﻿38 
  Dr. 
  H. 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  

  

  morphic 
  comparison, 
  let 
  us 
  see 
  what 
  these 
  " 
  colour-blind 
  " 
  

   insects 
  did. 
  

  

  To 
  the 
  instinct 
  of 
  a 
  positively 
  phototropic 
  creature, 
  

   light 
  and 
  freedom 
  are 
  probably 
  closely 
  associated. 
  The 
  

   imprisoned 
  bees 
  and 
  butterflies 
  presumably 
  responded 
  to 
  

   that 
  stimulus 
  which 
  guided 
  them 
  towards 
  what 
  in 
  their 
  

   experience, 
  or 
  nervous 
  reflexes, 
  or 
  whatever 
  conscious 
  or 
  

   unconscious 
  psychological 
  process 
  we 
  may 
  fancy, 
  indicated 
  

   escape. 
  I 
  imagine 
  that 
  a 
  human 
  being 
  bent 
  on 
  escaping 
  

   from 
  a 
  dark 
  cave 
  would 
  make 
  for 
  the 
  opening 
  whose 
  light 
  

   was 
  of 
  the 
  greatest 
  luminosity, 
  as 
  suggesting 
  the 
  shortest 
  

   route 
  to 
  the 
  outer 
  world. 
  Such 
  action 
  would 
  not 
  prove 
  

   him 
  to 
  be 
  totally 
  colour-bhnd. 
  Hess 
  is 
  at 
  some 
  pains 
  to 
  

   explain 
  that 
  the 
  existence 
  of 
  colours 
  is 
  no 
  proof 
  that 
  they 
  

   must 
  have 
  been 
  developed 
  in 
  order 
  to 
  be 
  seen, 
  and 
  calls 
  

   attention 
  to 
  the 
  colours 
  of 
  such 
  substances 
  as 
  egg 
  yolk, 
  

   blood, 
  chlorophyl, 
  and 
  the 
  green 
  bones 
  of 
  certain 
  fishes. 
  

   I 
  hardly 
  think 
  any 
  one 
  would 
  care 
  to 
  argue 
  very 
  long 
  over 
  

   so 
  obvious 
  and 
  well-known 
  a 
  point.* 
  Let 
  us 
  then 
  see 
  

   whether 
  there 
  is 
  any 
  evidence 
  that 
  butterflies 
  can 
  dis- 
  

   tinguish 
  colours, 
  or 
  alternatively 
  whether 
  it 
  can 
  be 
  shown 
  

   that 
  they 
  are 
  not 
  bhnd 
  to 
  those 
  portions 
  of 
  the 
  spectrum 
  

   which 
  would 
  probably 
  be 
  invisible 
  to 
  a 
  totally 
  colour-bhnd 
  

   eye. 
  

  

  The 
  only 
  serious 
  experiments 
  with 
  butterflies 
  which 
  I 
  

  

  have 
  been 
  able 
  to 
  find 
  are 
  those 
  of 
  Seitz, 
  recorded 
  in 
  a 
  paper 
  

  

  read 
  by 
  him 
  at 
  the 
  International 
  Congress 
  of 
  Entomology 
  

  

  at 
  Oxford 
  in 
  1912. 
  He 
  observed 
  that 
  at 
  El 
  Kantara 
  in 
  

  

  Algeria 
  the 
  top 
  of 
  a 
  certain 
  range 
  of 
  hills 
  was 
  frequented 
  

  

  by 
  a 
  yellow 
  black-margined 
  butterfly 
  {Anthocaris 
  charlonia), 
  

  

  and 
  was 
  a 
  meeting-place 
  for 
  the 
  males 
  who 
  came 
  there 
  to 
  

  

  mate. 
  He 
  made 
  coloured 
  paper 
  models 
  of 
  the 
  butterflies, 
  

  

  and 
  these 
  attracted 
  the 
  real 
  ones 
  to 
  such 
  an 
  extent 
  that 
  as 
  

  

  many 
  as 
  six 
  were 
  seen 
  at 
  one 
  time 
  trying 
  to 
  pair 
  with 
  the 
  

  

  paper 
  model. 
  They 
  did 
  not 
  appear 
  to 
  see 
  it 
  at 
  a 
  distance 
  

  

  of 
  more 
  than 
  eight 
  feet. 
  To 
  test 
  the 
  accuracy 
  of 
  their 
  

  

  vision 
  a 
  graduated 
  series 
  of 
  models 
  was 
  made 
  differing 
  in 
  

  

  size, 
  colour, 
  and 
  markings. 
  Exact 
  models 
  were 
  very 
  

  

  attractive, 
  whilst 
  those 
  which 
  were 
  of 
  the 
  right 
  colour 
  

  

  and 
  markings, 
  but 
  three 
  times 
  the 
  size, 
  attracted 
  the 
  real 
  

  

  males 
  only 
  for 
  an 
  instant. 
  Accurately 
  coloured 
  models 
  

  

  were 
  always 
  first 
  visited, 
  whilst 
  those 
  of 
  similar 
  but 
  not 
  of 
  

  

  exactly 
  matching 
  colours 
  were 
  only 
  noticed 
  after 
  the 
  correct 
  

  

  * 
  See 
  Poulton, 
  " 
  Colours 
  of 
  Animals," 
  1890, 
  pp. 
  12-14. 
  

  

  