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  III. 
  A 
  Migration 
  of 
  Yellow 
  Butterflies 
  (Catopsilia 
  statira) 
  

  

  in 
  Trinidad. 
  By 
  C. 
  B. 
  Williams, 
  M.A., 
  F.E.S. 
  

  

  [Read 
  March 
  5th, 
  1919.] 
  

  

  Plates 
  VI-X. 
  

  

  Introduction. 
  

  

  In 
  a 
  recent 
  number 
  of 
  the 
  Transactions 
  of 
  the 
  Entomolo- 
  

   gical 
  Society 
  (1917, 
  p. 
  154) 
  I 
  described 
  several 
  migrations 
  

   of 
  yellow 
  butterflies 
  in 
  British 
  Guiana, 
  most 
  of 
  the 
  records 
  

   relating 
  to 
  Callidryas 
  euhule. 
  In 
  October 
  of 
  this 
  year 
  I 
  

   have 
  been 
  again 
  fortunate 
  enough 
  to 
  witness 
  a 
  migration 
  

   of 
  butterflies 
  of 
  a 
  different 
  species, 
  this 
  time 
  in 
  the 
  Island 
  

   of 
  Trinidad, 
  and 
  on 
  a 
  scale 
  larger 
  than 
  anything 
  I 
  had 
  

   previously 
  seen. 
  The 
  migration 
  lasted 
  more 
  or 
  less 
  con- 
  

   tinually 
  for 
  nearly 
  three 
  weeks, 
  and 
  many 
  milhons 
  of 
  

   butterflies 
  must 
  have 
  passed 
  over 
  the 
  western 
  half 
  of 
  the 
  

   Island, 
  to 
  which 
  district 
  most 
  of 
  my 
  records 
  refer. 
  With 
  

   the 
  kind 
  assistance 
  of 
  a 
  number 
  of 
  friends 
  and 
  corre- 
  

   spondents 
  I 
  was 
  able 
  to 
  collect 
  over 
  two 
  hundred 
  separate 
  

   records 
  of 
  the 
  one 
  migration, 
  and 
  the 
  results 
  of 
  these 
  are 
  

   given 
  below. 
  

  

  Even 
  with 
  this 
  large 
  number 
  of 
  records, 
  no 
  claim 
  can 
  

   be 
  made 
  to 
  completeness, 
  and 
  data 
  are 
  sadly 
  lacking 
  for 
  

   the 
  eastern 
  half 
  of 
  the 
  Island, 
  which 
  is 
  thinly 
  populated. 
  

  

  Description 
  of 
  Locality. 
  

  

  Trinidad 
  is 
  an 
  Island 
  situated 
  just 
  north 
  of 
  the 
  mouth 
  of 
  

   the 
  Orinoco 
  River, 
  and 
  is 
  about 
  fifty 
  miles 
  in 
  a 
  north 
  to 
  

   south 
  direction, 
  and 
  about 
  seventy 
  miles 
  in 
  extreme 
  width. 
  

   At 
  both 
  the 
  north-western 
  and 
  south-western 
  corners 
  a 
  

   long 
  promontory 
  runs 
  out 
  towards 
  the 
  mainland 
  of 
  Vene- 
  

   zuela. 
  The 
  north-western 
  corner 
  is 
  about 
  fifteen 
  miles 
  

   from 
  Venezuela, 
  but 
  the 
  gap 
  is 
  partly 
  bridged 
  by 
  a 
  series 
  

   of 
  islands, 
  and 
  the 
  greatest 
  open 
  sea 
  space 
  is 
  about 
  eight 
  

   miles. 
  At 
  the 
  south-western 
  corner 
  the 
  distance 
  to 
  the 
  

   mainland 
  is 
  only 
  about 
  seven 
  miles. 
  

  

  Three 
  ranges 
  of 
  hills 
  run 
  from 
  east 
  to 
  west 
  across 
  the 
  

   Island, 
  that 
  along 
  the 
  northern 
  coast 
  rising 
  in 
  places 
  to 
  

   over 
  three 
  thousand 
  feet 
  above 
  sea-level; 
  the 
  central 
  

   and 
  southern 
  ranges, 
  however, 
  are 
  much 
  lower, 
  seldom 
  

  

  trans, 
  ent. 
  soc. 
  lond. 
  1919. 
  — 
  parts 
  i, 
  n. 
  (jtjly) 
  

  

  