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The Cambridge Manuals of Science and Literature




                               THE FLEA




                      CAMBRIDGE UNIVERSITY PRESS
                       London: FETTER LANE, E.C.
                          C. F. CLAY, MANAGER


[Illustration: LOGO]


                    Edinburgh: 100, PRINCES STREET
             London: H. K. LEWIS, 136, GOWER STREET, W.C.
            WILLIAM WESLEY & SON, 28, ESSEX STREET, STRAND
                       Berlin: A. ASHER AND CO.
                       Leipzig: F. A. BROCKHAUS
                     New York: G. P. PUTNAM’S SONS
             Bombay and Calcutta: MACMILLAN AND CO., LTD.


                         _All rights reserved_




[Illustration:
  _After a drawing by Dr Jordan_
Oriental rat-flea (_Xenopsylla cheopis_ Rothsch.). Male.]




[Illustration; DECORATED FRONT PAGE:

                               THE FLEA

                                  BY

                            HAROLD RUSSELL,
                        B.A., F.Z.S., M.B.O.U.


                        With nine illustrations


                              Cambridge:
                        at the University Press

                                 1913]




                               Cambridge


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


_With the exception of the coat of arms at the foot, the design on
the title page is a reproduction of one used by the earliest known
Cambridge printer, John Siberch, 1521_




PREFACE


THE aim of this book is to give in plain language some account of a
small, but noteworthy, group of insects. I have avoided, whenever I
could, using the technical terms of zoology. To avoid doing so entirely
is impossible in a book which describes insects in some detail. No
technical term has, I hope, been used without an explanation.

Over thirty years have elapsed since Taschenberg’s German book, _Die
Flöhe_, appeared. Our knowledge has made enormous strides since then.
More species of flea are now known from the British Islands alone
than were then known from the whole world. So far as I am aware, no
book, devoted to what is known about fleas, has ever been published in
English. The statements about these insects in the general text-books
of entomology are frequently antiquated and inaccurate. But there is
a fairly extensive literature on the _Siphonaptera_ scattered through
scientific periodicals mostly in English, German, Italian, Dutch and
Russian. I have given some references in the Bibliography.

The naturalists now living who have devoted any time to the special
study of fleas may almost be counted on one’s fingers. In England there
are Mr Charles Rothschild and Dr Jordan; in the Shetland Islands, the
Rev. James Waterston; in Germany, Taschenberg of Halle and Dampf of
Königsberg; in Russia, Wagner of Kieff; in Holland, Oudemans of Arnhem;
in Italy, Tiraboschi of Rome; in the United States, Carl Baker and a
few others. I have not mentioned medical men who have investigated
fleas in connection with plague.

There are small collections of fleas in the Natural History Museums at
South Kensington (London), Paris, Berlin, Königsberg, Vienna, Budapest,
S. Petersburg and Washington. Of private collections Mr Charles
Rothschild’s at Tring is by far the best in the world. It contains
something like a hundred thousand specimens and is most admirably kept.
I must express profound and sincere gratitude to Mr Rothschild for
having helped me in numberless ways and advised me in many difficulties.

It is well known that the mere mention of fleas is not only considered
a subject for merriment, but in some people produces, by subjective
suggestion, violent irritation of the skin. The scientific study
of fleas has, however, received a great impetus since it has been
ascertained that they are the active agents in spreading plague.
Rat-fleas are of various kinds, and not all fleas will bite man. A
knowledge of the different species has suddenly become useful. The
humble, but ridiculous, systematist with his glass tubes of alcohol for
collecting fleas, his microscopic distinctions, and Latin nomenclature
has become a benefactor of humanity. Some people seem to be practically
immune to the bites of fleas, but even to such persons their visits are
unwelcome. A famous Frenchwoman once declared: “_Quant à moi ce n’est
pas la morsure, c’est la promenade._”

                                                     H. R.

  LONDON,

  _September, 1913_.




CONTENTS


  CHAP.                                                     PAGE

         Preface                                               v

      I. Introductory                                          1

     II. The external structure of a flea                     21

    III. The mouth-parts and sense-organs                     38

     IV. The internal organs of a flea                        52

      V. The Human flea and other species                     62

     VI. The Chigoes and their allies                         74

    VII. Fleas and Plague                                     83

   VIII. Rat-fleas and Bat-fleas                              97


  Appendix A. Systematic view of the order _Siphonaptera_    108

      ”    B. A list of British fleas and their hosts        110

      ”    C. On collecting and preserving fleas             113

      ”    D. Bibliography                                   118

  Index                                                      122




LIST OF ILLUSTRATIONS


     Male Oriental rat-flea                    _frontispiece_

  FIGURE                                                     PAGE

  1. The larva of a flea                                       6

  2. Types of genal and thoracic combs of a flea              26

  3. The hind leg of a flea                                   30

  4. The mouth-parts of a flea                                43

  5. The antenna of a flea                                    47

  6. The alimentary canal of a flea                           53

  7. The head of a female dog-flea and a female cat-flea      71

  8. Pregnant female of _Dermatophilus cæcata_                81




CHAPTER I

INTRODUCTORY


FLEAS form a group of insects that have, until recently, been little
studied by zoologists. We call them insects because they are jointed
animals, or Arthropods, with three pairs of legs in the adult
condition. The reader will best understand the position which fleas
occupy in the general classification of animals by remembering that
the arthropods, or jointed animals, are one of a dozen subkingdoms, or
phyla, to which the various members of the great animal kingdom have
been assigned. There is good ground for believing that all the animals
included in each phylum trace their ancestry back to a common primitive
form which lived in more or less remote ages. Besides (1) _Insects_,
the arthropods, or jointed animals, include (2) _Crustaceans_, such as
crabs, lobsters, shrimps, wood-lice, water-fleas and barnacles; (3)
_Myriapods_, such as centipedes and millipedes; and (4) _Arachnids_,
such as spiders, scorpions, mites and ticks. To all these varied forms
of animal life fleas, and other insects, are therefore more or less
nearly related.

The animals belonging to this large and important collection, which
compose the arthropod phylum, have certain common characteristic
features. We find a body made up of a series of more or less completely
similar segments placed one behind the other. In this they resemble
certain worms which are far less highly organised. The body is
elongated, symmetrical on either side, and the mouth and anus are at
opposite ends. There is, however, an important advance on the segmented
worms. Each typical segment carries a pair of appendages which are very
different from the foot-stumps that are found on certain worms. These
appendages of arthropods are divisible into distinct limb-segments,
separated from one another by moveable joints, and acted upon by
special muscles.

The common ancestor of all the various arthropods which are found
living on the earth to-day, was probably composed of a series of
segments each very similar to the last and each bearing a pair of very
similar appendages. In the course of ages, these appendages have been
astoundingly modified in form and in function. So it happens that
we find in the arthropods of the present day pairs of antennæ, of
mandibles and other mouth-parts, of pincers, of legs, of swimming-feet
and of tail pieces which on close examination can all be traced back to
a common structure. The body-segments, also, have been strangely fused
together and modified. All that has been so far said applies equally to
fleas and to other insects.

It is of great interest, when one comes to make a minute study of
the form and external structure of a flea, to try and trace the
modifications