﻿42 
  BRITISH 
  LEPIDOPTERA. 
  

  

  that 
  is 
  to 
  say, 
  that 
  an 
  aberration 
  resulting 
  from 
  individual 
  constitutional 
  

   weakness, 
  or 
  other 
  temporary 
  cause, 
  is 
  not 
  to 
  be 
  developed 
  into 
  a 
  special 
  

   local 
  race, 
  nor 
  has 
  the 
  progeny 
  of 
  such 
  a 
  parent 
  reared 
  under 
  healthy 
  

   conditions 
  any 
  tendency 
  to 
  reproduce 
  the 
  form 
  of 
  the 
  individually 
  

   weak 
  parent. 
  

  

  Where, 
  however, 
  a 
  dimorphic, 
  trimorphic, 
  or 
  polymorphic 
  species 
  

   develops 
  its 
  various 
  forms 
  from 
  healthy 
  larvae 
  in 
  nature, 
  under 
  the 
  

   same 
  or 
  somewhat 
  similar 
  conditions, 
  it 
  affords 
  prima 
  facie 
  evidence 
  

   that 
  any 
  one 
  form 
  is 
  kept 
  from 
  becoming 
  predominant 
  because 
  the 
  

   others 
  are 
  equally 
  well 
  protected 
  and 
  enter 
  into 
  competition 
  with 
  it 
  on 
  

   equal 
  terms. 
  The 
  experiments 
  enumerated 
  tend 
  to 
  prove 
  that 
  this 
  is 
  

   the 
  case, 
  e.g., 
  in 
  the 
  case 
  of 
  Coremia 
  femtgata 
  (red-banded) 
  and 
  its 
  

   aberration 
  unidentaria 
  (black-banded), 
  the 
  two 
  forms 
  of 
  which 
  occur 
  

   together 
  in 
  most 
  parts 
  of 
  Britain, 
  it 
  is 
  possible 
  in 
  a 
  few 
  generations, 
  by 
  

   careful 
  selection 
  of 
  inbred 
  parents, 
  to 
  breed 
  purely 
  red- 
  or 
  black-banded 
  

   forms. 
  Similarly 
  the 
  experiments 
  with 
  Gonodontis 
  bidentata, 
  tend 
  to 
  

   prove 
  that 
  where 
  the 
  ab. 
  nigra 
  is 
  a 
  protected 
  form, 
  it 
  is 
  easy, 
  by 
  selec- 
  

   tion 
  of 
  black 
  parents 
  and 
  by 
  removing 
  the 
  ordinary 
  outside 
  competition 
  

   of 
  the 
  typical 
  form, 
  to 
  rear 
  artificially 
  a 
  race 
  of 
  almost 
  purely 
  black 
  

   individuals. 
  Almost 
  identical 
  with 
  this 
  are 
  the 
  cases 
  of 
  Lymantria 
  

   monacha 
  ab. 
  eremita, 
  Hemerophila 
  abruptaria 
  ab. 
  fuscata, 
  and 
  Amphida'xyz 
  

   betularia 
  ab. 
  doubledayaria, 
  of 
  which 
  careful 
  selection 
  and 
  the 
  removal 
  

   of 
  normal 
  outside 
  environmental 
  conditions 
  allow 
  one 
  to 
  rear 
  typical 
  

   or 
  melanic 
  races 
  at 
  will, 
  showing 
  that 
  very 
  little 
  variation 
  in 
  these 
  

   conditions 
  would 
  convert 
  these 
  melanic 
  formsfrom 
  mere 
  aberrations 
  into 
  

   local 
  races, 
  which 
  would 
  supplant 
  the 
  type 
  in 
  those 
  districts 
  where 
  the 
  

   conditions 
  were 
  favourable 
  to 
  their 
  development. 
  These 
  appear 
  to 
  

   us 
  to 
  be 
  much 
  more 
  nearly 
  of 
  the 
  character 
  of 
  natural 
  local 
  races 
  than 
  

   does 
  Sjnlosoma 
  lubricipeda 
  ab. 
  zatima, 
  which 
  appears 
  to 
  be 
  everywhere 
  

   a 
  rare 
  aberration 
  in 
  a 
  wild 
  state, 
  and 
  to 
  have 
  assumed 
  its 
  present 
  

   fixed 
  varietal 
  or 
  racial 
  characters 
  from 
  domestic 
  selection 
  spread 
  over 
  

   many 
  years, 
  in 
  some 
  cases, 
  perhaps 
  nearly 
  half-a-century. 
  The 
  racial 
  

   character 
  of 
  Boarmia 
  repandata 
  ab. 
  conversaria, 
  in 
  certain 
  districts, 
  is 
  

   almost 
  on 
  a 
  par 
  with 
  those 
  of 
  the 
  melanic 
  forms 
  of 
  the 
  species 
  already 
  

   noted, 
  viz., 
  that 
  it 
  is 
  a 
  form 
  able 
  to 
  hold 
  its 
  own 
  with 
  the 
  type 
  in 
  the 
  

   particular 
  areas 
  in 
  which 
  it 
  appears 
  and 
  is 
  possibly 
  due 
  to 
  comparatively 
  

   modern 
  changes 
  of 
  the 
  environment 
  in 
  the 
  areas 
  w 
  7 
  hich 
  it 
  affects. 
  One 
  

   of 
  the 
  most 
  remarkable 
  instances 
  of 
  racial 
  value, 
  in 
  what 
  would 
  other- 
  

   wise 
  have 
  been 
  deemed 
  a 
  purely 
  sporadic 
  and 
  incidental 
  sport, 
  is 
  that 
  

   of 
  Zonowma 
  annulata 
  ab. 
  obsoleta. 
  The 
  results 
  of 
  Eiding's 
  experiments 
  

   prove 
  the 
  racial 
  value 
  of 
  the 
  form, 
  but 
  our 
  ignorance 
  of 
  the 
  habits 
  of 
  the 
  

   insect 
  does' 
  not 
  enable 
  us 
  to 
  give 
  an 
  explanation 
  of 
  its 
  meaning. 
  We 
  

   may 
  surmise 
  fairly 
  that 
  Amphidasys 
  betularia, 
  Tephrosia 
  crepuscularia, 
  

   Gonodontis 
  bidentata, 
  Lymantria 
  monacha, 
  etc., 
  are 
  undergoing 
  racial 
  

   change 
  for 
  protective 
  purposes, 
  and 
  in 
  response 
  to 
  a 
  changing 
  environ- 
  

   ment, 
  that 
  possibly, 
  in 
  most 
  of 
  these 
  cases, 
  the 
  so-called 
  melanic 
  form 
  

   is 
  atavistic, 
  and 
  that 
  the 
  peculiar 
  colour 
  has 
  been 
  slowly 
  acquired 
  at 
  

   an 
  earlier 
  period 
  in 
  the 
  life-history 
  of 
  the 
  species, 
  so 
  that 
  it 
  has 
  

   always 
  had 
  potentialities 
  in 
  this 
  direction, 
  that 
  Boarmia 
  repandata 
  ab. 
  

   conversaria, 
  is 
  the 
  result 
  of 
  a 
  change 
  in 
  the 
  wooded 
  haunts 
  the 
  typical 
  

   form 
  loves, 
  and 
  is 
  also 
  most 
  probably 
  atavistic, 
  whilst 
  its 
  var. 
  sodoren- 
  

   sium, 
  has 
  been 
  produced 
  by 
  its 
  having 
  an 
  entirely 
  different 
  habit 
  (resting 
  

   on 
  rocks), 
  but, 
  as 
  we 
  have 
  just 
  noted, 
  we 
  are 
  unable 
  to 
  give 
  an 
  explanation 
  

  

  