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Full text of "Mimicry in butterflies"

MIMICRY IN BUTTERFLIES 



CAMBRIDGE UNIVERSITY PRESS 

C. F. CLAY, Manager 

Eonion: FETTER LANE, E.G. 

Eiiinburst: ^oo PRINCES STREET 




j^fbJ gorh: G. P. PUTNAM'S SONS 

JSotnbHB, CTalctitta anl) fflaliras: MACMILLAN AND Co., Ltd. 

^Toronto: J. M. DENT AND SONS, Ltd. 

arofeBo: THE MARUZEN-KABUSHIKI-KAISHA 



AU rights reserved 



MIMICRY IN BUTTERFLIES 



BY 
REGINALD CRUNDALL PUNNETT, F.R.S. 

Fellow of Gonville and Caius College 
Arthur Balfour Professor of Genetics in the University of Cambridge 



Cambridge : 

at the University Press 
1915 



PRINTED BY JOHN CLAY, M.A, 
AT THE UNIVEKSITY PRESS 



PREFACE 

rpHIS little book has been written in the hope that 
-^ it may appeal to several classes of readers. 

Not infrequently I have been asked by friends of 
different calhngs in hfe to recommend them some book 
on mimicry which shall be reasonably short, well 
illustrated without being very costly, and not too 
hard to understand. I have always been obliged to 
tell them that I know of nothing in our language 
answering to this description, and it is largely as an 
attempt to remedy this deficiency that the present 
little volume has been written. 

I hope also that it will be found of interest to those 
who live in or visit tropical lands, and are attracted by 
the beauty of the butterfly hfe around them. There 
are few such countries without some of these cases 
of close resemblance between butterflies belonging to 
different families and groups, and it is to those who 
have the opportunity to be among them that we must 
look for fuller light upon one of the most fascinating of 
all nature's problems. If this Httle book serves to 



vi PREFACE 

smooth the path of some who would become ac- 
quainted with that problem, and desire to use their 
opportunities of observation, the work that has gone to 
its making will have been well repaid. 

To those who cultivate biological thought from the 
more philosophical point of view, I venture to hope 
that what I have written may not be without appeal. 
At such a time as the present, big with impending 
changes in the social fabric, few things are more vital 
than a clear conception of the scope and workings 
of natural selection. Little enough is our certain 
knowledge of these things, and small though the 
butterfly's contribution may be I trust that it will 
not pass altogether unregarded. 

In conclusion I wish to offer my sincere thanks to 
those who have helped me in different ways. More 
especially are they due to my friends Dr Karl Jordan 
for the loan of some valuable specimens, and to 
Mr T. H. Riches for his kindly criticism on reading 
over the proof-sheets. 

R. C. P. 

February, 1915 



CONTENTS 



CHAP. 

I. Introductory .... 

II. Mimicry — Batesian and Mullerian 

III. Old-world mimics 

IV. New-world mimics 

V. Some criticisms .... 

VI. "Mimicry rings" .... 

VII. The case of Papilio polytes . 
VIII. The case of Papilio polytes (cont.) 

IX. The enemies of butterflies 

X. Mimicry and Variation 

XI. Conclusion ..... 
Appendix I . 

Appendix II . 



Plates I — XVI and descriptions 

I — V. Oriental Moths and Butterflies. 

VI — IX. African Butterflies. 

X — XIII. South American Butterflies. 

XIV. Scales of Lepidoptera. 

Central and South American 
Butterflies. 

North American Butterflies. 



XV. 
XVI. 



page 
I 

8 

18 

37 

50 

61 

76 

93 
104 
126 
139 
154 
167 

160 ff 



Index 



183 



"The process by which a mimetic analogy is brought 
about in nature is a problem which involves that of the 
origin of all species and all adaptations." 

H. W. Bates, 1861. 

"With mimesis, above all, it is wis«, when the law says 
that a thing is black, first to inquire whether it does not 
happen to be white." Henm Fabbe. 



CHAPTER I 

INTRODUCTORY 

It is now more than fifty years since Darwin gave 
the theory of natural selection to the world, and the 
conception of a gradual evolution has long ago become 
part of the currency of thought. Evolution for Darwin 
was brought about by more than one factor. He 
believed in the inherited effects of the use and disuse 
of parts, and he also regarded sexual selection as 
operating at any rate among the higher animals. Yet 
he looked upon the natural selection of small favour- 
able variations as the principal factor in evolutionary 
change. Since Darwin's time the trend has been to 
magnify natural selection at the expense of the other 
two factors. The doctrine of the inherited effects of 
use and disuse, vigorously challenged by Weismann, 
failed to make good its case, and it is to-day discredited 
by the great majority of biologists. Nor perhaps does 
the hypothesis of sexual selection command the 
support it originally had. At best it only attempted 
to explain those features, more especially among the 
higher animals, in which the sexes differ from one 
another in pattern, ornament, and the like. With 
the lapse of time there has come about a tendency to 

P.M. 1 



2 INTRODUCTORY [ch. 

find in natural selection alone a complete explanation 
of the process of evolution, and to regard it as the 
sole factor by which all evolutionary change is brought 
about. Evolution on this view is a gradual process 
depending upon the slow accumulation by natural 
selection of small variations, which are more or less 
inherited, till at last a well-marked change of type is 
brought about. Could we have before us all the stages 
through which a given form has passed as natural 
selection transforms it into another, they would con- 
stitute a continuous series such that even refined 
scrutiny might fail to distinguish between any two 
consecutive terms. If the slight variations are not of 
service they will get no favour from natural selection 
and so can lead to nothing. But if of use in the 
struggle for existence natural selection preserves them 
and subsequent variations in the same direction until 
at length man recognises the accumulation as a new 
form. Moreover when the perfect thing is once 
elaborated natural selection will keep it perfect by 
discouraging any tendency to vary from perfection. 

Upon this view, of which the most distinguished 
protagonist was Weismann, natural selection is the sole 
arbiter of animal and plant form. Through it and it 
alone the world has come to be what it is. To it must 
be ascribed all righteousness, for it alone is the maker. 
Such in its extreme form is the modern development 
of Darwin's great contribution to philosophy. 

But is it true ? Will natural selection really serve 
to explain all ? Must all the various characters of 



I] INTRODUCTORY 3 

plants and animals be supposed to owe their existence 
to the gradual operation of this factor working upon 
small variations ? 

Of recent years there has arisen a school of biolo- 
gists to whom the terms mutationist and Mendelian are 
frequently apphed. Influenced by the writings of 
Bateson and de Vries, and by the experimental results 
that have flowed from Mendel's discovery in heredity, 
they have come to regard the process of evolution as 
a discontinuous one. The new character that differ- 
entiates one variety from another arises suddenly as 
a sport or mutation, not by the gradual accretion of 
a vast number of intermediate forms. The white 
flowered plant has arisen suddenly from the blue, or 
the dwarf plant from the tall, and intermediates 
between them need never have existed. The ultimate 
fate of the new form that has arisen through causes 
yet unknown may depend upon natural selection. 
If better endowed than the parent form in the struggle 
for existence it may through natural selection come to 
supplant it. If worse endowed natural selection will 
probably see to its elimination. But if, as may quite 
possibly happen, it is neither better nor worse adapted 
than the form from which it sprang, then there would 
seem to be no reason for natural selection having 
anything to do with the relation of the new form 
to its parent. 

Between the older and the newer or mutationist 
point of view an outstanding difference is the role 
ascribed to natural selection. On the one view it 

1—2 



4 INTRODUCTORY [ch. 

builds up the new variety bit by bit, on the other 
the appearance of the new variety is entirely inde- 
pendent of it. From this there follows a radical 
difference with regard to the meaning of all the varied 
characters of plants and animals. Those who uphold 
the all-powerfulness of natural selection are bound 
to regard every character exhibited by an animal or 
plant as of service to it in the struggle for existence. 
Else it could not have arisen through the operation of 
natural selection. In other words every character in 
plant or animal must be adaptive. On the mutationist 
view this of course does not follow. If the new 
character which arises independently of natural selec- 
tion is neither of service nor disservice to its possessors 
in the struggle for existence, there seems no reason 
why it should not persist in spite of natural selection. 
In attempting to decide between the two conflicting 
views the study of adaptation is of the first importance. 
It was perhaps in connection with adaptation that 
Darwin obtained the most striking evidence in support 
of his theory, and it is clear from his writings that it 
was in this field he labom-ed with most delight. The 
marvellous ways in which creatiures may be adapted 
in structure and habit for the life they lead had not 
escaped the attention of the older naturalists. John 
Ray wrote a book^ upon the subject in which he 
pointed out that all things in the Universe, from the 
fixed stars to the structiu-e of a bird, or the tongue of 

1 The Wisdom of God manifested in the Works of the Creation, London, 
1691. 



I] INTRODUCTORY 5 

a chameleon, or the means whereby some seeds are 
wind distributed, are "argumentative of Providence 
and Design" and must owe their existence to "the 
Direction of a Superior Cause." Nor have there been 
wanting other authors who have been equally struck 
by the wonders of adaptation. But their studies 
generally led to the same conclusion, an exhortation 
to praise the infinite Wisdom of Him Who in the days 
of Creation had taken thought for all these things. 

The advent of natural selection tlu-ew a new Ught 
upon adaptation and the appearance of design in 
the world. In such books as those on The Fertiliza- 
tion of Orchids and The Forms of Flowers Darwin 
sought to shew that many curious and elaborate 
structures which had long puzzled the botanist were of 
service to the plant, and might therefore have arisen 
through the agency of natural selection. Especially 
was this the case in orchids where Darwin was able 
to bring forward striking evidence in favour of regarding 
many a bizarre form of flower as specially adapted 
for securing the benefits of cross-fertilization through 
the visits of insects. In these and other books Darwin 
opened up a new and fascinating field of investigation, 
and thenceforward the subject of adaptation claimed 
the attention of many naturalists. For the most part 
it has been an observational rather than an experi- 
mental study. The naturalist is struck by certain 
peculiarities in the form or colour or habits of a species. 
His problem is to account for their presence, and as 
nearly all students of adaptation have been close 



6 INTRODUCTORY [ch. 

followers of Darwin, this generally means an inter- 
pretation in terms of natural selection. Granted this 
factor it remains to shew that the character in question 
confers some advantage upon the individuals that 
possess it. For unless it has a utilitarian value of some 
sort it clearly cannot have arisen through the operation 
of natural selection. However when it comes to the 
point direct proof of this sort is generally difficult to 
obtain. Consequently the work of most students of 
adaptation consists in a description of the character 
or characters studied together with such details of 
its life-history as may seem to bear upon the point, 
and a suggestion as to how the particular character 
studied may be of value to its possessors in the struggle 
for existence. In this way a great body of most 
curious and interesting facts has been placed on 
record, and many ingenious suggestions have been 
made as to the possible use of this or that character. 
But the majority of workers have taken natural 
selection for granted and then interested themselves 
in shewing how the characters studied by them might 
be of use. Probably there is no structure or habit 
for which it is impossible to devise some use^, and 
the pursuit has doubtless provided many of its devotees 
with a pleasurable and often fascinating exercise of 
the imagination. So it has come about that the facts 

^ Ray gives the case of an elephant "that was observed always 
when he slept to keep his triink so close to the ground, that nothing 
but Air could get in between them," and explains it as an adaptation 
in habit to prevent the mice from crawling into its Ixmgs — "a strange 
sagacity and Providence in this Animal, or else an admirable instinct." 



I] INTRODUCTORY 7 

instead of being used as a test of the credibility of 
natural selection, serve merely to emphasise the 
paean of praise with which such exercises usually 
conclude. The whole matter is too often approached 
in much the same spirit as that in which John Ray 
approached it two centuries ago, except that the 
Omnipotency of the Deity is replaced by the Omni- 
potency of Natural Selection. The vital point, which 
is whether Natural Selection does offer a satisfactory 
explanation of the living world, is too frequently lost 
sight of. Whether we are bound or not to interpret 
all the phenomena of life in terms of natural selection 
touches the basis of modern philosophy. It is for the 
biologist to attempt to find an answer, and there are 
few more profitable lines of attack than a critical 
examination of the facts of adaptation. Though 
"mimicry" is but a smaU corner in this vast field of 
inquiry it is a peculiarly favourable one owing to the 
great interest which it has excited for many years 
and the consequently considerable store of facts that 
has been accumulated. If then we would attempt to 
settle this most weighty point in philosophy there is 
probably nothing to which we can appeal with more 
confidence than to the butterfly. 



CHAPTER II 

MIMICRY — BATESIAN AND MULLERIAN 

Mimicry is a special branch of the study of adap- 
tation. The term has sometimes been used loosely 
to include cases where an animal, most frequently 
an insect, bears a strong and often most remarkable 
resemblance to some feature of its inanimate sur- 
roundings. Many butterflies with wings closed are 
wonderfully like dead leaves ; certain spiders when 
at rest on a leaf look exactly like bird-droppings ; 
"looper" caterpillars simulate small twigs ; the names 
of the "stick-" and "leaf-" insects are in themselves 
an indication of their appearance. Such cases as 
these, in which the creature exhibits a resemblance to 
some part of its natural surroundings, should be 
classified as cases of "protective resemblance" in 
contradistinction to mimicry proper. Striking ex- 
amples of protective resemblance are abundant, and 
though we possess little critical knowledge of the 
acuity of perception in birds and other insect feeders 
it is plausible to regard the resemblances as being 
of definite advantage in the struggle for existence. 
However, it is with mimicry and not with protec- 
tive coloration in general that we are here directly 



CH. II] MIMICRY 9 

concerned, and the nature of the phenomenon may 
perhaps best be made clear by a brief accomit of the 
facts which led to the statement of the theory. 

In the middle of last centm-y the distinguished 
naturalist, H. W. Bates, was engaged in making 
collections in parts of the Amazon region. He paid 
much attention to butterflies, in which group he 
discovered a remarkably interesting phenomenon^. 
Among the species which he took were a large number 
belonging to the group Ithomiinae, small butterflies 
of peculiar appearance with long slender bodies and 
narrow wings bearing in most cases a conspicuous 
pattern (cf. PI. X, fig. 7). When Bates came to 
examine his catch more closely he discovered that 
among the many Ithomiines were a few specimens 
very like them in general shape, colour, and markings, 
but differing in certain anatomical features by 
which the Pierinae, or "whites," are separated from 
other groups. Most Pierines are very different from 
Ithomiines. It is the group to which our common 
cabbage butterfly belongs and the ground colour is 
generally white. The shaj)e of the body and also of the 
wings is in general quite distinct from what it is in the 
Ithomiines. Nevertheless in these particular districts 
certain of the species of Pierines had departed widely 
from what is usually regarded as their ancestral 
pattern (PI. X, fig. 1) and had come to resemble very 
closely the far more abundant Ithomiines among whom 
they habitually flew (cf. PI. X, figs. 2 and 3). To 

1 Trans. Linn. Soc. vol. 23, 1862. 



10 MIMICRY— [CH. 

use Bates' term they "mimicked" the Ithomiines, 
and he set to work to devise an explanation of how 
this could have come about. The Origin of Species 
had just appeared and it was natural that Bates 
should seek to interpret this peculiar phenomenon on 
the lines there laid down. How was it that these 
Pierines had come to depart so widely from the general 
form of the great bulk of their relations, and to mimic 
so closely in appearance species belonging to an 
entirely different group, while at the same time con- 
serving the more deeply seated anatomical features 
of their own family ? If the change was to be regarded 
as having come about through the agency of natural 
selection it must clearly be of advantage to the 
mimicking forms ; otherwise natural selection could 
not come into operation. What advantage then have 
the Ithomiines over the majority of butterflies in those 
parts ? They are small insects, rather flimsy in 
build, with comparatively weak powers of flight, and 
yet so conspicuously coloured that they can hardly 
be mistaken for anything else. In spite of all this 
they are little subject to the attacks of enemies such 
as birds, and Bates attributed this to the fact that 
the juices of their bodies are unpalatable. According 
to him their striking and conspicuous pattern is of 
the nature of a warning coloration, advertising their 
disagreeable properties to possible enemies. A bird 
which had once attempted to eat one would find it 
little to its taste. It would thenceforward associate 
the conspicuous pattern with a disagreeable flavour 



II] BATESIAN AND MULLERIAN 11 

and in future leave such butterflies severely alone. 
The more conspicuous the pattern the more readily 
would it be noticed by the enemy, and so it would 
be of advantage to the Ithomiine to possess as striking 
a pattern as possible. Those butterflies shewing a 
tendency to a more conspicuous pattern would be 
more immune to the attacks of birds and so would 
have a better chance of leaving progeny than those 
with a less conspicuous pattern. In this way vari- 
ations in the direction of greater conspicuousness would 
be accumulated gradually by natural selection, and 
so would be built up in the Ithomiine the striking 
warning coloration by which it advertises its disagree- 
able properties. Such is the first step in the making 
of a mimicry case — the building up through natural 
selection of a conspicuous pattern in an unpalatable 
species by means of which it is enabled to advertise its 
disagreeable properties effectively and thereby secure 
immunity from the attacks of enemies which are able 
to appreciate the advertisement. Such patterns and 
colours are said to be of a "warning" nature. The 
existence of an unpalatable model in considerable 
numbers is the first step in the production of a mimetic 
resemblance through the agency of natural selection. 

We come back now to our Pierine which must 
be assumed to shew the general characters and color- 
ation of the family of whites to which they belong 
(cf. PL X, fig. 1). Theoretically they are not specially 
protected by nauseous properties from enemies and 
hence their conspicuous white coloration renders 



12 MIMICRY— [CH. 

them especially liable to attack. If, however, they 
could exchange their normal dress for one resembling 
that of the Ithomiines it is clear that they would have 
a chance of being mistaken for the latter and con- 
sequently of being left alone. Moreover, in certain 
cases these Pierines have managed to discard their 
normal dress and assume that of the Ithomiines. On 
theoretical grounds this must clearly be of advantage 
to them, and being so might conceivably have arisen 
tln?ough the operation of natural selection. This 
indeed is what is supposed to have taken place on the 
theory of mimicry. Those Pierines which exhibited 
a variation of colour in the direction of the Ithomiine 
"model" excited distrust in the minds of would-be 
devourers, who had learned from experience to associate 
that particular type of coloration with a disagreeable 
taste. Such Pierines would therefore have a rather 
better chance of surviving and of leaving offspring. 
Some of the offspring would exhibit the variation in 
a more marked degree and these again would in con- 
sequence have a yet better chance of surviving. 
Natural selection would encourage those varying in 
the direction of the Ithomiine model at the expense of 
the rest and by its continuous operation there would 
gradually be built up those beautiful cases of resem- 
blance which have excited the admiration of naturalists. 
Wallace was the next after Bates to interest 
himself in mimicry and, from his study of the butterflies 
of the Oriental region^, shewed that in this part of 

1 Trans. Linn. Soc. vol. 25, 1866. 



II] BATESIAN AND MULLERIAN 13 

the world too there existed these remarkable resem- 
blances between species belonging to different families. 
Perhaps the most important part of Wallace's con- 
tribution was the demonstration that in some species 
not only was it the female alone that "mimicked" 
but that there might be several different forms of 
female mimicking different models, and in some cases 
aU unlike the male of their own species. One of the 
species studied by Wallace, Papilio polytes, is shewn 
on Plate V. We shall have occasion to refer to 
this case later on, and it is sufficient here to call 
attention to the three different forms of female, of 
which one is like the male while the other two resemble 
two other species of Papilio, P. hector and P. aristo- 
lochiae, which occur in the same localities. Instances 
where the female alone of some unprotected species 
mimics a model with obnoxious properties are common 
in all tropical countries. It has been suggested that 
this state of things has come about owing to the greater 
need of protection on the part of the female. Hampered 
by the disposal of the next generation the less protected 
female would be at a greater disadvantage as com- 
pared with the mimic than would the corresponding 
male whose obligations to posterity are more rapidly 
discharged. The view of course makes the assumption 
that the female transmits her peculiar properties to 
her daughters but not to her sons. 

A few years later Trimen^ did for Africa what 
Bates had done for America and Wallace for Indo- 

1 Trans. Linn. Soc. vol. 26, 1870. 



14 MIMICRY— [CH. 

Malaya. It was in this paper that he elucidated that 
most remarkable of all cases of mimicry — Papilio 
dardanus with his harem of different consorts, all 
tailless, all unlike himself, and often wonderfully 
similar to unpalatable forms found in the same 
localities (cf. p. 30). 

We may now turn to one of the most ingenious 
developments of the theory of mimicry. Not long 
after Bates' original memoir appeared attention was 
directed to a group of cases which could not be 
explained on the simple hypothesis there put forward. 
Many striking cases of resemblance had been adduced 
in which both species obviously belonged to the pre- 
sumably unpalatable groups. Instances of the sort 
had been recorded by Bates himself and are perhaps 
most plentiful in South America between species 
belonging respectively to the Ithomiinae and Heli- 
coninae. On the theory of mimicry all the members 
of both of these groups must be regarded as specially 
protected owing to their conspicuous coloration and 
distasteful properties. What advantage then can an 
Ithomiine be supposed to gain by mimicking a Heli- 
conine, or vice versa ? Why should a species exchange 
its own bright and conspicuous warning pattern for 
one which is neither brighter nor more conspicuous ? 
To Fritz Mtiller, the well-known correspondent of 
Darwin, belongs the credit of having suggested a way 
out of the difficulty. Miiller's explanation turns upon 
the education of birds. Every year there hatch into 
the world fresh generations of young birds, and each 



II] BATESIAN AND MULLERIAN 15 

generation has to learn afresh from experience what is 
pleasant to eat and what is not. They will try all 
things and hold fast to that which is good. They will 
learn to associate the gay colours of the Heliconine and 
the Ithomiine with an evil taste ^ and they will thence- 
forward avoid butterflies which advertise themselves 
by means of these particular colour combinations. But 
in a locaHtj^ where there are many models, each with 
a different pattern and colour complex, each will have 
to be tested separately before the unpalatableness of 
each is reahsed. If for example a thousand young 
birds started their education on a population of 
butterflies in which there were five disagreeable species, 
each with a distinct warning pattern, it is clear that 
one thousand of each would devote their hves to the 
education of these birds, or five thousand butterflies 
in all". But if these five species, instead of shewing 
five distinct warning patterns, all displayed the same 
one it is evident that the education of the birds would 
be accomplished at the price of but one thousand 
butterfly existences instead of five. Even if one of 
the five species were far more abundant than the 
others it would yet be to its advantage that the other 
four should exhibit the same warning pattern. Even 
though the losses were distributed pro rata the more 
abundant species would profit to some extent. For 

1 In attributing this quality to the butterflies in question I am 
merely stating what is held by the supporters of the mimicry theory. 
I know of scarcely any evidence either for or against the supposition. 

2 It is assvuned that the intelligence of the birds is such that they 
can learn a pattern after a single disagreeable experience of it. 



16 MIMICRY— [CH. 

the less abundant species the gain would of course be 
relatively greater. Theoretically therefore, all of the 
five species would profit if in place of five distinct 
warning patterns they exhibited but a single one in 
common. And since it is profitable to all concerned 
what more natural than that it should be brought 
about by natural selection ? 

Miiller's views are now widely accepted by students 
of mimicry as an explanation of these curious cases 
where two or more evidently distasteful species closely 
resemble one another. Indeed the tendency in recent 
years has been to see Mtillerian mimicry everywhere, 
and many of the instances which were long regarded 
as simple Batesian cases have now been relegated to 
this category. The hypothesis is, of course, based upon 
what appears to man to be the natural behaviour 
of young birds under certain conditions. No one 
knows whether young birds actually do behave in the 
way that they are supposed to. In the absence of 
any such body of facts the Mtillerian hypothesis 
cannot rank as more than a plausible suggestion, and, 
as will appear later, it is open to severe criticism on 
general grounds. 

Perhaps the next contribution to the subject of 
mimicry which must rank of the first importance was 
that of Erich Haase^, to whose book students of these 
matters must always be under a heavy obligation. 
It was the first and still remains the chief work of 
general scope. Since Haase's day great numbers of 

^ Untersuchungen iiher die Mimikry, 1893. 



II] BATESIAN AND MULLERIAN 17 

fresh instances of mimetic resemblance have been 
recorded from all the great tropical areas of the world, 
and the list is being added to continually. Most 
active in this direction is the Oxford School under 
Professor Poulton to whose untiring efforts are largely 
due the substantial increases in our knowledge of 
African butterflies contributed by various workers in 
the field during the past few years. Whatever the 
interpretation put upon them, there can be no question 
as to the value of the facts brought together, more 
especially those referring to the nature of the families 
raised in captivity from various mimetic forms. With 
the considerable additions from Africa^ during the 
past few years several hundreds of cases of mimicry 
must now have been recorded. Some of the best 
known and most striking from among these will be 
described briefly in the next two chapters. 

^ The African mimetic butterflies have been recently monographed 
by Eltringham in a large and beautifully illustrated work — African 
Mimetic Butterflies, Oxford, 1910. 



P. M. 



CHAPTER III 



OLD-WORLD MIMICS 



The earlier naturalists who studied butterflies 
made use of colour and pattern very largely in arranging 
and classifying their specimens. Insects shewing the 
same features in these respects were generally placed 
together without further question, especially if they 
were known to come from the same locality. In 
looking through old collections of butterflies from the 
tropics it is not infrequent to find that the collector 
was deceived by a mimetic likeness into placing model 
and mimic together. During the last century, however, 
more attention was paid to the anatomy of butterflies, 
with the result that their classification was placed 
upon a basis of structure. As in all work of the sort 
certain features are selected, partly owing to their 
constancy and partly for their convenience, the insects 
being arranged according as to whether they present 
these features or not. Everybody knows that the 
butterflies as a group are separated from the moths on 
the ground that their antennae are club shaped at the 
end, while those of the moth are generally filamentary 
and taper to a fine point. The butterflies themselves 



CH. Ill] 



OLD-WORLD MIMICS 



19 











Figs. 1—8. 



Terminal portion of front legs of butterflies belonging 
to dififerent families. (After Eltringham.) 



Hypolimnas misippus, 

Abisara savitri, 

Lycaena icarus, 
Cupido zoe, 
Ganoris rapae, 
Papilio echerioides, 



(Nymphalidae). 

( ,. ). 

(Erycinidae). 

( .. ). 
(Lycaenidae). 

( „ ). 

(Pieridae). 

(Papilionidae). 



2—2 



20 OLD-WORLD MIMICS [ch. 

may be subdivided into five main groups or families^ 
according to the structure of the first of their three 
pairs of legs. In the Papilionidae or "swallow-tails," 
the first pair of legs is well developed in both sexes 
(Fig. 8). In the Pieridae or "whites," the front legs 
are also similar in both sexes, but the claws are bifid 
and a median process, the empodium, is found between 
them (Fig. 7). In the remaining three families the 
front legs differ in the two sexes. The females of the 
Lycaenidae or "blues" have well-developed front legs 
in which the tarsus is terminated by definite claws 
(Fig. 5), whereas in the males the terminal part of the 
leg, or tarsus, is un jointed and furnished with but a 
single small claw (Fig. 6). This reduction of the 
front legs has gone somewhat further in the Erycinidae 
(Figs. 3 and 4), a family consisting for the most part 
of rather small butterflies and specially characteristic 
of South America. In the great family of the Nym- 
phahdae the reduction of the front legs is well marked 
in both sexes. Not only are they much smaller than 
in the other groups, but claws are lacking in the female 
as well as in the male (Figs. 1 and 2). 

Though the structure of the fore limbs is the 
character specially chosen for separating these different 
families from one another, it is of course understood 
that they differ from one another in various other 
distinctive features. The chrysalis of the Nymphalidae 
for example hangs head downwards suspended by the 

1 Omitting the Hesperidae which hardly enter into questions of 
mimicry. 



in] OLD-WORLD MIMICS 21 

tail, whereas in the Pieridae and PapiHonidae meta- 
morphosis takes place with the chrysalis attached by 
the tail but supported also by a fine girdle of silk 
round the middle so that the head is uppermost. The 
larvae also afford characters by which some of the 
families may be distinguished — those of the Papilionidae 
for example having a process on the back which can 
be extruded or retracted. 

Owing to the great size of the family of the Nym- 
phalidae, in which the number of species approaches 
5000, it is convenient to deal with the eight sub-groups 
into which it has been divided. The characters serving 
to mark off the sub-groups from one another are various. 
Sometimes it is the minuter structure of the tarsus, at 
others the form of the caterpillar or the chrysalis, at 
others the arrangement of the nervures that form the 
skeleton of the wing. Into these systematic details, 
however, we need not enter more fully here^. What is 
important from the standpoint of mimicry is that 
these divisions, made solely on anatomical structure, 
correspond closely with the separation of models from 
mimics. Of the eight sub-families into which the 
Nymphalidae are divided four, \az. the Danainae, 
Acraeinae, Heliconinae, and Ithomiinae, provide models 
and some, but far fewer, mimics ; two, the Satyrinae 
and Nymphalinae, provide many mimics and but few 
models, while two groups, the Morphinae and Bras- 
solinae, practically do not enter into the mimicry story. 

^ The classification adopted is that used by Dr Sharp in the 
"Cambridge Natural History," Insects, vol. 2, 1901. 



22 OLD-WORLD MIMICS [ch. 

Simple mimicry, explicable, at any rate in theory, 
on the Knes laid down by Bates, is a phenomenon of 
not infrequent occm'rence in tropical countries, though 
rare in more temperate lands. In each of the three 
great divisions of the tropical world we find certain 
groups of butterflies serving as models, and being 
mimicked by butterflies belonging as a rule to quite 
different groups. Speaking generally the models of 
any given region are confined to a few groups, while 
the mimics are drawn from a greater number. In Asia 
the principal models belong to the Danaines, the 
Euploeines, and to a group of swallow-tails which from 
the fact that their larvae feed on the poisonous Aris- 
tolochia plant are generally distinguished as the " Poison- 
eaters," or Pharmacophagus group. Of these the 
Danaines and Euploeines are closely related and have 
much in common. They are usually butterflies of 
medium size, of rather flimsy build and with a some- 
what slow and flaunting flight. In spite, however, of 
their slight build they are toughly made and very 
tenacious of life. Most butterflies are easily killed by 
simply nipping the thorax. There is a slight crack 
and the fly never recovers. But the collector who 
treats a Danaid in a way that would easily kill most 
butterflies is as likely as not many hours after to find 
it stiU alive in his collecting box or in the paper to 
which it may have been transferred when caught. 
They give one the impression of being tougher and 
more "rubbery" in consistence than the majority of 
Lepidoptera. Moreover, the juices of their bodies seem 



Ill] OLD-WORLD MIMICS 23 

to be more oily and less easily dried up. In general 
colour scheme they vary a great deal. Some, such as 
Danais chrysippus (PI. IV, fig. 1), are conspicuous 
with their bright fulvous-brown ground colour and the 
sharp white markings on the black tips of their fore 
wings. Others again such as Danais septentrionis (PI. I, 
fig. 3), with a dark network of lines on a pale greenish 
ground, are not nearly so conspicuous. Of the Euploe- 
ines some have a beautiful deep blue metallic lustre (cf. 
PI. II, fig. 4), though many are of a plain sombre 
brown relieved only by an inconspicuous border of 
lighter markings (cf. PI. I, fig. 10). 

Both Danaines and Euploeines serve as models for 
a great variety of species belonging to different groups. 
Danais septentrionis (PI. I, fig. 3) is a very abundant 
species in India and Ceylon, and in the same region 
there are several other very similar species. Flying 
with them in Northern India are two species of Papilio, 
P. macareus and P. xenocles (PI. I, fig. 4), which 
resemble these Danaids fairly closely. In Southern 
India and Ceylon one of the two forms of Papilio clytia 
(PI. I, fig. 7) is also regarded as a mimic of these 
Danaids. In the same part of the world there is a 
Pierine of the genus Pareronia, whose female is very 
like these Danaines on the upper surface (PI. I, fig. 1). 
The male of this Pierine is quite distinct from the 
female (PI. I, fig. 2). 

The common Danais chrysippus (PI. IV, fig. 1), 
found in this region, has been described as probably 
the most abundant butterfly in the world, and serves 



24 OLD-WORLD MIMICS [ch. 

as a model for several species belonging to different 
groups. It and its mimics will, however, be described 
in more detail later on. Mention must also be made 
of the strikmg case of the Danaid, Caduga tytia and 
its Papilionine mimic P. agestor from Sikkim (PL II, 
figs. 2 and 3). In both species the fore wings are 
pale blue broken by black; while the hind wings are 
pale with a deep outer border of rusty red. Not only 
in colour but also in shape the swallow-tail bears a 
remarkable resemblance to the Danaid. C. tytia is 
also mimicked by a rare Nymphaline Neptis imitans, 
which exhibits the same striking colour scheme so very 
different from that of most of its allies. 

No less remarkable are some of the cases in which 
the Euploeines serve as models. E. rhadamanthus, for 
example, is mimicked by the scarce Papilio mendax, 
and a glance at Figs. 8 and 9 on Plate II shews 
how well this butterfly deserves its name. Etiploea 
rhadamanthus also serves as a model for one of the 
several forms of female of the Nymphaline species 
Euripus halitherses. In some Euploeines the sexes are 
different in appearance — a somewhat unusual thing 
among butterflies serving as models in cases of mimetic 
resemblance. Such a difference is found in Euploea 
mulciber, the male being predominantly brown with a 
beautiful deep blue suffusion, while the female is a 
rather hghter insect with less of the blue suffusion 
and with hind wings streaked with lighter markings 
(PI. II, figs. 4 and 5). It is interesting to find that 
Elymnias malelas, a Satyrid which mimics this species. 



Ill] OLD-WORLD MIMICS 25 

shews a similar difference in the two sexes (PI. II, figs. 
6 and 7). 

It is remarkable that similar sexual difference is 
also shewn by the rare Papilio paradoxus^ the two 
sexes here again mimicking respectively the two sexes 
of Euploea midciher. 

Many of the Euploeines, more especially those from 
Southern India and Ceylon, lack the blue suffusion, and 
are sombre brown insects somewhat reheved by lighter 
markings along the hinder border of the hind wings. 
Euploea core (PI. I, fig. 10), a very common insect, is 
typical of this group. A similar coloration is found 
in one of the forms of Papilio clytia (PI. I, fig. 8) 
from the same region as well as in the female of the 
Nymphaline species Hypolimnas holina (PI. I, fig. 6). 
The male of this last species (PI. I, fig. 5) is quite 
unlike its female, but is not unlike the male of the 
alhed species, H. misippus, which it resembles in the 
very dark wings each with a white patch in the centre, 
the junction of light and dark being in each case 
marked by a beautiful purple-blue suffusion. There 
is also a species of Elymnias {E. singhala) in this part of 
the world which in general colour scheme is not widely 
dissimilar from these brown Euploeas (PI. I, fig. 9). 

The third main group of models characteristic of 
this region belongs to the Papilionidae. It was pointed 
out by Haase some 20 years ago that this great family 
falls into three definite sections, separable on anatom- 
ical grounds (see Appendix II). One of these sections 
he termed the Pharmacophagus or "poison-eating" 



26 OLD-WORLD MIMICS [ch. 

group owing to the fact that the larvae feed on the 
poisonous cHmbing plants of the genus Aristolochia. 
It is from this group that all Papilios which serve as 
models are drawn. No mimics of other unpalatable 
groups such as Danaines are to be found among the 
Oriental Poison-eaters. In the other two sections of 
the genus mimics are not infrequent (cf. Appendix II), 
though probably none of them serve as models. To 
the Pharmacophagus group belong the most gorgeous 
insects of Indo-Malaya — the magnificent Ornithoptera, 
largest and most splendid of butterflies. It is not a 
large proportion of the members of the group which 
serve as models, and these on the whole are among the 
smaller and less conspicuous forms. In all cases the 
mimic, when a butterfly, belongs to the Papilio section 
of the three sections into which Haase divided the 
family (cf. Appendix II). Papilio aristolochiae (PL V, 
fig. 5), for example, is mimicked by a female form of 
Papilio polytes, and the geographical varieties of this 
widely spread model are generally closely paralleled by 
those of the equally wide spread mimic. For both forms 
range from Western India across to Eastern China. 
Another poison-eater, P. coon, provides a model for 
one of the females of the common P. memnon. It is 
curious that in those species of the poison-eaters which 
serve as models the sexes are practically identical in 
pattern, and are mimicked by certain females only 
of the other two Papiho groups, whereas in the Orni- 
thoptera, which also belong to the poison-eaters, the 
difference between the sexes is exceedingly striking. 



Ill] OLD-WORLD MBIICS 27 

Though the Pharmacophagus Papilios are mimicked 
only by other Papihos among butterflies they may 
serve occasionally as models for certain of the larger 
day-flying moths. Papilio polyxe7ius, for example, is 
mimicked not only by the unprotected P. bootes but also 
by the moth Epicopeia polydora (PI. Ill, figs. 5 and 6). 
Like the butterfly the Epicopeia, which is compara- 
tively rare, has the white patch and the outer border 
of red marginal spots on the hind wing. Though it 
is apparently unable to provide itself with an orthodox 
tail it nevertheless makes a creditable attempt at one. 
There are several other cases of mimetic resemblance 
between day-flying moths and Pharmacophagus swal- 
low-tails — the latter in each case serving as the model. 
Rarely it may happen that the role of butterfly and 
moth is reversed, and the butterfly becomes the mimic. 
A very remarkable instance of this is found in New 
Guinea where the rare Papilio laglaizei mimics the 
common day-flying moth Alcidis agathyrsus. Viewed 
from above the resemblance is sufficiently striking 
(PI. Ill, figs. I and 2), but the most wonderful feature 
concerns the underneath. The ventral half of the 
moth's abdomen is coloured brilliant orange. When 
the wings are folded back they cover and hide from 
sight only the dorsal part of the abdomen, so that in 
this position the orange neutral surface is conspicuous. 
When, however, the wings of the butterfly are folded 
they conceal the whole of the abdomen. But the 
butterfly has developed on each hind wing itself a 
bright orange patch in such a position that when the 



28 OLD-WORLD MIMICS [ch. 

wings are folded back the orange patch Ues over the 
sides of the abdomen. In this way is simulated the 
brilliant abdomen of the moth by a butterfly, in which, 
as in its relations, this part is of a dark and sombre 
hue. 

A few models are also provided in the Oriental 
region by the genus Delias, which belongs to the Pier- 
ines. A common form, Delias eucharis, is white above 
but the under surface of the hind wings is conspicuous 
with yellow and scarlet (PI. II, fig. 1). It has been 
suggested that this species serves as a model for another 
and closely allied Pierine, Prioneris sita, a species 
distinctly scarcer than the Delias. There is some 
evidence that the latter is distasteful (cf. p. 115), but 
nothing is known of the Prioneris in this respect. 
Other species of Delias are said to function as models 
for certain day-flying moths belonging to the family 
Chalcosiidae, which may bear a close resemblance to 
them. In certain cases it may happen that the 
moth is more abundant than the Pierine that it re- 
sembles^. 

Tropical Africa is probably more wealthy in mimetic 
analogies than Indo-Malaya, and the African cases 
have recently been gathered together by Eltringham 
in a large and beautifully illustrated memoir^. The 
principal models of the region are furnished by the 
Danainae and the allied group of the Acraeinae. Of 
the Danaines one weU-known model, Danais chrysippus, 

1 Cf. Shelf ord, Proc. Zool. Soc. 1902. 

2 African Mimetic Butterflies, Oxford, 1910. 



Ill] OLD-WORLD MLMICS 29 

is common to Africa and to Indo-Malaya. Common also 
to the two regions are the mimics, Argynnis hyperbius 
and HypoUmnas misippus (cf. PI. IV, figs. 3 and 7). 
The case of the last named is pecuharly interesting 
because it presents well-marked varieties which can 
be paralleled by similar ones in D. chrysippus. In 
addition to the typical form with the dark tijiped 
fore wing relieved by a white bar there is in each species 
a form uniformly brown, lacking both the dark tip and 
the white bar of the fore wing. There is also another 
form in the two species in which the hind wing is 
almost white instead of the usual brown shade. In 
both species, moreover, the white hind wing may be 
associated either with the uniformly brown fore wing 
or with the typical form. There is also another common 
African butterfly, ylcraea encedon, inwhich. these different 
patterns are closely paralleled (cf. PI. IX). Several other 
species of butterflies and a few diurnal moths bear a 
more or less close resemblance to D. chrysippus. 

Danaine butterflies with the dark interlacing hnes 
on a pale greenish-blue ground, so characteristic of the 
Oriental region, are represented in Africa by the species 
Danais petiverana (PI. VI, fig. 1) ranging across the 
continent from Sierra Leone to British East Africa. 
A common Papilio, P. leonidas (PI. VI, fig. 2) has a 
similar extensive range, and has been regarded as a 
mimic of the Danaine. In S. Africa P. leonidas is 
represented by the variety brasidas in which the white 
spots are reduced and the blue-green ground is lacking. 
Brasidas bears a strong resemblance to the tropical 



30 OLD-WORLD MIMICS [ch. 

Danaine Amauris hyalites (PL VI, fig. 3) of which it 
has been regarded as a mimic. It must however be 
added that it is only over a small part of their respective 
ranges, viz. in Angola, that the two species are to be 
met with together. 

The butterflies belonging to the genus Amauris are 
among the most abundant and characteristic Danaine 
models of Africa. Some of the black and white species 
such as A. niavius (PI. VIII, fig. 6) are conspicuous 
insects in a cabinet. Others again, such as A. echeria 
(PI. VIII, fig. 7), are relatively sombre-looking forms. 
Among the best known mimics of the genus is a species 
of Hypoli^nnas^ — H. duhius. This interesting form is 
polymorphic and mimics different species of Amauris. 
The variety wahlbergi, for example, is very like A. 
niavius, while mima strongly resembles A. echeria 
(PI. VIII, figs. 8 and 9). It was at one time supposed 
that these two varieties of Hypolimnas duhius were 
different species and the matter was only definitely 
settled when the two forms were bred from the eggs 
of the same female. Other mimics of Amauris are 
found among the Papilios and the Nymphaline genus 
Pseudacraea. 

But among all the mimics of Danaines in Africa 
and elsewhere Papilio dardanus is pre-eminent, and 
has been described by more than one writer as the 
most important case of mimicry in existence. Not 
only does it shew remarkable resemblances to various 

^ These African species of Hypolimnas are frequently referred to the 
genus Eur alia. 



Ill] OLD-WORLD MIMICS 31 

Danaids, but it presents features of such peculiar 
interest that it must be considered in more detail. 
Papilio dardanus in its various sub-races is spread over 
nearly all the African continent south of the Sahara. 
Over all this area the male, save for relatively small 
differences, remains unchanged — a lemon-yellow insect, 
tailed, and with black markings on fore and hind wings 
(PL VIII, fig. 1). The female, however, exhibits an 
extraordinary range of variation. In South Africa she 
appears in three guises, (1) the cenea form resembling 
Amauris echeria, (2) the hippocoon form like Amauris 
niavius, and (3) the trophonius form which is a 
close mimic of the common Danais chrysippusK 
Except that cenea does not occur on the West Coast 
these three forms of female are found over almost all the 
great continental range of dardanus and its geographical 
races. Northwards in the latitude of Victoria Nyanza 
occurs a distinct form of female, planemoides, which 
bears a remarkable resemblance to the common and 
distasteful Planeina poggei, and is found only where 
the latter is abundant. All of these four forms are 
close mimics of a common Danaine or Acraeine model. 
Other forms of female, however, are known, of which 
two, dionysus and trimeni, are sufficiently distinct and 
constant to have acquired special names. Dionysus 
may be said to unite the fore wing of the hippocoon 
form with the hind wing of the trophonius form, except 
that the colour of the last part is yellow instead of 

^ Corresponding to the dorippus form of D. chrysippus (cf. PI. IX) 
there is a rare fonn of trophonius known as dorippoides. 



32 OLD-WORLD MIMICS [ch. 

bright brown. It is a western form and is unlike any 
model. Trimeni also is unlike any model but is 
of peculiar interest in that it is much more like the 
male with its pale creamy-yellow colour and the 
lesser development of black scales than occurs in 
most of the forms of female. At the same time the 
general arrangement of the darker markings is on the 
whole similar to that in the hippocoon and in the 
trophonius form. Trimeni is found on the Kikuyu 
Escarpment, near Mt Kenia, along with the four 
mimicking forms. 

Continental Africa, south of the equator, has 
produced no female similar to the male. But in 
Abyssinia is found another state of things. Here, so 
far as is known, occur three forms, all tailed, of which 
one is similar in general colour and pattern to the male, 
while the other two, niavioides and ruspina ^, resemble 
respectively a tailed hippocoon and a tailed trophonius. 
Lastly we have to record that Papilio dardanus is 
also found as the geographical race humbloti on Comoro 
Island, and as meriones on Madagascar. In both 
forms the females are tailed, and resemble the males. 

From this long series of facts it is concluded that 
the male of P. dardanus represents the original form 
of both sexes. On the islands of Comoro and Mada- 
gascar this state of things still survives. But it is 
supposed that on the African continent existed enemies 
which persecuted the species more than on the islands 

^ These two forms are figvired on Plate 10 of Eltringham's African 
Mimetic Butterflies. 



Ill] OLD-WORLD MIMICS 33 

and encouraged the development of mimetic forms 
in the female. The original female still hngers in 
Abyssinia though it is now accompanied by the two 
mimetic forms niavioides and ruspina. Over the 
rest of the area occupied by dardanus the females 
are always taiUess and, with the exception of trimeni 
and dionysus, wonderfully close mimics. Trimeni, 
the intermediate form, provides the clue to the way 
in which the mimetic females have been derived 
from the male, viz. by the prolongation across the 
fore wing of the dark costal bar already fomid in the 
females of the Madagascar and Abyssinian races, 
by the deepening of the dark edging to the wings, 
and by the loss of the tail. Through the gradual 
accumulation of small variations trimeni came from 
the male-hke female, and by further gradual accumula- 
tion of small favourable variations the mimetic forms 
came from trimeni. South of the equator the male- 
like form and the intermediate trimeni have dis- 
appeared owing to the stringency of selection being 
greater. Moreover the likeness of mimic to model 
is closer than in the north, a further proof of the 
greater stringency of natural selection in these parts. 
Such in brief is the explanation in terms of mimicry 
of the remarkable and complex case of dardanus. 

Although the Euploeinae are not represented on 
the African continent, it is the headquarters of another 
distasteful family of butterflies — the Acraeinae — which 
is but sparingly represented in the Oriental region^. 

^ Acraea violae, the only representative of the group in S. India 
P. M. 3 



34 OLD-WORLD MIMICS [ch. 

Of smaller size than the Danaines they are charac- 
terised, like this group, by their tenacity of life and 
by the presumably distasteful character of their 
body juices. They are said also to possess an offensive 
odour apparently exuded through the thorax. The 
majority of the members of the group fall into the 
two genera Acraea and Planema. Species of Acraea 
are on the whole characterised by their general bright 
red-brown colour and by the conspicuous black spots 
on both fore and hind wings. A typical Acraeine 
pattern is that of Acraea egina (PI. VI, fig. 7) which 
is mimicked remarkably closely by the Nymphaline 
Pseudacraea hoisduvali and by the Swallow-tail Papilio 
ridleyanus (PL VI, figs. 5 and 6). 

In the genus Planema the spots are as a rule fewer 
and clustered near the body, while on both fore and 
hind wings there is a tendency to develop clear wide 
band-like areas of orange or white (cf. PI. VII). 

Like the Acraeas the Planemas are principally 
mimicked by species of Pseudacraea and of Papilio. 
Some of the cases of resemblance between Planema 
and Pseudacraea are among the most striking known. 
Planema macarista is one of those comparatively rare 
instances in which a model shews a marked difference 
in the pattern of the two sexes. The clear area on the 
fore wing of the male is deep orange, whereas in the 
female it is somewhat different in shape, and, like the 
area on the hind wing, is white (cf. PI. VII, figs. 1 and 2). 

and Ceylon, is nevertheless a very abundant insect. It cannot, however, 
be said that it is definitely roimicked by any other species in this region. 



Ill] OLD-WORLD MIMICS 35 

Pseudacraea eurytus hohleyi (PI. VII, figs. 6 and 7) shews 
a similar difference in the sexes, the male and female of 
this species mimicking respectively the male and female 
of Plane7na macarista. The case is made even more 
remarkable by the fact that both of the sexual forms 
of Planema macarista are mimicked by the Satyrine 
Elymnias phegea (PL VII, fig. 9), though in this species 
either the black and white, or the black, white, and 
orange form may occur in either sex. Among the best 
Papilionine mimics of the Planemas is Papilio cynorta 
whose female is extraordinarily like the common 
Planema epaea (PL VII, figs. 5 and 10). The re- 
semblance of the 2:)lanemoides female of P. dardanus 
to P. poggei has already been noticed. 

A striking feature of the African continent is 
the frequency with which mimetic forms are found 
among the Lycaenidae. As a rule the "blues" rarely 
exhibit mimetic analogies, but in Africa there are 
several species, especially those of the genus Mim- 
acraea, which closely resemble Acraeines. Others again 
bear a marked resemblance to certain small Pierines, 
Citronophila similis from S. Nigeria for example 
being extraordinarily like the common Terias hrigitta, 
a small bright yellow Pierine with black-edged 
wings. 

A remarkable feature of the African continent 
is the absence of the Pharmacophagus Swallow-tails. 
Of such Papilios as exhibit mimicry, and as compared 
with the total number of the group present the pro- 
portion is large, the majority resemble one or other 

3—2 



36 OLD-WORLD MIMICS [ch. iii 

of the characteristic Danaines, while a few such as 
P. ridleyanus and P. cynorta resemble either an Acraeoid 
or a Planemoid model. 

As in the Oriental region the African Pierines 
do not offer many instances of mimetic analogies. 
The genus Mylothris, in which certain species are 
characterised by orange patches at the bases of the 
undersurfaces of the fore wings, is regarded by some 
authors as providing models for aUied genera such 
as Belenois and Phrissura. But as neither models 
nor mimics offer a marked divergence in appearance 
from the ordinary Pierine facies it is doubtful whether 
much stress can be laid on these cases. 

Africa also offers a few striking instances of mimicry 
in which day-flying moths play a part. The con- 
spicuous Geometer Aletis helcita is an abundant form, 
and with its strong red colour and black wing margins 
broken by white it is a striking object in the preserved 
state. Among the forms which bear a close resemblance 
to it are the NymphaUne Euphaedra ruspina, and the 
Lycaenid Telipna sanguinea^. 

1 Coloured figures of these and of the other African species referred 
to may be found in Eltringham's work on African Mimetic Butterflies. 



CHAPTER IV 

NEW-WORLD MIMICS 

Of all the continents South America affords the 
greatest wealth of butterfly life, and it is in the tropical 
part of this region that many of the most beautiful 
and striking cases of mimicry are to be found. Viewed 
as a whole the butterfly population presents several 
features which serve to mark it off from that of the 
other two great tropical areas. In the first place 
the proportion of gaily coloured forms is higher. 
Bright red, yellow or fulvous brown contrasted with 
some deep shade approaching black form the dominant 
notes. Sombre coloured species are relatively scarcer 
than in the Oriental and African regions. In the 
second place when looking over collections from this 
part of the world one cannot help being struck by the 
frequency with which similar colour combinations 
occur over and over again in different as well as in 
the same groups. Now it is a simple scheme of black 
with an oblique scarlet band upon the fore wings — 
now an arrangement with alternating stripes of bright 
brown and black relieved with patches of clear yellow — 
now again a scheme of pure transparency and black. 



38 NEW-WORLD MIMICS [ch. 

Gay and pleasing as are the designs turned out the 
palette is a small one and invention is circumscribed. 
Under such conditions it might well be supposed 
that instances of close resemblance between different 
species would be numerous, and this in effect is what 
we find. 

As in Asia with its Euploeines and Danaines, 
and in Africa with its Danaines and Acraeines, so 
in S. America are the fashions set by two dominant 
groups of models. These are the Heliconinae and 
the Ithomiinae, both pecuhar to this region and both 
characterised, like the Old-world Danaids, by slow 
flight and great tenacity of life. Both hve on poisonous 
plants — the Heliconines on Passifloras and the Itho- 
miines on Solanaceae. In both groups, but more 
especially in the Ithomiinae, the species are numerous, 
and the number of individuals in a species often 
beyond computation. From the point of view of 
mimicry these two groups have so much in common 
that they may conveniently be considered together. 

It was from among the Ithomiines, as already 
pointed out, that the models came for the Pierine 
mimics of the genus Dismorphia upon which Bates 
founded the theory of mimicry. Though the Pierine 
mimics are the most striking the Heliconines and 
Ithomiines are mimicked by members of other groups. 
A few PapiUos (PI. X, fig. 8), certain Nymphalines 
such as Protogonius (PI. X, fig. 9), Eresia, Phyciodes 
and Colaenis (PI. XI, fig. 4), together with various 
day-flying moths, more particularly of the genera 



IV] NEW-WORLD MIMICS 39 

Castnia and Pericopis, are among the well-known 
mimics of this group of models. The models themselves 
are very variable in appearance. In one locality the 
predominant pattern is black with a warm red-brown 
diagonal bar occupying rather more than a third of 
the fore wing (PI. XV, fig. 5), in another it consists 
of parallel bands of black and fulvous brown with clear 
yellow patches at the tips of the fore wings (cf. PI. X, 
fig. 7), while in yet another locahty it is different again. 
Different localities often have their own pecuHar pattern 
and this affects the various mimics as well as the 
Ithomiine and HeHconine models. 

These groups of different species, some belonging 
to palatable and some to unpalatable groups, all 
exhibiting a close resemblance in colour and pattern, 
are far more strikingly developed in S. America than 
in either Asia or Africa, and it is not uncommon 
for eight or ten species to enter into such an association. 
A group of this sort which possesses unusual interest 
is the so-called "Transparency Group" from certain 
parts of the Amazon region. It was originally de- 
scribed by Bates with seven species belonging to six 
different genera. To-day it is said that no less than 
28 species of this peculiar facies are known, though 
some are excessively rare. The majority are Itho- 
miines, but two species of the Danaine genus Itiina, 
the Pierine Dismorphia orise (PL XII, fig. 2), the 
Swallow-tail Papilio hahneli, and several species of 
diurnal moths belonging to different families (cf. 
PI. XII, fig. 4) also enter into the combination. 



40 NEW-WORLD MIMICS [ch. 

In connection with it there is a feature of peculiar 
interest in that the transparent effect is not always 
produced in the same way. In the Ithomiines such 
as Thyridia, where there are normally two kinds of 
scales, the wider ones for the most part lose their 
pigment, become much reduced in size and take on 
the shape of a stumpy V (PL XIV, fig. 3). Also they 
stand out for the most part more or less at right angles 
to the wing^, and the neck by which they are joined 
to the wing membrane is very short. The longer 
and narrow form of scales also tend to lose their 
pigment and become reduced to fine hairs. In Dis- 
morphia the scales, which are of one sort, are also 
reduced in size though apparently not in number. 
Like the wider scales of the Thyridia they tend some- 
times to project at right angles to the wing membrane, 
though not to the same extent as in the Ithomiine : 
possibly because the neck of the scale is not so 
short. As in Thyridia these reduced scales lose 
their pigment except in the transition region round 
the borders of the transparent patches. In Ituna 
there is a difference. The scales are not reduced to 
the same extent in point of size. Their necks are 
longer as in normal scales and they lie flat on the 
wing membrane. The majority of the scales, as in 
the preceding cases, lose their pigment, but mixed 
up with them is a certain proj)ortion, about one-quarter, 

^ These descriptions are taken from preserved specimens which 
I owe for the most part to the kindness of Dr Jordan. I have not 
had an opportunity of examining fresh ones. 



IV] NEW-WORLD MIMICS 41 

in which the pigment is retained. In Castnia and in 
Anthomysa the scales on the transparent parts which 
are without pigment are also somewhat reduced in 
size, being stumpier than the normal ones. At the 
same time they tend to stand out at right angles 
to the wing membrane^. The neck here again is 
shorter in the transparent than in the pigmented 
scales. A good deal of stress has been laid upon 
this case by some supporters of the theory of mimicry, 
since it is supposed to shew that a similar effect can 
be brought about in a variety of ways ; consequently 
the existence of this assembly of similar transparent 
forms belonging to various families cannot be put 
down as due to the effect of similar conditions, but 
must be regarded as having arisen in each instance 
in a different manner through the independent action 
of natural selection K It is doubtful, however, whether 
such a conclusion necessarily follows from the facts. 
In all of the cases the process would appear to be 
similar: loss of pigment, reduction in the size of the 
scales, and eventually a tendency for the scales to 
stand at right angles to the wing — this last part of 
the process apparently depending upon the reduction 
of the neck of the scale. It has been said that greater 
transparency is brought about by the scales standing 
out at right angles in this way, but as the scales them- 

^ This is more marked in Castnia than in Anthomysa. It appears 
to be a peculiarity of many members of the genus Castnia that the 
scales do not lie so tight as generally in moths. Owing to this, some 
of the large whole-coloured species have a somewhat fluffy look. 

2 Cf. Poulton, Essays on Evolution, 1908, pp. 264-6. 



42 NEW-WORLD MIMICS [ch. 

selves are already transparent there would appear 
to be no reason why this should be so. Of course 
the process has not proceeded in all of the forms 
to the same extent. There is least change in Ituna 
where the scales are not much reduced in size and 
where a fair proportion are still pigmented. There 
is probably most in an Ithomiine such as Thyridia, 
where the scales are not only small and entirely without 
pigment, but also are for the most part neckless so 
that they stand out at right angles to the wing. Having 
regard to the fact that several widely separate genera 
with different types of scaling formed the starting 
points, the final results do not seem to preclude the 
supposition that the transparency has arisen through 
a similar process in all of them. 

It is somewhat remarkable that no Satyrine exhibits 
mimicry in S. America, in spite of the fact that trans- 
parency of the wings, as in so many of the butterflies 
of this region, is quite common in the group. On 
the other hand the relatively large number of more 
or less mimetic Pierines is a striking feature of S. 
America. For the most part they belong to the 
genera Dismorphia and Perrhybris, and resemble the 
yeUow, black, and brown Heliconines and Ithomiines, 
though some of the former genus are mimics of the 
small transparent Ithomiines. Some of the species 
of Pereute with their dark ground colour and the 
bright red bar across the fore \ving (PI. XI, fig. 6) 
resemble Heliconius melpomene, as also does Papilio 
euterpinus. But some of the most interesting Pierine 



IV] NEW-WORLD MIMICS 43 

mimics are several forms belonging to the genus 
Archonias (PI. XI, fig. 10) which exhibit the simple 
and striking arrangement of black, red and white 
so characteristic of the Swallow-tail Poison-eaters of 
S. America. They form one of the rare instances of a 
Pharmacophagus Papilio being mimicked by a butterfly 
which does not belong to the Swallow-tail group. 

As everywhere in the tropics the Papilios of S. 
America supply a goodly proportion of the mimicry 
cases. A few, such as P. zagreus (PI. X, fig. 8), 
enter into the black-brown and yellow Ithomiine- 
HeHconine combination ; P. euterpinus resembles Heli- 
conius melpomene (PI. XI, fig. 5) ; P. pausanias is like 
Heliconius sulphurea (PI. XI, figs. 1 and 2). But this 
practically exhausts the list of Papilios which mimic 
Heliconines and Ithomiines. The great majority of 
mimicking Swallow-tails in S. America find their models 
among the Poison-eaters of their own family, offering 
in this respect a contrast to those of Asia where the 
majority of models are among the Danaines and 
Euploeines, and of Africa where they are exclusively 
Acraeines or Danaines. 

The Poison-eaters of S. America fall into two well- 
marked groups which we may call the red-spotted 
and the dark green groups respectively. The red 
spotted group form a remarkably compact and 
uniform assemblage. The general ground coloiu" is a 
deep black-brown (PI. XI, figs. 8 and 9), the hind mngs 
are almost invariably marked with red near the centre 
or towards the outer margin, and the fore wing may 



44 NEW-WORLD MIMICS [ch. 

or may not bear a patch which is generally whitish 
in the female, though often of a brilliant blue or green 
in the male. This simple colour scheme with varia- 
tions runs throughout about three-quarters (some 
40 species) of the Poison-eaters. The same general 
colour scheme is also found in about two dozen species 
of the unprotected Swallow-tails. As the total number 
of the unprotected species is placed by Seitz at less 
than 100 this means that fully one-quarter of them 
fall into the general colour scheme adopted by the 
majority of the Poison-eaters. In many cases the 
resemblance between mimic and model is so close as 
to have deceived the most expert entomologists before 
the structural differences between the groups had 
been appreciated (cf. Appendix II). The matter is 
further complicated by the fact that polymorphism is 
not uncommon, especially among the females of the 
mimetic forms. Papilio lysithous for instance has no 
less than six distinct forms of female, which differ 
chiefly in the extent and arrangement of the white 
markings on the wings, one form lacking them entirely. 
Several of these forms may occur together in a given 
locality, and may resemble as many distinct species 
of Poison-eaters. Thus the three forms lysithous, with 
white on both wings, rurik, with white on the fore 
wing only, and pomponius without any white, all fly 
together in Rio Grande do Sul and respectively mimic 
the three distinct Pharmacophagus species nephalion, 
chamissonia, and perrhehus (PI. XIII). It is worthy 
of note that mimics are provided by both unprotected 



IV] NEW-WORLD MIMICS 45 

groups of Swallow-tails in S. America, whereas in 
Asia the Cosmodesmus division never provides mimics 
for Pharmacophagus models (cf. Appendix II). 

In the second and smaller group of the Pharma- 
cophagus Swallow-tails the general colour scheme is a 
more or less dark metallic blue-green with a tendency 
towards the obhteration of light markings. Some 
idea of their appearance may be got from the figure of 
the Central and N. American P. philenor on PI. XVI, 
fig. 1. Though one or two unprotected PapiUos 
in S. America fall more or less into this colour scheme, 
the group, from the point of view of mimicry, is not 
nearly so important as the red-spotted one. 

Nevertheless the blue-green Pharmacophagus group 
as represented by P. philenor is supposed to play a con- 
siderable part in mimicry in N. America. P. philenor 
is found throughout the greater part of the Eastern 
United States, stragghng up as far as the Canadian 
border. On the west it is also found reaching up 
to North California. Over considerable parts of its 
range are three other Swallow-tails, belonging to 
the unprotected Papilios, which are regarded by 
Professor Poulton and others as mimics of philenor^. 
One of these, P. troilus, is dark brown with a dusting 
of blue scales over the hind wing (PI. XVI, fig. 2). 
The sexes here are more or less alike. Troilus stretches 
up into North-west Canada some way beyond the 
limits reached by its model. P. cjlaucus is a black 
and yellow Swallow-tail with two forms of female. 

1 Cf. Poulton, Darwin and the 'Origin; 1909, pp. 177-186. 



46 NEW-WORLD MIMICS [ch. 

One of these resembles the male while the other is 
darker and is said to mimic philenor. It is known 
as the turnus form and is found more commonly in 
the southern part of the range of the species, i.e. in 
the country where philenor is more plentiful. The 
third species, P. asterius, has a more southerly dis- 
tribution. Its female is darker and nearer to philenor 
than the male. It must, however, be admitted 
that none of the three species bears a very close 
resemblance to philenor. It is suggested that this 
is because P. philenor is a tropical form which has 
only recently invaded N. America. The crossing of 
philenor has, as it were, induced the three mimicking 
Papilios to turn dark, but the model has not been 
long enough in contact with them for the Hkeness 
to become a close one. The explanation, however, 
hardly accounts for the fact that the best mimic 
of the three, P. troilus, in which both sexes are dark, 
is found far north of philenor. Either the dark colour 
was estabhshed without the influence of the Pharma- 
cophagus model, or else the species rapidly extended 
its range northwards after having been modified 
under the influence of philenor in the south. But 
in that case the critic may ask why it does not revert to 
the original pattern now that it has got beyond the 
model's sphere of influence. On the whole it seems 
at present quite doubtful whether any relation of 
a mimetic nature exists between P. philenor and 
these three species of Papilio. 

P. philenor is also regarded as serving as a model 



IV] NEW-WORLD MIMICS 47 

for two Nymphaline butterflies in the United States. 
One of these is the large FritiUary Argynnis diana 
of which the dark female has a markedly blue tint 
on the upper surface (PI. XVI, fig. 3). The other 
is a Limenitis^ related to our own White Admiral. 
This form, L. astyanax (PI. XVI, fig. 5), is a dark form 
with a bluish iridescence on the upper surface. It is 
found, like P. phileiior, over the greater part of the 
Eastern States, while to the north, near the Canadian 
boundary, its place is taken by L. arthemis with 
prominent white bar across both wings (PI. XVI, fig. 4). 
There is reason for beUeving that where the two overlap 
there is occasional inbreeding, and that the hybrid 
is the form known as proserpina, resembUng astyanax 
more than arthemis. It must be admitted that in 
general appearance L. astyanax and Argynnis diana 
are more like Papilio troilus than P. philenor. In 
explanation it has been suggested that all the mimics 
are on the way to resembling P. philenor, and con- 
sequently we should expect them at certain stages 
to shew more resemblance to one another than to 
the form they have all as it were set out to mimic. 
On this view they will all arrive at a close resemblance 
to philenor in time. Another explanation is that 
favoured by Professor Poult on on which it is assumed 
that we are here deahng with a case of Miillerian 
Mimicry, all of the species in question being distasteful 
with the exception perhaps of A. diana. Thus troilus 
and astyanax though distasteful are less so than 

^ The N. American members of tliia genus are often referred to as 
Basilarchia. 



48 NEW-WORLD MIMICS [ch. 

philenor. Hence it is of advantage to them to have 
even a chance of being mistaken for the more obnoxious 
philenor, and so the one has come from the black 
and yellow Swallow-tail pattern and the other from 
the white-banded arthemis form to what they are, 
Le. more alike to one another than to philenor. They 
now form a Miillerian combination for mutual protection 
along with the dark females of glaucus and asterius. 
But they are themselves still moderately distasteful 
so that it is to the advantage of the female of Argynnis 
diana to mimic them. Whether they are all on the 
way to resembhng philenor more closely, or whether 
they have suiSiciently vindicated their inedible proper- 
ties and are now stationary, it is for the future to 
reveal to posterity. Lastly we have the view that 
these different species have attained their present 
coloration entirely independently of one another, 
and that we are not here concerned with mimicry 
at all. Since the sole evidence available at present 
is that based on general appearance and geographical 
distribution, the view taken of this case must rest 
largely upon personal inclination. 

Though the cases just quoted are only very pro- 
blematically mimetic, N. America has yet several 
examples of resemblance between distantly related 
forms as close as any that occur in the tropics. In 
this region are found two species of the genus Danais — 
D. archippus occurring all over the United States 
and reaching up northwards into Canada, D. herenice 
found in the South-eastern States, e.g. in Florida, 
where it is said to be more abundant than archippus. 



IV] NEW-WORLD MIMICS 49 

D. archippus (PI. XVI, fig. 8) is very similar to the 
oriental D. plexippus (PI. IV, fig. 2), from which 
perhaps its most notable difference lies in the extent 
and arrangement of the white spots near the tip of 
the fore wing. D. berenice is not unlike archippus in 
its general colour scheme but is smaller and darker 
(PI. XVI, fig. 9). 

We have already had occasion to mention the 
common Nymphaline, Limenitis arthemis (PI. XVI, 
fig. 4) which is found in Canada and the North- 
eastern States. Widely spread over N. America is 
a close ally of this species, L. archippus, which, though 
so similar in structure and habits, is very different 
in external appearance. As appears from PL XVI, 
fig. 6, L. archippus is remarkably like the Danaid 
which bears the same specific name. In the Southern 
States L. archippus is replaced by a form slightly 
different in details of pattern and distinctly darker, 
L. fioridensis {=eros) (PI. XVI, fig. 7). In Florida 
occiurs also the darker N. American Danaid, D. berenice, 
to which the colour of L. fioridensis approximates 
more than to D. archippus, and it is of interest 
that although the last named is also found in this 
locahty it is said to be much less abundant than 
D. berenice. Nevertheless it appears to be true that 
the range of L. fioridensis is much more extensive 
than that of its model ; in other words, that there 
are considerable regions where L. fioridensis and 
D. archippus coexist, and from which L. archippus 
and D. berenice are wanting. 

p. M. 4 



CHAPTER V 

SOME CRITICISMS 

The facts related in the last two chapters are 
sufficient to make it clear that these remarkable 
resemblances between species belonging as a rule 
to widely different groups constitute a real pheno- 
menon, and as such demand an explanation. One 
explanation, that in terms of the theory of mimicry, 
has already been outlined, and we may now turn to 
consider it in more detail. Some years ago Wallace^, 
combating the suggestion that these instances of 
resemblance might be mere coincidences, laid down 
five conditions which he stated were applicable to 
all such cases, and rendered utterly inadequate any 
explanation other than in terms of natural selection. 
These five conditions are of historical interest and 
may also serve as a peg for sundry criticisms in con- 
nection with the mimicry theory. They are as follows : 

(1) That the imitative species occur in the same 
area and occupy the very same station as the imitated. 

(2) That the imitators are always the more 
defenceless. 

1 Darwinism, 1890 (1st Edition 1889), p. 264. 



CH. v] SOME CRITICISMS 51 

(3) That the imitators are always less numerous 
in individuals. 

(4) That the imitators differ from the bulk of 
their aHies. 

(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. 

In offering certain criticisms of the mimicry ex- 
planation it will be convenient to do so in connection 
Avith these five conditions which Wallace regarded as 
constant for all cases of mimetic resemblance. 

(1) TJmt the imitative species occur in the same 
area and occupy the very same station as the imitated. 

This on the whole is generally true. It is well shewn 
in some of the most striking cases such as those of 
the Old-World Pai^ilios that mimic Danaines, or of 
the Dismorphias and their Ithomiine models. In 
many of these cases the range of neither model nor 
mimic is a very wide one, yet the mimic is found 
strictly inside the area inhabited by the model. Papilio 
agestor, for instance, is only found where Caduga tytia 
occurs, nor is P. m^endax known outside the area 
frequented by Euploea rhadamanthus. Even more 
striking in this respect are some of the Ithomiine- 
Dismorphia resemblances in the New World. The 
Ithomiine models are as a rule very local though 
very abundant. Two hundred miles away the pre- 
dominant Ithomiine often bears quite a distinct 
pattern, and when this is the case the mimicking 
Dismorphia is generally changed in the same sense. 

4—2 



52 SOME CRITICISMS [ch. 

But though mimic and model may be found together 
in the same locahty, they do not always occupy the 
same station in the sense that they fly together. 
According to Seitz^ the Dismorphias themselves do 
not fly with the Ithomiines which they mimic. The 
occurrence of butterflies is largely conditioned by the 
occiu*rence of the plants on which the larva feeds, 
and this is especially true of the female, which, as has 
already been noticed, is more commonly mimetic 
than the male. The female of Papilio polytes, for 
instance, is found flying where are to be found the 
wild citronaceous plants on which its larva feeds. 
On the other hand, its so-called models, Papilio hector 
and P. aristolochiae, are generally in the proximity 
of the Aristolochias on which their larvae feed. The 
two plants are not always found together, so that 
one frequently comes across areas where P. polytes 
is very abundant while the models are scarce or absent. 
Though in the great majority of cases the imitator 
and the imitated occur in the same locality, this is 
not always so. The female of the Fritillary Argynnis 
hyperhius (PI. IV, fig. 3), for instance, is exceedingly 
difficult to distinguish from Danais plexippus when 
Hying, although when at rest the difference between 
the two is sufficiently obvious. Both insects are 
plentiful in Ceylon but inhabit different stations. 
The Danaid is a low-country insect, while the Fritillary 
is not found until several thousand feet up. The two 
species affect entirely different stations and hardly 

1 Macrolepidoptera of the World. Fauna Americana, p. 98. 



v] SOME CRITICISMS 53 

come into contact vvdth each other. Where one is 
plentiful the other is not found. It has been suggested 
that migratory birds may have come into play in 
such cases. The bird learns in the low country that 
D. plexippus is unpleasant, and when it pays a visit 
to the hills it takes this experience with it and avoids 
those females of the Fritillary which recall the un- 
pleasant Danaine. 

Migratory birds have also been appealed to in 
another case where the resembling species are even 
further removed from one another than in the last 
case. Hypolimnas misippus is common and widely 
spread over Africa and Indo-Malaya, and the male 
(PI. IV, fig. 8) bears a simple and conspicuous 
pattern — a large white spot bordered with purple 
on each of the very dark fore and hind wings. The 
same pattern occurs in the males of two other Nym- 
phalines aUied to H. misippus, viz. Athyma punctata 
and Limenitis alhomaculata. The two species, however, 
have a distribution quite distinct from that of H. 
misippus, being found in China. It has nevertheless 
been suggested by Professor Poulton^ that the case 
may yet be one of mimicry. According to his explana- 
tion, H. misippus is unpalatable, the well-known 
association of its female with Danais chrysippus being 
an instance of Miillerian mimicry. Migratory birds 
did the rest. Having had experience of H. misippus 
in the south, on their arrival in China they spared 
such specimens of Athyma punctata and Limenitis 

^ Essays on Evolution, 1908, p. 381. 



54 SOME CRITICISMS [ch. 

albomaculata as approached most nearly to H. misippus 
in pattern, and so brought about the resemblance. 
The explanation is ingenious, but a simpler view will 
probably commend itself to most. Other cases are 
known in which two butterflies bear a close resemblance 
in pattern and yet are widely separated geographically. 
Several species of the S. American Vanessid genus 
Adelpha are in colour scheme like the African Planema 
poggei which serves as a model for more than one 
species. The little S. American Phyciodes leucodesma 
would almost certainly be regarded either as a model 
for or a mimic of the African Neptis nemetes, did the 
two occur together. Nevertheless examples of close 
resemblance between butterflies which live in different 
parts of the world are relatively rare and serve to 
emphasise the fact that the great bulk of these 
resemblance cases are found associated in pairs or in 
little groups. 

(2) That the imitators are always the more defenceless. 

In the case of butterflies '' defence" as a rule denotes 
a disagreeable flavour rendering its possessor distasteful 
to birds and perhaps to other would-be devourers. 
Feeding experiments with birds (cf. Chapter IX) 
suggest that certain groups of butterflies, notably 
the Danaines, Acraeines, Heliconines, Ithomiines and 
Pharmacophagus Papilios — groups from which models 
are generally drawn — are characterised by a disagreeable 
taste, while as a rule this is not true for the mimics. 
This distasteful quality is frequently accompanied 
by a more or less conspicuous type of coloration, 



V] SOME CRITICISMS 55 

though this is by no means always so. Many Eu^oloeas 
are sombre inconspicuous forms, and it is only some 
of the Ithomiines that sport the gay colours with which 
that group is generally associated. The members of 
the distasteful groups usually present certain other 
pecuHarities. Their flight is slower, they are less 
wary, their bodies are far tougher, and they are more 
tenacious of life. The slow flight is regarded as an 
adaptation for exhibiting the warning coloration to 
the best advantage, but from the point of view of 
utihty it is plausible to suggest that the insect would 
be better off if in addition to its warning coloration 
it possessed also the power of swift flight i. It is 
possible that the peculiar slowness of flight of these 
unpalatable groups is necessitated by the peculiar 
tough but elastic integument which may present an 
insufficiently firm and resistant skeletal basis for 
sharp powerful muscular contraction, and so render 
swift flight impossible. It is stated that the flight 
of the mimics is like that of the model, and in 
some cases this is undoubtedly true. But in a great 
many cases it certainly does not hold good. Papilio 
clytia (PI. I, figs. 7 and 8) is a strong s\vift flyer 
very unlike the Danaine and Euploeine which it is 
supposed to mimic. The flight of the female of 
Hypolimnas misippus (PI. IV, fig. 7) is quite distinct 
from that of Danais chrysippus, whfle the mimetic 

^ These "unpalatable" butterflies are sometimes extensively 
preyed upon by insectivorous birds, when they fall an easier prey owing 
to their slowness (cf. p. 112). 



56 SOME CRITICISMS [ch. 

forms of P. polytes fly like the non-mimetic one, a 
mode of flight so different from that of the two models 
that there is no difficulty in distinguishing them 
many yards away. Swift flight must be reckoned 
as one of the chief modes of defence in a butterfly, 
and on this score the mimic is often better off than 
the model. And of course it must not be forgotten 
that where the mode of flight is distinct the protective 
value of the resemblance must be very much discounted. 

(3) TJiat the imitators are always less numerous 
in individuals. 

In the majority of cases this is certainly true. 
Probably all the Old-World Papilios that mimic 
Danaines a.re scarcer, and frequently very much 
scarcer, than their models. This is very evident from 
a study of the more comprehensive priced catalogues 
of Lepidoptera. The mimic is generally a more 
expensive insect than the model, and not infrequently 
it costs as many pounds as the model does shillings. 
But the rule is not universal. Papilio polytes is often 
much more common than either of its models. The 
remarkable Pierines, Archonias tereas and A. critias 
(PI. XI, fig. 10) as a rule far outnumber the Pharmaco- 
phagus Swallow-tail which they mimic. Or again the 
Chalcosid moth Callamesia pieridoides'^ is a more 
abundant insect than the Bornean Pierine Delias 
cathara which it closely resembles. 

It has sometimes been suggested in explanation 

1 See Shelf ord, Proc. Zool. Soc. 1902, p. 260. A coloured figure 
of both species is given in the paper. 



v] SOME CRITICISMS 57 

of the greater abundance of the mimic that in such 
cases we are concerned with Miillerian mimicry, that 
since both of the species concerned are distasteful 
there is not, strictly speaking, either a mimic or a 
model, and consequently the relative proportions have 
not the significance that they possess where the 
mimicry is of the simple Batesian type. It is, however, 
very doubtful whether such an explanation is of any 
value, for, as will appear later, there are grave objections 
to accepting the current theory as to the way in which 
a resemblance is estabhshed on Miillerian lines (cf. 
pp. 72-74). 

(4) That the imitators differ from the hulk of their 
allies. 

What importance we attach to this condition 
must depend upon our interpretation of the word 
"allies" — ^whether, for example, we use it for a small 
group of closely connected species, for a genus, for 
a group of genera, or in an even wider sense. Perhaps 
an example will serve to make the difficulty more 
clear. As already noticed, the S. American genus 
Dismorphia belongs to the family of Pieridae or 
"whites." Also certain species of Dismorphia bear a 
close resemblance to certain species of Ithomiines, 
a noteworthy example being D. praxinoe and Mecha- 
nitis saturata (PI. X, figs. 3 and 7), in which the 
pattern, colour, and shape of the two species are 
all far removed from what is usually understood by 
a "white." It must not be forgotten, however, that 
these matters are generally discussed by European 



58 SOME CRITICISMS [ch. 

naturalists who have grown up in a region where 
the majority of the "whites" are more or less white. 
For this reason the statement that D. praxinoe differs 
from the bulk of its allies is likely to meet with 
general acceptance, especially as some of the species 
of the genus itself (e.g., D. cretacea, PI. X, fig. 1) 
are regular whites in appearance. But when we 
come to look at the genus DismorpJiia as a whole the 
matter assumes another complexion. Seitz ^ recognises 
75 species of which about a dozen are predominantly 
white. The rest present a wonderful diversity of 
colour and pattern. Black predominates on the fore 
wings, and the insect is frequently marked with gay 
patches of yellow, bright brown, scarlet, or blue. 
Forms which from their colour are clearly not mimics 
present nevertheless the general pattern and shape 
of other forms which bear a strong resemblance to 
some Ithomiine. Sometimes a change of colour in 
certain patches from blue or yellow to bright brown 
would make all the difference between a non-imitative 
and an imitative species. Moreover, the non-imitative 
forms frequently have the peculiar narrow wing, so 
unusual in a Pierine, which enhances the resemblance 
of the mimicking species to the Ithomiine model, 
and which to some extent occiurs even in D. cretacea. 
Clearly we are not justified in saying that D. praxinoe 
differs from the bulk of its allies, for inside the genus 
there are many non-imitative species which differ 

^ Macrolepidoptera of the World. Fauna Americana, pp. 98-104, 
Plates 28-30. 



V] SOME CRITICISMS 59 

from it in some particulars and are alike it in others. 
There is a distinct family resemblance among the bulk 
of the Dismorphias, including practically all the mimetic 
forms, and on the whole the resemblances between 
the imitative and the non-imitative forms are as 
noteworthy as the differences. Though not exhibited 
in so striking a fashion, the same is to a large extent 
true of a large proportion of the cases of mimicry. 
It is on the whole unusual to find cases where a single 
species departs widely from the pattern scheme of 
the other members of the genus and at the same time 
resembles an unrelated species. Two of the best 
instances are perhaps those of Limenitis archippus 
(p. 49) and of the Pierid Pareronia (p. 23). Of 
the total number of mimicry instances a high propor- 
tion is suppUed by relatively few groups. In each 
region several main series of models and mimics run 
as it were parallel to one another. In Asia, for example, 
we have the Papilio-Danaine series where the colour- 
patterns of a series of Danaines, aU nearly related, 
are closely paralleled by those of a section of the 
genus Papilio, and by those of the Satyrid genus 
Elymnias. In Africa there is a similar Papilio-Danaine 
series though of less extent. Africa has a group of 
models not found in Asia, and the Papiho-Danaine 
series is as it were curtailed by the Papilio-Planema 
series with which to some extent runs parallel the genus 
Pseudacraea. These phenomena of parallel series have 
been mentioned here as shewing that mimicry tends 
to run in certain groups and that in many cases at 



60 SOME CRITICISMS [ch. v 

any rate little meaning can be attached to the state- 
ment that the imitators differ from the bulk of 
their alhes. 

The fifth of Wallace's conditions is clear and needs 
no discussion. 

It is evident that at any rate a large proportion 
of the instances of close resemblance do not fulfil 
all of the conditions laid down by Wallace. Never- 
theless we should expect them to do so if the resemblance 
has been brought about by the cumulative effect of 
natural selection on small favourable variations. Clearly 
there is a 'prima facie case for doubting whether we 
must of necessity ascribe all resemblance of the kind 
to natural selection, and in the next few chapters 
we shall discuss it in more detail from several points 
of view. 



CHAPTER VI 

"MIMICRY rings" 

Having reviewed briefly some of the most striking 
phenomena of what has been termed mimicry, we 
may now inquire whether there are good grounds 
for supposing that these resemblances have been 
brought about through the operation of natural 
selection or wdiether they are due to some other cause. 
If w^e propose to offer an explanation in terms of 
natural selection we are thereby committed to the 
view that these resemblances are of the nature of 
adaptation. For unless we grant this we cannot 
suppose that natural selection has had anything to 
do either with their origin or w4th their survival. 
Granting then for the present the adaptational nature 
of these mimetic resemblances, we may attempt to 
deduce from them what we can as to the mode of 
operation of natural selection. In doing so we shall 
bear in mind what may be called the two extreme 
views : viz. (a) that the resemblance has been brought 
about through the gradual accumulation of very 
numerous small variations in the right direction through 
the operation of natural selection, and (6) that the 
mimetic form came into being as a sudden sport or 



62 "MIMICRY RINGS" [ch. 

mutation, and that natural selection is responsible 
merely for its survival and the eUmination of the less 
favoiured form from which it sprang. 

There is a serious difficulty in the way of accepting 
the former of these two views. If our two species, 
model and would-be mimic are, to begin with, markedly 
different in pattern, how can we suppose that a slight 
variation in the direction of the model on the part 
of the latter would be of any value to it ? Take for 
example a well-known South American case — the 
resemblance between the yellow, black, and brown 
Ithomiine, Mechanitis saturata (PL X, fig. 7) and 
the Pierine, Dismorphia praxinoe (PI. X, fig. 3). 
The latter belongs to the family of the "whites," and 
entomologists consider that in all probabihty its 
ancestral garb was white with a little black like the 
closely allied species D. cretacea (PL X, fig. I). Can 
we suppose that in such a case a small development 
of brown and black on the wings would be sufficient 
to recall the Ithomiine and so be of service to the 
Dismorphia which possessed it ? Such a relatively 
slight approach to the Ithomiine colouring is shewn 
by the males of certain South American "whites" 
belonging to the genus Perrhyhris (PL X, figs. 4 and 5). 
But the colour is confined to the under-surface and 
the butterflies possessing it could hardly be confused 
with a Mechanitis more than their white relations 
which entirely lack such a patch of colour. If birds 
regarded white butterflies as edible it is difficult to 
suppose that they would be checked in their attacks 



VI] "MIMICRY RINGS" 63 

by a trifling patch of colour while the main ground 
of the insect was still white. But unless they avoided 
those with the small colour patch there would be an 
end of natural selection in so far as the patch was 
concerned, and it would have no opportunity of 
developing further through the operation of that 
factor. This is the difficulty of the initial variation 
which has been clearly recognised by most of the 
best known supporters of the theory of mimicry. 
Bates himself offered no suggestion as to the way 
in which such a form as a Pierid could be conceived 
of as beginning to resemble an Ithomiine^. Wallace 
supposed that the Ithomiines were to start with 
not so distinct from many of the edible forms as they 
are to-day, and that some of the Pierines inhabiting 
the same district happened to be sufficiently like some 
of the unpalatable forms to be mistaken for them 
occasionally ^. 

The difficulty of the initial variation had also 
occurred to Darwin, and he discusses it in an interesting 
passage which is so important that we may quote 
it here in full : 

It should be observed that the process of imitation probably 
never commenced between forms widely dissimilar in colour. But 
starting with species already somewhat like each other, the closest 
resemblance, if beneficial, could readily be gained by the above 
means ; and if the imitated form was subsequently and gradually 

^ "In what way our Leptalis { = Dismorphia) originally acquired 
the general form and colour of Ithomiae I must leave vmdiscovered." 
Trans. Linn. Soc. vol. 23, 1862, p. 513. 

2 Darwinis7n, 1890, pp. 242-244. 



64 -MIMICRY RINGS" [ch. 

modified through any agency, the imitating form would be led 
along the same track, and thus be altered to almost any extent, so 
that it might ultimately assume an appearance or colouring wholly 
unlike that of the other members of the family to which it belonged. 
There is, however, some difficulty on this head, for it is necessary 
to suppose in some cases that ancient members belonging to several 
distinct groups, before they had diverged to their present extent, 
accidentally resembled a member of another and protected group 
in a sufficient degree to afford some slight protection ; this having 
given the basis for the subsequent acquisition of the most perfect 
resemblance^. 

Both Darwin and Wallace recognised clearly this 
difficulty of the initial variations, and both suggested 
a means of getting over it on similar lines. Both 
supposed that in general colour and pattern the groups 
to which model and mimic belonged were far more 
alike originally than they are to-day. They were 
in fact so much ahke that comparatively small varia- 
tions in a favourable direction on the part of the mimic 
would lead to its being confused with the unpalatable 
model. Then as the model became more and more 
conspicuously coloured, as it developed a more and 
more striking pattern warning would-be enemies of 
its unpleasant taste, the mimic gradually kept pace 
with it through the operation of natural selection, 
in the shape of the discriminating enemy, eliminating 
those most unlike the model. The mimic travelled closely 
in the wake of the model, coaxed as it were by natural 
selection, till at last it was far removed in general 
appearance from the great majority of its near relations. 

1 Origin of Species, 6th Edition, 1891, p. 354. 



VI] *' MIMICRY RINGS" 65 

In this way was offered a comparatively simple 
method of getting over the difficulty of applying 
the principle of natm'al selection to the initial varia- 
tions in a mimetic approach on the part of one species 
to another. But it did not escape Darwin's penetra- 
tion that such an argument would not always be 
easy of application — that there might be cases where 
a given model was mimicked by members of several 
groups of widely differing ancestral pattern, and that 
in these cases it would be difficult to conceive of 
members of each of the several groups shewing simul- 
taneous variations which would render them liable to be 
mistaken for the protected model. The difficulty may 
perhaps be best illustrated if we consider a definite case. 

It is a feature of mimetic resemblances among 
butterflies that a given species in a given locality 
may serve as a model for several other species belonging 
to unrelated groups. Generally such mimics belong 
to presumably palatable species, but other presumably 
unpalatable species may also exhibit a similar colora- 
tion and pattern. In this way is formed a combine 
to which the term "mimicry ring" has sometimes 
been applied. An excellent example of such a mimicry 
ring is afforded by certain species of butterflies in 
Ceylon, and is illustrated on Plate IV. It is made 
up in the first place of two species belonging to the 
presumably distasteful Danaine group, viz. Danais 
chrysippus and D. plexippus. The latter is a rather 
darker insect but presents an unmistakable general 
likeness to D. chrysippus. Those who believe in 

F M. 5 



66 "MIMICRY RINGS" [ch. 

MiiUerian mimicry would regard it as an excellent 
example of that phenomenon. For those who believe 
only in Batesian mimicrj^ D. plexippus, being the 
scarcer insect, must be regarded as the mimic and 
D. ckrysippus as the model. In both of these species 
the sexes are similar, whereas in the other tlnree members 
of the " ring " the female alone exhibits the resemblance. 
One of these three species is the common Nymphaline, 
Hypolimrias misippus, of which the female bears an 
extraordinary likeness to D. ckrysippus when set and 
pinned out on cork in the ordinary way. The male, 
however (PI. IV, fig. 8), is an insect of totally 
different appearance. The upper surfaces of the wings 
are velvety black with a large white patch bordered 
with purple in the middle of each^. The ''ring" is 
completed by the females of Elymnias undularis and 
Argynnis hyperhius. The former of these belongs to 
the group of Satyrine butterflies and the female is 
usually regarded as a mimic of D. plexippus, which 
it is not unhke in so far as the upper surface of the 
wings is concerned. Here again the male is an insect 
of totally dissimilar appearance. Except for a border of 
Ughter brown along the outer edges of the hind wings 
the upper surface is of a uniform deep purple-brown 

1 H. misippus was at one time regarded as a clear case of Batesian 
mimicry. But in view of its plentifulness, of the fact that it may be 
abundant outside the area inhabited by its model, and of the ease 
with which it can establish itself in parts remote from its original 
habitat, e.g. S. America, it has come to be regarded by certain supporters 
of the mimicry theory as a MiiUerian mimic. Cf. Povilton, Essays on 
Evolution, 1908, pp. 215-217. 



VI] "MIMICRY RINGS" 67 

aU over (PI. IV, fig. 6). In Argynnis hyperhius 
the appearance is in general that of the Fritillary 
group to which it belongs. But in the female the 
outer portion of the fore wings exhibits much black 
pigment and is crossed by a broad white band similar 
to that found in the same position on the wing of 

D. plexippus (PI. IV, fig. 2). 

Of the five species constituting this little " mimicry 
ring " in Ceylon two, on the current theory of mimicry, 
are to be regarded as definitely unpalatable, one 
{H. misippus) as doubtfully so, while the Satyrine 
and the Fritillary are evidently examples of simple 
or Batesian mimicry. 

Now such examples as this of simultaneous mimicry 
in several species are of peculiar interest for us when 
we come to inquire more closely into the process 
by which the resemblances can be supposed to have 
been brought about. Take for example the case of 

E. undularis. The male is evidently an unprotected 
insect in so far as mimicry is concerned, while the 
female exhibits the general pattern and coloration 
characteristic of the warningly coloured and pre- 
sumably distasteful species D. plexippus or D. chrysip- 
pus. If we are to suppose this to have been brought 
about by the operation of natural selection it is clear 
that we must regard the colour and pattern of the 
male as the original colour and pattern of both sexes. 
For natural selection cannot be supposed to have 
operated in causing the male to pass from a protected 
to an unprotected condition, or even in causing him 

5—2 



68 "MIMICRY RINGS" [ch. 

to change one unprotected condition for another. 
Probably all adherents of the mimicry theory would 
be agreed in regarding the male of Elymnias undularis 
as shewing the ancestral coloration of the species, and 
in looking upon the female as having been modified to 
her own advantage in the direction of D. plexippus. 
The question that we have to try to decide is how 
this has come about — whether by the accumulation 
of shght variations, or whether by a sudden change 
or mutation in the pattern and colour of the female 
by which she came to resemble closely the Danaine. 
It is clear that if D. plexippus were what it is to-day 
before the mimetic approach on the part of E. undularis 
began, small variations in the latter would have been 
of no service to it. The difference between the two 
species would have been far too great for individuals 
exhibiting slight variation in the direction of D. 
plexippus to stand any chance of being confused 
with this species. And unless such confusion were 
possible natural selection could not work. There is, 
however, an immediate way out of the difficulty. 
We may suppose that the coloration of the male 
of the mimic, E. undularis, is not only the ancestral 
colour of its own species but also of the model. D. 
plexippus on this supposition was very like E. undularis, 
of which both sexes were then similar to what the 
male is to-day. The pattern is, however, an incon- 
spicuous one, and it can be imagined that it might 
be to the advantage of D. plexippus to don a brighter 
garb for the advertisement of its unpleasant qualities. 



VI] "MIMICRY RINGS" 69 

Variations in the direction of a more conspicuous 
pattern would for that reason tend to be preserved 
by natural selection, until eventually was evolved 
through its means the well-marked pattern so charac- 
teristic of the model to-day. If in the meantime 
variations in the same direction occurred among the 
females of E. undularis these would tend to be preserved 
through their resemblance to the developing warning 
pattern of the distasteful Danaine model. The develop- 
ment of model and mimic would proceed pari passu, 
but if the sexes of the mimic differ, as in this case, 
we must suppose the starting-point to have been the 
condition exhibited by the male of the mimicking 
species. 

But Argynnis hyperbhis is also a species in which 
the female mimics D. plexippus ; and by using the 
same argument as that just detailed for Elymnias 
undularis we can shew that the Danaine model, D. 
plexippus, must also have been like the male of Argynuis 
hyperbius. And if the resemblance of A. hyperbius 
was developed subsequently to that of E. undularis, 
then both D. plexippus and E. undularis must at one 
time have been like the male of A. hyperbius, a pro- 
position to which few entomologists are likely to assent. 
Further, since the female of H. misippus also comes 
into the plexippus-chrysippus combine we must suppose 
that these species must at some time or another have 
passed through a pattern stage Uke that of the misippus 
male. 

It is scarcely necessary to pursue this argument 



70 *' MIMICRY RINGS" [ch. 

further, for ^ even the most devoted adherents of the 
theory of mimicry as brought about by the operation 
of natural selection on small variations are hardly 
likely to subscribe to the phylogenetic consequences 
which it must entail in cases where a model is mimicked 
by the females of several species whose males are 
widely dissimilar in appearance. 

Even if we suppose the two Danaines to have 
been originally like the male of one of the three mimics, 
we must stiU suppose that the females of the other 
two originated as " sports," sufficiently near to Danaines 
to be confused with them. But if such sports can 
be produced suddenly by some mutational process 
not at present understood, why should not these 
sports be the females of the three mimicking species 
as we see them at present ? Why need we suppose 
that there were intermediate stages between the 
mimicking female and the original hypothetical female 
which was like the male ? If a sport occiu-red which 
was sufficiently similar to an unpalatable species to 
be confused with it, it is theoretically demonstrable 
that, although relatively scarce to start with, it would 
rapidly increase at the expense of the unprotected 
male-like female until the latter was eliminated. We 
shall, however, return in a later chapter (p. 96) to 
the argument by which this view can be supported. 

So far we have discussed what we called the two 
extreme views as to the way in which a mimetic 
resemblance may be supposed to have originated. Of 
the two that which assumes the resemblance to have 



VI] ''MIMICRY RINGS" 71 

been brought about by a succession of slight vari- 
ations must also assume that model and mimic were 
closely alike to start with, and this certainly cannot 
be true in many cases. On the other hand, there is 
so far no reason against the idea of supposing the 
resemblance to have originated suddenly except what 
to most minds will probably appear its inherent im- 
probability. 

There are writers on these questions of mimicry 
who adopt a view more or less intermediate between 
those just discussed. They regard the resemblance as 
having arisen in the first place as a sport of some 
magnitude on the part of the mimic, rendering it 
sufficiently like the model to cause some confusion 
between the two. A rough-hewn resemblance is first 
brought about by a process of mutation. Natural 
selection is in this way given something to work on, 
and forthwith proceeds to polish up the resemblance 
until it becomes exceedingly close. Natural selection 
does not originate the likeness, but, as soon as a rough 
one has made its appearance, it comes into operation 
and works it up through intermediate stages into the 
finished portrait. It still plays some part in the 
formation of a mimetic resemblance though its role is 
now restricted to the putting on of the finishing touches. 
Those who take this view hold also that the continued 
action of natural selection is necessary in order to keep 
the likeness up to the mark. They suppose that if 
selection ceases the likeness gradually deteriorates 
owing to the coming into operation of a mysterious 



72 "MIMICRY RINGS" [ch. 

process called regression. This idea involves certain 
conceptions as to the nature of variation which we 
shall discuss later. 

Though it is difficult to regard Batesian mimicry 
as produced by the accumulation of small variations 
through natural selection, it is perhaps rather more 
plausible to suppose that such a process may happen 
in connection with the numerous instances of Miillerian 
mimicry. For since the end result is theoretically to 
the advantage of both species instead of but one, it 
is possible to argue that the process would be sim- 
plified by their meeting one another halfway, as Miiller^ 
himself originally suggested. Variations on the part 
of each in the direction of the other would be favourably 
selected, the mimicry being reciprocal. 

Difficulties, however, begin to arise when we inquire 
into the way in which this unification of pattern may 
be conceived of as having come about. By no one 
have these difficulties been more forcibly presented 
than by Marshall^ in an able paper published a few 
years ago, and perhaps the best way of appreciating 
them is to take a hypothetical case used by him as 
an illustration. 

Let us suppose that in the same area live two equally 
distasteful species A and B, each with a conspicuous 
though distinct warning pattern, and each sacrificing 
1000 individuals yearly to the education of young 

^ An English translation of Miiller's paper is given by Meldola, 
Proc. Ent. Soc, 1879, p. xx. 

2 Trans. Ent. Soc. Lond., 1908, p. 93. 



VI] "MIMICRY RINGS" 73 

birds. Further let it be supposed that ^ is a common 
species of which there are 100,000 individuals in the 
given area, while B is much rarer, and is represented by 
5000. The toll exacted by young birds falls relatively 
more lightly upon A than upon B, for A loses only 
1 %, whereas 5's loss is 20 %. Clearly if some members 
of B varied so that they could be mistaken for A it 
would be greatly to their advantage, since they would 
pass from a population in which the destruction by 
young birds was 20 % to one in which it would now be 
rather less than 1 %. Moreover, as the proportion of 
B resembling A gradually increased owing to this advan- 
tage, the losses suffered by those exhibiting the original 
B pattern would be relatively heavier and heavier until 
the form was ultimately eliminated. In other words, 
it is theoretically conceivable that of two distasteful 
species with different 2:)atterns the rarer could be 
brought to resemble the more abundant. 

We may consider now what would happen in the 
converse case in which the more numerous species 
exhibited a variation owing to which it was confused 
with the rarer. Suppose that of the 100,000 individuals 
of A 10,000 shewed a variation which led to their being 
mistaken for B, so that there are 90,000 of the A 
pattern and 15,000 of the B pattern of which 10,000 
belong to species A. A will now lose 1000 out of the 
90,000 having the A pattern, and | x 1000 out of the 
10,000 of species A which exhibit the B pattern. The 
toll of the birds will be J^ of those keeping the original 
A pattern, and ^-^ of those of species A which have 



74 "MIMICRY RINGS" [ch. vi 

assumed the B pattern. The mortality among the 
mimetic members of A is six times as great as among 
those which retain the type form. It is clear therefore 
that a variation of A which can be mistaken for B is 
at a great disadvantage as compared with the type 
form^, and consequently it must be supposed that the 
Miillerian factor, as the destruction due to experi- 
mental tasting by young birds is termed, cannot bring 
about a resemblance on the part of a more numerous 
to a less numerous species. Further, as Marshall goes 
on to shew, there can be no approach of one species to 
the other when the numbers are approximately equal. 
A condition essential for the establishing of a mimetic 
resemblance on Miillerian lines, no less than on Bate- 
sian, is that the less numerous species should take on 
the pattern of the more numerous. Consequently the 
argument brought forward in the earlier part of this 
chapter against the establishing of such a likeness by 
a long series of slight variations is equally valid for 
Miillerian mimicry^. 

1 Provided of coiirse that the type form remains in the majority. 
If the variation occurred simultaneously in more than 50 % of ^ the 
advantage would naturally be with the variation. 

^ It is possible to imagine an exceptional case though most lonlikely 
that it would occur. Suppose for example that there were a number 
of distasteful species, say 20, all of different patterns, and suppose 
that in all of them a particular variation occiirred simultaneously ; 
then if the total shewing that variation from among the 20 species were 
greater than the nvunber of any one of the species, all of the 20 species 
would come to take on the form of the new variation. In this way it is 
imaginable that the new pattern wovild gradually engulf all the old ones. 



CHAPTER VII 

THE CASE OF PAPILIO POLYTES 

Many instances of mimicry are known to-day, but 
comparatively few of them have been studied in any 
detail. Yet a single carefully analysed case is worth 
dozens which are merely superficially recorded. In 
trying to arrive at some conception of the way in which 
the resemblance has come about we want to know the 
natiu-e and extent of the likeness in the living as well 
as in the dead; the relative abundance of model and 
mimic ; what are likely enemies and whether they could 
be supposed to select in the way required, whether the 
model is distasteful to them; whether intermediate 
forms occur among the mimics ; how the various forms 
behave when bred together, etc., etc. Probably the 
form that from these many points of view has, up to 
the present, been studied with most care is that of the 
SwaUow-tail, Papilio polytes. It is a common butterfly 
throughout the greater part of India and Ceylon, and 
closely allied forms, probably to be- reckoned in the 
same species, reach eastwards through China as far as 
Hongkong. P. polytes is one of those . species which 
exhibit polymorphism in the female sex. Three dis- 
tinct forms of female are known, of which one is like the 
male, while the other two are very different. Indeed 



76 THE CASE OF PAPILIO POLYTES [ch. 

for many years they were regarded as distinct species, 
and given definite specific names. To Wallace belongs 
the credit of shewing that these three forms of female 
are all to be regarded as wives of the same type of 
male^. He shewed that there were no males corre- 
sponding to two of the females ; also that the same one 
male form was always to be found wherever any of the 
females occurred. As the result of breeding experi- 
ments in more recent years Wallace's conclusions have 
been shewn to be perfectly sound. 

The male of polytes (PI. V, fig. 1) is a handsome 
blackish insect with a wing expanse of about four 
inches. With the exception of some yellowish-white 
spots along their outer margin the fore wings are entirely 
dark. Similar spots occur along the margin of the hind 
wing also, while across the middle runs a series of six 
yellowish-white patches producing the appearance of 
a broad light band. The thorax and abdomen are full 
black, though the black of the head is relieved by a few 
lighter yellowish scales. The under surface is much 
like the upper, the chief difference being a series of 
small and slightly reddish lunules running outside the 
light band near the margin of the hind wing (PI. V, 
fig. 1 a). In some specimens these markings are almost 
absent. One form of female is almost exactly like 
the male (PI. V, fig. 2), the one slight difference being 
that the lunules on the under surface of the hind wing 
are generally a trifle larger. For brevity she may 
be called the M form. The second form of female 

^ Trans. Linn. Soc. vol. 24, 1866. 



VII] THE CASE OF PAPILIO POLYTES 11 

differs in many respects from the male and the M 
female. Instead of being quite dark, the fore wings are 
marked by darker ribbed lines on a lighter ground ^ 
(PI. V, fig. 3). The hind wings shew several marked 
differences from those of the male. Of the series of 
six patches forming the cross band the outermost 
has nearly disappeared, and the innermost has become 
smaller and reddish. The middle four, on the other 
hand, have become deeper, reaching up towards the 
insertion of the wing, and are pure white. A series 
of red lunules occurs on the upper surface outside the 
white band, and the yellowish-white marginal markings 
tend to become red. These differences are equally 
well marked on the under surface (PL V, fig. 3 a). 
The colour of the body, however, remains as in the 
male. From the resemblance shewn by this form to 
another species of Swallow-tail, Papilio aristolochiae 
(PI. V, fig. 5), we shall speak of it as the A form. 

The third form of female is again very distinct 
from the other two. The fore wings are dark but are 
broken by an irregular white band running across the 
middle (PI. V, fig. 4), and there is also an irregular 
white patch nearer the tips of the wing. The hind 
wings, on the other hand, are characterised by having 
only red markings. The yellowish-white band of the 
male is much reduced and is entirely red, while the red 
lunules are much larger than in the A form. The under 
surface (PL V, fig. 4 a) corresponds closely with the 

^ These darker ribs are also present in the male and M female but 
are obscured owing to the generally deeper colour. 



78 THE CASE OF PAPILIO POLYTES [ch. 

upper. The body remains black as in all the other 
forms. This type of female bears a resemblance to 
Papilio hector (PI. V, fig. 6), and for that reason we 
shall speak of it as the H form. It should be added 
that these three forms of female are quite indistinguish- 
able in the larval and chrysalis stages. 

It was Wallace who first offered an explanation of 
this interesting case in terms of mimicry. According 
to this interpretation P. polytes is a palatable form. 
The larva, which feeds on citronaceous plants, and the 
chrysalis are both inconspicuous in their natural 
surroundings. They may be regarded as protectively 
coloured, and consequently edible and liable to per- 
secution. The original coloration is that of the male 
and the if female. From this the other two forms of 
female have diverged in the direction of greater instead 
of less conspicuousness, although the presumed edi- 
bility of the insect might have led us to think that a 
less conspicuous coloration would have been more to 
its advantage. But these two females resemble the 
two species Papilio aristolochiae and Papilio hector, 
which, though placed in the same genus as P. polytes, 
belong to a very different section of it^. The larvae 
of these two species are conspicuously coloured black 
and red with spiny tubercles. They feed upon the 
poisonous Aristolochia plants. For these reasons and 
also from the fact that the butterflies themselves are 
both conspicuous and plentiful it is inferred that they 
are unpalatable. In short, they are the models upon 

1 See Appendix II, p. 158. 



VII] THE CASE OF PAPILIO POLYTES 79 

which the two polytes females that are unlike the male 
have been built up by natural selection. 

The suggestion of mimicry in this case is supported 
by the fact that there is a general correspondence 
between the areas of distribution of model and mimic. 
P. hector is not found outside India and Ceylon, and 
the H female of P. polytes is also confined to this area. 
P. aristolochiae, on the other hand, has a much wider 
range, almost as wide indeed as that of P. polytes 
itself. Generally speaking the A female accompanies 
P. aristolochiae wherever the latter species is found. 
Beyond the range of P. aristolochiae, in northern China, 
the 31 female alone is said to occur. On the other 
hand, as the matter comes to be more closely studied 
exceptions are beginning to turn up. The H female, 
for instance, is found on the lower slopes of the Hima- 
layas, far north of the range of P. hector, and there 
are indications that a careful study of the distribution 
in China and Japan may prove of importance. 

Moreover, the investigation of a smaller area may 
also bring to light points of difficulty. In Ceylon, for 
example, P. polytes is common up to several thousand 
feet, while P. hector is rare at half the height to which 
polytes ascends. Nevertheless the H form of female is 
relatively just as abundant up-country where hector 
is rarely found as it is low down where hector is plenti- 
fuP. On the other hand, P. aristolochiae may be exceed- 
ingly abundant at altitudes where hector is scarce. Yet 
the A form of polytes is no more relatively abundant 

* Spolia Zeylanica, 1910. 



80 THE CASE OF PAPILIO POLYTES [ch. 

here than elsewhere on the island. All over Ceylon, 
in fact, the relative proportions of the three forms of 
female appear to be the same, quite irrespective of the 
abundance or scarcity of either of the models. As, 
however, we shall have to return to this point later, 
we may leave it for the moment to consider other 
features of this case of P. polytes. 

In collections of insects from India or Ceylon it is 
not unusual to find specimens of the A form of female 
of polytes placed with P. aristolochiae, and the H form 
with P. hector. When the insects are old and faded 
and pinned out on cork the mistake is a very natural 
one. But after all the enemies of polytes do not hunt 
it in corked cabinets, and any estimation of resemblance 
to be of use to us must be based upon the living insects. 
Are the resemblances of the mimics to the models when 
alive so close that they might be expected to deceive 
such enemies^ as prey upon them and have no difficulty 
in distinguishing the male form of polytes from P. aris- 
tolochiae or P. hector ? 

To answer for a bird is a hazardous undertaking. 
We know so little of the bird's perceptive faculties 
whether of taste or sight. But on general grounds, 
from the specialization of their visual apparatus, it 
is probable that the sense of sight is keen, though 
whether the colour sense is the same as our own is 
doubtful^. On the other hand, the olfactory apparatus 

^ We shall take it for the present that, from the point of view of 
mimicry, birds are the main enemies of butterflies (cf. Chap. IX). 
2 See later, p. 119. 



vn] THE CASE OF PAPILIO POLYTES 81 

is relatively poorly developed in birds, and from this 
we can only argue that the senses of smell and taste 
are not especially acute. Really we can do little more 
than to describe how these mimetic resemblances 
appear to our own senses, and to infer that they do not 
appear very different to the bird. If there is any 
difference in keenness of perception we shall probably 
not be far wrong in presuming that the advantage 
rests with the bird. After all if there is any truth in 
the theory of mimicry the bird has to depend largely 
upon its keenness of sight in making its living, at 
any rate if that living is to be a palatable one. If 
natural selection can bring about these close resem- 
blances among butterflies it must certainly be supposed 
to be capable of bringing the bird's powers of vision to 
a high pitch of excellence. 

Returning now to the case of P. polytes, there is 
not the least doubt that to the ordinary man accustomed 
to use his eyes the A form of female is easily distinguish- 
able from P. aristolochiae, as also is the H form from 
P. hector. The two models have a feature in common 
in which they both differ from their respective mimics. 
In both of them the body and head are largely of a 
brilliant scarlet, whereas neither of the mimics has a 
touch of red on the body. In the living insect when 
the body is swelled by its natural juices the effect is 
very striking^. It gives at once a "dangerous" look 

^ The specimens figured on PL V were dried in papers when taken. 
The body is consequently much compressed and the characteristic 
scarlet of P. hector and P. aristolochiae is largely hidden. 

P. M. 6 



82 THE CASE OF PAPILIO POLYTES [ch. 

to the insect when settled, even at a distance of several 
yards, and this although one may be perfectly famihar 
with its harmless natm*e. The mimics on the other 
hand with their sombre-colom'ed bodies never look 
otherwise than the inoffensive creatm?es that they are. 
The "dangerous" look due to the brilliant scarlet of 
the body and head of hector and aristolochiae is re- 
inforced by the quality of the red on the markings of 
the wings. In both models it is a strong clamorous 
red suggestive of a powerful aniline dye, whereas such 
red as occurs in the mimics is a softer and totally 
distinct colour. The difference in quahty is even more 
marked on the under than on the upper surface (PL V, 
figs. 3 a — 6 a), and the net result is that when settled, 
with wings either expanded or closed, there is no possi- 
biUty of an ordinarily observant man mistaking mimic 
for model in either case, even at a distance of several 
yards. 

It may, however, be argued that it is not when at 
rest but during flight that the mimetic resemblance 
protects the mimic from attack. Actually this can 
hardly be true, for the mode of flight constitutes one 
of the most striking differences between model and 
mimic. P. hector and P. aristolochiae fly much in the 
same way. They give one the impression of flying 
mainly with their fore wings, which vibrate rapidly, 
so that the course of the insect, though not swift, is 
on the whole sustained and even. The flight of all the 
different forms of polytes is similar and quite distinct 
from that of the models. It is a strong but rather 



VII] THE CASE OF PAPILIO POLYTES 83 

heavy and lumbering up-and-down flight. One gets 
the impression that all the wing surface is being used 
instead of principally the fore wings as appears in 
P. hector and P. aristolochiae. The difference is difficult 
to put into words, but owing to these peculiarities of 
flight the eye has no difficulty in distinguishing between 
model and mimic even at a distance of 40 to 50 yards. 
Moreover, colour need not enter into the matter at all. 
It is even easier to distinguish model from mimic when 
flying against a bright background, as for instance when 
the insect is between the observer and a sunlit sky, 
than it is to do so by reflected light. I have myself 
spent many days in doing little else but chasing polytes 
at Trincomalee where it was flying in company with 
P. hector, but I was never once lured into chasing the 
model in mistake for the mimic. My experience was 
that whether at rest or flying the species are perfectly 
distinct, and I find it difficult to imagine that a bird 
whose living depended in part upon its ability to dis- 
criminate between the different forms would be likely 
to be misled. Certainly it would not be if its powers 
of discrimination were equal to those of an ordinary 
civilised man. If the bird were unable to distinguish 
between say the A form of female and P. aristolochiae 
I think that it would be still less likely to distinguish 
between the same A form and the male or the 31 form 
of female. For my experience was that at a Uttle 
distance one could easily confuse the A form of 
polytes with the male. Except when one was quite 
close the red on the A form was apt to be lost, the 

6—2 



84 THE CASE OF PAPILIO POLYTES [ch. 

white markings on the hind wing were readily confused 
with those of the male, and one had to depend entirely 
on the lighter fore wing. Unless the bird were keener 
sighted than the man the A form would be more likely 
to be taken in mistake for its unprotected relative than 
avoided for its resemblance to the presumably un- 
palatable model. On the other hand, if the bird were 
sufficiently keen sighted never to confuse the A female 
with the male form its sight would be too keen to be 
imposed upon by such resemblance as exists between 
the A female and P. aristolochiae. 

These, however, are not the only criticisms of the 
theory of mimicry which the study of this species forces 
upon us. Papilio polytes is one of the few mimetic 
species that has been bred, and in no other case of 
polymorphism is the relation between the different 
forms so clearly understood. For this result we are 
indebted mainly to the careful experiments of Mr J. C. F. 
Fryer, who recently devoted the best part of two years 
to breeding the different forms of this butterfly in 
Ceylon^. Fryer came to the conclusion that an ex- 
planation of this curious case is possible on ordinary 
Mendelian lines. At first sight the breeding results 
appear complicated, for any one of the three forms of 
female can behave in several different ways. For the 
sake of simplicity we may for the moment class together 
the A and H females as the mimetic females, the non- 
mimetic being represented by the M or male-like females. 

^ Philosophical Transactions of the Royal Society, vol. 204, 1913. 



vn] THE CASE OF PAPILIO POLYTES 85 

The different kinds of families which each of the three 
females can produce may be tabulated as follows :— 

(a) The M form may give either: — 

(1) 31 only. 

(2) M and mimetics in about equal numbers. 

(3) Mimetics only. 

{^) The A form may give either: — 

(1) M and mimetics in about equal numbers. 

(2) M and mimetics in the ratio of about 1 : 3. 

(3) Mimetics only. 

(y) The H form may give either: — 

(1) M and mimetics in about equal numbers. 

(2) M and mimetics in the ratio of about 1 : 3. 

(3) Mimetics only. 

The males are in all cases alike to look at but it must 
nevertheless be supposed that they differ in their 
transmitting powers. In fact the evidence all points 
to there being three different kinds of male correspond- 
ing to the three different kinds of female. But they 
cannot shew any difference outwardly because there 
is always present in the male a factor which inhibits 
the production of the mimetic pattern even though the 
factor for that pattern be present. 

Returning now to the records of the females it 
will be noticed that although the M form may breed 
true the mimetics never give the M form alone. Where 
they give the M form among their progeny they produce 
mimetics and non-mimetics either in the ratio 1 : 1 
or of 3 : 1. This at once suggests that the non- 



a XX 


lixx 


= <?(!) 


a XX 


liXX 


- (?(2) 


or a Xx 


liXx 


= c?(3) 



86 THE CASE OF PAPILIO POLYTES [ch. 

mimetic is recessive to the mimetic forms — that the 
mimetics contain a factor which does not occur in the 
non-mimetics. If this factor, which may be called X, 
be added to the constitution of a non-mimetic female 
it turns it into a mimetic. If X be added to a male 
such an individual, though incapable of itself exhibiting 
the mimetic jjattern owing to the inhibitory factor 
always present in that sex, becomes capable of trans- 
mitting the mimetic factor to its offspring. Expressed 
in the usual Mendelian way the formulae for these 
different butterflies are as follows: — 

Mimetic) f 

?? / = I 

where X stands for the mimetic factor and / for the 
factor which inliibits the action of X. All males are 
heterozygous for 7, but during the segregation of 
characters at some stage in the formation of the 
families only the male-producing sperms come to contain 
the factor /. It is lacking in aU the female-producing 
sperms formed by the male. 

(? (1) does not contain the factor for the mimetic 
condition and gives only daughters of the M form when 
mated with an if?. ^ (2) on the other hand is homo- 
zygous for the factor X, and consequently all of his 
germ cells contain it. This is the male that gives 
nothing but mimetic daughters with whatever form of 
female he is bred, c? (3) is heterozygous for X ; that is 
to say, one half of his germ cells contain it, the other 
half not. With the Jf ? he must give equal numbers 



VII] THE CASE OF PAPILIO POLYTES 87 

of offspring with and without X, i.e. haK of his daughters 
will be mimetic and the other half non-mimetic. With 
a heterozygous mimetic female {iiXx), which is also 
producing germ cells with and without X in equal 
numbers, he may be expected to give the usual result, 
viz. dominants and recessives in the ratio 3:1; or 
in other words mimetic and non-mimetic females in 
the ratio 3:1. 

One of Fryer's experiments may be given here in 
illustration of the nature of the evidence upon which 
the above hypothesis depends. 

H ? (wild) H $ (wild) 



' ' — I 1 I \ I 

18<J<J 10 M$? 7H?$ 26 ^(J 7M$? 26H$$ 



/ 



->M$x (J 



7 c?o" 1 2H,?? 



I I ^ I I I 

14<J(J 6//?? IM? 8(J(J 10H?$ 2Af$$ 

Families were reared from the two wild R females 
of whom nothing was known either as to ancestry or 
husband. The first family contained 10 Jf and 7 R 
females. Hence the original wild mother was probably 
iiXx and had mated with a male of the constitution 



88 THE CASE OF PAPILIO POLYTES [ch. 

lixx. The family from the second wild H female con- 
tained 26 H and 7 M females; i.e. the ratio in which 
these two forms appeared was not far from 3:1. 
Hence the wild female was probably iiXx and her 
husband liXx. If this were so some of the 26 cJc? 
should receive the X factor from both parents and 
consequently be liXX in constitution. This was 
almost certainly so in the case of the single male in 
this brood tested by mating with an M female from 
the other brood. All of his 12 daughters were of the 
H form, as should have been the case had his con- 
stitution been liXX. Supposing this to be so, all his 
offspring, of both sexes, must be heterozygous for X. 
Consequently any pair mated together should give 
both H and M females in the ratio of three of the 
former to one of the latter. In Mr Fryer's experiment 
two males and two females chosen at random were 
mated together. In the one case six H and one M 
female were produced, in the other ten H and two M 
females. As was expected both classes of female 
appeared, and the looked-for ratio of three H to one M 
was, in view of the smallness of the numbers, not 
departed from widely in either instance. 

In the experiments selected as an illustration, the 
mimetic females happen to be all of the H form. In 
other experiments, however, both the H form and the 
A form occurred. As the result of his experiments 
Mr Fryer came to the conclusion that here again the 
difference is one of a single hereditary factor. All 
mimetic females contain the X factor, but the H 



vn] THE CASE OF PAPILIO POLYTES 



89 



females contain in addition a factor which we may- 
call Y. The function of the Y factor is to carry the 
change made by the X factor a step further, and to 
turn the A form of female into the H form. F is a 
modifier of X, but unless X is present Y can produce 
no effect. All the different individuals which are to be 
found among P. polytes in Ceylon may be represented 
as follows : — 



6S 

lixxYY 
li XX Yy 
li XX yy 
liXxYY 
li Xx Yy 
li Xx yy 
liXXYY 
li XX Yy 
liXXyy 



ii XX YY 
ii XX Yy 
ii XX yy 



4?$ 



ii Xx yy 
ii XX yy 



Hn 



iiXxYY 
ii Xx Yy 

iiXXYY 
ii XX Yy 



In this way is offered a simple explanation in terms 
of three Mendelian factors which serves at once to 
explain the various results of the breeding experiments, 
and the fact that intermediates between the different 
forms of female are not found. 

The only other experiments comparable with these 
on P. polytes are some made by Jacobsen on Papilio 
memnon in Java^. Here again there are three forms 
of female, one of which, laomedon, is something like the 
male, while the other two, agenor and achates, are 
quite distinct. Of these three achates, unlike the male 
and the other two females, is tailed, and resembles 

1 Tljdschr. voor Entomologie, vol. 53, 1909. A more accessible 
accovmt is given by de Meijere, Zeit. f. indukt. Abstamm. u. Vererbungs- 
lehre, vol. 3, 1910. 



90 THE CASE OF PAPILIO POLYTES [ch. 

the species Papilio coon which belongs to the same 
presumably distasteful group as P. aristolochiae. These 
experiments of Jacobsen's are not so complete as the 
series on P. polytes, but Professor de Meijere and 
Mr Fryer have both pointed out that they are capable 
of being interpreted on the same simple lines. 

Another instance of experimental breeding involving 
polymorphism and mimicry in the female sex is that 
of the African Papilio dardanus, but the case is here 
complicated by the greater number of female forms 
(cf. pp. 30-33). The data, too, are far more scanty 
than in the other two cases, but so far as they go 
there is nothing to preclude an explanation being 
eventually arrived at on similar lines ^. 

And now we may consider briefly the bearing of 
these experiments on the theory of mimicry. Through- 
out the work no individuals intermediate between the 
three well-marked forms of polytes were met with. 
There is no difference in appearance between the hetero- 
zygous and the homozygous mimetic insects, whether 
they belong to the A or to the H form. The factor 
X, whether inherited from both parents, or from one 
only, produces its full effect, and the same is also 
true of the action of the factor Y. Now the most 
generally accepted hypothesis as to the formation of 
these mimetic resemblances supposes that they have 
been brought about through the gradual operation 
of natural selection accumulating slight variations. 

1 For further information see Poulton, Trans. Ent. Soc. Lond. 1909, 
and various notes in Proc. Ent. Soc. Lond. subsequent to tliis date. 



VII] THE CASE OF PAPILIO POLYTES 91 

Professor Poulton, for example, a prominent exponent 
of this school, considers that the A form of female was 
first evolved gradually from the M form, and later on 
the H form came by degrees from the A form. If this 
be true we ought, by mingling the 31 germ plasm with 
the H germ plasm and by subsequently breeding from 
the insects produced, to get back our series of hypo- 
thetical intermediates, or at any rate some of them. 
We ought as it were to reverse the process by which 
the evolution of the different forms has taken place. 
But as is shewn by the experiment of Mr Fryer, which 
was quoted above, nothing of the sort happens. 

From experiments with cultivated plants such as 
primulas and sweet peas, we have learnt that this 
discontinuous form of inheritance which occurs in 
P. polytes is the regular thing. Moreover, we have 
plenty of historical evidence that the new character 
which behaves in this way is one that has arisen suddenly 
without the formation of intermediate steps. The 
dwarf " Cupid" form of sweet pea, for instance, behaves 
in heredity towards the normal form as though the 
difference between them were a difference of a single 
factor. It is quite certain that the " Cupid " arose as 
a sudden sport from the normal without the inter- 
vention of anything in the way of intermediates. And 
there is every reason to suppose that the same is true 
for plenty of other characters involving colour and 
pattern as well as structure, both in the sweet pea, 
the primula, and other species. Since the forms of 
polytes female behave in breeding like the various 



92 THE CASE OF PAPILIO P0LYTE8 [ch. vn 

forms of sweet pea and primula there is every reason 
to suppose that they arose in the same way, that is to 
say, as sudden sports or mutations and not by the 
gradual accumulation of slight differences. 

But if we take this view, which is certainly most 
consonant with the evidence before us, we must assign 
to natural selection a different role from that which is 
generally ascribed to it. We cannot suppose that 
natural selection has played any part in the formation 
of a mimetic likeness. The lil^eness turned up suddenly 
as a sport quite independently of natural selection. 
But although natural selection may have had nothing 
to do with its production, it may nevertheless have 
come into play in connection with the conservation of 
the new form. If the new form possesses some advan- 
tage over the pre-existing one from which it sprang, 
is it not conceivable that natural selection will come 
into operation to render it the predominant form? 
To this question we shall try to find an answer in 
the next chapter. 



CHAPTER VIII 

THE CASE OF PAPILIO POLYTES (cont.) 

It was suggested in the last chapter that if a new 
variation arose as a sport — as a sudden hereditary 
variation — and if that variation were, through resem- 
blance to a different and unpalatable species, to be more 
immune to the attacks of enemies than the normal 
form, it was conceivable that the newer mimetic sport 
would become established, and in time perhaps come 
to be the only form of the species. We may suppose, 
for example, that the A female of P. polytes arose 
suddenly, and that owing to its likeness to the pre- 
sumably distasteful P. aristolochiae it became rapidly 
more numerous until in some localities it is the common- 
est or even the only form. However, before discussing 
the establishing of a mimetic form in this manner we 
must first deal with certain general results which may 
be expected to follow on a process of selection applied 
to members of a population presenting variations 
which are inherited on ordinary Mendelian lines. 

Let us suppose that we are dealing with the in- 
heritance of a character which depends upon the pre- 
sence of the genetic factor X ; and let us also suppose 
that the heterozygous form {Xx) is indistinguishable 



94 THE CASE OF PAPILIO POLYTES [ch. 

from the homozygous form {XX) in appearance. In 
other words the character dependent upon X exhibits 
complete dominance. With regard to X then all the 
members of our population must belong to one or 
other of three classes. They may be homozygous {XX) 
for X, having received it from both parents, or they 
may be heterozygous {Xx) because they have received 
it from only one parent, or they may be devoid of X, 
i.e. pure recessives {xx). An interesting question arises 
as to the conditions under which a population con- 
taining these three kinds of individuals remains stable. 
By stability is meant that with the three kinds mating 
freely among themselves and being all equally fertile, 
there is no tendency for the relative proportions of 
the three classes to be disturbed from generation to 
generation. The question was looked into some years 
ago by G. H. Hardy, who shewed that if the mixed 
population consist of p XX individuals, 2q Xx in- 
dividuals and r xx individuals, the population will be 
in stable equilibrium with regard to the relative pro- 
portions of these three classes so long as the equation 
pr = q^ is satisfied^. 

Now let us suppose that in place of equality of 
conditions selection is exercised in favour of those 
individuals which exhibit the dominant character. It 
has been shewn by Mr Norton that even if the selection 
exercised were slight the result in the end would be 
that the recessive form would entirely disappear. 
The total time required for bringing this about would 

1 Science, July, 1908. 



VIII] THE CASE OF PAPILIO POLYTES 95 

depend upon two things, (1) the proportion of domi- 
nants existing in the population before the process of 
selection began, and (2) the intensity of the selection 
process itself. Suppose, for example, that we started 
with a population consisting of pure dominants, hetero- 
zygotes, and recessives in the ratio 1:4:4. Since 
these figiures satisfy the equation pr = q^, such a popu- 
lation mating at random within itself is in a state of 
stable equihbrium. Now let us suppose that the 
dominant form (including of course the heterozygotes) 
is endowed with a selection advantage over the re- 
cessives of 10%, or in other words that the relative 
proportion of the recessives who survive to breed is 
only 90% of the proportion of dominants that sur- 
vive^. It is clear that the proportion of dominants 
must gradually increase and that of the recessives 
diminish. 

At what rate will this change in the population take 
place? Mr Norton has worked this out (see App. I) 
and has shewn that at the end of 12 generations the 
proportions of pure dominants, heterozygotes, and re- 
cessives will be 1:2:1. The population wiU have 
reached another position of equilibrium, but the pro- 
portion of recessives from being four-ninths of the 

^ If for example there were 5000 dominants and 4000 recessives, 
and if only half of the population survives to mate, then we should 
be left with 2500 dominants and 2000 recessives as parents of the next 
generation. But if there were also a 10 % selective disadvantage 
working against the recessives, their numbers would be further reduced 
from 2000 to 1800 and the proportion of dominants to recessives would 
be changed from 5 : 4 to 25 : 18. 



96 THE CASE OF PAPILIO POLYTES [ch. 

total is now reduced to one-quarter. After 18 more 
generations the proportions 4:4:1 are reached, the 
recessives being only one-ninth of the total; after 40 
further generations of the process they become reduced 
to one-fortieth. In other words a selective advantage 
of 10% operating against the recessives will reduce 
their numbers in 70 generations from nearly one-half 
of the population to less than one-fortieth. 

With a less stringent selective rate the number of 
generations elapsing before this result is brought about 
will be larger. If, for example, the selective rate is 
diminished from 10 % to 1 % the number of genera- 
tions necessary for bringing about the same change is 
nearly 700 instead of 70 — roughly ten times as great. 
Even so, and one can hardly speak of a 1 % selective 
rate as a stringent one, it is remarkable in how brief 
a space of time a form which is discriminated against, 
even lightly, is bound to disappear. Evolution, in so 
far as it consists of the supplanting of one form by 
another, may be a very much more rapid process than 
has hitherto been suspected, for natural selection, if 
appreciable, must be held to operate with extra- 
ordinary swiftness where it is given established varia- 
tions with which to work. 

We may now consider the bearing of these theo- 
retical deductions upon the case of Papilio polytes in 
Ceylon. Here is a case of a population Hving and 
breeding together under the same conditions, a popu- 
lation in which there are three classes depending upon 
the presence or absence of two factors, X and Y, 



VIII] THE CASE OF PAPILIO POLYTES 97 

exhibiting ordinary Mendelian inheritance. For the 
present we may consider one of these factors, X, which 
involves the proportion of mimetic to non-mimetic 
forms. It is generally agreed among observers who 
have studied this species that of the three forms of 
female the M form is distinctly the most common, 
while of the other two the H form is rather more 
numerous than the A form. The two dominant 
mimetic forms taken together, however, are rather more 
numerous than the recessive M form. The most 
recent observer who studied this question, Mr Fryer, 
captured 155 specimens in the wild state as larvae. 
When reared 66 turned out to be males, while of the 
females there were 49 of the two mimetic forms and 40 
of the M form, the ratio of dominants to recessives 
being closely 5:4^. Now as has already been pointed 
out the ratio 5:4 of dominants and recessives is 
characteristic of a population exhibiting simple Men- 
delian inheritance when in a state of stable equilibrium. 
The natiu-al deduction from Mr Fryer's figures is that 
with regard to the factor that differentiates the mimetic 
forms from the non-mimetic, the polytes population is, 
for the moment at any rate, in a position of stable 
equilibrium. This may mean one of two things. 
Either the population is definitely in a state of equi- 
librium which has lasted for a period of time in the past 

^ As these larvae were for the most part fotind simply over a consider- 
able time it follows that they are the offspring of different females 
and represent the relative proportions of the three forms in the general 
population. 

P. M. 7 



98 THE CASE OF PAPILIO POLYTES [ch. 

and may be expected to endure for a further period in 
the future, or else the population is in a condition of 
gradual change as regards the numerical proportion of 
mimetics and non-mimetics, progressing towards the 
elimination of the one or the other, the present state 
of equilibrium being merely transitory and accidental. 
In this connection a few scraps of historical evidence 
are of interest. Of the various forms of P. polytes the 
A form of female was the first to be described in 1758, 
and not long after (1776) the H form was registered as 
a species under the name of Papilio Eques Trojanus 
romulus. Later on the female resembling the male 
found its way into the literature as Papilio pammon. 
From the fact that the mimetic forms were known before 
the non-mimetic, it is unlikely that they can have been 
scarce a century and a half ago. As P. polytes cer- 
tainly produces at least four broods a year in Ceylon 
this period of time represents something like 600 
generations in the life of the species, and we have 
already seen that even if the mimetic forms have but 
a 1 % advantage over the non-mimetic the proportion 
of the latter would decrease from nearly equality 
down to but 1 in 40 in about 700 generations. 
Actually for P. polytes the decrease would not be so 
marked because the male is non-mimetic. Owing to 
this peculiar feature the rapidity of change in the 
proportion of the different forms is reduced to about 
one-half of what it would be if the males were also 
mimetic. Nevertheless the change from nearly equality 
to about one non-mimetic in 40 would have taken place 



vni] THE CASE OF PAPILIO POLYTES 99 

during the time P. polytes has been known if a 2% 
selection advantage had operated during that period 
in favour of the mimetic. If there has been any- 
appreciable selection going on during that time mi- 
metics must have been far rarer when the species was 
first discovered, but the fact that both the mimetic 
forms made their way into collections before the 
non-mimetic tells distinctly against this supposition. 
Nor is there any reason to suppose that the non-mimetic 
form has been dwindling in numbers relatively to the 
mimetics during the last half century. Moore^ in 1880 
records an earlier observation of Wade's that " These 
three butterflies are very common, especially those of 
the first form ; the second being perhaps least so." 
The first form alluded to is the M form, and the 
second is the A form, so that at the time Wade wrote 
the relative proportions of these three forms must 
have been very much what they are to-day. Even 
during half a century and with such a relatively weak 
selection rate as 2% in favour of the mimetics, the 
proportion of non-mimetics should drop from about 
4 : 5 down to about 1 : 5. Therefore we must either 
infer that in respect of mimetic resemblances natural 
selection does not exist for P. polytes in Ceylon, or else 
we must suppose its force to be so slight that in half a 
century certainly, and perhaps in a century and a 
half, it can produce no effect appreciable to the neces- 
sarily rough method of estimation employed. 

1 The Lepidoptera of Ceylon, 1880. 

7—2 



100 THE CASE OF PAPILIO POLYTES [ch. 

It may, however, be argued that even an exceedingly 
low selection rate is able to bring about the elimination of 
one or other type provided that it acts for a sufficiently 
long time. This is perfectly true. A selective rate 
of '001 % would reduce the proportion of recessives 
to dominants from 4 : 5 down to 1 : 40 in the course 
of about 1,400,000 generations where the mimetic 
resemblance is already established. Such a form of 
selection entails the death of but one additional non- 
mimetic in 100,000 in each generation. If, however, 
the mimetic resemblance is not fully established and 
the mimic bears only what supporters of the mimicry 
theory term a "rough" resemblance to the model, it is 
clear that it will have far less chance of being mistaken 
for the model. Its advantage as compared with the 
non-mimetic form will be very much less. Even 
supposing that the slight variations concerned are in- 
herited, an intensity of selection which would produce 
a certain change in 1,400,000 generations where a 
mimetic resemblance is already established must be 
supposed to take an enormously greater time where 
an approach to a model has to take place from a 
"rough" resemblance. 

From the data as to the relative proportions of the 
polymorphic females of P. polytes during the past and 
at present, and from the behaviour of their different 
forms in breeding, the following conclusions only can 
be drawn. Either natural selection, from the point of 
view of mimicry, is non-existent for this species in 
Ceylon, or else it is so slight as to be unable in half a 



vni] THE CASE OF PAPILIO POLYTES 101 

century to produce an appreciable diminution in the 
proportion of non-mimetic females. For even if the 
mimetic resemblance brings about but the survival of 
one additional protected form in 100 as compared with 
the unprotected, this means a marked diminution in 
the proportion of M females in 50 years — a diminution 
such as there are no grounds for supposing to have 
taken place. 

It has been argued that in populations exhibiting 
Mendelian heredity even a relatively low selection rate 
must bring about a rapid change in the constitution of 
a mixed population. Have we any grounds for sup- 
posing that populations of this sort can undergo such 
rapid changes? In cases where mimetic resemblances 
are involved we have no examples of the sort. But 
some interesting evidence as to the rate at which a 
population may change is to be gathered from the 
study of melanism in certain moths. It is well 
known that in some parts of England the common 
peppered moth, Amphidasys hetularia has been almost 
entirely supplanted by the darker melanic form double- 
dayaria. It first made its appearance near Manchester 
in 1850, and from that centre has been gradually 
spreading over northern England, the Midlands, and 
the south-eastern counties. At Huddersfield, for 
instance, fifty years ago only the type form hetularia 
existed; to-day there is nothing but douhledayaria. 
In Lancashire and Cheshire the tjrpe is now rare. 
On the continent, too, there is the same story to 
be told. The melanic form first appeared in Rhenish 



102 THE CASE OF PAPILIO POLYTES [ch. 

Prussia in 1888 ; to-day it is much more abundant than 
the older t3rpe. There, too, it is spreading eastwards 
and southwards to Thuringia, to Saxony, to Silesia. 
What advantage this new dark form has over the older 
one we do not know^. Some advantage, however, it 
must have, otherwise it could hardly supplant hetularia 
in the way that it is doing. From our present stand- 
point two things are of interest in the case of the 
peppered moth — the rapidity with which the change 
in the nature of the population has taken place, and the 
fact that the two forms exhibit Mendelian heredity, 
doubledayaria being dominant and hetularia recessive 2. 
Moreover, mixed broods have been reared from wild 
females of both sorts, and so far as is known the two 
forms breed freely together where they co-exist. This 
case of the peppered moth shews how swiftly a change 
may come over a species^. It is not at all improbable 
that the establishing of a new variety at the expense 
of an older one in a relatively short space of time is 
continually going on, especially in tropical lands where 

^ From the experience of breeders it would appear that the melanic 
form is somewhat hardier, at any rate in captivity. 

2 Intermediates may also occttr in some strains (cf . Bowater, Journal 
of Genetics, vol. 3, no. 4, 1914). 

3 An interesting case of a similar nature has recently been published 
by Hasebroek {Die Umschau, 1913, p. 1020). A melanic form of the 
moth, Cymatophora or, suddenly appeared near Hamburg in 1904. 
This new form, to which the name alhingensis was given, rapidly became 
the predominant one. In 1911-1912 over 90 % of the moths reared 
from caterpillars taken in the open were of the alhingensis form; nor 
were any intermediates found between it and the typical form. Some 
experiments were also made which shew that the alhingensis form 
behaves as a dominant to the original type form. 



VIII] THE CASE OF PAPILIO POLYTES 103 

the conditions appear to be more favourable to exuber- 
ance of variation and where generations succeed one 
another in more rapid succession. At present, however, 
we are without data. A form reported by an old col- 
lector as common is now rare ; a variety once regarded 
as a great prize is now easily to be found. Such to-day 
is the sort of information available. For the solution 
of our problem it is, of course, useless. The develop- 
ment of Mendelian studies has given us a method, 
rough perhaps but the best yet found, of testing for 
the presence, and of measuring the intensity, of natural 
selection. Much could be learned if some common 
form were chosen for investigation in which, as in 
P. polytes, there are both mimetic and non-mimetic 
forms. Large numbers should be caught at stated 
intervals, large enough to give trustworthy data as to 
the proportions of the different forms, mimetic or non- 
mimetic, that occurred in the population. Such a 
census of a polymorphic species, if done thoroughly, 
and done over a series of years at regular intervals, 
might be expected to give us the necessary data for 
deciding whether the relative proportion of the different 
forms was changing — whether there were definite 
grounds for supposing natural selection to be at work, 
and if so what was the rate at which it brought the 
change about. 



CHAPTER IX 

THE ENEMIES OF BUTTERFLIES 

The theory of mimicry demands that butterflies 
should have enemies, and fiurther that those enemies 
should exercise a certain discrimination in their attacks. 
They must be sufficiently observant to notice the 
difference between the mimetic and the non-mimetic 
form ; they must be sufficiently unobservant to confuse 
the mimetic form with the unpalatable model. And, 
of course, they must have enough sense of taste to 
dislike the unpalatable and to appreciate the palatable 
varieties. What these enemies are and whether they 
can be supposed to play the part required of them we 
may now go on to consider. 

Butterflies are destroyed in the imago state princi- 
pally by three groups of enemies — predaceous insects, 
lizards, and birds. It is known that monl^eys also 
devour butterflies to some extent, but such damage 
as they inflict is almost certainly small in comparison 
with that brought about by the three grouj)s already 
mentioned. In view of the very different nature of 
these groups it will be convenient to consider them 
separately. 



CH. IX] THE ENEMIES OF BUTTERFLIES 105 

I. Predaceous Insects. Butterflies are known to 
be preyed upon by other insects of different orders, 
and a considerable number of observations have 
recently been gathered together from various sources 
and put on record by Professor Poulton^. These 
observations shew that butterflies may be devoured by 
mantids, dragon-flies, and blood-sucking flies of the 
families Empiidae and Asilidae. For mantids the 
records are scanty, but they have been observed to 
kill presumably distasteful forms as often as those 
which are considered palatable. An interesting set 
of experiments was made by G. A. K. Marshall on 
captive mantids in Africa 2. Of the eleven individuals 
representing several species with which he experi- 
mented, some ate every butterfly offered, including the 
distasteful Danaines and Acraeines. Others, however, 
shewed some distaste of the Acraeines and would not 
devour them so freely as butterflies of other species. 
There are no grounds, however, for supposing that the 
mantids had any appreciation of the warning color- 
ation of the Acraeines. Whether completely eaten or 
not the Acraeines were apparently sufficiently damaged 
to prevent their taking any further part in the pro- 
pagation of their species. Warning coloration is not 
of much service to its possessor who has to be tasted 
and partially eaten before being eventually rejected. 
Even if some mantids shew distaste of certain unpalat- 
able butterflies, that distaste is probably seldom 

1 Trans. Ent. Soc. Lond. 1907. 

2 Trans. Ent. Soc. Lond. 1902. 



106 THE ENEMIES OF BUTTERFLIES [ch. 

exercised with a gentleness sufficient to ensure that the 
butterfly reaps the reward of its disagreeable nature. 
And unless, of course, the butterfly is allowed to do so 
the enemy can play no part in the production or 
maintenance of a mimetic resemblance. 

What is true for mantids is probably also true for 
the other groups of predaceous insects. Dragon-flies 
and wasps have been recorded as attacking the dis- 
tasteful as well as butterflies of unprotected groups. 
Among the most serious enemies of butterflies must 
probably be reckoned the blood-sucking Asilids. These 
powerful and ferocious flies seize butterflies on the wing 
with their strong claws and plunge their proboscis into 
the thorax. Apparently they inject some swift poison, 
for the butterfly is instantly paralysed, nor is there any 
sign of struggle. The Asilid flies oii with its victim, 
sucking the juices as it goes. There can be no doubt 
in the mind of any one who has watched these creatures 
hawking butterflies that their natural gifts are such as 
to enable them to exercise discrimination in their food. 
Most insect life is at their mercy but they appear to 
exercise no choice, seizing and devouring the first 
flying thing that comes within easy reach. Certainly 
as regards butterflies palatability or the reverse makes 
no difference, and they are known to feed indiscrimin- 
ately both upon the evil-flavoured and upon the good. 
Taking it all together the evidence is such that we can- 
not suppose predaceous insects to pay any attention to 
warning colours, and, therefore, we cannot regard them as 
playing any part in connection with mimetic resemblance. 



IX] THE ENEMIES OF BUTTERFLIES 107 

II. Lizards. In those parts of the world where 
lizards of larger size are abundant there is plenty of 
evidence that certain species are very destructive to 
butterfly life. As might be expected this is especially 
true of forms which are either arboreal or semi-arboreal 
in habit. Among the reptiles of Ceylon, for example, 
are several species of the genus Calote-s, of which two, 
C. ophiomachus and C. versicolor, are particularly abun- 
dant. In appearance and habits they are not unlike 
chameleons though far more active in their movements. 
Like chameleons, too, they are able to change colour, 
and the fact that they can assume a brilliant scarlet 
hue about the head and neck has probably led to their 
popular name of "blood-suckers." It is not impossible 
that the assumption of this scarlet coloration may 
serve as a lure to bring insects within range. These 
lizards have often been observed to seize and devour 
butterflies. Moreover, it is a common thing to find 
butterflies with a large semi-circular patch bitten out 
of the hind wings, and there is little doubt but 
that such injuries have been inflicted by lizards. 
There is, however, no evidence to suggest that they 
exercise any discrimination in their choice of the 
butterflies which they attack. This is borne out by 
their behaviour towards various species offered to 
them, both when at liberty and when caged. In an 
ingenious series of experiments Col. Manders brought 
various butterflies within reach of a Calotes by the 
help of a fishing-rod and a long line of fine silk, by this 
means simulating natural conditions as far as possible. 



108 THE ENEMIES OF BUTTERFLIES [ch. 

He found that the lizards ate the so-called distasteful 
forms such as Danais chrysippus, Euploea core, Acraea 
violae, and Papilio hector, as readily as the presumably 
more palatable forms^. In captivity, too, they will 
take any butterfly as readily as another. Experiments 
by Finn^ and by the writer^ proved that they ate 
Danaids, Euploeas, and Papilio aristolochiae without 
any hesitation so long as the insects were alive and 
moving. When, too, a mixture of different species, 
some with and some without warning coloration, was 
given to them all were eaten, nor was there any dis- 
crimination evidenced in the order in which they were 
taken. The lizard simply took the first that came 
within reach and went on until the whole lot was 
devoured, wings and all. 

Some experiments by Miss Pritchett on the American 
lizard Sceleporus floridanus point to the same con- 
clusion*. She found that it took without hesitation 
any butterfly offered to it including the presumably 
distasteful models Danais archippus and Papilio pliil- 
enor (cf. pp. 45 and 49). On the other hand, another 
species of lizard with which Miss Pritchett experimented, 
Gerrhonotus infernalis, refused all the butterflies offered 
to it, though it fed freely on Orthopterous insects as 
well as on spiders and scorpions. 

It seems clear from these various observations and 

1 Proc. Zool. Soc. 1911. 

2 Journ. Roy. Asiat. Soc. Bengal, vol. 65, 1897. 
^ Spolia Zeylanica, 1910. 

■* Biological Bulletin, vol, 5, 1903. 



IX] THE ENEMIES OF BUTTERFLIES 109 

experiments that certain lizards devour butterflies 
freely, but that they do not exercise any discrimination 
in the species which they attack. All are caught and 
devoured indiscriminately, so that in spite of the fact 
that such lizards are among the most serious enemies 
of butterflies we cannot suppose them to play any part 
in estabhshing a mimetic resemblance. 

III. Birds. The relations which exist between 
butterflies and their bird enemies have for many years 
been the subject of keen discussion. It is generally 
recognised that if mimetic resemblances become estab- 
lished through the agency of discriminating enemies 
those enemies must be birds. Hence those interested 
in the question of mimicry have for some years past 
turned their attention to birds more than to the other 
enemies of butterflies. That many birds systemati- 
cally feed on butterflies is a fact that does not admit 
of doubt. It is true that, as Mr Marshall points out 
in the valuable paper in which he has summarised the 
evidence^, observations of birds eating butterflies are 
relatively scanty. Though, as he points out, this is 
equally true for other groups of insects besides butter- 
flies, bird attacks on butterflies, owing to the con- 
spicuous nature of the victim, are much more likely to 
attract attention than attacks on other groups. We 
are still without much information as to the extent to 
which birds destroy butterflies and as to whether they 
shew any decided preference for certain species over 
others. A careful examination of the contents of the 

1 Trans. Ent. Soc. Lond. 1909. 



110 THE ENEMIES OF BUTTERFLIES [ch. 

stomachs of large numbers of insectivorous birds in a 
tropical area would go some way towards deciding the 
matter, but at present such information is lacking. 
We have to rely upon the existing observations of birds 
attacking butterflies in the wild state, and upon certain 
feeding experiments made with captive birds. 

Observations on birds attacking butterflies where 
mimetic forms occur have been made almost entirely 
in certain parts of Africa, in India, and in Ceylon. For 
Africa, Marshall has collected some forty-six obser- 
vations of which almost half are concerned with 
Pierines. The remainder include four instances of 
attacks on species of Acraea, a genus which on the 
mimicry theory must be regarded as among the most 
unpalatable of butterflies. 

The records from the Indo-Malayan region (prin- 
cipally India and Ceylon) are somewhat more numerous 
and here again more than one-third of them refer to 
Pierines. Among the others are records of the dis- 
tasteful forms Euploea core, E. rafflesii, Acraea violae, 
and Papilio hector being taken and devoured. 

There is one interesting record which seems to 
suggest that Swinhoe's Bee-Eater {Melittophagus swin- 
hoei) may exercise that discrimination in the butterflies 
it attacks which is demanded on the mimicry theory. 
Lt.-Col. Bingham on one occasion in Burma noticed 
this species hawking butterflies. He records that they 
took Papilio erithonius, P. sarpedon, Charaxes athamas, 
Cyrestis thyodamas, and Terias hecabe, and probably also 
species of the genera Prioneris, Hebomoia (Pierines), 



IX] THE ENEMIES OF BUTTERFLIES 111 

Junonia and Precis (Vanessids). And he goes on to 
say: "I also particularly noticed that the birds never 
went for a Danais or Euploea, or for Papilio macareus 
and P. xenodes, which are mimics of Danais, though 
two or three species of Danais, four or five of Eujplom, 
and the two above-mentioned mimicking Papilios 
simply swarmed along the whole road^." 

Marshall also quotes a case of attack by a green 
bee-eater on a Danais in which the butterfly was caught 
and subsequently rejected, after which it flew away. 
Little stress, however, can be laid upon this case in 
view of the more recent data brought together by 
Col. Manders and Mr Fryer. Discussing the attacks 
of birds on butterflies in Southern India and Ceylon, 
Col. Manders gives the following quotation^ from a 
letter of Mr T. N. Hearsy, Indian Forest Service : 

"Coimbatore, 6. 6. 10.. . . I have frequently seen 
the common green bee-eater {Merops viridis) and the 
king-crow [Buchanga atra) take butterflies on the wing, 
the butterflies being Catopsilia pyranthe, C. florella, 
Terias hecahe and Papilio demoleus. The bee-eater 
I have also seen taking Danais chrysippus and Danais 
septentrionis, and I remember to have been struck 

with their taste for those latter " 

Col. Manders also brings forward evidence for these 
Danaids and Euploeas being eaten by Drongos and by 
the paradise flycatcher. Still more recently an mter- 
esting contribution to the matter has been made by 

1 Trans. Ent. Soc. Lond. 1902. 

2 Trans. Ent. Soc. Lond. 1911. 



112 THE ENEMIES OF BUTTERFLIES [ch. 

Mr J. C. F. Fryer^. The Ashy Wood-swallow {Artamus 
fuscus) had been recorded on two occasions as having 
attacked Euploea core, Mr Fryer was fortunate in 
coming across this bird in the gardens at Peradeniya, 
near Kandy, at a time when Euploea core and Danais 
septentrionis were particularly abundant, and he watched 
a number of them systematically hawking these pre- 
sumably unpalatable species. As he observes, "in 
Ceylon a resemblance to the genera Danais and Euploea 
is doubtfully of value ; in fact in the neighbourhood of 
Wood-swallows it is a distinct danger." Fr3^er also 
noted that the mimetic forms of P. polytes were taken as 
well as the non-mimetic. 

For tropical Central and South America, that other 
great region where mimetic forms are numerous, there 
are unfortunately hardly any records of butterflies 
attacked by birds. Bates stated that the Pierines were 
much persecuted by birds, and his statement is con- 
firmed by Hahnel, but exact observations for this 
region are remarkably scanty. Belt observed a pair 
of birds bring butterflies and dragon-flies to their 
young, and noticed that they brought no Heliconii to 
the nest although these swarmed in the neighbourhood 2. 
On the other hand, Mr W. Schaus^, from an experience 
of many years spent in the forests of Central America, 
considers that the butterflies of this region are hardly, 
if ever, attacked by birds. 

1 Proc. Zool. Soc. 1913. 

2 A Naturalist in Nicaragua, 1874, p. 316. 

^ /"■ Congr. Internat. d'Entomologie, Bruxelles, 1911. 



IX] THE ENEMIES OF BUTTERFLIES 113 

For North America Marshall records over 80 cases 
of birds attacking butterflies. Among them is an 
interesting record of a bird seizing and rejecting a 
specimen of Anosia plexippus {=Danais archippus), one 
of the few Danaines found in this region. 

It must be admitted that the data at present 
available with regard to the attacks of birds upon 
butterflies under natural conditions are too meagre to 
allow of our coming to definite conclusions on the 
points at issue. It is safe to say that a number of species 
of birds have been known to attack butterflies — that a 
few out of the number feed upon butterflies system- 
atically — that some of the most persistent bird enemies 
devour the presumably protected forms as freely as 
the unprotected — but that in a few instances there is 
some reason for supposing that the bird discriminates. 
Beyond this it is unsafe to go at present. 

In attempting to come to a decision as to the part 
played by birds in the destruction of butterflies an 
evident desideratum is a knowledge of the contents of 
the stomachs of freshly killed birds. Unfortunately 
few systematic observations of this nature exist. 
G. L. Bates^, when collecting in the Southern Came- 
roons, noted the stomach contents of a considerable 
number of birds. The remains of beetles were re- 
cognised in 213 cases: Orthoptera in 177: ants in 57 
(mostly in stomachs of birds of the genus Dendromus) : 
other Hymenoptera in 8: coccids in 32: bugs in 19: 
white ants in 31 : slugs and snails in 24: spiders in 85 

1 Ibis, 1911. 
p. M. 3 



114 THE ENEMIES OF BUTTERFLIES [ch. 

(mostly in Sunbirds) : millipedes in 20 ; but in no single 
instance were the remains of butterflies found. More 
recently Bates' account has been criticized by Swynner- 
ton^ who comments on the difficulty of identifying 
butterfly remains as compared with those of beetles 
and grasshoppers. He states that the pellets ejected 
by captive birds after a meal of butterflies contain only 
fine debris which is very difficult to identify. Further, 
he found that of twenty small bird excreta collected in 
the forest no less than eighteen contained scales and 
small wing fragments of Lepidoptera. 

Some attention has been paid to the relation be- 
tween birds and butterflies in the United States, and 
under the auspices of the Department of Agriculture 
a large number of birds' stomachs have been investi- 
gated. Careful examination of some 40,000 stomachs 
of birds shot in their natural habitats resulted in the 
discovery of butterfly remains in but four. It cannot, 
therefore, be supposed that birds play much part in 
connection with such mimetic resemblances as are 
found in North America (cf. pp. 45-49). Nevertheless, 
it is known that on occasion large numbers of butter- 
flies may be destroyed by birds. An interesting case 
is described by Bryant^ of an outbreak in North 
California of Eugonia californica, a close relative of 
the tortoiseshell. The butterfly was so abundant as to 
be a plague, and five species of birds took advantage 
of its great abundance to prey largely upon it. From 

1 Ibis, 1912. 

2 The Condor, vol. 13, 191^ pp. 195-208. 



IX] THE ENEMIES OF BUTTERFLIES 115 

his examination of the stomachs Bryant came to the 
conclusion that some 30 % of the food of these five 
species was composed of this butterfly. The stomachs 
of many other species were examined without ever 
encountering butterfly remains. Nor did field obser- 
vations support the view that any species, other than 
the five specially noted, ever attacked these butterflies. 
The case is of interest in the present discussion as 
evidence that the identification of butterfly remains 
in the stomachs of birds is by no means so difficult as 
some observers suggest. 

Besides this evidence derived from observations 
upon birds in the wild state some data have been 
accumulated from the experimental feeding of birds 
in captivity. Of such experiments the most extensive 
are those of Finn^ in South India. He experimented 
with a number of species of insectivorous birds be- 
longing to different groups. Of these he found that 
some, among which may be mentioned the King-crow, 
StarHng, and Liothrix^, objected to Danaines, Papilio 
aristolochiae and Delias eucharis, a presumably dis- 
tasteful Pierine with bright red markings on the under 
surface of the hind wings (PI. II, fig. 1 ). In some cases 
the bird refused these forms altogether, while in others 
they were eaten in the absence of more palatable 
forms. The different species of birds often differed in 

1 Journ. Asiat. Soc. Bengal, vol. 64, 1895, and vol. 66, 1897. 

2 Nevertheless a Liothrix is recorded as eating Danais plexippus 
and a Euploea even though two male specimens of the palatable 
Elymnias undularis were in the cage. 

8—2 



116 THE ENEMIES OF BUTTERFLIES [ch. 

their behaviour towards these three "nauseous" forms. 
The Hornbill, for example, refused the Danaines and 
P. aristolochiae absolutely, but ate Delias eucharis. 
Some species again, notably the Bulbuls (Molpastes) 
and Mynahs, shewed little or no discrimination, but 
devoured the "protected" as readily as the "un- 
protected" forms. Finn also states that ^'Papilio 
polytes was not very generally popular with birds, but 
much preferred to its model, P. aristolochiae.''^ 

In many of Finn's experiments both model and 
mimic were given to the birds simultaneously so that 
they had a choice, and he says that "in several cases 
I saw the birds apparently deceived by mimicking 
butterflies. The Common Babbler was deceived by 
Nepheronia Tiippia^ and Liothrix by Hypolimnas misip- 
pus. The latter bird saw through the disguise of the 
mimetic Papilio polites, which, however, was sufficient 
to deceive the Bhimraj and King-crow. I doubt if 
any bird was impressed by the mimetic appearance of 
the female Elymnias undularis^'' (cf. PI. IV, fig. 5). 
Finn concluded from his experiments that on the whole 
they tended to support the theory of Bates and Wallace, 
though he admits that the unpalatable forms were 
commonly taken without the stimulus of actual hunger 
and generally without signs of dislike. Certainly it 
is as well to be cautious in drawing conclusions from 
experiments with captive birds. The King-crow, for 
instance, according to Finn shewed a marked dislike 
for Danaines in captivity; yet Manders records this 

' A form closely resembling P. ceylonica figured on PI. I, fig. 1. 



IX] THE ENEMIES OF BUTTERFLIES 117 

species as feeding upon Danaines under natural con- 
ditions (cf. p. 111). 

A few further experiments with the birds of this 
region were carried out by Manders^ in Ceylon. The 
results are perhaps to be preferred to Finn's, as the 
birds were at liberty. Manders found that the Brown 
Shrike {Laiiius cristatus) would take butterflies which 
were pinned to a paling. In this way it made off with 
the mimetic females of Hypolimnas holina and H. 
misippus, as well as with Danais chrysippus and 
Acraea violae which were successively offered to it. 
Evidently this species had no repugnance to unpalat- 
able forms. Manders also found that a young Mynah 
allowed complete liberty in a large garden would eat 
such forms as Acraea violae and Papilio hector. As the 
result of his experience Manders considers that the 
unpalatabihty of butterflies exhibiting warning color- 
ation has been assumed on insufficient data, and he is 
further inclined to doubt whether future investigations 
will reveal any marked preference in those birds which 
are mainly instrumental in the destruction of butter- 
flies. 

A few experiments on feeding birds with South 
African butterflies are recorded by Marshall. A young 
Kestrel {Cerchneis naumanni) was fed from time to 
time with various species of butterflies. In most 
cases the butterflies offered were eaten even when they 
were species of Acraea. On the other hand Danais 
chrysippus was generally rejected after being partly 

1 Proc. Zool. Soc. Lond. 1911. 



118 THE ENEMIES OF BUTTERFLIES [ch. 

devoured. When first offered this unpalatable species 
was taken readily and it was only after it had been 
tasted that the bird rejected it. When offered on 
several subsequent occasions it was partly eaten each 
time, and the behaviour of the Kestrel did not suggest 
that it associated a disagreeable flavour even with this 
conspicuous pattern. Another young Kestrel {Cerch- 
neis rupicoloides) was also used for experiment. At 
first it would not take butterflies and at no time did 
it shew any fondness for them. Indeed it is doubtful 
from the way in which they seem to have shaped at 
the insects whether either of these Kestrels had had any 
experience of butterflies before the experiments began. 

A Ground HornbiU with which Marshall also ex- 
perimented ate various species, including Acraea, but, 
after crushing it, refused the only Danais chrysippus 
offered. It is hardly likely that this large omnivorous 
bird operates as a selecting agent in cases of mimicry. 

In an interesting paper published recently McAtee^ 
discusses the value of feeding experiments with animals 
in captivity as a means of indicating their preference 
for different articles of diet. After reviewing the 
various evidence brought forward he concludes that 
the food accepted or rejected by captive animals is 
very little guide to its preferences under natural con- 
ditions. He points out that a bird in captivity not 
infrequently rejects what is known to form a main 
staple of its diet in nature, and that conversely it may 
eagerly accept something which, in the wild state, it 

^ Proc. Acad. Nat. Sci. Philadelphia, 1912. 



IX] THE ENEMIES OF BUTTERFLIES 119 

would have no opportunity of obtaining. Great cau- 
tion must, therefore, be exercised in the interpretation 
of feeding experiments made with birds in captivity. 

It appears to be generally assumed that colour 
perception in birds is similar to what it is among 
human beings, but some experiments made by Hess^ 
render it very doubtful whether this is really the case. 
In one of these experiments a row of cooked white 
grains of rice was illuminated by the whole series of 
spectral colours from violet to deep red. Hens which 
had been previously kept in the dark so that their 
eyes were adapted to light of low intensity were then 
allowed to feed on the spectral rice. The grains 
illuminated by green, yellow, and red were quickly 
taken, but the very dark red, the violet, and the blue 
were left, presumably because the birds were unable to 
perceive them. Again, when the birds were given a 
patch of rice grains of which half was feebly illuminated 
by red light and the other half more strongly by blue 
light, they took the red but left the blue. Previous 
experiment had shewn that with ordinary white light 
the birds always started on the best illuminated grains. 
It seems reasonable to conclude, therefore, that in the 
red-blue experiment the feebly illuminated red grains 
were more visible than the far more strongly lighted 
blue ones. It might be objected that the birds had a 
prejudice against blue, but, as Hess points out, this is 
almost certainly not the case because they took grains 

^ C. Hess, Handhuch der vergleichenden Phyaiologie (herausgegeben 
von H. Winterstein), Bd. 4, 1912, p. 563. 



120 THE ENEMIES OF BUTTERFLIES [ch. 

which were very strongly illuminated with blue. 
Results of a similar nature were also obtained from 
pigeons, and from a kestrel which was fed with pieces 
of meat lighted with different colours. 

On the whole these experiments of Hess convey a 
strong suggestion that the colour perceptions of birds 
may be quite different from our own, more especially 
where blue is concerned. Great caution is needed in 
discussing instances of mimicry in their relation to 
the bird, for we have no right to assume that the bird 
sees things as we do. On the other hand, it is a matter 
of much interest to find that in general blue plays 
relatively little part in cases of mimetic resemblance 
among butterflies; some combination of a dark tint 
with either red, white, brown, or yellow being far more 
common. 

It will probably be admitted by most people that 
the evidence, taken all together, is hardly sufficient 
for ascribing to birds that part in the establishing of a 
mimetic likeness which is required on the theory of 
mimicry. That birds destroy butterflies in considerable 
numbers is certainly true, but it is no less true that some 
of the most destructive birds appear to exercise no 
choice in the species of butterfly attacked. They simply 
take what comes first and is easiest to catch. It is 
probably for this reason that the Wood-swallow feeds 
chiefly on Euploeines and Danaines (cf. p. 112). It 
is probably for this reason also that such a large pro- 
portion of the records of attacks on butterflies under 
natural conditions refer to the Pierines; for owing to 



IX] THE ENEMIES OF BUTTERFLIES 121 

their light colour it is probable that the " Whites " are 
more conspicuous and offer a better mark for a bird in 
pursuit than darker coloured species. 

Mmnmals. Apart from man it is clear that only- 
such mammals as are of arboreal habits are likely to 
cause destruction among butterflies in the imago state. 
Apparently there are no records of any arboreal 
mammal, except monkeys, capturing butterflies in the 
wild state, nor is there much evidence available from 
feeding experiments. But such evidence as exists is 
of considerable interest. As the result of feeding 
butterflies of different sorts to an Indian Tree-shrew 
{Tupaia ferruginea) Finn^ found that it shewed a strong 
dislike to Danaids and to Papilio aristolochiae though 
it took readily Papilio demoleus, Neptis kamarupa, and 
Catopsilia (a Pierine). It is fairly certain that if the 
Tree-shrew is an enemy of butterflies in the wild state 
it is a discriminating one. 

The other mammals with which experiments have 
been made are the common baboon, a monkey {Cerco- 
pithecus pygerythrus), and a mongoose {Herpestes 
galera) — all by Marshall^ in South Africa. The mon- 
goose experiments were few and inconclusive, nor is 
this a matter of much moment as it is unlikely that this 
mammal is a serious enemy of butterflies. 

The monkey ate various forms of Precis (a Vanessid), 
after which it was given Acraea halali. This distaste- 
ful form was "accepted without suspicion, but when 

1 Journ. As. Soc. Bengal, vol. 66 ^ 1898. 
* Trans. Ent. Soc. Lond. 1902. 



122 THE ENEMIES OF BUTTERFLIES [ch. 

the monkey put it into his mouth, he at once took it 
out again and looked at it with the utmost surprise 
for some seconds, and then threw it away. He would 
have nothing to do with an Acraea caldarena which I 
then offered him^." 

The experiments with the baboons were more ex- 
tensive. Two species of Acraea, halali and axina, 
were recognised when first offered and refused un- 
tasted. Danais chrysippus, on the other hand, was 
tasted on being offered for the first time, and then 
rejected. This species was twice offered subsequently 
and tasted each time before being rejected. When 
offered the fourth time it was rejected at sight. The 
baboon evidently learned to associate an unpleasant 
taste with the chrysippus pattern. At this stage it 
would have been interesting to have offered it some 
well-known mimic of chrysippus, such as the female 
of Hypolimnas misippus or the trophonius form of 
Papilio dardanus, but this experiment was unfortunately 
not made. Marshall did, however, offer it at the same 
time a specimen each of Byhlia ilithyia (a Vanessid) 
and of Acraea axina to which it bears a general 
resemblance. The baboon took the former but ne- 
glected the latter altogether. The general resemblance 
between the two species was not sufficiently close to 
deceive it. 

These experiments with mammals, though few in 
number, are of unusual interest. Should they be 
substantiated by further work it is not impossible 

1 Marshall, loc. cit. p. 379. 



IX] THE ENEMIES OF BUTTERFLIES 123 

that, as a factor in the establishing of a mimetic like- 
ness, a stronger case may be made out for the monkey 
than the bird. The monkey apparently eats butterflies 
readily^ : owing probably to a keener sense of smell it 
shews far less hesitation as to its likes and dishkes: 
its intelligence is such that one can easily imagine it 
exercising the necessary powers of discrimination; 
in short it is the ideal enemy for which advocates of 
the mimicry theory have been searching — if only it 
could fly. As things are its butterfly captures must be 
made when the insect is at rest, probably near sunrise 
and sunset, and this leads to a difficulty. Most butter- 
flies rest with their wings closed. In many of the 
well-known cases of mimicry the pattern on the under 
surface of the mimic's wings which would meet the 
monkey's eye is quite different from that of its model. 
It is difficult in such cases to imagine the monkey 
operating as a factor in establishing a resemblance 
between the upper surfaces of the wings of the two 
unrelated species. On the other hand, some butterflies, 

^ In this connection may be quoted a letter from Capt. N. V. Neal 
near Lagos to Mr W. A. Lamborn which was recently published in the 
Proceedings of the Entomological Society. 

"You have asked me about monkeys eating butterflies. This is 
very common, as every native will tell you. I have seen it myself. 
The monkey runs along a path, sees some butterflies fluttering roimd 
some filth, goes very quietly, and seizes one by the wings, puts the 
solid part (body) into his mouth, then pulls the wings off. The poor 
butterfly goes down like any oyster.. . .The dog-faced baboon and the 
large brown monkey with a very long tail, wliich seems to be the most 
common species in this colony, are great butterfly-eaters. The little 
spider-monkey also considers a butterfly a treat, and prefers one to 
a spider." 



124 THE ENEMIES OF BUTTERFLIES [ch. ix 

e.g. Papilio polytes, rest with wings outspread, and 
there are rare cases, such as that of P. laglaizei 
(p. 27), where the most striking point about the re- 
semblance is only to be appreciated when the insects 
are at rest with their wings closed. In such cases it is 
conceivable that the monkey may play a part in the 
elimination of the non-mimetic elements of a palatable 
species which at the same time possessed a mimetic 
form closely resembling another species disagreeable to 
the monkey's taste. As has been pointed out earlier 
(p. 96) even a slight persecution directed with adequate 
discrimination will in time bring about a marked result 
where the mimetic likeness is already in existence. It 
is not impossible therefore that the estabUshing of such 
a likeness may often be due more to the discrimination 
of the monkey than to the mobility of the bird. 



CHAPTER X 

MIMICRY AND VARIATION 

It is clear from the last few chapters that the 
theory of mimicry in butterflies with its interpretation 
of the building up of these likenesses by means of 
natural selection in the form of predaceous birds and 
other foes is open to destructive criticism from several 
points of view. The evidence from mimicry rings 
makes it almost certain that in some cases the resem- 
blance must be founded on an initial variation of such 
magnitude that the mimic could straightway be con- 
fused with the model. Till the mimic can be mistaken 
for the model natural selection plays no part. The 
evidence from breeding suggests strongly that in certain 
cases {e.g. Papilio polytes) the likeness arose in the 
form in which we know it to-day. In such cases there 
is no reason for supposing that natural selection has 
had anything to do with the formation of the finished 
mimic. Considerations of this nature may be said to 
have destroyed the view, current until quite recently, 
that in the formation of a mimetic resemblance the 
exclusive agent was natural selection. During the past 
few years it has come to be admitted by the staunchest 
upholders of the theory of mimicry that natural 



126 MIMICRY AND VARIATION [ch. 

selection would not come into play until the would-be 
mimic was sufficiently like the model to be confused 
with it under natural conditions i. The part now 
often attributed to natural selection is to put a polish 
on the resemblance and to keep it up to the mark by 
weeding out those which do not reach the required 
standard. It is supposed that if natural selection 
ceases to operate the mimetic resemblance is gradually 
lost owing to the appearance of variations which are 
no longer weeded out. An interesting case has recently 
been brought forward by Carpenter ^ and explained on 
these lines: The Nymphaline Pseudacraea eurytus is 
a polymorphic species found in Central Africa. In 
Uganda it occurs in several distinct forms which were 
originally supposed to be distinct species. Three of 
these forms bear a marked resemblance to three species 
of the Acraeine genus Planema. 

Mimic Model 

Pseudacraea eurytus Planema 

Form hobleyp (PI. VII, macarista (PI. VII, fig. 2) 
figs. 6, 7) 

terra (PL VII, fig. 8) tellus (PL VII, fig. 3) 

obscura paragea (PL VII, fig. 4) 

These different species occur round Victoria Nyanza 
and also on some of the islands in the lake. Some 

1 Cf. E. B. Poulton in Bedrock for Oct. 1913, p. 301. 

2 Trans. Ent. Soc. London, 1914. 

^ In the female hobleyi, with rare exceptions, the orange of the 
male is replaced by white, and it has received the name tirikensis. 
The female of P. macarista also shews white in place of the orange of 
the male. 



X] MIMICRY AND VARIATION 127 

interesting points are brought out by a comparison of 
the occurrence and variation of the si^ecies on the 
mainland with what is found on Bugalla Island in the 
Sesse Archipelago. On the mainland the Pseud- 
acraeas are abundant but the Planemas even more so, 
outnumbering the former by about 5 : 2^. Moreover, 
it is rare to find individuals more or less intermediate 
between the three forms, though they are known to 
occur. On Bugalla Island, however, a different state 
of things is found. The Pseudacraeas are very abund- 
ant, whereas the Planemas, owing doubtless to the 
scarcity of their food plant, are relatively rare, and are 
very greatly outnumbered by the Pseudacraeas. At 
the same time the proportion of transitional forms 
among the Pseudacraeas is definitely higher than on 
the mainland. These facts are interpreted by Car- 
penter as follows: — 

On the mainland where the models are abundant 
there is a vigorous action on the part of natural selection. 
The mimetic forms have a strong advantage and the 
non-mimetics have been gradually weeded out. But 
on the island, where the Pseudacraeas outnumber the 
models, the advantage obtained tlirough mimicry is not 
so great. The so-called transitional forms are little, 
if at aU, worse off than those closely resembling the 
scarce models, and consequently have as good a chance 
of surviving as any of the typical mimetic forms. On 

^ Cf. Poulton, E. B., /"■ Congr. Internal. d'Entomol., Bruxelles 1911. 
This proportion is founded on several hundreds caught at random. 
Observers are agreed that Pseudacraea is both a warier insect and a 
stronger flyer than the various Planemas which it resembles. 



128 MIMICRY AND VARIATION [ch. 

the mainland, however, the enemies of Pseudacraea 
are weU acquainted with the Planema models which are 
here common, and discriminate against individuals 
which are not close mimics of the Planemas. The 
result is that on the mainland transitional forms are 
scarcer than on the island. Natural selection main- 
tains a high standard for the mimetic likeness on the 
mainland owing to the abundance of the model; but 
when the model is scarce the likeness ceases to be 
kept up to the mark strictly, and tends to become 
lost owing to the appearance of fresh variations which 
are no longer weeded out. 

Here it should be stated that the various Pseud- 
acraeas form a population in which the different forms 
mate freely with one another. In the few breeding 
experiments that Dr Carpenter was able to make he 
found that ohscura could produce terra, and that 
tirikensis was able to give ohscura, the male in each case 
being, of course, unknown. Far too little work has as 
yet been done on the genetics of these various forms, 
and it would be rash to make assumptions as to the 
nature of the intermediates until the method of experi- 
mental breeding has been more extensively employed 
in analysing their constitution. Possibly it is not 
without significance that the abundance or scarcity of 
the ohscura form runs parallel with the abundance or 
scarcity of the intermediates. It suggests that the 
intermediates are heterozygous in some factor for 
which the typical ohscura is homozygous, and the 
fact that the intermediates are more numerous than 



x] MIMICRY AND VARIATION 129 

ohscura is what is to be looked for in a population mating 
at random. This case of the polymorphic Pseudacraea 
eurytus is one of the greatest interest, but it would be 
hazardous to draw any far-reaching deductions from 
such facts as are known at present. When the genetics 
of the various tj^ical forms and of the intermediates 
has been worked out it will be disappointing if it does 
not throw clear and important light on these problems 
of mimetic resemblance. 

As the result of modern experimental breeding 
work it is recognised that an intermediate form between 
two definite varieties may be so because it is hetero- 
zygous for a factor for which one variety is homozygous 
and which is lacking in the other — because it has 
received from only one parent what the two typical 
varieties receive from both parents or from neither. 
Its germ cells, however, are such as are produced by 
the two typical forms, and the intermediate cannot be 
regarded as a stage in the evolution of one variety from 
the other. In these cases of mimicry the existence of 
intermediate forms does not entail the deduction that 
they have played a part in the evolution of one pattern 
from another under the influence of a given model. 
It is quite possible that the new mimetic pattern 
appeared suddenly as a sport and that the intermediates 
arose when the new form bred with that which was 
already in existence. But before we are acquainted 
with the genetic relationships between the various 
forms, both types and intermediates, speculation as to 
their origin must remain comparatively worthless. 

p. M. 9 



130 MIMICRY AND VARIATION [ch. 

In this connection a few words on another source 
of variation may not be out of place. The patterns of 
butterflies are often very sensitive to changes in the 
conditions to which they are exposed during later 
larval and pupal life. Many moths and butterflies in 
temperate climates are double brooded. The eggs laid 
by the late summer brood hatch out, hibernate in the 
larval or pupal state, and emerge in the foUowing 
spring. This spring brood produces the summer brood 
during the same year. In these cases it often happens 
that the two broods differ in appearance from one 
another, a phenomenon to which the term "Seasonal 
Dimorphism ' ' has been applied. A well-marked instance 
is that of the little European Vanessid, Araschnia 
levana. The so-called levana form which emerges in 
the spring is a small black and orange-brown butterfly 
(PI. VI, fig. 10). From the eggs laid by this brood 
is produced another brood which emerges later on in 
the summer, and is, from its very different appearance, 
distinguished as the prorsa form (PI. VI, fig. 9). 
It is very much darker than the spring form and is 
characterised by white bands across the wings. The 
eggs laid by the prorsa form give rise to the levana 
form which emerges in the following spring. It has 
been shewn by various workers, and more especially 
by the extensive experiments of Merrifield^, that the 
appearance of the levana or the prorsa form from any 
batch of eggs, whether laid by prorsa or levana, is 
dependent upon the conditions of temperature under 

^ /"■ Congr. Internal. d'Entom., Bruxelles 1911. 



X] MIMICRY AND VARIATION 131 

which the later larval and early pupal stages are passed. 
By cooling appropriately at the right stage levana can 
be made to produce levana instead of the prorsa which 
it normally produces under summer conditions. So 
also by appropriate warming prorsa will give rise to 
prorsa. Moreover, if the conditions are properly ad- 
justed an intermediate form porima can be produced, 
a form which occurs occasionally under natural con- 
ditions. The pattern is, in short, a function of the 
temperature to which certain earHer sensitive stages 
in this species are submitted. What is true of A. levana 
is true also of a number of other species. In some 
cases temperature is the factor that induces the vari- 
ation. In other countries where the year is marked 
by wet and dry seasons instead of warm and cold ones 
moisture is the agent that brings about the change. 
In some of the South African butterflies of the genus 
Precis the seasonal change may be even more con- 
spicuous than in A. levana. In Precis octavia, for 
example, the ground colour of the wet season form is 
predominantly red, while in the dry season form of 
the same species the pattern is different, blue being 
the predominating colour (cf. PI. VI, figs. 11 and 12). 
Such examples as these are sufficient to shew how 
sensitive many butterflies are to changes in the con- 
ditions of later larval and earlier pupal life. The 
variations brought about in this way are as a rule 
smaller than in the examples chosen, but in no case 
are they known to be inherited, and in no case conse- 
quently could variation of this nature play any part in 

9—2 



132 MIMICRY AND VARIATION [ch. 

evolutionary change. Before any given variation can 
be claimed as a possible stage in the development 
of a mimetic likeness satisfactory evidence must be 
forthcoming that it is not of this nature, but that it 
is transmissible and independent of chmatic and 
other conditions. 

Many species of butterflies, especially such as are 
found over a wide range, exhibit minor varieties which 
are characteristic of given localities. These minor 
varieties may be quite small. In Danais chrysippus, 
for example, African and Asiatic specimens can gener- 
ally be distinguished. On examples from India a 
small spot is seen just below the bar on the fore wing 
and on the inner side of it. Eastwards towards China 
this spot tends to become larger and confluent with 
the white bar, giving rise to an L-shaped marking; 
westwards in Africa the spot tends to disappear al- 
together. The existence of such local races has been 
used as an argument for the hereditary transmission of 
very small variations — in the present instance the size 
of a small white spot^. For if it can be supposed that 
small differences of this nature are always transmitted, 
it becomes less difficult to imagine that a mimetic 
resemblance has been brought about by a long series 
of very small steps. But before this can be admitted 
it is necessary to shew by experiment that the size 
of this spot is independent of environmental conditions, 
both climatic and other. Apart from temperature and 
moisture it is not improbable that the formation of 

1 Cf. Poulton, Bedrock, Oct. 1913, p. 300. 



x] MIMICRY AND VARIATION 133 

pigment in the wings may depend in some degree upon 
the nature of the food. The larvae of D. chrysippus 
feed upon various Asclepiads, and it is at any rate 
conceivable that the pigment formation, and con- 
sequently the details of pattern, may be in shght 
measure affected by the plant species upon which they 
have fed. The species of food plants are more likely 
to be different at the extremities of the range of a 
widely distributed form like D. chrysippus, and if they 
are reaUy a factor in the pattern it is at the extremities 
that we should expect to find the most distinct forms ^. 
Actually we do find this in D. chrysippus, though it 
does not, of course, follow that the cause suggested is 
the true one, or, if true, the only one. Of the nature 
of local races too little at present is known to enable 
us to lay down any generalization. We must first 
learn by experiment how far they remain constant 
when transported from their own environment and 
bred in the environment under which another distinct 
local race is Hving. The behaviour of the transported 
race under the altered conditions would help us in 
deciding whether any variation by which it is character- 
ised had a definite hereditary basis or was merely a 
fluctuation dependent upon something in the conditions 
under which it had grown up. The decision as to 
whether it is hereditary or not must depend upon the 

^ The size of the wliite spot may shew much variation in specimens 
from the same region. I have seen African specimens in which it is 
large, while in the Ceylon specimen figured on Plate IV it is as small as 
in the typical African specimen shewn on Plate VIII. 



134 MIMICRY AND VARIATION [ch. 

test of breeding, through which alone we can hope to 
arrive at a satisfactory verdict upon any given case. 

The particular geographical variation which has 
just been considered happens to be a small one. But it 
may happen that a geographical variety is much more 
distinct. Indeed it is not impossible that butterflies 
which are at present ranked as distinct species may 
prove eventually to be different forms of the same 
species. Especially is this likely to be true of many 
forms in South America, of which Bates long ago 
remarked "that the suspicion of many of the species 
being nothing more than local modifications of other 
forms has proved to be well founded." Since Bates' 
day more material has been forthcoming^ and it has 
been shewn that certain colour schemes are character- 
istic of distinct geographical regions in South America 
where they may occur in species belonging to very 
different genera and families. In Central America, for 
example, the pattern common to many species is deter- 
mined by horizontal and oblique black bands on a bright 
fulvous brown ground, with two broken yellow bars 
towards the tip of the fore wing. The general type is 
well shewn by Mechanitis saturata and the female of 
Dismorphia praxinoe (PI. X, figs. 7 and 3). Belonging 
to this pattern group are a number of different species 
belonging to various families, including several Heli- 
conines and Ithomiines, Pierids such as Dismorphia 
and Perrhyhris, Nymphahnes of the genera Eresia and 

^ See Moulton, J. C, Trans. Ent. Soc. London, 1909. 



X] MIMICRY AND VARIATION 135 

Protogonius, and other forms. In Eastern Brazil the 
predominant pattern is one characterised by a yellow 
band across the hind wing and a white or yellow apical 
fore wing marking (cf. PI. XV, figs. 3 and 8). Here 
also, with the exception of the Perrhyhris, all the 
various genera which figured in the last group are again 
represented. It is true that the members of this 
second group are regarded as belonging to different 
species from those of the first group, but as species 
here are made by the systematist chiefly, if not entirely, 
on the colour pattern this fact may not mean much. 
Passing now to Ega on the Upper Amazons the general 
ground colour is a deep chestnut purple and the apical 
area of the fore wings presents a much mottled appear- 
ance (cf. PI. XV, figs. 4 and 9). In this group again 
we find represented the different genera found in the 
other groups, the only notable absentees being Eresia 
and Perrhybris. Lastly in Ecuador, Peru, and Bohvia 
the general pattern scheme consists of orange- tawny 
markings on a black ground (cf. PI. XV, figs. 5 and 10). 
This group differs somewhat in composition from the 
preceding in that it contains no Pierid and no Danaid. 
On the other hand its numbers have been strengthened 
by the accession of a Papilio, an Acraea, and two 
species of the Satyrid genus Pedaliodes. Certain WTiters 
have seen in the theory of mimicry the only explanation 
of these peculiar geographical pattern groups. The 
fashion is in each case set by the most abundant form, 
generally an Ithomiine of the genus Melinaea. The rest 
are mimics of this dominant species, either in the 



136 MIMICRY AND VARIATION [ch. 

Batesian or Miillerian sense. Batesian mimics are such 
genera as Dismorphia and Protogo7iius, to which there 
are no reasons for attributing disagreeable properties. 
Of the nature of Miillerian mimics on the other hand are 
the various Heliconines and Ithomiines which enter 
into the combination. In each case the whole assem- 
blage is a great "mimicry ring," of which the pattern 
is dictated by the Ithomiine that predominates in point 
of numbers. It is, however, very doubtful whether 
this can be accepted as a satisfactory explanation. The 
four groups which we have considered are all character- 
ised by a peculiar and distinctive coloration, and in 
each case the pattern must on the theory of mimicry 
be regarded as a highly efficient warning pattern. One 
or other of these patterns must doubtless be looked upon 
as the most primitive. If so the question at once 
arises as to why a distasteful genus should change from 
one efficient warning pattern to another quite distinct 
one. If the newer pattern affords better protection 
we should expect it to have spread and eventually to 
have ousted the older one. That it has not done so 
must probably be attributed to the old pattern being 
as efficient as the new one. But if this is so we are 
left without grounds for assuming the change to have 
been brought about by natural selection through the 
agency of enemies to whom warning colours appeal. 
For natural selection can only bring about a change 
that is beneficial to the species. Hence we must 
suppose the change on the part of the dominant model 
to have been independent of natural selection by 



X] MIMICRY AND VARIATION 137 

enemies, and due to some condition or set of conditions 
of which we are ignorant. It is not inconceivable 
that the new colour scheme was associated with some 
physiological peculiarity which was advantageous to 
the species in its altered surroundings. If so natural 
selection may have favoured the new variety, not 
because of its colour scheme, but owing to the under- 
lying physiological differences of which the pattern is 
but an outward sign. And if this could happen in one 
species there seems to be no reason why it should not 
happen in others. The weak point of the explanation 
on the mimicry hyj^othesis is that it offers no explana- 
tion of the change in the so-called dominant Ithomiine 
pattern as we pass from one region to another. What- 
ever the cause of this change may be there would 
appear to be nothing against it having also operated 
to produce similar changes in other unrelated species, 
in which case the mimicry hypothesis becomes super- 
fluous. It is not unlikely that the establishing of these 
new forms was due to natural selection. If they were 
associated with physiological peculiarities better adapted 
for their environment it is reasonable to suppose that 
natural selection would favour their persistence as 
opposed to the older type until the latter was ehmi- 
nated. But such action on the part of natural selection 
is quite distinct from that postulated on the mimicry 
hjrpothesis. On the one view the colour itself is 
selected because it is of direct advantage to its possessor ; 
on the other view the colour pattern is associated with 
a certain physiological constitution which places the 



138 MIMICRY AND VARIATION [ch. x 

butterflies possessing it at an advantage as compared 
with the rest^. 

It is, nevertheless, possible that mimicry may have 
played some part in connection with establishing the 
new colour pattern in some of these South American 
species. For if the new pattern had become estab- 
lished in the predominant distasteful species, and if 
some of the members of a palatable form {e.g. Proto- 
gonius) were to shew a variation similar to that already 
estabhshed in the distasteful species, and if further 
there be granted the existence of appropriate enemies, 
then it would be almost certain that the newer form in 
palatable species would eventually replace the older 
form. In such a case the part played by natural 
selection would be the preservation of a chance sport 
which happened to look like an unpalatable form. 
There is no reason for regarding the change as neces- 
sarily brought about by the gradual accumulation of 
a long series of very small variations through the 
operation of natural selection. 

^ In this connection it is of interest that a recent observer with 
considerable breeding experience finds that the dark doubledayaria 
variety of the Peppered Moth is more hardy than the typical form 
(cf. p. 101). The swift success of the dark variety led some to regard 
it as better protected against bird enemies. It is, however, not unlikely 
that the deeper pigmentation is associated with some physiological 
difference wliich makes for greater hardiness. See Bowater, Journal 
of Genetics, vol. 3, 1914. 



CHAPTER XI 

CONCLUSION 

From the facts recorded in the preceding chapters 
it is clear that there are difficulties in the way of 
accepting the mimicry theory as an explanation of the 
remarkable resemblances which are often found between 
butterflies belonging to distinct groups. Of these 
difficulties two stand out beyond the rest, viz., the 
difficulty of finding the agent that shall exercise the 
appropriate powers of discrimination, and the difficulty 
of fitting in the theoretical process involving the in- 
cessant accumulation of minute variations with what 
is at present known of the facts of heredity. 

With regard to the former of these two difficulties 
we have seen that the supporters of the theory regard 
birds as the main selective agent. At the outset we 
are met with the fact that relatively few birds have been 
observed to prey habitually on butterflies, while some 
at any rate of those that do so shew no discrimination 
between what should be theoretically pleasant to eat 
and what should not be pleasant. Even if birds are 
the postulated enemies it must be further shewn 
that they exercise the postulated discrimination. It 
is required of them that they should do two things. 



140 CONCLUSION [ch. 

In the first place they must confuse an incipient or 
"rough" mimic with a model sufficiently often to give 
it an advantage over those which have not varied in 
the direction of the model. In other words, they must 
be easily taken in. Secondly, they are expected to 
bring about those marvellously close resemblances that 
sometimes occur by confusing the exact mimicking 
pattern with the model, while at the same time elimin- 
ating those which vary ever so little from it. In other 
words, they must be endowed with most remarkably 
acute powers of discrimination. Clearly one cannot 
ask the same enemy to play both parts. If, therefore, 
birds help to bring about the resemblance we must 
suppose that it is done by different species — that there 
are some which do the rough work, others which do 
the smoothing, and others again which put on the final 
polish and keep it up to the mark. This is, of course, 
a possibility, but before it can be accepted as a pro- 
bability some evidence must be forthcoming in its 
favour. 

But even if the difficulty of the appropriate enemy 
be passed over, and it be granted that a mimetic 
resemblance can be built up through a number of small 
separate steps, which have become separately estab- 
lished through the agency of separate species of birds 
with various but distinct discriminating powers, we 
are left face to face with an even more serious physio- 
logical difficulty. For why is it that when the end 
form which is supposed to have resulted from this 
process is crossed back with the original form all 



XI] CONCLUSION 141 

the intermediate steps do not reappear? Why is it 
that when the altered germplasm is mingled Tvith the 
original germplasm the various postulated stages be- 
tween them are not reformed ? For in various cases 
where we know the course of evolution this does occur. 
The pale pink sweet-pea has come from the wild purple 
b}^ a series of definite steps, and when it is crossed back 
with the wild form the resulting plants give the series 
of stages that have occurred in the evolution of the 
pink. So also when the orange rabbit is crossed with 
the wild grey form and the offspring are inbred there 
are reproduced the black, the tortoiseshell, and the 
chocolate, forms which are stages in the evolution of 
the orange from the wild grey. If then, to take an 
example, the " aristolochiae " form of Papilio polyies 
has been derived from the male-like form by a series 
of steps, why do we not get these steps reproduced 
after the germplasms of the two forms have been 
mingled? From the standpoint of modern genetic 
work the inference is that these postulated inter- 
mediate steps have never existed — that the one form 
of polytes female came directly from the other, and 
was not built up gradually through a series of stages 
by the selective agency of birds or any other dis- 
criminating enemy. 

These two objections, viz. the difficulty of finding 
the appropriate enemy, and the non-appearance of 
intermediates when the extreme forms are crossed, 
may, perhaps, be said to constitute the main objections 
to the current theory of mimicry. Others such as 



142 CONCLUSION [ch. 

the relative scarcity of mimicry in the male sex and the 
existence of cases of polymorphism among females of 
a species which cannot possibly be explained on mimetic 
lines have already been mentioned. But while the 
main objections remain it is hardly necessary to insist 
upon these others. Looked at critically in the light 
of what we now know about heredity and variation the 
mimicry hypothesis is an unsatisfactory explanation of 
the way in which these remarkable resemblances be- 
tween different species of butterflies have been brought 
about. Sometimes this is admitted by those who never- 
theless embrace the theory with a mild aloofness. 
For they argue that even though it does not explain 
all the facts no other theory explains so many. Others 
have sought an explanation in what has sometimes 
been termed the hypothesis of external causes, regarding 
these resemblances as brought about by similar con- 
ditions of soil and climate, and so forth. It is not 
inconceivable that certain tjrpes of colour and pattern 
may be the expression of deep-seated physiological 
differences, which place their possessors at an advan- 
tage as compared with the rest of the species. Were 
this so it is but reasonable to suppose that they would 
become established through the agency of natural 
selection. But it is difficult, if not impossible, to regard 
this as a satisfactory solution, if for no other reason than 
that it offers no explanation of polymorphism. For 
example, each of the three forms of polytes female 
holds its own and all must, therefore, be regarded as 
equally well adapted to the circumstances under which 



XI] CONCLUSION 143 

they live. They are so distinct in colour that it is 
difficult on this hypothesis to suppose that they are 
all on the same footing in respect to their environment. 
Yet if one is better off than the others, how is it that 
these still exist? 

Those who have examined long series of these 
cases of resemblance among butterflies find it hard to 
believe that there is not some connection between 
them apart from cUmatic influence. One feels that 
they are too numerous and too striking to be all ex- 
plained away as mere coincidences engendered by like 
conditions. Nor is it improbable that natural selection 
in the form of the discriminating enemy may have 
played a part in connection with them, though a 
different one from that advocated on the current theory 
of mimicry. If we assume that sudden and readily 
appreciable variations of the nature of "sports" turn 
up from time to time, and if these variations happen to 
resemble a form protected by distastefulness so closely 
that the two can be confused by an enemy which has 
learned to avoid the latter, then there would appear 
to be good grounds for the mimicking sport becoming 
established as the type form of the species. For it 
has already been seen that a rare sport is not swamped 
by intercrossing with the normal form, but that on the 
contrary if it possess even a sUght advantage, it must 
rapidly displace the form from which it sprang (cf. 
Chap. VIII). On this view natural selection in the form 
of the discriminating enemy will have played its part, 
but now with a difference. Instead of building up a 



144 CONCLUSION [ch. 

mimetic likeness bit by bit it will merely have con- 
served and rendered numerically preponderant a like- 
ness which had turned up quite independently. The 
function of natural selection in respect of a mimetic 
likeness lies not in its formation but in its conservation. 
It does not bring about the likeness, neither does it 
accentuate it: it brings about the survival of those 
forms which happen to shew the likeness. Why vari- 
ations on the part of one species should bear a strong 
resemblance to other, and often distantly related, 
species is another question altogether. 

Even a superficial survey of the facts makes it 
evident that cases of mimicry tend to run in series — 
that a closely related series of mimics, though often of 
very different pattern and colour, tends to resemble 
a closely related series of models. In Asia we have 
the Cosmodesmus Papilios mimicking a series of 
Danaines, while the true Papilios (cf. Appendix II) 
tend to resemble a series of the less conspicuous mem- 
bers of the Pharmacophagus group. In the same 
region the various species of Elymnias form a series 
resembling a series of Danaines. In Africa there stands 
out the Cosmodesmus group again mimicking a Danaine 
series, and in part also an Acraeine series. Over- 
lapping the Acraeines again are various forms of the 
Nymphaline genus Pseudacraea. It is also of interest 
that in Danais chrysippus and Acraea encedon the 
Danaine and Acraeine series overlap (cf. PI. IX). Similar 
phenomena occur also in South America, where closely 
parallel series of colour patterns are exhibited by several 



XI] CONCLUSION 145 

Ithomiines, by Heliconius, Lycorea, Dismorphia, and 
other genera (cf. p. 39). On the other hand such mimetic 
resemblances as are shewn by the South American 
Swallow-tails of the Papilio and Cosmodesmus groups 
are almost all with the Pharmacophagus group, and 
almost all of the red-black kind (cf. p. 43). 

On the whole it may be stated that the majority 
of cases of mimicry fall into one or other of such series 
as the above. If we select a case of mimicry at random 
we shall generally find that there are at least several 
close allies of the mimic resembling several close allies 
of the model. Isolated cases such as the resemblance 
between Pareronia and Danais (p. 23), between 
Archonias and a Pharmacophagus Papilio (p. 43), or 
the extraordinary instance of Papilio laglaizei and 
Alcidis agathyrsus, must be regarded as exceptional. 

We have before us then a number of groups of 
butterflies each with a series of different colour patterns. 
In each group a portion of the series overlaps a portion 
of the series belonging to another more or less distantly 
related group. In the light of recent discoveries 
connected with heredity and variation the natural 
interpretation to such a set of phenomena would be 
somewhat as follows : Each group of Lepidoptera, such 
as those just discussed, contains, spread out among 
its various members, a number of hereditary factors 
for the determination of colour pattern. Within the 
group differences of pattern depend upon the presence 
or absence of this or that factor, the variety of pattern 
being the result of the many possible permutations and 

p. M. 10 



146 CONCLUSION [ch. 

combinations of these colour factors. Within the 
limits of each group is found a definite number of these 
factors — more in one group, less in another. But some 
factors may be common to two or more groups, in 
which case some of the permutations of the factors 
would be similar in the groups and would result in 
identical or nearly identical pattern. To take a simple 
example in illustration, let us suppose that a given 
group, (a), contains the eight factors A — H. Since 
any species in the group may exhibit any combination 
of one or more of these factors it follows that a con- 
siderable number of different forms are possible. Now 
suppose that another group, (/3), distinguished from 
(a) by definite structural features, also contains eight 
factors within the group, and that these factors are 
F — M, Fy G, and H being common to both (a) and 
(/S). Any combination therefore in (a) lacking the 
factors A — E will be paralleled by any combination in 
(j8) lacking the factors / — M. For in both cases we 
should be dealing only with the factors jP, G, and H^ 
which are common to each group. So again a third 
group might have some factors in common with (a) 
and some with (j8), and so on for other groups. In 
this way certain of the series of colour patterns found 
in (jS) would overlap certain of those in (a), while others 
of the groups {^) and (a) might overlap those found in 
different groups again. The striking resemblances not 
infrequently found between species belonging to quite 
distinct groups would on this view depend upon the 
hereditary factors for pattern and colour being Umited 



XI] CONCLUSION 147 

in number, so that the same assortment might not 
infrequently be brought together even though the 
group whose members exhibited the resemblance 
might, owing to structural differences, be placed in 
different families. 

We know from recent experimental work that 
something of the sort is to be found in the coat colours 
of different rodents. Agouti, black, chocolate, blue- 
agouti, blue, and fawn form a series of colours common 
to the rabbit, the mouse, and the guinea-pig. These 
colours are related to each other in the same way in 
these different beasts. In the rat, on the other hand, 
there occur of this range of colours only the agouti and 
the black. Each of these species again has certain 
colour patterns which are pecuUar to itself, such as 
the "EngUsh" type in the rabbit, the tricolor pattern 
in the guinea-pig, or the "hooded" variety in the rat. 
The total range of colour and pattern is somewhat 
different for each species, but a few are common to 
them all. Moreover, there are others which are com- 
mon to the mouse and the rabbit but are not found 
in the guinea-pig, and others again which may occur 
in the rabbit and the guinea-pig but have not been 
met with in the other two. In certain features the 
rabbit might be said to "mimic" the mouse, and in 
other features the guinea-pig. It is not, of course, 
suggested that the case of the butterflies is so simple 
as that of the rodents, but so far as we can see at 
present there would seem to be no reason why the 
explanation should not be sought along the same lines. 

10—2 



148 CONCLUSION [ch. 

On this view the various colour patterns found among 
butterflies depend primarily upon definite hereditary- 
factors of which the number is by no means enormous. 
Many of these factors are common to several or many 
different groups, and a similar aggregate of colour 
factors, whether in an Ithomiine, a Pierid, or a Papilio, 
results in a similar colour scheme. The likeness may 
be close without being exact because the total effect is 
dependent in some degree on the size and relative 
frequency of the scales and other structural features. 
In so far as pattern goes Hypolimnas dubiits and 
Arnauris echeria (PI. VIII, figs. 7 and 8) are exceed- 
ingly close. But inspection at once reveals a difference 
in the quality of the scaling, giving to the Hypolimnas, 
where the black and yellow meet, a softness or even 
raggedness of outline, which is distinct from the sharper 
and more clear-cut borders of the Amauris. It is not 
unreasonable to suppose that these species carry 
identical factors for colour pattern, and that the 
differences by which the eye distinguishes them are 
dependent upon the minuter structural differences such 
as occur in the scaling. So the eye would distinguish 
between a pattern printed in identical colours on a 
piece of cretonne and a piece of glazed calico. Though 
pattern and colour were the same the difference in 
material would yield a somewhat different effect. 

On the view suggested the occurrence of mimetic 
resemblances is the expression of the fact that colour 
pattern is dependent upon definite hereditary factors 
of which the total number is by no means very great. 



XI] CONCLUSION 149 

As many of the factors are common to various groups 
of butterflies it is to be expected that certain of the 
colour patterns exhibited by one group should be 
paralleled by certain of those found in another group. 
That cases of resemblance should tend to run in parallel 
series in different groups is also to be expected, for 
in some groups the number of factors in common is 
likely to be greater than in other groups. In con- 
sonance with this view is the fact that where poly- 
morphism occurs among the females of a mimicking 
species the models, though often widely different in 
appearance, are, as a rule, closely related. Some of 
the Asiatic Pai^ilios, for instance, resemble Danaines, 
while others resemble Pharmacophagus Papilios. But 
although the polymorphism exhibited by the females of 
a given species may be very marked, we do not find 
one of them resembling a Danaine and another a 
Pharmacophagus Swallow-tail. The models of a poly- 
morphic mimic are almost always closely related 
species^. 

In discussing the problems of mimicry more atten- 
tion is naturally paid to groups which exhibit the 
phenomenon than to those which either do not do so, 
or else only do so to a very limited extent. Yet the 
latter may be of considerable interest. Among the 
Pieridae of the Old World the phenomenon of mimicry 
is very rare. Pareronia and Aporia agaihon conform 

1 As examples may be mentioned P. polytes, Hypolimnas misippus, 
H. dubius, and Pseudacraea hobleyi. With the exception of the planemoides 
form it is true also for P. dardanus, the most polymorpliic of them all. 



150 CONCLUSION [ch. 

closely to the common Danaid type represented by 
Danais vulgaris and other species, but apart from these 
none of the many Pierids in Asia resemble any of the 
recognised models. Africa is apparently destitute of 
Pierids which mimic species belonging to other groups. 
Yet no group of butterflies is more persecuted by 
birds. Of all the instances of bird attacks collected 
together by Marshall ^ more than one-third are instances 
of attacks upon this group alone. If birds are the 
agents by which mimetic likenesses are built up through 
the cumulative selection of small variations, how can 
the rarity or absence of mimetic Pierids in the Old 
World be accounted for? For the species of Pierids, 
like the species of other families, shew considerable 
variation, and if this process of selection were really 
at work one would expect to find many more Pierid 
mimics in these regions than actually occur. It is 
true that the white, yellow, and red pigments found 
in Pierids differ from those of other butterflies in being 
composed either of uric acid or of some substance 
closely allied to that body^. These substances are 
generally found between the two layers of chitin, of 
which the scale is composed, whereas the black pigment 
is intimately associated with the chitin of the scale 
itself. What is perhaps the principal factor in the 
formation of a mimetic likeness is the distribution of 
the black pigment with reference to the lighter pig- 
ments ; and although the latter are chemically distinct 

1 Trans. Ent. Soc. Lond. 1909. 

2 Cf. F. G. Hopkins, Phil. Trans. Roy. Soc. 1895. 



XI] CONCLUSION 151 

in the Pierids as compared with other butterflies, there 
would seem to be no reason why the same factors 
governing the distribution of black should not be 
common to members of different groups. A distri- 
bution of black pigment similar to that found in a 
model and its mimic may occur also in a non-mimetic 
ally of the mimic. Dismorphia astynome, for example, 
resembles the Ithomiine Mechanitis lysimnia (PI. XV, 
fig. 8) both in the distribution of black as weU as 
of yeUow and bright brown pigments. A similar 
distribution of the black pigment is also found in 
Dismorphia avonia, but the yellow and bright brown 
of the other two species is here replaced with white. 
By a slight though definite alteration in chemical 
composition this white pigment could be changed into 
bright brown and yellow with the result that D. avonia 
would closely resemble D. astyno^ne in its colour scheme 
and would in this way also become a mimic of Mecha- 
nitis lysimnia. Another good instance is that of the 
females of Perrhybris demophile and P. lorena, the 
former being black and white, whereas in the latter 
the white is replaced by yeUow and bright brown, 
giving the insect a typical Ithomiine appearance^. 
Here again a definite small change in the composition 
of the pigment laid down in the scales would result in 
the establishing of a mimetic likeness where there would 
otherwise be not even a suggestion of it. It is in 
accordance with what we know to-day of variation 

1 Coloured representations of these two species will be found on 
PL 20 of Seitz, Macrolepidoptera of the World, Fauna Americana. 



152 CONCLUSION [ch. 

that such a change should appear suddenly, complete 
from the start. And if so there is no difficulty in sup- 
posing that it might be of some advantage to its 
possessor through the resemblance to an unpalatable 
form. Even were the advantage but a slight one it 
is clear from previous discussion (p. 96) that the new 
variety would more or less rapidly replace the form 
from which it had sprung. With the continued 
operation of natural selection the new form would 
entirely supplant the original one, but it is not im- 
possible that in some cases the selecting agent may be 
removed before this result has been achieved. In this 
event the proportions of the new and the old form 
would fall into a condition of equilibrium as in P. 
polytes in Ceylon, until some other selective agent 
arose to disturb the balance. On this view natural 
selection is a real factor in connection with mimicry, 
but its function is to conserve and render preponderant 
an already existing likeness, not to build up that like- 
ness through the accumulation of small variations, as 
is so generally assumed. Recent researches in heredity 
and variation all point to this restriction of the scope 
of natural selection. Hitherto an argument in favour 
of the older view has been that derived from the study 
of adaptation — of an apparent purpose, which, at first 
sight, appears to be behind the manner in which 
animals fit into their surroundings. For many the 
explanation of this apparent purpose has been found 
in the process of natural selection operating gradually 
upon small variations, accumulating some and rejecting 



XI] CONCLUSION 153 

others, working as it were upon a plastic organism, 
moulding it little by little to a more and more perfect 
adaptation to its surroundings. On this view adapta- 
tion is easy to understand. The simplicity of the 
explanation is in itself attractive. But when the 
facts come to be examined critically it is evident that 
there are grave, if not insuperable, difficulties in the way 
of its acceptance. To outline some of these has been 
the object of the present essay. Though suggestions 
have been made as to the lines along which an ex- 
planation may eventually be sought it is not pre- 
tended that the evidence is yet strong enough to 
justify more than suggestions. Few cases of mimicry 
have as yet been studied in any detail, and until this 
has been done many of the points at issue must remain 
undecided. Nevertheless, the facts, so far as we at 
present know them, tell definitely against the views 
generally held as to the part played by natural selection 
in the process of evolution. 



APPENDIX I 

For the table on p. 155 I am indebted to the kindness of 
Mr H. T. J. Norton of Trinity College, Cambridge. It affords 
an easy means of estimating the change brought about through 
selection with regard to a given hereditary factor in a population 
of mixed nature mating at random. It must be supposed that 
the character depending upon the given factor shews complete 
dominance, so that there is no visible distinction between the 
homozygous and the heterozygous forms. The three sets of 
figures in the left-hand column indicate different positions of 
equilibrium in a population consisting of homozygous domi- 
nants, heterozygous dominants, and recessives. The remaining 
columns indicate the number of generations in which a popu- 
lation will pass from one position of equilibrium to another, 
imder a given intensity of selection. The intensity of selection 
is indicated by the fractions \l>^, i^f, etc. Thus ^-^ means 
that where the chances of the favoured new variety of surviving 
to produce offspring are 100, those of the older variety against 
which selection is operating are as 75 ; there is a 25 % selection 
rate in favour of the new form. 

The working of the table may perhaps be best explained by 
a couple of simple examples. 

In a population in equilibrium consisting of homozygous 
dominants, heterozygous dominants and recessives the last 
named class comprises 2-8 % of the total: assuming that a 
10 % selection rate now operates in its favour as opposed to 
the two classes of dominants — in how many generations will 
the recessive come to constitute one-quarter of the population ? 
The answer is to be looked for in column B (since the favoured 
variety is recessive) under the fraction ^-. The recessive 



APPENDIX I 



155 



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156 APPENDIX I 

passes from 2-8 % to 11-1 % of the population in 36 generations, 
and from 11-1 % to 25 % in a further 16 generations — i.e. under 
a 10 % selection rate in its favour the proportion of the 
recessive rises from 2-8 % to 25 % in 52 generations. 

If the favoured variety is dominant it must be borne in 
mind that it can be either homozygous or heterozygous — that 
for these purposes it is represented in the left-hand column by 
the hybrids as well as by the homozygous dominant. In a 
population in equilibrium which contains about 2 % of a 
dominant form, the great bulk of these dominants will be 
heterozygous, and the relative proportion of recessives, hetero- 
zygous, and homozygous dominants is given in the second line 
of the left-hand column. 

Let us suppose now that we want to know what will be 
the percentage of dominants after 1000 generations if they 
form 2 % of the population to start with, and if, during 
this period, they have been favoured with a 1 % selection 
advantage. After 165 generations the proportion of recessives 
is 90-7, so that the proportion of dominants has risen to over 
9 % ; after 153 further generations the percentage of dominants 
becomes 27-7 + 2-8 = 30-5; after 739 generations it is 88-8 %, 
and after 1122 generations it is 69-0 -f 27-7 = 96-7. Hence 
the answer to our question will be between 89 % and 97 %, 
but nearer to the latter figure than the former. 

Mr Norton has informed me that the figures in the table 
are accurate to within about 5 %. 



APPENDIX II 

The genus Papilio is a large and heterogeneous collection. 
It was pointed out by Haase^ that it falls into three distinct 
sections, of which one — the Pharmacophagus section — provides 
those members which serve as models in mimicry ; while in 
the other two sections are found mimics, either of Pharma- 
cophagus Swallow-tails, or of models belonging to other groups. 
Though Haase's terms have not yet come into general use 
with systematists, there is httle doubt that the genus Papilio 
as it now stands must eventually be broken up on these hnes. 
To say that one species of Papilio mimics another is therefore 
somewhat misleading ; for the differences between the Pharma- 
cophagus group and the other two are such as to constitute at 
any rate generic distinction in other groups. For convenience 
of reference a table has been added in which the various 
Papihos mentioned in the text have been assigned to their 
appropriate sections, and referred to their respective models. 

1 Untersuchungen iiber die Mimikry, 1893. 



158 



APPENDIX II 



Pharmacophagus 

(POISON-EATERS) 



Antennae without 
scales. 

Outer ventral row 
of spines of tarsi 
not separated 
from the dorsal 
spines by a spine- 
less longitudinal 
depression. 

Larva covered with 
short hairs — 
with fleshy tu- 
bercles but no 
spines. 



Pupa with row of 
well - marked 
humps on each 
side of abdomen. 



Larva feeds on Aris- 
tolochia. 



Papilio 

(FLUTED SWALLOW- 
TAILS) 

Antennae without 

scales. 

Outer ventral row 
of spines of tarsi 
separated from 
the ^orsal spines 
by a spineless 
longitudinal de- 
pression. 

Larva either smooth 
or with hard 
spiny tubercles. 
Tliird andfoxirth 
thoracic seg- 
ments enlarged. 

Pupa wrinkled — 
generally with 
short dorsal 

horn. Humps 
if present very 
short. 

Larva does not feed 
on Aristolochia. 

Abdominal margin 
of hind wing 
curved down- 
wards forming 
a kind of groove. 
No scent organ. 



Cosmodesmus 

(KITE SWALLOW- 
TAILS) 

Antennae scaled 
on upper side. 

As in Papilio. 



Larva with third 
thoracic seg- 
ment enlarged 
(known only in 
a few species). 



Pupa short with 
long four-sided 
thoracic horn. 



As in Papilio. 



Abdominal margin 
of liind wing 
bent over in ^, 
and with scent 
organ in fold 
so formed. 



APPENDIX II 



159 



ORIENTAL 



AFRICAN 



AMERICAN 



P 

o 









s-^ 



Q to (» 

§ a s 



!-^.? — S!-^ 



C oj <^ 




GO 




O 




§ 


ca 


1— 1 


cs 


S 


a - 




M O 




0) a 




aa 


o 


CQ 

o 




o 



1—1 





(MHH 


l-i 


X 


X 


d _^ 


* 


t;^ 


C3 

8 


,2 V 








■<?* 


a 


!> 



fo 










^H 










o 










05 








c^ cc ^ ^_^ 


H 

CO 


.2 


o 






•r* 








h-; hH* w 2 

hH hH hH ^ 


1— ( 


f— 4 


hH 






*<7A 






/— s*-v e<i 


hH hH hH 


h4 


1 

Pi 


S 


^^ 




§ 


S" 




OfO+ ss'-' -.s^ 

0= o^S 


>>> s 




1— 1 






> 


hH 


CO 


OfCM-Of oo!C 

1 111 










.e 


r 


parad 
polyte 

>> 
memn 
bootes 
laglav. 




SB 




















lOfl 














lo 






eg 

o 
o 


J 












> 
























eg 


o 












•/or (V 
stoloch 

lyxenu 






s 

















g 



X 






c 



00 2 S 
J? §-t 



i» s 



•ghH > 



-< C o S, 



8 



PLATE I 



ORIENTAL BUTTERFLIES 
Pareronia ceylonica 



Danais septentrionis 
Papilio xenocles 
Hypolimnas bolina 



7, Papilio clytia var. dissimilis 

8, „ „ var. lankeswara 

9, Elymnias singhala 
10. Euploea core 



(Pieridae) 

(Danainae) 
(Papilionidae) 

(Nymphalinae) 

(Papilionidae) 

(Satyrinae) 
(Danainae) 



Plate I 




OIUFATAI/ lU'l TKItri.lKS 



11 



PLATE II 



ORIENTAL BUTTERFLIES 



L 


Delias eucharis 




(Pieridae) 


2. 


Caduga tytia 




(Danainae) 


3. 


Papilio agestor 




(Papilionidae) 


4. 
5. 


Euploea mulciber 


l) 


(Danainae) 


6. 
7. 


Elymnias malelas 
»» »» 


l\ 


(Satyrinae) 


8. 


Euploea rhadamanthus 


(Danainae) 


9. 


Papilio mendax 




(Papilionidae) 



X t 



Plate II 




O RIENTAl. liUTTERFLIES 



11- 



PLATE III 

ORIENTAL MOTHS AND BUTTERFLIES 

The three upper figures are those of moths, and the three lower 
ones are those of butterflies. 

1. Alcidis agathyrsus (New Guinea) 

2. Papilio laglaizei ,, ,, 

The moth is here supposed to serve as a model for the far rarer 
Papilio. 

3. Cyclosia hestinioides 

4. Ideopsis daos 

The butterfly is very common and must be regarded as the model, 
the rarer moth as the mimic. 

5. Epicopeia polydora (Assam) 

6. Papilio bootes „ 

Both of these species are to be regarded as mimics of the abundant 
Pharmacophagus Papilio, P. polyxenus, which is very like P. bootes in 
appearance. 



X 




K 
E-i 

P 



PLATE IV 

ORIENTAL BUTTERFLIES 

1. Danais chrysippus ^ ") 

o 7 • ^ ( (Danainae) 

2. „ plexippus ? J 

3. Argynnis hyperbius $ ) 

A ^ \ (Nymphalinae) 

5. Elymnias undularis ? 

7. Hypolimnas misippus $ 

8- „ „ S 



> (Satyrinae) 

> (Nymphalinae) 



The two Danaids together with the females of the other three 
species form a "mimicry ring," For explanation see text, pp. 65-69. 



X f 



Plate IV 




Oil 1 i:XTAL BUTTEli VIA EH 



PLATE V 



ORIENTAL BUTTERFLIES 



1. Papilio polytes S 



2. 


„ „ ?, var. cyrus (M form) 


3. 


„ „ ?5 var. polytes {A form) 


4. 


„ „ 9, var. romulus {H form) 


5. 


„ aristolochiae 


6. 


„ hector 



The specimens figured on this plate were taken in Ceylon where 
they are all plentiful. 

Figures la-6a represent the under surfaces of the hind wings 
belonging to specimens 1-6. 



X i 



Plate V 




()itii:x'iAi, iu'i"i'i-:i'vFLii:s 



PLATE VI 



AFRICAN BUTTERFLIES 
(except A. levana, Figs. 8-10, which is Eiiropean) 

1. Danais petiverana (Danainae) 

2. Papilio leonidas (Papilionidae) 

3. Amauris hyalites (Danainae) 

4. Papilio leonidas var. brasidas (Papilionidae) 

5. Pseudacraea boisduvali (Nymphalinae) 

6. Papilio ridleyanus (Papilionidae) 

7. Acraea egina (Acraeinae) 

8. Araschnia levana var. porima 

9. „ „ var. prorsa 
10. 

11. Precis octavia var. sesamus 

12. „ „ var, natalensis 



Plate VI 




%^ 




12 



Ai'iticw i5r'i"n:i{KLiKs 



PLATE VII 



TROPICAL AFRICAN BUTTERFLIES 

1. Planema macarista ^ (Acraeinae) 

2. ft „ ? tf 

Oa fy Z&vLUS ff 

4. „ paragea „ 

5. ,, epaea „ 

6. Psevdacraea hobleyi ^ (Nymphalinae) 
• • »» >» + >> 

8. „ terra „ 

9. Elymnias phegea 
10. Papilio cynorta 



? (Satyrinae) 
$ (Papilionidae) 



(Note. Psevdacraea hobleyi and P. terra (Figs. 6-8) were at one 
time regarded as separate species. More recently they have been shewn 
to be forms of the polymorphic species, Pseudacraea eurytus.) 



X f 



Plate VII 






%T^ 



TKOI'K AL AKi;i('.\.\ lU I'l'l^li KhI KS 



PLATE VIII 

AFRICAN BUTTERFLIES 

1. Papilio dardanus ^ 

2. ,, ,, ?, var. trophonius 

3. „ ,, ?, var. hippocoon 

4. ,, „ ?, var. cenea 

5. Danais chrysippus (Danainae) 

6. Amauris niavius „ 

7. „ echeria „ 

8. Hypolimnas dubius var. mima (Nymphalinae) 

9. „ „ var. wahlbergi „ 



X 4 



riate VTII 




AFRICAN BUTTER FJJES 



Plate IX 




Danais chrysippus 
a. 'l\v[Mcal form 
I). .Mcippus form 
c. 1 )()ri ppua foi'iii 



Acraea enccdoyi 

d. Typical form 

e. Alcippina form 

f. Daira form 



HypoVnimas mlsippus ? 
g. Typical form 
h. Alcippoidcs form 
i. Iiutiia form 

(After Auriviliius) 



PLATE X 



SOUTH AMERICAN BUTTERFLIES 



1. 


Dismorphia cretacea 


(? 


(Pieridae) 


2. 


„ praxinoe 


(? 


»» 


3. 


>> j> 


? 


»» 


4. 


Perrhybris tnalenka 


^ 


>» 


5. 


}> 55 


(J (under 


surface) „ 


6. 


5J 55 


$ 


>> 


7. 


Mechanitis saturata 




(Ithomiinae) 


8. 


Papilio zagreus 




(Papilionidae) 


9. 


Protogonius tithoreidet 




(Nymphalinae) 


10. 


Tithorea pseudonytna 




(Ithomiinae) 



(Note. The figure of the Mechanitis (Fig. 7) is taken from a rather 
worn specimen. The quaHty of the orange brown is better shewn by 
the specimen illustrated in Fig. 7 on Plate XV.) 



Plate X 




SOI TFf AMERICAN BUTTERFLIES 



12 



PLATE XI 

SOUTH AMERICAN BUTTERFLIES 

1. Heliconius sulphurea (Heliconinae) 

2. Papilio pausanias (Papilionidae) 

3. Heliconius telesiphe (Heliconinae) 

4. Colaenis telesiphe (Nymphalinae) 

5. Heliconius melpomene (Heliconinae) 

6. Pereute char ops $ (Pieridae) 
'• »» »» o >> 

8. Papilio osyris ^ (Papilionidae) 

O. tj ff 5f tf 

10. Archonias critias ? (Pieridae) 



xf 



Plate XI 




SOl'TH A.MHPvlCAX BI^ITKI? FLI l-:S 



Plate XII 




SOUTH AMERICAN BUTTERFLIES 



Plate XI II 




MODKLS :MTMKS 

1. rapilio nephalion 4. PapUto lysllhoms \ar. li/i<ill)ous 

2. „ chamissonia 5. „ „ var, rurik 

3. „ perrhebu.s (i. ,. ,, var. potnponiiis 

(For furthor details of this case sec Jordan. /' Conr/r. Iiilcnidl. 
d'Eniotnologie, Bruxelles, 1911, p. 39G.) 



Plate XIV 










^. ■^t. 



JSIethona confusa, x90 
(Ithoniiiuae) 



F^./^*^ ^^> 



J' 






^j 



'ti-' 






^o 







«iMfc»e^-': 



2. Dismorphla orise, XloO 
(Pierinae) 




"1'^^*.'^/' V.V V ... 'J »^ . 



W- 






W. ' - »^ 



>* 



^ 3 



L 



V*.. 



WJ Vv 












'^*. \'J^^^^r, 



:^S 



^^ 






3. Thijrldla themisto, x 90 
(lUiomiinac) 




^ 




^^^^B i,' k 





5. Castnia sp., x()0 



4. Ilitna illo)ie, x 90 
(Danainae) 

Micropliotograi^hs of the scales of various LepidopU'ra in tlu' S. Aiiu'iicau 
"Transparency group." For explanation see text, pp. .'?9 42. 



12—2 



PLATE XV 

CENTRAL AND SOUTH AMERICAN BUTTERFLIES 

Illustrating the closely parallel series of patterns occurring in the 
two distinct groups Hehconinae and Ithomiinae. 



L 


Heliconius 


mirus 


2. 


»j 


telchinw, 


3. 


»» 


eucrate 


4. 


55 


pardalinus 


6. 


JJ 


splendens 


6. 


Mechanitis elisa 


7. 


}> 


saturata 


8. 


j» 


lysimnia 


9. 


J5 


egaensis 


10. 


>> 


methona 



X * 



Plate XV 




CENTRA!. \y,\) .SOL Til A.MEKICAX BLTTEKELIES 





PLATE 


XVI 






NORTH AMERICAN BUTTERFLIES 


1, 


Papilio philenor 




(Papilionidae) 


2. 


„ troilus 




J5 


3. 


Argynnis diana ? 




(Nymphalinae) 


4. 


Limenitis arthemis 




»> 


5. 


„ astyanax 




» 


6. 


„ archippus 




>> 


7. 


„ floridensis 1 


[=eros) 


j» 


8. 


Danais archippus 




(Danainae) 


9. 


„ berenice 




>? 



X f 



Plate XV T 




NORTH a.mi<:hicax butterflies 



INDEX 



References to the plates are given in thicker type 



Acraea, taken by kestrel, 118: 
A. axina, 122; A. caldarena, 
122; A. egina, 34, VI. 7; 
A. encedon, patterns of dif- 
ferent forms in relation to 
those of Danais chrysippus, 29, 
144; typical form of, IX. d; 
alcippina form of, IX. e ; daira 
form of, IX. f; ^. halali, 122; 
A. violae, 33 note; eaten by 
lizards, 108 ; attacked by birds, 
110, 117 

Acraeinae, as models for African 
butterflies, 33 

Adaptation and Natural Selection, 
61 

Adelpha, 54 

African butterflies, mimicry 
among, 28-36 

Alcidis agathyrsus, 27, 145, III. 1 

Aletis helcita, 36 

Amauris echeria, 30, 148, VIII. 7; 
A. hyalites, 30, VI. 2; A. 
niavius, 30, VIII. 6 

Amphidasys betularia, rapidity of 
increase in melanic sport of, 
101 

Anosia plexippus { = Danais ar- 
chippus), 113 

Anthomysa, 41 

Aporia agathon, 149 

Araschnia levana, seasonal dimor- 
phism in, 130; typical form, 
VI. 10 ; prorsa form, VI. 9 ; 
porima form, VI. 8 

Archonias, 43, 56, 145; A. critias, 
XI. 10 



Argynnis diana, 47, XVI. 3 ; 
A. hyperbius, 29; as mimic 
of Danais plexippiis, 52 ; in 
mimicry ring, 66, IV. 3, 4 

Artamus fuscus, 112 

Asilid flies, as enemies of butter- 
flies, 106 

Athyma punctata, 53 

Bates, G. L., on contents of birds' 
stomachs, 113 

Bates, H. W., on mimicry, 9; on 
resemblances between unpalat- 
able forms, 14; on initial 
yariation in mimetic resem- 
iDlance, 63; on S. American 
Pierines attacked by birds, 112 

Bateson, 3 

Belenois, 36 

Bingham, on birds eating butter- 
flies, 110 

Birds, as enemies of butterflies, 
109; stomach contents of, 
113; feeding experiments with, 
115; colour perception in, 119 

Bowater, on Amphidasys betularia, 
102, 137 note 

Breeding experiments, with Hypo- 
limnas dubius,SO ; with Papilio 
polytes, 84 ; with Papilio mem- 
non, 89 ; with Papilio dardanus, 
90; with Psevdacraea eurytus, 
128 

Bryant, on birds eating butter- 
flies, 114 

Btichanga atra. 111 

Byblia ilithyia, 122 



184 



INDEX 



Caduga tytia, 24, 51, II- 2 
Callamesia pieridoides, 56 
Calotes ophiomachus, 107 ; C. versi- 
color, 107 
Carpenter, on intermediates in 
Psevdacraea eurytus, 126; on 
breeding experiments with 
Pseudacraea eurytus, 128 
Castnia, as mimic, 39, XII. 4; 

scales of, 41, XV. 5 
Catopsilia, 121; C. florella. 111; 

C. pyranthe. 111 

Cerchneis rupicoloides, 118; C. 

naumanni, 117 
Cercopithecus pygerythrus, 121 
Char axes athamas, 110 
Citronophila similis, 35 
Classification of butterflies, 18-21 
Colaenis telesiphe, 38, XI. 4 
Cyclosia hestinioides, III. 3 
Cymatopkora or, establishment of 

melanic sport in, 102 note 
Cyrestis ihyodamas, 110 

Danainae, characteristics of, 22 ; 
as models for Oriental butter- 
flies, 23 ; as models for African 
butterflies, 28 

Danais, 111, 145; D. archippus, 
48 ; eaten by lizard, 108 ; 
rejected by bird, 113, XVI. 8; 

D. berenice, 48, XVI. 9 ; D. 
ehrysippus, 23, 28 ; flight of, 
55 ; in mimicry ring, 65 ; eaten 
by lizards, 108 ; eaten by Bee- 
eater, 111; eaten by Brown 
Shrike, 117; rejected by Kes- 
trel, 118; rejected by baboon, 
122; local variation in, 132; 
patterns overlapping with those 
of Acraea encedon, 144 ; alcip- 
pus form, IX. b; dorippus 
form, IX. C; typical form, 
IV. 1, Vni. 5; D. plexippus, 
as model for Argynnis hyper - 
bius, 52 ; in mimicry ring, 65 ; 
eaten by Liothrix, 115 note, 
IV. 2 ; D. petiverana, 29, VI. 1 ; 
D. septentrionis, 23, 111, 112, 
I. 3 ; D. vulgaris, 150 



Darwin, on natural selection, 1 ; 
on adaptation, 5; on initial 
variation in mimetic resem- 
blance, 63 ; on a difficulty of 
the mimicry theory, 65 

Defence in butterflies, 54 

Delias cathara, 56 ; D. eucharis, 
28, 115, 116, II. 1 

de Meijere, on breeding Papilio 
memnon, 89 

de Vries, 3 

Distnorphia, as mimics of Itho- 
miinae, 38, 42 ; restricted 
range of many forms, 5 1 ; 
diversity of pattern in genus, 
58; as Batesian mimics, 135; 
patterns parallel with those of 
Ithomiinae, 145; D. astynome, 
151; D. avonia, 151; D. 
cretacea, 5, 8, 62, X. 1; D. orise, 
as mimic, 39, XII. 2 ; scales of, 
40, XIV. 2; D. praxinoe, as 
mimic, 57, 62, X. 2, 3; as 
member of mimicry ring, 134 

Distasteful groups, characteristics 
of, 55 

Eltringham, 17 note, 32 note, 
36 note 

Elymnias, patterns in genus com- 
pared with those of Danaidae, 
59, 144; E. malelas, 24, II. 6, 
7 ; E. phegea, 35, VII. 9 ; 
E. singhala, 25, I. 9 ; E. undu- 
laris, in mimicry ring, 66, 115 
note, 116, IV. 5, 6 

Epicopeia polydora, 27, in. 5 

Equilibrium, conditions of in 
mixed population, 93 

Eresia, 134, 135 

Eugonia californica, 114 

Euphaedra ruspina, 36 

Euploea core, 25, 108, 110, 112, 

I. 10; E. mulciber, 24, 51, 

II. 4, 5; E. rhadamanilius, 24, 
51, II. 8; E. rafflesii, 110 

Euploeinae, characteristics of, 22 ; 
as models for Oriental butter- 
flies, 24 ; in relation to birds, 

III. 112, 115 note 



INDEX 



185 



Euripus halitherses, 24 

Feeding experiments, with Man- 
tids, 105; with hzards, 107; 
with birds, 115; \^'ith mam- 
mals, 121 

Finn, on feeding experiments with 
Hzards, 108; on feeding experi- 
ments with Indian birds, 115; 
on feeding experiments with a 
Tree-shrew, 121 

Flight, different in model and 
mimic, 55 ; difference of in 
Papilio polytes and its models, 
82 

Fryer, on breeding Papilio polytes, 
84; on relative abundance of 
females ot Papilio polytes in 
Ceylon, 97 ; on birds eating 
"unpalatable" butterflies, 112 

Gerrhonotus infemalis, 108 

Haase, on mimicry, 16; on classi- 
fication of Papilionidae, 25 

Hahnel, on S. American Pierines 
attacked by birds, 112 

Hardy, on conditions of equili- 
brium in a mixed popvilation, 
94 

Hearsy, on birds eating butterflies, 
111 

Hebomoia, 110 

Heliconinae, as models for S. 
American butterflies, 38 

Heliconius, 145 ; H. eucrate, XV. 3 ; 
H. melpomene, as model, 42, 
43, XI. 5 ; H. mirus, XV. 1 ; 
H. pardalinus, XV. 4; H. 
splendens, XV. 5 ; H. sulphur ea, 
43, XI. 1 ; H. telchinia, XV. 2 ; 
H. telesiphe, XI. 3 

Herpestes galera, 121 

Hess, on colour perception in 
birds, 119 

Hopkins, on pigment of Pierids, 150 

Hypolimnas dubius, polymorphism 
in, 30 ; as mimic of Danaines, 
30, VII. 8, 9 ; breeding experi- 
ments with, 30; var. mima 



compared with model, 148; 
patterns of in relation to 
models, 149; H. bolina, 25, 
117, I. 5, 6; H. misippus, 25, 
29, as model, 53; flight of, 
55; in mimicry ring, 66, 116; 
eaten by Brown Shrike, 117; 
alcippoides form, IX. h; inaria 
form, IX. i; typical form, 
IV. 7, 8, IX. g 

Ideopsis daos, HI. 4 
Initial variation, difficulty of, 63 
Insect enemies of butterflies, 105 
Intermediates, between different 

forms of Pseudacraea eurytus, 

128; in relation to mimicry, 

129, 140 
Ithomiinae, characteristics of, 10; 

as models for S. American 

butterflies, 38 
Ituna, 39 ; /. ilione, 40, XIV. 4 ; 

/. phenarete, XII. 3 

Jacobsen, experiments with Pa- 
pilio memnon, 89 
Jordan, 40 note 
Junonia, 111 

Lanius cristatus, 117 

Limeniiis albomaculata, 53; L, 

archippus, 49, 59, XVI. 6 ; 

L. arthemis, 47, 49, XVI. 4; 

L. astyanax, 47, XVI. 5 ; L. 

floridensis { = eros), 49, XVI. 7; 

L. proserpina, 47 
Lizards, as enemies of butterflies, 

107 
Local varieties, in connection 

with mimicrjs 132 
Lycaenidae, as mimics in Africa, 35 
Lycorea, 145 

McAtee, on feeding experiments 
with birds, 118 

Mammals, as enemies of butter- 
flies, 121 

Manders, on feeding experiments 
with lizards, 107 ; with birds, 
117 



186 



INDEX 



Mantids, as enemies of butterflies, 
105 

Marshall, on Miillerian mimicry, 
72 ; on feeding experiments 
vpith Mantids, 105 ; on birds as 
enemies of butterflies, 107 ; on 
feeding experiments with S. 
African birds, 117; with mon- 
keys, 121 ; on birds attacking 
Pierids, 150 

Mechanitis egaensis, XV. 9; M. 
elisa, XV. 6; M. lysimnia, 151, 
XV. 8 ; M. methona, XV. 10 ; 
M. saturata, as model for 
Dismorphia praxinoe, 57, 62; 
as member of mimicry ring, 
134, XV. 7 

Melanic sports in moths, 101 

Melinaea, 135 

Melinda formosa, App. II 

Melittophagus swinhoei, 110 

Merops viridis. 111 

MerrifieldjOn seasonal dimorphism, 
130 

Methona confusa, XII. 1, XIV. 1 

Migratory birds, suggested in- 
fluence on mimicry of, 53 

Mimacraea, 35 

Mimetic resemblance, as induced 
through gradual slight changes, 
64 

Mimic, occupying same station as 
model, 51; occupying station 
apart from model, 53 ; scarcer 
than model, 56 ; pattern of in 
relation to allies, 57 

Mimicry, Wallace's conditions of, 
50; Batesian, 9; Miillerian, 14 

Mimicry rings, 65 ; in S. American 
butterflies, 134; and natural 
selection, 136 

Mimicry theory, difficiolties of, 139 

Monkeys, as enemies of butterflies, 
121 

Moths, mimicry in, 27, 36 

Moulton, on S. American mimicry 
rings, 134 

Miiller, 14, 72 

Miillerian mimicry, 53, 57, 66; 
difiiculties of, 72 



Mutation, see Sports 
Mylothris, 36 

Natural selection and mimicry, 
10-12, 61, 92, 152 

Neal, on monkeys as enemies of 
butterflies, 123 

Nepheronia { = Pareronia) hippia, 
116 

Neptis imitans, 24; N. nemetes, 
54; N. kamarupa, 121 

North American butterflies, mimi- 
cry among, 45 

Norton, on rapidity of changes 
in mixed populations through 
natural selection, 94, App. I 

Oriental butterflies, mimicry 
among, 23 

Overlapping in patterns of dif- 
ferent groups of butterflies, 
144 

Papilio aristolochiae, as model for 
female of P. polytes, 13, 26, 
52, 77; range of, 79; likeness 
to P. polytes, 80 ; character- 
istics of, 81; flight of, 82; 
eaten by lizards, 108; rejected 
by certain birds, 115, 116; 
disliked by Tree-shrew, 121, 
V. 5, 5a; P. agestor, 24, 51, 
n. 3 ; P. asterius, 46 ; P. 
backus, App. II ; P. bootes, 27, 
III. 6 ; P. brasidas, 29, VI. 4 ; 
P. chamissonia, 44, XIII. 2; 
P. clytia, 23, 25, 55, I. 7, 8 ; 
P. coon, 26, 89 ; P. cynorta, 35, 
36, VII. 10; P. dardanus, in- 
vestigated by Trimen, 14; 
mimicry in, 30; breeding ex- 
periments with, 90; poly- 
morphic forms of in relation to 
models, 149 note; var. hum- 
bloti, 32 ; var. meriones, 32 ; 
$ cenea, 31, VIII. 4 ; ? dionysus, 
31, 33; 2 hippocoon, 31, 
VIII. 3; $ niavioides, 32, 33; 
$ planemoides, 31 ; ? ruspina, 
33; ? trimeni, 31, 32, 33; 



INDEX 



187 



$ trophoniu^, 31, 122, VIII. 
2 ; P. delesserti, App. II ; 
P. demoleus. 111, 121; P. 
echerioides, App. II ; P. eri- 
thonius, 110; P. euterpinus, 
42, 43 ; P. glaticus, 45 ; var. 
turnus, 46 ; P. hahneli, 39 ; 
P. hector, model for female of 
P. poli/tes, 13, 52, 78; range 
of, 79; characteristics of, 81 
flight of, 82 ; eaten bv lizards, 
108; eaten by birds, 110, 117; 
V. 6, 6a ; P. hippason, App. II ; 
P. laglaizei, 27, 124, III. 2; 
P. leonidas, 29, VI. 3 ; P. 
lysithous, polymorphism in, 44 ; 
$ lysithous, XIII 4; $ rurik, 
Xni. 5 ; $ pomponius, XIII. 6 ; 
P. macareus, 23, 111 ; P. mem- 
non, 26, 89 ; P. rnendax, 24, 
51, II. 9; P. nephalion, 44, 
Xm. 1 ; p. os2/ns, XI. 8.- 9 ; 
P. paradoxus, 25; P. joaw- 
sanias, 43, XI. 2 ; P. perrhebus, 
44, xm. 3 ; P. philenor, as 
model, 45; taken by lizard, 
108 ; XVI. 1 ; P. polytes, poly- 
morpliism in females of, 13, 
75 ; mimic of Pharmacophagus 
Papilio, 26 ; habits of, 52, 124 ; 
often more abundant than 
models, 56 ; description of, 
76-78; relative abundance of 
models in Cejdon, 79 ; breeding 
experiments with, 84; equi- 
libriiim among females of in 
Ceylon, 96 ; relative abund- 
ance of three forms of female 
of in Ceylon, 97 ; historical 
notes on abundance of forms 
of female in Ceylon, 98 ; origin 
of forms of female in, 125, 141 ; 
relation of polymorphic forms 
to models in, 149 note ; preyed 
on by Wood-Swallow, 112; 
feeding experiments with, 116; 
V. 1-4, 1 a-4 a ; P. polyxenus, 
27; P. rex, App. II; P. rid- 
leyanus, 34, 36, VI. 6; P. 
sarpedon, 110; P. troilus, 45, 



XVI. 2; P. xenocles, 23, 111, 
I. 4; P. zagreus, 43, X. 8 

Papilionidae, as mimics of Orien- 
tal models, 23-25 ; of African 
models, 29, 30, 35; of S. 
American models, 43 ; of N. 
American models, 45 

Parallel patterns, in different 
butterfly groups, 144 

Pareronia, 145, 149; P. ceylanica, 
23, 59, 116 note, I. 1, 2 

Pattern and physiological pro- 
perties, possible connection be- 
tween, 137 

Patterns, overlapping series of in 
different groups of butterflies, 
145 

Pedaliodes, 135 

Pereute charops, 42, XI. 6, 7 

Pericopis, 39 

Perrhybris, as mimics of Itho- 
miines, coloration of male in 
P. malenka, 62 ; as members 
of mimicry rings, 134, 135; 
P. demophile, 151; P. lorena, 
151; P. malenka, X. 4, 5, 6 

Pharmacophagus Swallow-tails, 
characteristics of, 22, App. II ; 
as models for Oriental butter- 
flies, 25 ; absence of in Africa, 
35 ; as models in S. America, 
43 ; as models in N. America, 45 

Phrissura, 36 

Phyciodes, 38, 54 

Physiological properties, possible 
connection of with pattern, 1 37 

Pieridae, as models for Oriental 
butterflies, 28 ; mimicry in 
African, 36 ; mimicry in S. 
American, 43; frequency of 
bird attacks on, 150 

Planema epaea, 35, VII. 5 ; P. 
macarista, sexual difference in, 
34, VII. 1,2; mimicked by 
Elytnnias phegea, 35 ; hy Pseud- 
acraea eurytus, 126; P. poggei, 
as model for planemoides fe- 
male of Papilio dardanus, 31; 
P. paragea, 126, VII. 4; P. 
iellus, 126, Vn. 3 



188 



INDEX 



Poison - eaters, see Pharmaeo- 
phagus Swallow-tails 

Polymorphism, in females of 
mimicking species, 13; among 
females of P. dardanus, 30; 
among females of P. polytes, 75 

Popvilation, conditions of equi- 
librium in mixed, 93 

Ponlton, 17 ; on N. American 
mimetic butterflies, 45 ; on the 
"Transparency group," 41 ; on 
mimicry through agency of 
migratory birds, 53 ; on Hypo- 
limnas misippus, 66 note ; on 
the relation between mimetic 
forms of P. polytes, 90 ; on 
predaceous insects, 105; on 
relative proportion of different 
forms of Pseudacraea eurytus, 
127 ; on local variation in 
D. chrysippus, 132 

Precis, 111, 122, 131; P. octavia, 
seasonal dimorphism in, 131, 

VI. 11, 12 

Prioneris, 110; P. sita, 28 
Pritchett, feeding experiments 

with lizards, 108 
Protective resemblance, 8 
Proiogonius, as mimics of Itho- 
miines, 38 ; as members of 
mimicry rings, 134, 135, 138; 
P. tithoreides, X. 9 
Pseudacraea, 59, 144; P. hois- 
duvali, 34, VI. 5 ; P. eurytus, 
relative proportion of different 
forms in, 127; polymorpliism 
of in relation to model, 149 
note; var. hobleyi as mimic of 
Planema macarista, 35, 127, 

VII. 6, 7 ; var. terra, as mimic 
of Planema tellus, 126, VII. 8; 
var. obscura as miinic of Pla- 
nema paragea, 126 



Ray, on adaptation, 4, 6 
Rodents, bearing on mimicry of 
recent genetic work with, 147 

Satyrinae, transparency in S. 

American, 42 
Sceleporus floridanus, 108 
Schaus, on birds as enemies of 

butterflies, 112 
Seasonal dimorphism, 130 
Seitz, 44, 52, 58 
Shelford, 56 note 
S. American butterflies, mimicry 

among, 38 
Sports, as foundation of mimetic 

resemblances, 70, 91, 143 
Sweet-peas, experiments on, 91 
Swynnerton, on contents of 

stomachs of birds, 114 

Telipna sanguinea, oQ 

Terias hrigitta, 35; T. hecabe, 110 

Thyridia, 40, XIV. 3 

Tithorea pseudonyma, X. 10 

"Transparency group," in S. 

America, 39 
Trimen, on mimicry in African 

butterflies, 13 
Tupaia ferruginea, 121 

Variation, difficulty of initial, 
63 

Wade, on relative abundance of 
the three forms of P. polytes in 
Ceylon, 99 

Wallace, on mimicry in Oriental 
butterflies, 12; on the con- 
ditions of mimicry, 50 ; on the 
females of P. polytes, 76 ; on 
initial variation, 64 

Warning colours, 10, 11 

Weismann, 1, 2 



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