d'Orville;  see  "  Zoological  Record,"  1869,  p.  349,


INSECTS.  371

naoious;  and  some  few  are  furaislied  with  special  weapons
for  fighting  with  their  rivals.  But  the  law  of  battle  does
not  prevail  nearly  so  widely  with  insects  as  with  the  higher
animals.  Hence  it  probably  arises  that  it  is  in  only  a
few  cases  that  the  males  have  been  rendered  larger  and
stronger  than  the  females.  On  the  contrary,  they  are
usually  smaller,  so  that  they  may  be  developed  within  a
shorter  time,  to  be  ready  in  large  numbers  for  the  emerg-
ence of  the  females^

CJn  two  families  of  the  Homoptera  and  in  three  of  the
Orthoptera,  the  males  alone  possess  sound-producing  organs
in  an  efficient  state.  These  are  used  incessantly  during  the
breeding-season,  not  only  for  calling  the  females,  but  ap-
parently for  charming  or  exciting  them  in  rivalry  with
other  males.  Xo  one  who  admits  the  agency  of  selection
of  any  kind,  will,  after  reading  the  above  discussion,  dis-
pute that  these  musical  instruments  have  been  acquired
through  sexual  selection  J  In  four  other  orders  the  mem-
bers of  one  sex,  or  more  commonly  of  both  sexes,  are  pro-
vided with  organs  for  producing  various  sounds,  which  ap-
parently serve  merely  as  call-notes.  When  both  sexes  are
thus  provided  the  individuals  which  were  able  to  make  the
loudest  or  most  continuous  noise  would  gain  partners  before
those  which  were  less  noisy,  so  that  their  organs  have  proba-
bly been  gained  through  sexual  selection.  It  is  instructive
to  reflect  on  the  wonderful  diversity  of  the  means  for  pro-
ducing sound,  possessed  by  the  males  alone,  or  by  both
sexes  in  no  less  than  six  orders.  We  thus  learn  how  effectual
sexual  selection  has  been  in  leading  to  modifications  which
sometimes,  as  with  the  Homoptera,  relate  to  important
parts  of  the  organization.
