﻿THE 
  BIONOMICS 
  OF 
  SOME 
  MALAYAN 
  ANOPHELINES. 
  139 
  

  

  The 
  previous 
  experiments 
  having 
  afforded 
  some 
  guide 
  as 
  to 
  the 
  length 
  of 
  time 
  

   the 
  ova 
  of 
  A 
  . 
  vagus 
  at 
  an 
  advanced 
  state 
  of 
  incubation 
  are 
  able 
  to 
  withstand 
  desiccation, 
  

   the 
  following 
  experiment 
  was 
  conducted 
  in 
  an 
  endeavour 
  to 
  reproduce 
  some 
  greater 
  

   approximation 
  to 
  natural 
  conditions. 
  On 
  30th 
  June 
  62 
  ova, 
  about 
  seven 
  hours 
  old, 
  

   were 
  transferred 
  to 
  a 
  thin 
  film 
  of 
  water 
  covering 
  mud 
  brought 
  in 
  a 
  few 
  days 
  pre- 
  

   viously 
  from 
  a 
  breeding-place 
  of 
  the 
  species. 
  Twenty-four 
  hours 
  later 
  the 
  mud 
  was 
  

   found 
  to 
  be 
  hard 
  and 
  fissured, 
  in 
  which 
  state 
  it 
  was 
  allowed 
  to 
  remain 
  for 
  48 
  hours 
  

   more. 
  Water 
  was 
  then 
  gradually 
  added, 
  so 
  as 
  to 
  simulate 
  the 
  gradual 
  filling 
  up 
  of 
  

   a 
  hollow 
  by 
  rain 
  ; 
  within 
  four 
  hours 
  6 
  larvae 
  were 
  counted, 
  and 
  there 
  was 
  a 
  gradual 
  

   increase 
  in 
  number, 
  until 
  5th 
  July, 
  when 
  at 
  8 
  a.m. 
  36 
  were 
  counted. 
  The 
  remainder 
  

   failed 
  to 
  hatch. 
  

  

  This 
  result, 
  showing 
  that 
  some 
  of 
  the 
  ova 
  in 
  which 
  incubation 
  must 
  have 
  been 
  

   initiated 
  are 
  able 
  to 
  retain 
  their 
  vitality 
  up 
  to 
  72 
  hours 
  when 
  dried, 
  was 
  confirmed 
  

   by 
  experiments 
  on 
  other 
  species 
  than 
  A. 
  vagus. 
  Thus, 
  in 
  the 
  case 
  of 
  A. 
  barbirostris, 
  

   88 
  eggs 
  laid 
  during 
  the 
  previous 
  night 
  were 
  on 
  25th 
  May 
  divided 
  into 
  six 
  batches, 
  

   (a) 
  of 
  12 
  ova, 
  (6) 
  of 
  8, 
  (c) 
  of 
  12, 
  (d) 
  of 
  13, 
  (e) 
  of 
  16, 
  and 
  (/) 
  of 
  27. 
  Batch 
  (a) 
  was 
  left 
  

   on 
  the 
  water 
  to 
  test 
  the 
  fertility 
  of 
  the 
  ova. 
  On 
  27th 
  May 
  1 
  larva 
  had 
  hatched, 
  and 
  

   then 
  unfortunately 
  the 
  bowl 
  was 
  upset 
  so 
  that 
  the 
  rest 
  were 
  lost. 
  Batches 
  (b), 
  (c), 
  

   (d), 
  (e), 
  and 
  (/) 
  were 
  gradually 
  dried; 
  (b), 
  (c), 
  and 
  (d) 
  in 
  the 
  laboratory, 
  (e) 
  and 
  (/) 
  

   in 
  the 
  open 
  air. 
  When 
  these 
  ova 
  were 
  examined 
  24 
  hours 
  later, 
  all 
  were 
  found 
  to 
  

   be 
  much 
  wrinkled 
  and 
  distorted. 
  At 
  8.30 
  a.m. 
  on 
  26th 
  May 
  batch 
  (b), 
  having 
  been 
  

   off 
  the 
  water 
  for 
  the 
  greater 
  part 
  of 
  24 
  hours, 
  was 
  restored 
  to 
  tap 
  water, 
  and 
  the 
  

   following 
  hatchings 
  of 
  larvae 
  took 
  place 
  : 
  — 
  

  

  1 
  larva 
  at 
  about 
  8 
  a.m. 
  27th 
  May. 
  

  

  2 
  „ 
  „ 
  9 
  „ 
  28th 
  „ 
  

   1 
  „ 
  9 
  „ 
  30th 
  „ 
  

   1 
  ,, 
  ,,8 
  ,, 
  31st 
  

  

  The 
  remaining 
  3 
  eggs 
  failed 
  to 
  hatch. 
  

  

  Batch 
  (c) 
  was 
  restored 
  to 
  water 
  on 
  27th 
  May 
  at 
  8 
  a.m., 
  having 
  been 
  off 
  for 
  the 
  

   greater 
  part 
  of 
  48 
  hours, 
  a 
  note 
  being 
  then 
  made 
  that 
  they 
  were 
  exceedingly 
  wrinkled 
  

   and 
  distorted. 
  By 
  10.30 
  all 
  had 
  recovered 
  their 
  normal 
  shape, 
  and 
  four 
  days 
  later 
  

   4 
  larvae 
  were 
  found 
  to 
  have 
  hatched. 
  The 
  remaining 
  8 
  failed 
  to 
  hatch. 
  

  

  Batches 
  (d) 
  and 
  (e) 
  placed 
  on 
  the 
  water 
  on 
  28th 
  May 
  failed 
  to 
  hatch, 
  death 
  having 
  

   presumably 
  resulted 
  from 
  the 
  length 
  of 
  time 
  (three 
  days) 
  that 
  they 
  had 
  been 
  off 
  the 
  

   water, 
  or 
  from 
  the 
  exposure 
  to 
  which 
  they 
  had 
  been 
  subjected. 
  

  

  The 
  ova 
  of 
  A. 
  barbirostris, 
  therefore, 
  even 
  in 
  the 
  preliminary 
  stages 
  of 
  incubation, 
  

   will 
  withstand 
  drying 
  for 
  24 
  hours, 
  and 
  a 
  percentage 
  even 
  for 
  48 
  hours. 
  A 
  further 
  

   effect 
  would 
  appear 
  to 
  be 
  the 
  slowing 
  of 
  intra-oval 
  development, 
  whereby 
  larvae 
  

   may 
  take 
  from 
  48 
  to 
  144 
  hours 
  before 
  emergence, 
  the 
  normal 
  hatching 
  of 
  barbirostris 
  

   ova, 
  when 
  kept 
  under 
  usual 
  conditions, 
  having 
  been 
  found 
  by 
  repeated 
  observations 
  

   to 
  take 
  place 
  within 
  about 
  48 
  hours 
  after 
  the 
  eggs 
  have 
  been 
  laid. 
  

  

  The 
  result 
  was 
  confirmed 
  with 
  other 
  species. 
  Thus, 
  38 
  ova 
  laid 
  by 
  an 
  A 
  . 
  fuliginosus 
  

   were 
  divided 
  into 
  two 
  batches, 
  (a) 
  of 
  12, 
  (b) 
  of 
  16. 
  Batch 
  (a) 
  left 
  on 
  the 
  water 
  afforded 
  

   on 
  the 
  second 
  day 
  4 
  larvae, 
  and 
  24 
  hours 
  later 
  6 
  more, 
  the 
  remaining 
  2 
  ova 
  failing 
  to 
  

   hatch. 
  Batch 
  (b) 
  was 
  removed 
  after 
  about 
  31 
  hours 
  on 
  the 
  water, 
  and 
  the 
  ova 
  were 
  

   allowed 
  to 
  dry 
  in 
  the 
  laboratory 
  for 
  48 
  hours. 
  They 
  were 
  then 
  restored 
  to 
  water 
  ; 
  

   24 
  hours 
  later 
  12 
  larvae 
  had 
  hatched 
  out 
  of 
  the 
  16 
  ova, 
  the 
  rest 
  having 
  perished. 
  In 
  

   another 
  experiment 
  18 
  ova 
  were 
  removed 
  from 
  the 
  water, 
  having 
  been 
  afforded 
  the 
  

   chance 
  of 
  incubating 
  for 
  about 
  31 
  hours, 
  and 
  24 
  hours 
  later 
  exactly, 
  at 
  11 
  a.m., 
  

   they 
  were 
  restored 
  in 
  a 
  wrinkled 
  state 
  to 
  the 
  water. 
  By 
  midday 
  their 
  shape 
  was 
  

   fully 
  restored, 
  and 
  at 
  2 
  p.m. 
  it 
  was 
  observed 
  that 
  3 
  of 
  the 
  ova 
  showed 
  at 
  one 
  end 
  a 
  

   split, 
  indicating 
  the 
  approaching 
  emergence 
  ; 
  2 
  larvae 
  emerged 
  shortly 
  afterwards, 
  

   when 
  3 
  more 
  ova 
  showed 
  the 
  heads 
  of 
  larvae 
  presenting, 
  though 
  only 
  one 
  was 
  successful 
  

  

  