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  separation 
  of 
  islands 
  from 
  the 
  mainland, 
  this 
  intercrossing 
  is 
  

   stopped, 
  and 
  the 
  usual 
  result 
  would 
  be 
  that 
  two 
  closely 
  allied 
  races 
  

   are 
  formed. 
  Possibly 
  each 
  of 
  these 
  pairs 
  of 
  forms 
  under 
  altered 
  

   conditions 
  goes 
  on 
  varying, 
  and 
  segregate 
  in 
  course 
  of 
  time 
  into 
  two 
  

   species. 
  The 
  amount 
  of 
  divergence 
  of 
  these 
  two 
  races 
  or 
  two 
  allied 
  

   species 
  becomes 
  a 
  measure 
  of 
  the 
  length 
  of 
  time 
  which 
  has 
  elapsed 
  

   since 
  the 
  more 
  or 
  less 
  permanent 
  separation 
  of 
  the 
  two 
  areas. 
  

  

  The 
  distribution 
  of 
  insects 
  is 
  determined 
  largely 
  by 
  climatic 
  and 
  

   general 
  physiographical 
  conditions, 
  as 
  well 
  as 
  also 
  to 
  a 
  great 
  extent 
  

   by 
  the 
  nature 
  of 
  the 
  food 
  supply, 
  many 
  forms 
  as 
  we 
  all 
  know 
  being 
  

   dependent 
  for 
  their 
  sustenance 
  in 
  one 
  stage 
  or 
  another 
  upon 
  the 
  

   development 
  of 
  a 
  particular 
  vegetable 
  product 
  just 
  at 
  a 
  particular 
  

   period 
  of 
  its 
  existence. 
  Indeed, 
  localisation 
  or 
  restriction 
  of 
  its 
  

   area 
  of 
  distribution 
  of 
  a 
  species 
  appears 
  to 
  be 
  more 
  frequently 
  

   brought 
  about 
  as 
  the 
  result 
  of 
  changes 
  in 
  the 
  vegetation, 
  than 
  by 
  

   the 
  interposition 
  of 
  physical 
  barriers, 
  which 
  by 
  their 
  power 
  of 
  flight 
  

   insects 
  can 
  in 
  a 
  great 
  measure 
  overcome. 
  The 
  effect 
  of 
  climate 
  is, 
  

   however, 
  well-marked, 
  as 
  is 
  seen 
  in 
  the 
  general 
  restriction 
  of 
  

   numerous 
  forms 
  to 
  particular 
  climatic 
  zones. 
  A 
  broad 
  horizontal 
  

   or 
  latitudinal 
  distribution 
  characterises 
  the 
  insect 
  fauna 
  of 
  the 
  North 
  

   temperate 
  zone. 
  A 
  large 
  proportion 
  of 
  European 
  species, 
  for 
  

   example, 
  are 
  spread 
  over 
  the 
  far 
  interior 
  of 
  the 
  Asiatic 
  continent, 
  

   and 
  some 
  reappear 
  in 
  America. 
  Pryer 
  tells 
  us, 
  in 
  1885, 
  that 
  not 
  

   less 
  than 
  128 
  species 
  of 
  Macro-lepidoptera 
  are 
  common 
  to 
  both 
  

   Japan 
  and 
  Great 
  Britain, 
  about 
  16% 
  of 
  the 
  entire 
  British 
  fauna. 
  

  

  The 
  Japanese 
  Islands 
  lie 
  in 
  the 
  Palfearctic 
  Region, 
  and 
  before 
  

   discussing 
  the 
  various 
  species 
  it 
  would 
  be 
  as 
  well 
  to 
  know 
  what 
  this 
  

   area 
  is 
  generally 
  accepted 
  as 
  comprising. 
  I 
  cannot 
  do 
  better 
  than 
  

   quote 
  Wallace's 
  words; 
  — 
  " 
  This 
  very 
  extensive 
  region 
  comprises 
  all 
  

   temperate 
  Europe 
  and 
  Asia, 
  from 
  Iceland 
  to 
  Behring's 
  Straits, 
  and 
  

   from 
  the 
  Azores 
  to 
  Japan. 
  Its 
  southern 
  boundary 
  is 
  somewhat 
  

   indefinite, 
  but 
  it 
  seems 
  advisable 
  to 
  comprise 
  in 
  it 
  all 
  the 
  extra- 
  

   tropical 
  part 
  of 
  the 
  Sahara 
  and 
  Arabia, 
  and 
  all 
  Persia, 
  Cabul, 
  and 
  

   Beloochistan 
  to 
  the 
  Indus. 
  It 
  comes 
  down 
  to 
  a 
  little 
  below 
  the 
  

   upper 
  limit 
  of 
  forests 
  in 
  the 
  Himalayas, 
  and 
  includes 
  the 
  larger 
  

   northern 
  half 
  of 
  China, 
  not 
  quite 
  so 
  far 
  down 
  the 
  coast 
  as 
  Amoy," 
  

   This 
  enormous 
  area 
  more 
  or 
  less 
  naturally 
  falls 
  into 
  subdivisions. 
  

   They 
  are 
  the 
  European, 
  the 
  Mediterranean, 
  the 
  Siberian, 
  and 
  the 
  

   Manchurian 
  sub-regions. 
  Japan 
  and 
  N. 
  China, 
  with 
  the 
  lower 
  

   Amoor 
  and 
  a 
  narrow 
  strip 
  along 
  the 
  Himalayas, 
  just 
  below 
  the 
  

   uppar 
  limit 
  of 
  trees, 
  comprises 
  the 
  Manchurian 
  sub-region. 
  Japan 
  

   then 
  forms 
  the 
  insular 
  portion 
  of 
  this 
  sub-region, 
  just 
  as 
  the 
  British 
  

   Isles 
  form 
  the 
  insular 
  portion 
  of 
  the 
  European 
  sub-region. 
  

  

  Papilionid^. 
  

  

  Pajiilio 
  niachaon. 
  The 
  whole 
  Pal. 
  Reg. 
  

   hijjipocrates. 
  Jap. 
  race. 
  

  

  Iii/ppocratiiles, 
  g.v. 
  * 
  hi/pjincrateii, 
  g.a. 
  

   septentrionalis. 
  S. 
  Jap. 
  

  

  