



Produced by Chris Curnow, Keith Edkins and the Online
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Transcriber's note: The conventional male and female symbols are rendered
as [M] and [F] in this edition. In the discussion of _Papilio polytes_
the male symbol [M] must be distinguished carefully from the unbracketted
M denoting the male-like variety of females.

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  CAMBRIDGE UNIVERSITY PRESS
  C. F. CLAY, MANAGER
  LONDON: FETTER LANE, E.C.
  EDINBURGH: 100 PRINCES STREET

[Illustration]

  NEW YORK: G. P. PUTNAM'S SONS
  BOMBAY, CALCUTTA AND MADRAS: MACMILLAN AND CO.
  TOKYO: THE MARUZEN-KABUSHIKI-KAISHA



_All 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

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PREFACE

This 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 callings in life
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 life
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 little book serves to smooth the path of some
who would become acquainted 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.                                                 PAGE
     I. INTRODUCTORY                                       1
    II. MIMICRY--BATESIAN AND MUeLLERIAN                    8
   III. OLD-WORLD MIMICS                                  18
    IV. NEW-WORLD MIMICS                                  37
     V. SOME CRITICISMS                                   50
    VI. "MIMICRY RINGS"                                   61
   VII. THE CASE OF _Papilio polytes_                     75
  VIII. THE CASE OF _Papilio polytes_ (_cont._)           93
    IX. THE ENEMIES OF BUTTERFLIES                       104
     X. MIMICRY AND VARIATION                            125
    XI. CONCLUSION                                       139
        APPENDIX I                                       154
        APPENDIX II                                      157
        PLATES I-XVI AND DESCRIPTIONS                    160 ff
          I-V.  ORIENTAL MOTHS AND BUTTERFLIES.
         VI-IX. AFRICAN BUTTERFLIES.
        X-XIII. SOUTH AMERICAN BUTTERFLIES.
          XIV.  SCALES OF LEPIDOPTERA.
          XV.   CENTRAL AND SOUTH AMERICAN BUTTERFLIES.
          XVI.  NORTH AMERICAN BUTTERFLIES.
        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 wise, when the law says that a thing is
    black, first to inquire whether it does not happen to be white."--HENRI
    FABRE.

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{1}

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 favourable 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 {2} 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
constitute 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 {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 biologists to whom the terms
mutationist and Mendelian are frequently applied. 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
differentiates 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
{4} builds up the new variety bit by bit, on the other the appearance of
the new