﻿10 
  \V. 
  A. 
  LAMBORN. 
  

  

  to 
  escape. 
  It 
  is 
  therefore 
  probable 
  that 
  all 
  other 
  instincts 
  were 
  subordinated 
  to 
  those 
  

   of 
  self-preservation, 
  and 
  that 
  oviposition 
  was 
  effected 
  only 
  when 
  it 
  could 
  be 
  no 
  longer 
  

   deferred, 
  and 
  then 
  in 
  the 
  first 
  bowl 
  on 
  which 
  the 
  insect 
  happened 
  to 
  chance. 
  

  

  However, 
  the 
  female 
  mosquito, 
  like 
  other 
  insects, 
  is 
  probably 
  influenced 
  in 
  her 
  

   choice 
  primarily 
  by 
  the 
  odours 
  characteristic 
  of 
  particular 
  spots, 
  which 
  connote 
  the 
  

   general 
  suitability 
  of 
  the 
  situation 
  as 
  to 
  temperature, 
  composition 
  of 
  water, 
  presence 
  

   of 
  particular 
  foods. 
  The 
  guiding 
  odours 
  may 
  or 
  may 
  not 
  be 
  such 
  as 
  are 
  perceptible 
  to 
  

   the 
  imperfect 
  sense 
  of 
  smell 
  possessed 
  by 
  the 
  ordinary 
  human 
  being. 
  For 
  instance, 
  

   A. 
  umbrosus, 
  breeding 
  largely 
  in 
  jungle 
  pools 
  (when 
  away 
  from 
  the 
  coast), 
  may 
  con- 
  

   ceivably 
  be 
  attracted 
  thereto 
  by 
  the 
  moist 
  rich 
  smell 
  of 
  the 
  rotting 
  leaves 
  neces- 
  

   sarily 
  associated 
  with 
  the 
  presence 
  of 
  shade 
  and 
  of 
  water, 
  conditions 
  which 
  may 
  afford 
  

   these 
  larvae 
  suitability 
  of 
  temperature 
  and 
  may 
  favour 
  the 
  growth 
  of 
  the 
  foods 
  on 
  which 
  

   they 
  depend. 
  The 
  odour 
  of 
  many 
  breeding-places 
  which 
  harbour 
  the 
  larvae 
  of 
  A. 
  

   vagits 
  in 
  the 
  neighbourhood 
  of 
  native 
  habitations 
  is 
  often 
  such 
  as 
  grievously 
  offends 
  the 
  

   nostrils 
  and 
  may 
  well 
  serve 
  to 
  attract 
  the 
  mosquitos 
  from 
  afar 
  to 
  oviposit. 
  The 
  water 
  

   in 
  which 
  large 
  collection 
  of 
  A. 
  aconilus 
  was 
  obtained 
  seemed 
  to 
  be 
  almost 
  odourless 
  

   to 
  human 
  nostrils. 
  

  

  If 
  odour 
  influences 
  the 
  female 
  it 
  should 
  be 
  possible 
  to 
  mask 
  it 
  experimentally 
  by 
  

   adding 
  to 
  the 
  water 
  of 
  a 
  breeding-place 
  a 
  strongly 
  odorous 
  substance, 
  the 
  expectation 
  

   then 
  being 
  that 
  the 
  female, 
  repelled 
  by 
  it, 
  or 
  unable 
  to 
  detect 
  the 
  guiding 
  odour, 
  

   would 
  no 
  longer 
  oviposit. 
  The 
  two 
  bodies 
  with 
  pungent 
  odours 
  which 
  first 
  came 
  to 
  

   mind 
  were 
  chlorine 
  and 
  formalin 
  ; 
  and 
  a 
  test 
  was 
  made 
  with 
  the 
  latter. 
  The 
  breeding- 
  

   place 
  selected 
  was 
  a 
  pool 
  in 
  secondary 
  jungle 
  of 
  considerable 
  size, 
  long 
  known 
  to 
  be 
  

   favoured 
  as 
  a 
  breeding- 
  place 
  by 
  A 
  . 
  umbrosus. 
  This 
  had 
  the 
  advantage 
  that 
  it 
  was 
  of 
  

   the 
  size 
  suitable 
  for 
  such 
  an 
  experiment 
  ; 
  it 
  was 
  in 
  a 
  shaded 
  situation, 
  in 
  which, 
  owing 
  

   to 
  the 
  improbability 
  of 
  rapid 
  evaporation, 
  the 
  formalin 
  was 
  likely 
  to 
  be 
  effective 
  over 
  

   a 
  longer 
  period 
  than 
  in 
  a 
  pool 
  out 
  in 
  the 
  open 
  ; 
  and 
  the 
  data 
  in 
  reference 
  to 
  the 
  collec- 
  

   tion 
  of 
  larvae 
  from 
  it 
  extended 
  over 
  a 
  considerable 
  period 
  of 
  time, 
  showing 
  that 
  it 
  was 
  

   an 
  old-established 
  breeding-place. 
  Formalin 
  was 
  added, 
  until 
  a 
  very 
  faint 
  odour 
  was 
  

   perceptible 
  and 
  this 
  was 
  detected 
  again 
  a 
  few 
  hours 
  later. 
  Thereafter 
  collections 
  of 
  

   larvae 
  of 
  A. 
  umbrosus 
  were 
  made 
  after 
  four 
  or 
  five 
  days. 
  The 
  addition 
  of 
  so. 
  small 
  

   an 
  amount 
  of 
  formalin 
  would 
  probably 
  have 
  little 
  effect 
  on 
  larvae 
  already 
  approxima- 
  

   ting 
  maturity 
  but, 
  besides 
  preventing 
  oviposition, 
  might 
  well 
  also 
  prevent 
  hatching, 
  

   or 
  might 
  have 
  a 
  prejudicial 
  effect 
  on 
  young 
  and 
  delicate 
  larvae. 
  But 
  no 
  results 
  at 
  all 
  

   were 
  obtained, 
  for 
  the 
  larvae 
  were 
  as 
  numerous 
  after 
  the 
  experiment 
  as 
  before 
  it. 
  

  

  No 
  ova 
  of 
  A. 
  umbrosus 
  were 
  available 
  for 
  experimental 
  purposes, 
  but 
  about 
  half 
  of 
  

   a 
  batch 
  of 
  166 
  freshly 
  laid 
  ova 
  of 
  A 
  . 
  vagus, 
  placed 
  on 
  a 
  solution 
  of 
  formalin 
  just 
  strong 
  

   enough 
  to 
  afford 
  a 
  perceptible 
  odour, 
  duly 
  hatched 
  out 
  equally 
  well 
  as 
  the 
  control 
  half, 
  

   and 
  the 
  young 
  larvae 
  seemed 
  unaffected 
  for 
  three 
  days, 
  moving 
  their 
  mouth 
  brushes 
  

   as 
  if 
  hoping 
  to 
  obtain 
  food. 
  They 
  then 
  gradually 
  died 
  off. 
  An 
  attempt 
  to 
  obtain 
  

   positive 
  evidence 
  of 
  the 
  predilections 
  of 
  the 
  female 
  Anopheline 
  as 
  to 
  waters 
  was 
  made 
  

   by 
  supplying 
  the 
  captive 
  insects 
  with 
  two 
  alternative 
  waters 
  in 
  addition 
  to 
  some 
  

   from 
  the 
  breeding-place 
  in 
  which 
  the 
  larvae 
  were 
  readily 
  obtainable 
  in 
  the 
  expectation 
  

   that 
  they 
  would 
  select 
  the 
  latter. 
  The 
  water 
  samples 
  were 
  placed 
  in 
  small 
  bowls 
  side 
  

   by 
  side 
  in 
  lamp 
  glasses 
  containing 
  the 
  insects. 
  The 
  results, 
  again, 
  were 
  entirely 
  nega- 
  

   tive 
  ; 
  no 
  preferences 
  were 
  shown. 
  But 
  here 
  again 
  the 
  experiments 
  are 
  open 
  to 
  the 
  

   objection 
  that 
  the 
  insects 
  were 
  bent 
  mainly 
  on 
  self-preservation. 
  Furthermore 
  the 
  

   odours 
  from 
  the 
  different 
  waters 
  may 
  well 
  have 
  blended, 
  so 
  misleading 
  the 
  insects, 
  

   or 
  may 
  have 
  been 
  lost, 
  the 
  gases 
  in 
  solution 
  coming 
  off 
  rapidly 
  in 
  the 
  tropics. 
  

  

  The 
  question 
  as 
  to 
  how 
  far 
  the 
  larvae 
  of 
  different 
  species 
  can 
  thrive 
  in 
  waters 
  other 
  

   than 
  those 
  in 
  which 
  they 
  are 
  usually 
  found 
  seemed 
  a 
  more 
  promising 
  line 
  of 
  investiga- 
  

   tion 
  and 
  was 
  initiated 
  by 
  a 
  series 
  of 
  experiments 
  made 
  with 
  a 
  view 
  to 
  determining 
  if 
  

   the 
  hatching 
  of 
  the 
  ova 
  of 
  the 
  various 
  species 
  is, 
  to 
  any 
  degree, 
  prejudiced 
  by 
  their 
  

   transfer 
  to 
  water 
  in 
  which 
  they 
  are 
  not 
  usually 
  found. 
  The 
  results 
  of 
  the 
  experiments- 
  

   were 
  again 
  negative 
  where 
  natural 
  waters 
  were 
  concerned. 
  

  

  