﻿82 
  Mr. 
  C. 
  B. 
  Williams 
  on 
  

  

  specimen 
  to 
  become 
  worn, 
  this 
  must 
  be 
  taken 
  as 
  a 
  possible 
  

   suggestion 
  and 
  not 
  as 
  a 
  proved 
  occurrence. 
  

  

  At 
  the 
  other 
  end 
  of 
  their 
  flight 
  we 
  have 
  definite 
  proof 
  of 
  

   their 
  passage 
  over 
  to 
  Venezuela 
  via 
  Patos 
  on 
  the 
  north-west, 
  

   and 
  there 
  can 
  be 
  little 
  doubt 
  that 
  they 
  also 
  crossed 
  at 
  

   the 
  south-western 
  corner, 
  where 
  only 
  a 
  few 
  miles 
  separate 
  

   the 
  Island 
  from 
  the 
  mainland. 
  We 
  have 
  here, 
  however, 
  the 
  

   confusing 
  records 
  of 
  easterly 
  flights 
  at 
  Cedros 
  already 
  

   referred 
  to, 
  but 
  in 
  view 
  of 
  the 
  milUon 
  of 
  butterflies 
  which 
  

   passed, 
  and 
  of 
  the 
  fact 
  that 
  there 
  was 
  no 
  general 
  abundance 
  

   of 
  them 
  a 
  week 
  or 
  two 
  afterwards, 
  it 
  is 
  certain 
  that 
  the 
  

   greater 
  number 
  must 
  have 
  left 
  the 
  Island. 
  

  

  There 
  were 
  in 
  all 
  seven 
  records 
  of 
  flight 
  over 
  the 
  sea. 
  One 
  

   on 
  the 
  extreme 
  north 
  coast, 
  where 
  a 
  few 
  were 
  flying 
  about 
  

   a 
  hundred 
  yards 
  from 
  the 
  shore 
  and 
  parallel 
  to 
  the 
  coast 
  

   (25. 
  ix) 
  ; 
  one 
  record 
  off 
  the 
  north 
  coast 
  of 
  the 
  south-western 
  

   promontory 
  (1. 
  x.), 
  and 
  the 
  remainder 
  between 
  the 
  north- 
  

   western 
  promontory 
  and 
  Venezuela 
  on 
  various 
  dates. 
  

  

  It 
  might 
  perhaps 
  be 
  mentioned 
  here 
  that 
  a 
  resident 
  of 
  

   Patos 
  Island 
  reported 
  that 
  he 
  had 
  seen 
  butterflies 
  flying 
  

   towards 
  Trinidad, 
  but 
  I 
  cannot 
  place 
  too 
  much 
  reliance 
  on 
  

   this 
  record. 
  It 
  has 
  been 
  added 
  to 
  Plate 
  X, 
  with 
  a 
  query. 
  

  

  Speed 
  of 
  Flight. 
  

  

  The 
  flight 
  of 
  butterflies 
  on 
  migration 
  .is 
  always 
  very 
  

   distinct 
  from 
  that 
  of 
  those 
  flying 
  casually. 
  The 
  most 
  

   noticeable 
  characteristics 
  are 
  the 
  speed 
  and 
  the 
  fixity 
  of 
  

   direction. 
  In 
  a 
  previous 
  account 
  of 
  migration 
  of 
  Callidryas 
  

   eubule 
  in 
  British 
  Guiana 
  (^c, 
  p. 
  159) 
  I 
  estimated 
  the 
  rate 
  

   as 
  from 
  twelve 
  to 
  sixteen 
  miles 
  per 
  hour 
  (across 
  the 
  wind). 
  

   Several 
  correspondents 
  in 
  the 
  present 
  case 
  remark 
  on 
  the 
  

   speed 
  of 
  flight 
  being 
  quite 
  unprecedented. 
  Fortunately 
  

   an 
  opportunity 
  occurred 
  to 
  get 
  accurate 
  data. 
  At 
  Port 
  of 
  

   Spain 
  on 
  the 
  27th 
  September 
  the 
  butterflies 
  happened 
  to 
  

   be 
  flying 
  directly 
  down 
  a 
  foot-ball 
  field 
  on 
  the 
  Savannah, 
  

   the 
  length 
  of 
  which 
  was 
  found 
  to 
  be 
  110 
  yards. 
  With 
  a 
  

   stop-watch 
  eleven 
  butterflies 
  were 
  timed 
  from 
  one 
  end 
  of 
  the 
  

   field 
  to 
  the 
  other 
  by 
  three 
  different 
  observers 
  (including 
  

   myself) 
  and 
  the 
  following 
  results 
  were 
  obtained 
  : 
  12, 
  14, 
  

   13, 
  12, 
  13, 
  13, 
  13, 
  12, 
  U, 
  14, 
  15 
  seconds. 
  This 
  gives 
  an 
  

   average 
  of 
  13*2 
  seconds, 
  or 
  17 
  miles 
  an 
  hour. 
  

  

  At 
  this 
  rate, 
  and 
  in 
  the 
  direction 
  they 
  were 
  flying, 
  they 
  

   could 
  have 
  reached 
  the 
  mainland 
  of 
  Venezuela 
  two 
  hours 
  

   after 
  leaving 
  Port 
  of 
  Spain. 
  

  

  