﻿40 
  Dr. 
  H. 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  

  

  colour 
  used 
  for 
  painting 
  lantern 
  slides. 
  With 
  this 
  I 
  painted 
  

   over 
  the 
  eyes 
  of 
  numerous 
  examples 
  of 
  urticae. 
  I 
  was 
  very 
  

   careful 
  by 
  microscopical 
  examination 
  to 
  see 
  that 
  this 
  was 
  

   thoroughly 
  done 
  and 
  that 
  no 
  pinhole 
  of 
  normal 
  hght 
  could 
  

   reach 
  the 
  eye. 
  All 
  the 
  butterflies 
  were 
  marked 
  so 
  that 
  

   they 
  could 
  be 
  easily 
  recognised 
  again. 
  That 
  the 
  insects 
  so 
  

   treated 
  were 
  certainly 
  not 
  totally 
  blind, 
  as 
  they 
  would 
  

   have 
  been 
  had 
  they 
  been 
  red-bhnd, 
  was 
  very 
  completely 
  

   shown 
  by 
  the 
  fact 
  that 
  they 
  immediately, 
  or 
  at 
  least 
  after 
  

   a 
  short 
  period 
  of 
  " 
  shock," 
  flew 
  to 
  the 
  window 
  of 
  the 
  room, 
  

   and 
  also 
  in 
  some 
  cases 
  ahghted 
  on 
  the 
  curtains, 
  the 
  latter 
  

   performance 
  necessitating 
  a 
  judgment 
  of 
  distance 
  little 
  

   if 
  anything 
  removed 
  from 
  the 
  normal. 
  All 
  my 
  butterflies 
  

   were 
  then 
  hberated, 
  and 
  both 
  on 
  that 
  and 
  succeeding 
  days 
  

   I 
  observed 
  them 
  flying 
  in 
  the 
  garden 
  and 
  alighting 
  on 
  

   flowers. 
  Unfortunately 
  I 
  had 
  not 
  a 
  sufficiently 
  large 
  

   number 
  to 
  judge 
  fairly 
  the 
  extent 
  to 
  which 
  their 
  selection 
  

   of 
  flowers 
  was 
  modified 
  by 
  their 
  " 
  red 
  spectacles." 
  One 
  

   I 
  caught 
  two 
  days 
  later 
  was 
  found 
  on 
  examination 
  to 
  have 
  

   its 
  coating 
  of 
  red 
  quite 
  unimpaired. 
  The 
  behaviour 
  of 
  

   these 
  insects 
  was 
  in 
  marked 
  contrast 
  to 
  that 
  of 
  one 
  whose 
  

   eyes 
  I 
  covered 
  with 
  black 
  dye. 
  This 
  totally 
  bhnded 
  

   example, 
  though 
  repeatedly 
  thrown 
  into 
  the 
  air, 
  merely 
  

   fell 
  to 
  the 
  ground 
  and 
  remained 
  motionless, 
  except 
  for 
  a 
  

   certain 
  amount 
  of 
  aimless 
  creeping 
  about. 
  It 
  would 
  

   appear 
  that 
  Ganoris 
  brassicae, 
  Pieris 
  napi, 
  and 
  P. 
  ra/pae 
  

   are 
  distinctly 
  shorter 
  in 
  the 
  red 
  than 
  V. 
  urticae, 
  for 
  similar 
  

   treatment 
  had 
  a 
  different 
  effect. 
  They 
  still 
  flew 
  to 
  a 
  window, 
  

   showing 
  that 
  a 
  degree 
  of 
  hght 
  perception 
  remained, 
  but 
  on 
  

   being 
  liberated 
  flew 
  aimlessly, 
  and 
  with 
  marked 
  lack 
  of 
  

   control. 
  

  

  It 
  may 
  be 
  suggested 
  that 
  the 
  examples 
  of 
  urticae 
  which 
  

   found 
  the 
  flowers 
  in 
  spite 
  of 
  their 
  eyes 
  being 
  red, 
  did 
  so 
  by 
  

   the 
  sense 
  of 
  smefl. 
  That 
  this 
  sense 
  has 
  httle 
  to 
  do 
  with 
  

   their 
  feeding 
  habits 
  I 
  was 
  easily 
  able 
  to 
  show 
  by 
  coating 
  

   the 
  antennae 
  of 
  several 
  specimens 
  with 
  shellac 
  varnish. 
  

   These 
  continued 
  to 
  find 
  the 
  flowers 
  with 
  the 
  same 
  facility 
  

   as 
  before. 
  In 
  my 
  view 
  a 
  strong 
  scent 
  may, 
  and 
  doubtless 
  

   often 
  does, 
  help 
  to 
  attract 
  butterflies, 
  as, 
  for 
  instance, 
  in 
  

   the 
  case 
  of 
  the 
  well-known 
  Buddleia 
  flowers. 
  I 
  believe, 
  

   however, 
  that 
  having 
  once 
  discovered 
  a 
  source 
  of 
  food, 
  

   butterflies 
  will 
  return 
  to 
  it 
  day 
  after 
  day, 
  guided 
  in 
  great 
  

   measure 
  by 
  the 
  same 
  remarkable 
  locality 
  sense, 
  which 
  in 
  a 
  

   much 
  higher 
  development 
  has 
  been 
  so 
  frequently 
  observed 
  

  

  