﻿the 
  markings 
  and 
  colouring 
  of 
  Leimlojptera. 
  165 
  

  

  ascertained 
  certainly 
  point 
  to 
  tlie 
  probability 
  of 
  some 
  

   general 
  connection 
  between 
  the 
  temperature 
  during 
  

   the 
  pupal 
  period 
  and 
  the 
  colouring 
  of 
  Lepidoptera. 
  

   As 
  regards 
  the 
  species 
  experimented 
  on 
  by 
  me, 
  how- 
  

   ever, 
  though 
  I 
  am 
  satisfied 
  that 
  temperature 
  is 
  the 
  

   chief 
  cause 
  of 
  the 
  general 
  changes 
  of 
  colour, 
  as 
  dis- 
  

   tinguished 
  from 
  individual 
  variations 
  produced, 
  there 
  

   are 
  certain 
  slighter 
  variations 
  of 
  a 
  general 
  character 
  

   which 
  rather 
  indicate 
  that 
  other 
  external 
  influences 
  also 
  

   operate; 
  and 
  these, 
  I 
  hope, 
  may 
  be 
  made 
  the 
  subject 
  of 
  

   further 
  investigation. 
  

  

  The 
  results 
  obtained 
  appear 
  also 
  to 
  indicate 
  that 
  pro- 
  

   bably 
  some 
  local 
  climatic 
  varieties, 
  and 
  even 
  seasonal 
  

   varieties, 
  may 
  be 
  found 
  to 
  be, 
  in 
  part 
  at 
  least, 
  tempera- 
  

   ture 
  forms 
  of 
  the 
  individual 
  ; 
  and, 
  looked 
  at 
  from 
  this 
  

   point 
  of 
  view, 
  they 
  appear 
  to 
  me 
  to 
  lend 
  some 
  support 
  

   to 
  Lord 
  Walsingham's 
  theory 
  as 
  to 
  the 
  advantages 
  

   derived 
  by 
  an 
  insect 
  in 
  a 
  cold 
  region 
  from 
  being 
  of 
  a 
  dark 
  

   colour, 
  for 
  they 
  show 
  that, 
  if 
  that 
  is 
  an 
  advantage, 
  it 
  is 
  

   one 
  that 
  can 
  be 
  acquired, 
  not 
  only 
  by 
  a 
  race 
  for 
  use 
  in 
  

   a 
  cold 
  locality, 
  but 
  by 
  individuals 
  for 
  use 
  in 
  a 
  cold 
  

   season. 
  I 
  think 
  it 
  quite 
  clear 
  that 
  if 
  a 
  cool 
  week 
  super- 
  

   vened 
  in 
  Southern 
  England 
  between 
  the 
  beginning 
  and 
  

   the 
  middle 
  of 
  July, 
  or 
  a 
  hot 
  week 
  in 
  the 
  middle 
  of 
  

   April, 
  at 
  either 
  of 
  which 
  times 
  many 
  of 
  the 
  pupae 
  of 
  

   illustraria 
  would 
  be 
  in 
  what 
  I 
  have 
  called 
  the 
  penultimate 
  

   pupal 
  stage, 
  most 
  of 
  these 
  insects 
  which 
  it 
  found 
  in 
  that 
  

   stage 
  would 
  have 
  their 
  colouring 
  affected. 
  It 
  would 
  

   appear 
  that 
  even 
  two 
  or 
  three 
  hot 
  days, 
  if 
  they 
  came 
  

   exactly 
  at 
  the 
  right 
  period, 
  would 
  be 
  enough 
  for 
  the 
  

   purpose; 
  and 
  I 
  need 
  hardly 
  observe 
  that 
  it 
  is 
  very 
  

   unlikely 
  that 
  these 
  are 
  the 
  only 
  species 
  that 
  would 
  be 
  so 
  

   affected. 
  

  

  There 
  is 
  another 
  general 
  suggestion 
  which 
  I 
  venture 
  

   to 
  make 
  in 
  concluding. 
  If 
  Prof. 
  Weismann's 
  theory 
  is 
  

   accepted, 
  that 
  the 
  existing 
  forms 
  of 
  most 
  European 
  and 
  

   some 
  North 
  American 
  Lepidoptera 
  have 
  come 
  to 
  us 
  

   from 
  a 
  glacial 
  period 
  or 
  climate, 
  and 
  that 
  icing 
  the 
  

   pupa 
  causes 
  the 
  insect 
  to 
  "throwback" 
  to 
  its 
  earlier 
  

   form, 
  then 
  experiments, 
  of 
  the 
  kind 
  tried, 
  on 
  the 
  pupse 
  

   might 
  assist 
  us 
  in 
  tracing 
  the 
  evolution 
  of 
  the 
  markings 
  

   on 
  the 
  wings 
  of 
  some 
  of 
  the 
  most 
  highly 
  developed 
  

   modern 
  forms. 
  

  

  