the aid of the
microscope, I was fortunate in discovering the raison @ctre of
their early revels. It was, in fact, their general wedding
morn, and these their wedding junketings. Each worm was

268 ANIMAL COLORATION.

laden with ova or milt, which was discharged in little thim
milky streams, one from each side of the body, as they swam
through the water. The reproductive elements commingling
under these conditions were fertilised after the manner of the
spawn of certain fishes.”

These facts are evidently of the highest importance in
estimating the value of the theory of sexual selection. It has.
been shown that at the epoch of sexual maturity these worms
indulge in unusual antics and gyrations, which cannot captivate:
either sex—as there is no pairing, but merely a fortuitous
concurrence of the sexual elements shed into the sea.

As a general rule, sexual dimorphism is not found among
inactive animals low in the scale; but there are plenty of
exceptions. The “complemental males ” of the Cirripeds and
the parasitic male of the Gephyrean Bonellia are examples ;
there can be no question here of female likes and dislikes.

More positive facts are quoted by Mr. Wallace*: ‘Some
peahens preferred an old pied peacock; albino birds in a state:
of nature have never been seen paired with other birds ; a
Canada goose paired with a Bernicle gander ; a rush widgeon
preferred a pintail duck to its own species ; a hen canary pre-
ferred a male greenfinch to either linnet, goldfinch, siskin, or
chaffinch. ... Messrs. Hewitt, Tegetmeier, and Brent, three of
the highest authorities, ‘do not believe that the females prefer
certain males on account of the beauty of their plumage.’ .
Evidence is adduced that a female pigeon will sometimes take
an antipathy to a particular male without any assignable
cause; or, in other cases, will take a strong fancy to some one:
bird, and will desert her own mate for him; but it is not
stated that superiority or inferiority of plumage has anything
to do with these fancies.”

* “ Darwinism,” p. 285.

SEXUAL COLORATION. 269

Mr. Wallace goes on to remark “that female birds have
unaccountable likes and dislikes in the matter of their partners,
just as we have ourselves”; and, it may be added, just as they
and other animals have in the choice of their food, some eating
greedily creatures coloured in such a way as to cause other
animals to refuse them. As to sexual selection in our own
species, it is quite clear that a girl selects her husband, just as
a bird often does, because he is the first comer ; and when a
real selection occurs, it is by no means always beauty of body
or of mind that wins the day.

Mr. Poulton, who is a strong believer in ‘“ sexual selection,”
admits that it is “still to some extent sub judice,” simply
because there is a lack of evidence from careful watching of
the phenomena of courtship.

Some Arguments in Favour of Sexual Selection.

Mr. Poulton supports the theory of sexual selection by
several very ingenious considerations. He points out that
‘the appearance of beautiful colours and patterns, which are
displayed in courtship, invariably occurs in diurnal, or par-
tially diurnal, animals.” Goatsuckers and owls undoubtedly
support this conclusion; and yet the enormously elongated
tail of the night-jar, shown in the figure (fig. 33), might be
put down to sexual selection; the day-flying moths, such
as the magnificent Uraniide and the Castniide, are more
brilliant in their coloration than the generality of nocturnal
moths. Sexual colours, moreover, “are not developed on
parts of the body which move so rapidly that they become
invisible.” In the humming birds, for instance, it is the
breast which commonly shows the brilliant metallic colora-
tion which is so characteristic of the order, and not the

rapidly vibrating wings.

a
270 ANIMAL COLORATION.

In certain moths, where the female is partly degenerate, the
male is not very brightly coloured. A striking case of this is

Tig. 33,—NIGuT-Jar.

afforded by the Vapourer moth (see fig. 15): the female is
here wingless, and does not therefore get very far away from
the cocoon ; the male is comparatively plainly coloured. In the

SEXUAL COLORATION. 27k

genus Psyche, the dull colours of the male insect are still more
marked ; the Vapourer is a rich brown, with a white spot in
the centre of each fore-wing, but the colour of Psyche is a dull
greyish brown; in Psyche (fig. 28), the female is still more

Fig. 34.—Male and Female of Winter Moth.

degenerate. Figs. 34, 35, represent the males and the wing-
less females of two Geometers: it can hardly be said that
these two moths are conspicuously inferior in their coloration
to some of their immediate allies which have a winged female.

aS SS . = Ss a \ is
SOK S~ BAER A SY:
LSS SERN

Fig. 35.—Male and Wingless Female of Winter Moth.

The antenne of the female Vapourer moth are thread-like, and
not * pectinated,” as in the male; they are doubtless, therefore,
as Mr. Poulton remarks, less efficient as sense organs ; but
it must be noted that we have no evidence that the eves are at

272 ANIMAL COLORATION.

all degenerate in this insect ; and it is the eyes rather than the
olfactory organs which are important for the female, on the
theory of sexual selection. Besides, we commonly meet with
simple, non-pectinated antenne among females of Bombyces,
which are not wingless, and in which there is a more or less
marked sexual dimorphism ; for instance, in the following :

Fig. 36.—Gypsy Moth (male, female, cocoon, and larva),

the Gypsy moth (fig. 33), the December moth, the Lackey,
the Fox moth, Oak Eggar, etc.

The Courtship of Spiders.

The “ courtship” of spiders has been used as an argument in
favour of the development of special colours and markings in
the male, through selection by the female.

Jt appears to be an undoubted fact that the males of certain
spiders indulge in the most singular antics previously to

SEXUAL COLORATION. 273

pairing ; the facts relating to these “love dances” are to be
found in two interesting papers* by Mr. and Mrs. Peckham,
which are well worth a careful reading. One, out of many in-
stances described by these two observers, will be sufficient for
the present purpose.

The male of a species of Habvocestum differs from the female,
in having his first legs of a delicate green colour fringed with
white hairs; these ornamental appendages are displayed to
every advantage while the male is paying his addresses to the
female ; the remarkable positions which the spider assumes
are illustrated by figures; the authors mention that during
the performance the female “eyed him intently,” and seemed
to be “interested ‘in his display”; with reference to the
mating habits of another spider, the female is said “to become
excited, and watch the male with absorbing interest.” The
late M. Alphonse Karr, in his delightful essays entitled “A
Tour round my Garden,” gives a humorous description of the
courtship in spiders. ‘My friend,’ he says, “was more
fortunate, for the belle advanced towards him, whilst he waited
for her in visible anxiety ; but whether he perceived in her
behaviour any unsatisfactory sign, or whether the coquette had
not sufficient skill to compose her countenance, which I could
not: distinguish from the smallness of its proportions, or
whether she permitted to appear in her air more hunger than
love, or whether, in short, the lover was not struck with one of
those intense flames which brave all dangers, he took to flight
with such rapidity that I lost sight of him.” The American
naturalists, through long familiarity with the objects of their
study, appear to be able to read with more accuracy the
countenance of the female. They speak of her as gazing

* “Qccasional Papers of the Natural History Society of Wisconsin,”

vol. i., two numbers.
Is

274 ANIMAL COLORATION,

towards the male in a softer mood, evidently admiring the
grace of his antics.

Generally speaking, the elaborate performances of the male
spider are for some time to no purpose, or they rouse the
female to make a sudden dash, which looks suspiciously like
a desire to eat him ; sometimes the female runs away; it
appears to be a comparatively rare occurrence for mating to
take place at once; this, of course, looks like an intelligent
selection on the part of the female.

Mr. and Mrs. Peckham refer to a male of Synageles picata,
which was placed in a mating box with six females: he mated
with all of them! This does not look so much like selection
unless it be urged that the females yielded to the one male
faute de mieux.

In Astia vittata there are two kinds of males, one red like
the female, the other black ; the attitudes of courtship were
observed to be quite different in the two varieties, and when-
ever the two varieties were seen to compete for a female, the
black one was successful.” It does not appear what are the
proportionate numbers of the two kinds of males ; but they
are connected by intermediate forms. Now, on the supposition
that the black form was the result of deliberate choice on the
part of the female, the black males ought to be the most
numerous ; furthermore, there should not be a large series of
intermediate forms; the despised males at one end of the
serles ought to have ceased to be; it can hardly be suggested
that this has been the case, and that there has been a gradual
blackening of the males, because the unpopular males are
coloured like the females, and were thus probably the start-
ing-point of the series of changes. While admitting. the great
value of Mr. and Mrs. Peckham’s investigations, it would be
desirable that some experiments like those of M. Platean’s

SEXUAL COLORATION. 275

(see p. 229) should be made upon these spiders. M. Plateau
thought himself justified in stating that hunting spiders,
belonging to the same family as some of those treated of by
Mr. and Mrs. Peckham (Adtide), could only distinguish their
prey well enough to capture it at a distance of from three-
eighths to three-quarters of an inch ; and even, at that short
distance, their vision was not accurate, since mistakes were
frequently made. It should also be shown that blinding the
spiders put an end to any selection. Until such experiments
have been made, it is premature to draw too detailed con-
clusions from the very interesting facts which the two
memoirs contain.

On the other hand, Dr. McCook * quotes experiments which
seem to indicate that the Saltigrades can see for a distance
of ten inches or so. In fact, observations on this exceedingly
important subject are most contradictory.

Sexual Dimorphism partly due to a Need for Protection on the

part of the Female.

Mr. Wallace, in criticising the theory of “ sexual selection,”
has offered two alternative views of sexual dimorphism, which
are not necessarily opposed to each other ; they might both be
accepted. In Darwin’s theory, stress is laid upon the brilliant
colours of the male birds, and it is to be inferred that originally
both sexes were similarly and plainly coloured, that coloration
being often retained in the female. It is perfectly true that
the male sex is in many respects the most specialised ; in many
animals with a pronomnced sexual dimorphism, the young
males are like the females ; it is only on the approach of sexual
maturity that the distinctive secondary attributes of the male
are acquired.

* « American Spiders and their Spinning Work.”

276 | ANIMAL COLORATION.

Mr. Wallace would explain the secondary differences in
colour between the two sexes as due to a divergence in two
opposite directions.

The hen bird nearly always sits upon her eggs ; instances to
the contrary are rare. During the period of incubation, and
for a short time after the young birds are hatched, the mother
is subject to special dangers which are not shared by the
active male; she is more liable to attacks from predatory
animals, which circumstances make it difficult to resist. An
inconspicuous coloration is thus clearly a desideratum. There
is also a remarkable relation between the sex coloration and
the nesting habits. Birds which build their nests in exposed
situations appear to be almost always dull-coloured ; on the
other hand, the females of those species which build in holes,
or construct elaborate nests that completely conceal them, are
generally as brightly coloured in one sex as in the other.

The difference between the two sexes is farthur accentuated
by the “greater vigour and excitability” of the male, which
leads to a more pronounced development of colouring ; but the
further consideration of Mr. Wallace’s important views upon
this important branch of the subject will be deferred, until
after some account of Mr. Stolzmann’s theory of sexual dimor-
phism has been given ; for it is more fitting to conclude this
chapter with the most probable theory.

Mr. Stolzmann’s Views.

Mr. Wallace’s views of sexual dimorphism attribute, as
has already been mentioned, the difference between the sexes
partly to a need for protection of the female bird. He replaces.
in fact, “ sexual” by “natural selection,” but only as regards the
female bird. Mr. Stolzmann * has endeavoured to account for

* Proc. Zool. Soc., 1885, p. 615.

SEXUAL COLORATION. 277

the brilliant colours of the male birds, for their appendages,
wattles, spurs and so forth, on the same erounds.

It appears that among birds—and this is clearly the group
in which sexual selection must exist, if anywhere—the males
are more numerous than the females; this at least is Mr.
Stolzmann’s statement, based upon the examination of large
series of birds collected by himself in Peru. A collection of
birds made by Mr. Guillemard during the cruise of the yacht
darvchesa in New Guinea and neighbouring islands contained
O84 males, 285 fenaales and 111 of undetermined sex; so that,
supposing the extreme case that all the 111 specimens were
females, there is still a preponderance of the opposite sex.

Here is an obvious criticism upon the supposed fact, that
females are less numerous than males in collections of birds ;
the very fact that the females are shyer and harder to see, more
protectively coloured, often sitting upon the nest, renders them
less likely to fall victims to the gun of the collector ; hence,
possibly, the greater abundance of males in collections of skins.

Another fact, upon which Stolzmann bases his ingenious
theory, is the influence of nutrition upon sex ; badly nourished
exes produce males, well nourished eggs females. There are
other facts which tend to show that this is probably true.
The queen bee the only female in the hive, is produced from a
larva which has been specially “fed up” for that very purpose.

Among insects there are other instances which tend to prove
the same generalisation—that excess of nourishment is favour-
able to the production of females, and that defective nutrition
is correlated with the development of males. Some interesting
experiments upon the subject were made some years ago by Mrs.
Mary Treat.* This lady found that larve of a Swallow-tail,
Papilio asterias, if encouraged to go on feeding as long as

* American Naturalist for 1873.

278 ANIMAL COLORATION.

possible, nearly always produced female butterflies ; on the
other hand, by cutting short the food supplies a preponderance
of males were hatched. Similar experiments were made with
the Camberwell Beauty anda moth. Dr. C. V. Riley made a
larger number of experiments, which did not appear to him
to be quite so conclusive as to the direct influence of food ; but
he admitted that “there is a certain relation between organic
vigour and sex, and that the latter may be determined in the
offspring, by the amount of vigour or vitality—creative or
organic force—in the parents, and that the female is in some
way connected with increased, and the male with lessened,
vitality.” This question, however, is not one which can be
treated of in the present volame; the reader is referred to
Messrs. Geddes and Thomson’s work “ The Origin of Sex ” for
further details: all that I desire to point out is that Mr.
Stolzmann’s conclusions are, on the whole, borne out by ex-
periments.

Now, seeing that upon the females devolve the chief cares
of nest building—at least in the majority of species—it is not
surprising that the greater number of eggs laid should be
badly nourished: the bird has less opportunity of looking
after her own comfort; and on the other hand, if we may
suppose that the active males will tend to reproduce in their
offspring a preponderance of males, if they themselves, as will
probably be the case, are in a better condition than the females
with whom they pair. This statement, I should observe, is M.
Stolzmann’s. In any case there is clearly evidence tending
to show that the percentage of male births among birds is
greater than that of females.

Now, the preponderance of males over females is not advan-
tageous to the species. And natural selection, as M. Stolamann
points out, is less concerned with the well-being of the

SEXUAL COLORATION. 279

individual than with the well-being of the species. The
bachelor males (/.e. those who have not found a mate) are apt
to persecute with their attentions the females while sitting
upon the eggs; the ideal condition, for monogamous birds,
would be an exactly equivalent number of males and females ;
but this is precisely what we do not get. The bachelor males,
therefore, are useless for the species, not only on account of
their interference with the females during an important period
of their existence, but also because they occupy valuable space
and lessen the supplies of food.

Anything, therefore, tending to lessen the undue preponder-
ance of the less useful sex would be, M. Stolamann thinks,
seized upon and perpetuated by natural selection. Hence
the gaudy colours, crests and spurs, and pugnacious habits
of the males. The bright colours render them visible, not
only to each other, but to hawks and other enemies ; the long
plumes, such as we find in the birds of paradise, lessen the
rapidity of their flight, and cause them to fall an easier prey ;
and thus the equilibrium of the species is readjusted. The
curious humming bird Loddigesia mirabilis has, in addition to
the longer tail feathers, a wing shorter by some millimetres
than those of the female ; both these facts of structure tend to
lessen the capacity for flight ; a double purpose may be served
by this and similar cases; the birds fall easier victims to
predaceous birds, and they are unable to secure so great an
abundance of insect food, as their better equipped mates. Here,
again, we have two causes which operate in the direction of
lowering the numbers of males, and at the same time raising
the numbers of the females.

But not only are comparatively defenceless birds preyed
upon by hawks and other stronger birds : they show often, in
the breeding season, a pugnacious disposition which leads

280 ANIMAL COLORATION.

to fights among themselves, frequently terminating in fatal
consequences—particularly among such species as have spurs ;
they also indulge in curious antics—the “love dances,” which
have been so well described by Mr. W. H. Hudson, of many
South American species. Both the combats and the dances
are set down, by those who support the theory of sexual
selection, to the influence of the female. The favour of the
female is, it is supposed, gained by the victor in a combat, or
by the more graceful dancer.

M. Stolzmann, on the contrary, believes that the duels
among the males have the primary result of reducing’ their
numbers ; hence the pugnacious disposition, the spurs, and all
the paraphernalia of warfare, have been cultivated by natural
selection, just as in the days of cock-fighting the same attri-
butes, mental and physical, were sedulously cultivated for a
nearly identical end by artificial selection. As to the dances and
the rival singing of male birds, this is not to be regarded as
a peaceful strife to win the regard of the females, but merely a
distraction to protect the females against the too constant
attentions of the males.

It cannot be doubted that this theory is among the most
ingenious, and that an array of facts, of which the above is only
a very small selection, support it. Granting the principal
fact upon which it rests is the great numerical superiority of
the males over the females, it would be difficult to dispute,
were it not almost impossible to believe in any theory which
ignores the deep-seated differences between the two sexes.

Mr. Wallace's Views.
Mr. Wallace connects the greater brilliancy of such colora-
tion, with the greater vigour and activity of that sex due to:
“a surplus of vitality ” exhibited in the combats, and amorous

SEXUAL COLORATION. 281

dances and displays already referred to; he points out that
accessory plumes, so often found in the male sex, are commonly
placed above the most powerful muscles. Such plumes are
in themselves—apart from their use on the theory of “ preferen-
tial mating ”’—often not only useless, but injurious to their
possessor. The horns of a stag are beautiful, and useful for
fighting ; but we are reminded by Msop that they entangled
their possessor in the boughs of the forest ; like the long hair
of Absalom, also a sexual adornment. The very fact that these
structures are so greatly developed in certain species is “an
indication of such perfect adaptation to the conditions of exist-
ence, such complete success in the battle of life, that there is,
in the adult male at all events, a surplus of strength, vitality,
and growth-power, which is able to expend itself in this way
without injury.”
Mr. Wallace also brings forward an argument, which shows
that female preference can hardly be responsible for sexual
diversity of this kind. Natural selection, or rather natural
elimination, is continually removing unfit varieties ; there are
but few survivors out of each season’s eggs ; and one of the
very important qualities for which birds are selected is that
they should be well able to discharge their duties towards
their offspring. ‘“ This extremely rigid action of natural selec-
tion must render any attempt to select mere ornament utterly
nugatory, unless the most ornamented always coincide with
‘the fittest’ in every other respect ; while, if they do so coin-
cide, then any selection of ornament is altogether superfluous.
If the most brightly-coloured and fullest-plumaged males are
not the most healthy and vigorous, have xot the best instincts
for the proper construction and concealment of the nest, and
for the care and protection of the young, they are certainly not
the fittest, and will not survive, or be the parents of survivors.

282 ANIMAL COLORATION.

If, on the other hand, there is generally this correlation—if,
as has been here argued, ornament is the natural product and
direct outcome of superabundant health and vigour, then no
other mode of selection is needed to account for the presence
of such ornament. The action of natural selection does not
indeed disprove the existence of female selection of ornament
as ornament, but it renders it entirely ineffective.”

Summary.

In short, we find that the secondary sexual characters of
animals are dependent upon the germ glands themselves ;.
and that the sexual diversity of animals is also associated
with differences of disposition and habit. There is a funda-
mental difference between males and females, based upon the
actual difference of sex, which generally finds an expression
in outward unlikeness. These superficial differences may also
be partly due to the different mode of life led by the two:
sexes. We meet with them in animals which cannot be
moved by any choice or esthetic preference ; but it is also”
true that they are most highly developed in the higher animals.
where such choice is at least conceivable ; the mammal, how-
ever, forms a very important exception to this statement.
Butterflies and birds show the most marked sexual dimorphism
in colour ; and it is precisely in these two groups that there
is the greatest opportunity for colour development, owing to
the structure of their feathers and scales respectively. Colour
differences become necessarily exaggerated in these animals,
through mere multiplication of details. Nevertheless, it is
quite possible that sexual selection may have played a subordi-
nate part in the production of sexual coloration, and we may
also allow some force to Stolzmann’s suggestions.

GENERAL INDEX.

Abraxas grossulariata, 50,
148, 165, 202.
Accipiter cooperi, 239.
Acreea, 197, 198, 215,
Acronycta alni, 189.
ligustri, 104.
—— megacephala, 104,
—— menyanthidis, 4.
-—— psi, 120, 164, 167.
——-— tridens, 120.
Actias selene, 6U.
Aeluredus, 240.
pbuccoides, 240.
Aeolosoma, 8, 95, 127.
—— headleyi, 95.
Agriopis aprilina, 211.
Agrotidee, 63.
Alcyonium digitatum, 128.
Alder moth, 189.

Allolobophora fcetida, 157. :

Alcyonia, 45.
American hare, 74.
Amphibia, 20.
Amphibolurus muricatus,
154, 160, 164, 165,
Amphiprion percula, 186.
Amphisbaena, 208.
Ancula cristata, 174.
Ani, 17, 239.
Angerona prunaria, 63.
Anosia plexippus, 210,
Antennarius, 131.
Anthophora, 204.
Anthophylla, 45.
Apamea, Y8.
Aphomia sociella, 225,
Apis mellifica, 205.
Arctic fox. 74, 75, 77, 78.
Arge galathea, +, 211.
Argus pheasant, 258, 265.
Argynnis paphia, 59,
valezina, 59.
Arion empiricorum, 59.
Armadillo vulgaris, 164.
Arnoglossus, 256.
—— lanterna, 256.
— lophotes, 256.

—_——

Asio galapagoensis, 58.
-—— brachyotus, 58.
Astrea, +5.
Astrophyton, 32.
Atyoida, 145.
Australian plover, 156.
Basilarchia, 210.
hipparchus, 210.
Basileuterus, 265.
—— castaneiceps, 265.
—— coronatus, 265.
Bee, 154, 176, 205.
Bee-eater, 217.
Bee hawk moth, 27,
Belone, 11.
Bernicla magellanica, 251).
Bernicle goose, 268.
Biston, 63.
—— betularia, 119, 247.
-— pilosarius, 94.
Blackbird, 162.
“ Blue” butterflies, 14, 16,
211, 214, 246, 254.
Blue tit, 157.
Boarmia, 63.
- repandata, +3.
Bombinator igneus, 183.
Bonellia, 268.
Bombyx trifolii, 43.
Brambling, 164, 165.
Brandling, 157.
Brephos nothum, 282, 252.
Brimstone butterfly, 40.
moth. 106.
Bryophila alge, 129.
Buff-tip. 150, 154, 167, 172.
Bufo viridis, 150.
Burnet moth, 165.
Caddis fly, 234.
Callidryas, 213.
Camberwell beauty, 278.
Canada goose, 268.
Canary, 51, 53, 268.
Canis lagopus, 74.
Carabus auratus, 72.
violaceus, 160.
Caradrina, 98.

Carpococcyx radiatus, 149;
238.

Catocala, 220.

—— amica, 220.
-—— linelea, 220.
Cebus, 149, 173, 194.
Centipedes, 67.

_ Centropus phasianus, 238.
_ Ceratocephalus grayanus.
254,

Cercopithecus, 16.
callitrichus, 149.
Cervus duvaucelli, 70.
-—- mantchuricus, 70.
Ceuthorhynchus urticre.

Cherocampa elpenor, 2:3.
Chaffinch, 151, 262, 268.
Chalcides viridanus, 159.

. Chameleon, 143, 154.

Chelonia caja, 49, 52, 165.

hebe, 49.

Chimpanzee, 10.

Chrysochloris, 32.

Chrysopa, 197.

Cicindela campestris, 63.

Cincinnurus regius, 254,

260.

Cidaria russata, 43.

Cilix spinula, 117.

Cinnabar moth, 150, 15s,
165, 171, 180, 191.

Cladobates, 236.

223, 24.
Clearwings, 202, 204, 242.
Cleora glabraria, 119.

“ Clifden blue,” 61.

“ Clouded yellow,” 40, 40.
Clytus, 200,

arietis, 245.

Cobra, i82.

Cockroach, 155.

Ceeliodes didymus, 221.
Codfish, 130.

Colias edusa, 46.

—— helice, 4h.

284

Colias lesbia, 46.

Comatula, 255,

“Comma” butterfly, 81.

“ Common White,” 40.

Convoluta schultzei, 7.

Convolvulus hawk moth,
23.

Coronella cana, 59.

phocarum, 59.

Cosside, 63.

Cowbird, 239.

“Crimson underwings,”
63, 84, 85.

Crocodile, 177.

Crotophaga ani, 239.

Cryptocope, 36.

Cuckoos, 238.

Cuculus canorus, 240. |

Cunner, 130. |

Curassow, 259. |

Currant clearwing, 243.

Cyaniris pseudargiolus,
24

Cymatophora, 104. !
Dagger moths, 120, 167.
Danais, 196, 211. ?
—~- chrysippus, 137. |
Dasydia obfuscata, 43.
December moth, 272. |
Deer, 29, 70. |
Deilephila galii, 9.
Dendrocopus, 4.
Dendronotus, 128. I
arborescens, 174.
Diphthera orion, 166, 211. |
Dolphin, 115.
Doris lamellata, 174.
Doristichus niger, 160, 164.
Draco, 206.
Earthworms, 67, 157.
Earwig, 162.
Echinoderms, 16. |
Eclectus, 259, |
-—— polychlorus, 4. I
Elaps, 181. :
Elephant hawk moth, 23, :
151.

Emerald moth, 39, 60, 83,
108, 135.

Ennomos angularia, 49.

—— autumnaria - tiliaria,
82.

—— subsignaria, 91.

Kolis, 174.

Epeira trifolium, 12.

Epunda lichenaria, 119.

Eristalis tenax, 154, 165,
232.

Ermine moth, 163.

GENERAL INDEX.

Eucheliajacobeee, 150,158.
Endynamis taitensis, 239.
Eunice, 127, 132.
Eurycope, 36.

Euterpe, 195. 209.

Eyed hawk moth, 134, 247.
Fer cle lance, 182.
Fire-bellied toad, 183.
Fishing frog, 189.

Flat fishes, 119.
Flounder, 64.

Flying lizard, 206.
Forester moth, 108.

| Forficula auricularia, 164.

Formicariide, 217.

Fox moth, 272.

Friar birds, 241.

Fritillary, 59.

Duke of Burgundy, 99.

Galleria cerella, 225.

—— melolella, 226.

Garden carpet moth, 117,
189.

Gatekeeper butterfly, 25,
211.

Gelasimus, 256.

Geometra — papilionaria,
135, p

Ghost swift, 42, 254.

| Giraffe, 85.
_ Glaucus, 123.

Glossy starling, 155, 163,
164, 165.

Glutton, 73.

Goatsucker, 237, 269.

Golden mole, 32.

plover, 30.

Goldfinch, 258, 268.

Gold pheasant, 62.

' “Goose egg.” 117.

Grapta Fabricii, 81, 82.
—— interrogationis, 81.
umbrosa, 81, 82.

| Grasshopper, 71.
. Grayling, 191.

-— butterfly, 100.

Great spotted woodpecker,
154, 155. 156, 157,
162.

Great tit, 154, 162.

Greenfinch, 263.

Green hairstreak, $3, 108,
ll.

Greenland falcon, 73.

Ground cuckoo, 14%).

hornbill, 182.

Guinea fowl, 157.

Gull, 29, 59.

Gurnard, 192.

Gymnalia, 22].

Gypsy moth, 272.

Habrocestum, 273.

Hadena adusta, 49.

Halias quercana, 21.

Hang nest, 156.

Hapalemur griseus, 261.

Harpy eagle, 178.

Hedgehog, 20.

Helix aspersa, 52.

nemoralis, 56.

Heliconide, 14, 178, 193.

Heliconius, 17, 195.

beskii, 197.

— eucrate, 202.

Heloderm lizard, 18, 180.

Hemithea thymiaria, 60.

Hepialus humuli, £2.

Heteropora, 45.

Hipparchia semele, 100.

cassiope, 211.

Horned toad, 144.

Hornet, 175.

clearwing, 203, 231.

Humming bird, 258, 269,
279.

Humming bird hawk
moth, 27, 98, 204.

Hybernia defoliata, 50.

— progemmaria, 94.

Hydra, 66.

Hydrophis, 182.

Hyla, 146.

—~- arborea, 145.

Hymenopus bicornis, 87.

Hypocolius, 156.

Iguana, 17, 32. 83, 93, 133.

Ischnosoma, 36.

Ithomia, 199, 215.

ilerdina, 194, 199.

Jaguar, 18, 85, 93.

Jay, 151.

John Dory. 190.

Kagu, 149. 162.

Kallima, 88, 115, 120, 139.

Lace-wing fly, 165, 197,

Lacerta galloti, 158, 163,
164, 257.

—— muralis, 149.

ocellata, 43, 158. 160.

—— Nimonyi, 43.

viridis, 92, 134, 149,

159, 160, 161, 164,
169.

Lackey moth, 150, 272.

Laertias philenor. 170.

Lanius collaris, +4.

Lappet moth, $7, 88.

Larentia ceesiata, 43.

Larentia didymata, 43.

Larus fuliginosus, 59.

- modestus, 59.

Laughing jackass, 161,162,
164, 182.

Leaf-cutting ant, 217.

insect, 22.

Lemur macaco, 262.

Lemming, 74, 76.

Leopard moth, 157. 165,
254,

Lepidosiren, 11.

Leptalis, 14, 17, 195, 209,
215,

— Theonoé, 194, 199.

-—— melite, 249.

Leptocephalus, 123,

Leptocircus virescens, 204. :

Leptogorgia virgulata,130.

Lepus americanus, 74, 75.

Leucania, 98,

Leucophasia sinapis, 209,
215.

Linnet, 268.

Lithobius forficatus, 161,
164.

Locusta viridissima, 72.

Lophopteryx camelina, 12.

carmelita, 104.

Lyceenidee, 16.

Lyceena agestis, 211.

—— alexis, 266.

-—— argus, 211.

Lyncornis macrotis, 238.

Macroclemmys tem-
mincki, 190.

Macroglossafuciformis, 27.

Madrepora, 45.

Magpie, 155, 164, 165.

167, 172.

Mamestra persicariz, 155.
165.

Mammalia, 16.
Mania typica, 167.
Mantis, 87, 109, 187.
Marmoset, 149, 154.
Meadow browns, 25, 98.
Mechanitis, 215.
lysimma,
Medusa, 33.
Melanippe fluctuaria, 117.
——-~ hastata, 43.
—— montanata, 43.
Melicophila picata, 240,
Melite, 213.
Melitza artemis, 49.
Melitta, 204.
Membranipora, 131.

moth, 21, 106, 148,

GENERAL INDEX.

Mephitis mephitica, 179.

Merveil du jour, 8+, 97,166,
211, 220.

Miana. 98.

Micaria scintillus, 217.

Midas rufimanus, 149.

Millepora, 45.

Mimonectes, 222, 233.

Meeandrina, 45.

Mole, 13.

Molothrus, 17.

bonariensis, 239.

Mongoose, 182.

Monticulopora, 45.

Moon moth, 60.

Morpho, 61.

Motmot, 156, 199.

Munnopsis, 36.

Musk deer, 177.

—— ox, 73, 77, 78, 177.

Myodes lemmus, 7+.

Myrmecobius, 180.

Mysis, 124.

Myxicola, 222, 223, 224.

Nautilograpsus, 145.

Nemeobius lucina, 99.

' Nemeophila plantaginis,
49

Neptunus hastata, 256.
Night-heron, 59.
Night-jar, 13, 269, 270.
Nonagria, 98.
sparganii, 167.
Notodonta chaonia, 104.
-—— dodonea, 104.
trepida, 102.
Nudibranchs, 123, 127,
174 :

Numida mitrata, 157.

Nycticeins temmincki,
262.

Nycticorax pauper, 59.

—— violaceus, 59.

Oak eggar, 262, 272.

tortrix, 83.

Ocelot, 93.

C£dicnemus grallarius, 162.

CE£neis, 99, 101.

Ophiophagus, 182.

“ Orange tip,” 40, 87, 108.

Orang-outan, 10.

Oreocephalus, 57.

Orgvia antiqua, 159, 165.

Orioles, 241.

Ovulum uniplicatum, 130.

Owls, 58, 237, 269.

Oyster-catcher, 162.

“ Painted lady,” 15.

Palamedea, 233.

285

Paleocr ita vernata. 91.

Palolo worm, 267.

Papilio, 211.

—- asterias, 277.

machaon, 169.

Paradise bird, 257, 258,
260, 264.

Parrots, 15, 83, 102.

“ Peach blossom,” 84.

Peacock, 263, 267,-268.

—— butterfly, 8, 21, 50,
63, 190, 254. fvaro

Pelopzus madraspatanus,
176.

Penguin, 115.

Pepper - and-salt moth,
106, 247.

Petroica bicolor, 240.

Phalarope, 71.

Phronima, 123.

Phrynosoma, 144.

Phyciodes, 47.

Phycis carbonariella, 113.

Phyllium, 22.

Phyllornis, 32.

Pieride, 14, 195.

Pieris brassice, 165.

rapee, 44.

Pigeon, 268.

Pintail, 268.

Pleurogonium, 36.

Ploseria diversata,
252,

Polar bear, 73, 78.

hare, 73.

Poplar hawk moth, 247.

Porcellanaster, 36.

Privet hawk moth, 23.

“ Prominents,” 103.

Proteus, 67.

Protopterus, 11.

Pseudis, 11.

Psophia, 149, 162.

Psyche, 271.

-—— helix, 254.

Pterophryne histrio, 131.

Ptilophora plumigcra,104.

Puff adder, 120, 182, 257.

Puma, 28, 30, 178.

Puss moth, 133, 136, 168.

Pygrera bucephala, 4°),
164.

232.

Rabbit, 13.

Rattlesnake, 182.

Raven, 17, 73, 77.

“ Red admiral,” 15, 21, 61,
62, 254.

Red kangaroo, 26+.

Reindeer, 73.

286

Rhinophis oxyrhynchus, °
64

Ringlet, 211.
Robin, 260.

Rock eel, 130.
Rosc-coloured pastor, 154,
146, 162, 164.

Rumia crategata, 106.

Rush widgeon, 268.

Sabella. 4.

Sable, 77.

Sagitta, 33.

Salamander, 18, 183.

Salamandra maculosa,138.

Salmon, 1380.

Salpa, 33, 122.

Sand skink, 154, 159.

Saturnia, 51.

carpini, 94.

Ratyrids, 62, 98, 99.

Scarce “ Merveil du Jour,”
211, 220.

Scarlet ibis, 42.

Sceleporus, 144.

Screamer, 233.

Seylleea pelagica, 132.

Sea fan, 130, ;

raven, 130.

Secretary bird. 183.

Selenia illunaria. 28.

illustraria, 82.

Serolis, 36, 39, 261.

Sesia apiformis, 243.

bembeciformis, 244,

—-— bombyliformis, 242,
244,

— fuciformis, 242.

tabaniformis, 242.

~— tipuliformis, 204,242,
244.

Sesiidee, 63,177, 204,221.

Shrew, 205.

Simonella americana, 217.

Siskin, 268.

Sitta, 94,

Skippers, 98.

Skunk, 178, 237.

Sloth, 16, 86, 95.

Slug, 59, 162,

Snail, 52, 56.

Snakes, 64, 83,120,146, 182.

Snow bunting, 71.

Snowy owl, 73, 113.

Sole, 140.

Solea vulgaris, 141.

GENERAL INDEX.

Sparrow, 151.

Sphingidee, 23.

Sphinx populi, 53.

Spiders, 110, 216, 272, 273,
274, 275.

Spilogale, 179.

Spilosoma = Iubricipeda,
154, 165.

Spirorbis, 131.

Sponge, 7, 66, 127.

Squilla stylifera, 256.

Stauropus fagi, 94.

Stoat, 75.

Strongylocentrotus
dus, 255.

Sun bittern, 162.

Synageles picata, 216, 274.

Synemosyna formica, 216.

Syrphus, 164.

livi-

| “'Swallow-tail,” 40, 187,

169, 196, 266, 277.
Swallow-tail moth,62, 277.
Tadpoles, 20.

Tanager. 149.
Tanais, 261.

Tapirs, 28.

Tetracis lorata, 87.
Thecla rubi, 83, 108.
Thick-knee, 30, 162.

, Thomisus onustus, 112.
Thorn moths, 28, 49, 82.

Thylacinus, 17.

Tiger, 18, 20, 62, 85, 145.

beetle, 63.

— moth, 49, 52, 63,110,
157,

Toad, 159.

Tortoiseshell, 15, +1, 42,
48, 137, 151, 211,
254, 266.

Toucan, 156, 260.

Touracou, 15. :

Tree frog, 17, 83, 109.

Trichiura. 203.

Tridacna, 45.

| Tripheena fimbria, 220.

—— orbona, 220.
Tritonia plebeia, 128.
Trumpeter, 162.
Tubifex rivulorum, 6.
Tussoch moths, 168.
Typhlotanais, 36.
Upland goose, 259.
Uraniscodon plica,
164.

160,

Urapteryx sainbucaria, 63.
Urocheta, 234.
Uromastix spinipes, 159.
Uta symmetrica, 144.
Vanessa, io, 50. ’
-— levana, +7, 79, 80.
—— polychloros, 48, 51.
—— prorsa, 47, 79, 80.
urtice, 48, 51, 266.
Vanessidw, 15, 16, 41, 62,
138, 151.

Vapourer moth, 159, 168,

254, 270, 271.
Velella, 122.
Vespa vulgaris, 164.
Viper, 182.
Vipera arietans, 257.
Volucella, 225.
bombylans, 227.

—— inanis, 228.

pellucida, 22s.

Wall butterfly, 211.

Wasp, 147, 154, 161, 175,
218,

—— beetle, 164, 200.

—— clearwing, 231.

Whale, 208.

“White” butterflies, 14.
114, 137, 202, 214.
266.

White egret, 116.

~— eye, 149,

Winter moth, 254, 271.

Wireworm, 162, 164.

Woodhen. 163.

Wood white, 14. 209, 215.

“Woolly bear,” 52.

Wrymouth, 130.

Xanthia, 84.

Xenopus levis, 184.

Xylophasia hepatica, 103.

lithoxylea, 103.

or

| —— polyodon, 44), 103.

rurea, 103.

— scolopacina, 103.

“Yellow underwing,” 8+,
190, 191, 220. 232.

Ypomoneuta padella. 163,
164.

Zebra, 19, 85.

Zonurus cordylus, 154, 163,

Zootoca vivipara, 257.
Zosterops, 149.

Zygenidve, 243.

INDEX OF AUTHORS’ NAMES.

—_—>—__

Agassiz, Prof. A., 36, 38, 39, 121, 124.
Allen, Mr., 20.

Azara, 239.

Baker, Sir 8., 84.

Barrett, Mr. J. P., 189.

Bates, Mr. H. W., 193, 207, 214, 252.
Bateson, Mr. W.. 174.

Belt, Mr., 183, 194, 207, 217, 234, 248.

Bennett, Mr. A. W., 231.

Bert, Prof. P., 185.

Bertkau, Dr., 263.

Blanchard, Prof., 118.

Bovallius, Dr. C., 221.

Brown, Mr., 78.

Brown-Goode, J., 130.

Buckler, 12.

Buller, Sir W., 114, 239.

Butler, Mr. A. G., 148, 163.

Cambridge, Rev. O. P., 113, 217.

Camerano, Dr. L., 44, 255.

Carpenter, Dr. W. B., 34.

Collnett, Capt. B., 58.

Comstock, Prof., 234.

Conn, Dr. H. W., 256.

Coues, Dr. Elliott, 144.

Cox, Mr, Ramsay, 50.

Cunningham, Mr. J. T., 64, 68, 119,
140, 256.

Darwin, Dr. C., 51, 57, 150, 256, 264.
275.

Dobson, Dr., 262.

Dorfmeister, Dr. W., 80.

Druce, Mr. H., 219.

Drummond, Prof., 101, 110, 117, 120.

Edwards, Mr., 81.

Eimer, Prof., 30, 49, 52, 56, 59, 79, 137,
214.

Kisig, Dr. H., 127, 172. 178.

Finn. Mr. F., 92, 153, 155, 161, 163,
239.

Forbes, Mr. H. O., 110, 188, 20£.

Forster, W., 123.

Gadow, Dr. H., 2, 44.

Garrod, Prof., 238.

Gaskell, Dr, W. H., 4.

Geddes, Prof., 7, 187, 278.

Goss, Mr. H., 49.

Gould, Mr, J., 240.

Grant Allen, Mr., 187, 226.

Gregson, Mr., $9.

Guillemard, Dr. 277.

Giinther, Dr, A., 130,

Gurney, Mr. J. H., 263.

Haacke, Dr. W. 30.

Haeckel, Prof., £5.

Heckel, Prof. Ed., 111.

Herdman, Prof., 127, 174.

Hill, Dr., 235.

Hopkins, Mr. F. G., 40.

Horne & Smith, Messrs., 225.

Howes, Mr, G. B., 184.

Hudson, Mr. W. H., 86, 116, 178, 239,

_ 280.

Huxley, Prof., 29.

Jacoby. Mr. M., 109.

Jordan, Mr., 53.

Karr, M. A., 273.

Kent, Mr. Savile, 185, 267.

Kirby & Spence, Messrs., 105, 129, 133,
204, 225.

288

Koch, Dr., 49, 52.

Kriikenberg, Dr., 2, 3, 7, 72, 73, 143.

Kiinckel d’Herculais, M., 227, 228.

Leconte, Dr., 91.

Leydig, Prof. F., 56, 71.

Lubbock, Sir J., 98, 228.

M‘Cook, Dr., 12, 217, 218, 219, 275.

M‘Munn, Dr., 2.

Macintosh, Prof. W. C., 125.

Meldola, Prof. R., 63, 107.

Merriam, Dr. Hart, 179.

Merrifield, Mr., 82.

Meulen, Mr. De W. 157.

Meyer, Dr. A. B., 259.

Milford, Mr., 43.

Milne Edwards, Prof., 261.

Mivart, Prof., 51.

Morgan, Prof. Lloyd, 51, 225.

Morris, Mr., 137.

Moseley, Prof., 35, 37, 121, 131.

Miiller, Fritz, 145, 194, 213, 215, 231,
249, 261.

Murray, Mr. A., 22, 46, 64, 215, 226.

Newman, Mr. E., 48, 49, 100.

Newstead, Mr., 227.

Newton, Prof., 258.

Packard, Dr. A. S., 65, 66, 67, 68.

Peal, Mr. 8. E., 205.

Peckham, Mr. E. C., 216, 217, 273.

Penny, Rev. C. W., 113.

Plateau, Prof. F., 89. 194, 229.

Poulton, Mr. E. B., 23, 26, 28, 41,
67, ct passim.

Prince, Mr. E. B., 125.

Ransonnet, Mr., 45,

Riley, Dr. C. V., 278.

Rogenhofer, Dr., 242.

Romanes, Dr. J. G., 9.

Ross, Sir John, 76, 77.

Salvin, Mr. 0., 58, 59, 146, 180, 182.

Sauermann, Dr., 54, 55,

Schmidt, Prof. O., 255.

Schweinfurth, Dr., 95.

Selater, Dr. P. L., 70, 239, 259.

Scudder, Dr., 55, 97, 99, 101, 170, 201,
210, 246, 247, 248, 249, 266.

INDEX OF AUTHORS’ NAMES.

Seitz, Dr. A., 46, 47, 94, 197, 198, 199,
203, 204, 220, 232.

Semper, Dr. C., 48, 49, 78, 142, 222.
236, 252.

Sharp, Dr. D., 90, 221, 229.

Sharpe, Mr. R. B., 240.

Skertchly, Mr., 172.

Smith, Mr. W. W., 61.

Sorby, Dr. H.. 2, 96, 134.

Spence Bate, Mr. C., 191.

Spencer, Prof. W. B., 157.

Stainton, Mr. H. T., 120.

Stanley, Bishop, 114.

Steere, Mr. J. B., 206.

Stevenson, Mr., 13.

Stewart, Mr. C., 18.

Stolzmann, M., 31, 265, 276, 278.

Stradling, Dr., 146, 157.

Sutton, Mr. J. B., 263.

Swinhoe, Col. C., 202.

Tawell, Mr. J., 48.

Thomson, Sir C. W., 24, 36.

Thomson, Mr. J. A., 187, 278.

Treat, Mrs. M., 277.

Trimen, Mr. R., 172, 196, 197.

Trouessart, Prof., 74.

Tylor, Mr. A., 19, 30.

Urech, Dr., 41.

Van Dyck, Prof., 264.

Wallace, Dr. A. R., 8, 10, 19, 30, 60,
61, ct passin.

Waterhouse, Mr. C. O., 40.

Weber, Prof. Max, 262.

Weed, Mr. C. M., 87.

Weir, Mr. J. J., 42, 148, 163, 266.

Weismann, Prof., 23, 25, 26, 63, 69, 79,
et passim.

Welch, Mr., 76.

Weldon, Prof., 116.

Werneburg, Dr., 62.

Westwood, Prof. J. O., 110.

Willemoes-Suhm, Dr., 36.

Wood, Mr. T. W., 87, 108, 137.

Wood Mason, Mr. J., 187.

Wurm, Dr., 7.

Yarrow, Dr., 144.

Printed by Hazell, Watson, & Viney, Ld., London and Aylesbury