﻿Dr. 
  H, 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  37 
  

  

  " 
  The 
  value 
  of 
  such 
  numerous 
  observations 
  and 
  laborious 
  

   experiments 
  is 
  discounted 
  by 
  the 
  fact 
  that 
  they 
  have, 
  

   almost 
  without 
  exception, 
  been 
  undertaken 
  without 
  know- 
  

   ledge 
  of 
  colour 
  physiology. 
  Perusal 
  of 
  the 
  extensive 
  

   hterature 
  bearing 
  on 
  the 
  subject 
  has 
  not 
  disclosed 
  to 
  me 
  

   a 
  single 
  fact 
  which 
  makes 
  even 
  probable, 
  from 
  the 
  point 
  

   of 
  view 
  of 
  scientific 
  chromatology, 
  the 
  existence 
  of 
  a 
  

   colour 
  sense 
  in 
  bees. 
  In 
  my 
  own 
  experiments 
  the 
  bees, 
  

   hke 
  all 
  other 
  invertebrates 
  investigated, 
  behaved 
  as 
  they 
  

   must 
  do 
  if 
  their 
  visual 
  power 
  were 
  the 
  same 
  as, 
  or 
  similar 
  

   to, 
  that 
  of 
  a 
  totally 
  colour-blind 
  man. 
  In 
  all 
  the 
  results 
  

   hitherto 
  obtained 
  in 
  this 
  direction 
  by 
  zoologists 
  and 
  

   botanists, 
  there 
  is 
  nothing 
  to 
  contradict 
  this." 
  

  

  As 
  to 
  whether 
  the 
  experiments 
  of 
  others, 
  which 
  Hess 
  so 
  

   ponderously 
  dismisses 
  as 
  valueless, 
  are 
  really 
  so 
  devoid 
  of 
  

   merit 
  as 
  he 
  maintains, 
  I 
  will 
  leave 
  others 
  to 
  form 
  their 
  own 
  

   judgment. 
  Let 
  us 
  suppose 
  for 
  the 
  sake 
  of 
  argument 
  that 
  

   all 
  the 
  accumulated 
  work 
  of 
  Avebury, 
  Forel, 
  Plateau, 
  and 
  

   others 
  has 
  failed 
  to 
  prove 
  that 
  insects 
  distinguish 
  colours. 
  

   To 
  what 
  extent 
  does 
  the 
  work 
  of 
  this 
  expert 
  in 
  scientific 
  

   chromatology 
  prove 
  that 
  insects 
  are 
  colour-bUnd 
  ? 
  

  

  He 
  takes 
  certain 
  insects 
  having 
  a 
  marked 
  positive 
  photo- 
  

   tropism, 
  and 
  having 
  confined 
  them 
  in 
  a 
  cage 
  makes 
  the 
  

   surprising 
  discovery 
  that 
  they 
  tend 
  on 
  the 
  whole 
  to 
  make 
  

   their 
  way 
  towards 
  the 
  light. 
  Caterpillars 
  and 
  mosquito 
  

   larvae 
  we 
  should 
  hardly 
  credit 
  with 
  a 
  high 
  degree 
  of 
  colour 
  

   sense 
  in 
  any 
  case. 
  As 
  to 
  the 
  bees, 
  they 
  showed 
  a 
  tendency 
  

   to 
  regard 
  a 
  dark 
  blue 
  as 
  more 
  luminous 
  than 
  a 
  bright 
  red, 
  

   and 
  the 
  peacock 
  butterflies 
  showed 
  the 
  same 
  preference. 
  

   At 
  the 
  most 
  this 
  only 
  suggests 
  a 
  " 
  short 
  vision 
  " 
  at 
  the 
  red 
  

   end 
  of 
  the 
  spectrum. 
  Avebury 
  has 
  shown 
  that 
  ants 
  at 
  

   least 
  are 
  sensitive 
  to 
  the 
  ultra-violet 
  rays 
  which 
  are 
  invisible 
  

   to 
  us. 
  Why 
  not 
  bees 
  also 
  and 
  even 
  butterflies 
  ? 
  Avebury 
  

   submitted 
  negatively 
  phototropic 
  ants 
  to 
  light 
  from 
  two 
  

   screens 
  of 
  a 
  colour 
  which 
  appeared 
  the 
  same 
  to 
  the 
  human 
  

   eye, 
  but 
  one 
  of 
  the 
  screens 
  was 
  made 
  opaque 
  to 
  ultra- 
  

   violet 
  rays. 
  The 
  ants 
  chose 
  the 
  latter 
  colour 
  to 
  hide 
  under, 
  

   as 
  it 
  evidently 
  appeared 
  to 
  them 
  the 
  darker. 
  

  

  Hess 
  considers 
  that 
  his 
  insects 
  behaved 
  exactly 
  as 
  a 
  

   totally 
  colour-bhnd 
  person 
  would 
  have 
  done. 
  Now 
  totally 
  

   colour-bhnd 
  persons 
  are 
  extremely 
  rare, 
  and 
  their 
  behaviour 
  

   under 
  given 
  circumstances 
  is 
  not 
  exhaustively 
  tabulated. 
  

   But 
  even 
  accepting 
  the 
  very 
  unsatisfactory 
  anthropo- 
  

  

  