﻿148 
  W. 
  A. 
  LAMBORN. 
  

  

  such 
  species 
  having, 
  perhaps, 
  bred 
  in 
  running 
  water 
  before 
  there 
  were 
  large 
  numbers 
  

   of 
  small 
  open 
  pools 
  available. 
  But 
  Dr. 
  J. 
  W. 
  Scott 
  Macfie 
  has 
  suggested 
  a 
  more 
  

   probable 
  explanation 
  : 
  that 
  such 
  larvae 
  may 
  use 
  their 
  hooks 
  to 
  prevent 
  themselves 
  

   being 
  driven 
  before 
  the 
  wind. 
  

  

  Such 
  differences 
  of 
  habit 
  may 
  well 
  have 
  important 
  practical 
  bearings, 
  as 
  is 
  sug- 
  

   gested 
  by 
  the 
  following 
  observation 
  in 
  regard 
  to 
  Stegomyia. 
  A 
  considerable 
  number 
  

   of 
  larvae 
  of 
  5. 
  albopicta 
  were 
  found 
  in 
  water 
  that 
  had 
  collected 
  in 
  an 
  old 
  iron 
  pan 
  under 
  

   shelter. 
  On 
  the 
  surface 
  of 
  this 
  was 
  poured 
  a 
  mixture 
  of 
  heavy 
  oil 
  (Mobil-oil 
  A) 
  and 
  

   kerosene, 
  and 
  a 
  complete 
  film 
  being 
  formed, 
  the 
  larvae 
  all 
  perished. 
  A 
  few 
  days 
  

   later 
  the 
  film 
  of 
  oil 
  was 
  found 
  to 
  be 
  no 
  longer 
  complete, 
  for 
  the 
  volatile 
  constituents 
  

   had 
  evaporated, 
  and 
  the 
  residual 
  globules 
  had 
  run 
  together 
  into 
  masses 
  which 
  had 
  

   collected 
  largely 
  at 
  the 
  sides. 
  In 
  the 
  spaces 
  free 
  from 
  oil 
  young 
  larvae 
  of 
  Stegomyia, 
  

   which 
  must 
  have 
  originated 
  from 
  eggs 
  most 
  carefully 
  disposed 
  by 
  the 
  female 
  parent, 
  

   were 
  found. 
  These 
  thrived 
  and 
  increased 
  in 
  size, 
  though 
  the 
  fact 
  of 
  their 
  ultimate 
  

   pupation 
  was 
  not 
  ascertained. 
  The 
  presence 
  of 
  the 
  larvae, 
  indicating 
  their 
  instinct 
  

   and 
  ability 
  to 
  keep 
  free 
  from 
  a 
  broken 
  film 
  of 
  oil, 
  suggests 
  the 
  high 
  importance 
  of 
  

   an 
  investigation 
  as 
  to 
  the 
  relative 
  fate, 
  under 
  such 
  conditions, 
  of 
  species 
  such 
  as 
  

   A 
  . 
  maculatus, 
  with 
  a 
  strong 
  tendency 
  to 
  attach 
  itself 
  to 
  supports 
  (round 
  which 
  globules 
  

   of 
  oil 
  in 
  incomplete 
  film 
  tend 
  to 
  accumulate), 
  and 
  of 
  species, 
  such 
  as 
  A. 
  vagus, 
  which 
  

   tend 
  to 
  dispense 
  with 
  supports. 
  Correlated 
  with 
  this 
  there 
  tends 
  to 
  be 
  a 
  difference 
  

   of 
  feeding 
  habit 
  between 
  such 
  as 
  like 
  to 
  attach 
  themselves 
  to 
  objects 
  and 
  those 
  which 
  

   more 
  often 
  than 
  not 
  swim 
  freely. 
  The 
  former, 
  anchoring 
  at 
  one 
  spot, 
  would 
  seem 
  to 
  

   trust 
  largely 
  to 
  chance 
  to 
  send 
  them 
  the 
  necessaries 
  of 
  life, 
  either 
  down 
  current 
  or 
  

   wafted 
  along 
  the 
  surface 
  of 
  the 
  water 
  by 
  the 
  wind. 
  In 
  this 
  connection 
  a 
  definite 
  

   tendency 
  to 
  collect 
  all 
  at 
  one 
  side 
  was 
  noticed 
  in 
  the 
  case 
  of 
  larvae 
  kept 
  in 
  bowls 
  in 
  

   the 
  open, 
  though 
  its 
  relationship 
  to 
  wind 
  and 
  to 
  conditions 
  of 
  light 
  was 
  not 
  investigated. 
  

   The 
  free-swimming 
  larvae 
  exhibit 
  a 
  more 
  definite 
  tendency 
  to 
  go 
  in 
  search 
  of 
  food. 
  

   The 
  larvae 
  of 
  A 
  . 
  vagus, 
  for 
  instance, 
  were 
  often 
  watched 
  repeatedly 
  swimming 
  slowly 
  

   along 
  the 
  bottom 
  moving 
  their 
  mouth-brushes 
  and 
  evidently 
  feeding, 
  in 
  Stegomyia 
  

   fashion. 
  It 
  is 
  of 
  interest 
  that 
  these 
  small-pool 
  breeders 
  are 
  among 
  the 
  more 
  dominant 
  

   varieties 
  of 
  Anophelines, 
  for 
  even 
  so 
  small 
  an 
  advantage 
  of 
  habit 
  may 
  be 
  the 
  factor 
  

   accounting 
  for 
  their 
  greater 
  success 
  compared 
  with 
  other 
  species. 
  The 
  activity 
  of 
  

   the 
  larvae 
  of 
  Stegomyia 
  is 
  certainly 
  one 
  of 
  the 
  factors 
  which 
  have 
  resulted 
  in 
  the 
  

   dominance 
  of 
  certain 
  species. 
  Those 
  of 
  5. 
  albopicta, 
  for 
  instance, 
  are 
  far 
  more 
  active 
  

   than 
  those 
  of 
  any 
  Anopheline. 
  They 
  are 
  on 
  the 
  move 
  constantly, 
  either 
  swimming 
  

   at 
  the 
  surface 
  and 
  feeding 
  on 
  the 
  surface 
  material, 
  often 
  rotating 
  as 
  if 
  the 
  tail 
  end 
  was 
  

   at 
  a 
  more 
  or 
  less 
  fixed 
  point 
  ; 
  or 
  groping 
  at 
  the 
  bottom 
  of 
  water 
  in 
  receptacles, 
  often 
  

   of 
  considerable 
  depth, 
  for 
  food 
  in 
  the 
  debris, 
  into 
  which 
  they 
  will 
  often 
  burrow 
  so 
  that 
  

   their 
  tails 
  only 
  can 
  be 
  seen. 
  They 
  can 
  swim 
  just 
  as 
  fish 
  do 
  in 
  direct 
  line, 
  head 
  first, 
  

   altering 
  their 
  direction 
  by 
  a 
  mere 
  flick 
  of 
  the 
  tail 
  ; 
  they 
  can 
  rise 
  or 
  fall 
  just 
  as 
  suits 
  

   them 
  without 
  great 
  effort 
  ; 
  and, 
  by 
  reason 
  of 
  the 
  greater 
  flexibility 
  of 
  their 
  bodies, 
  

   they 
  can 
  wriggle 
  violently 
  in 
  all 
  directions 
  so 
  as 
  to 
  escape 
  their 
  enemies. 
  

  

  So 
  it 
  seems 
  likely 
  that 
  the 
  dominance 
  among 
  Anophelines 
  of 
  A 
  . 
  vagus, 
  for 
  instance, 
  

   may 
  be 
  related 
  to 
  similar 
  characteristics. 
  

  

  A 
  surprising 
  lack 
  of 
  wariness 
  was 
  exhibited 
  by 
  the 
  young 
  larvae 
  of 
  all 
  the 
  species 
  

   of 
  Anophelines. 
  It 
  was 
  possible 
  gradually 
  to 
  advance 
  a 
  spoon 
  in 
  the 
  water 
  and 
  remove 
  

   numbers 
  at 
  a 
  time 
  in 
  their 
  first 
  and 
  second 
  ecdyses. 
  But 
  as 
  the 
  larvae 
  became 
  older, 
  

   so 
  they 
  became 
  more 
  and 
  more 
  alert, 
  until 
  in 
  the 
  last 
  ecdysis 
  it 
  was 
  difficult 
  to 
  secure 
  

   any, 
  and 
  with 
  some 
  species, 
  A 
  . 
  ludlowi 
  and 
  A 
  . 
  subpictus 
  var. 
  malayensis 
  in 
  particular, 
  

   almost 
  an 
  impossibility. 
  The 
  larvae 
  in 
  some 
  families 
  were 
  more 
  alert 
  than 
  in 
  others 
  of 
  

   the 
  same 
  species, 
  an 
  indication 
  possibly 
  of 
  a 
  better 
  state 
  of 
  health, 
  and 
  for 
  this 
  reason 
  

   it 
  was 
  difficult 
  to 
  arrive 
  at 
  any 
  definite 
  conclusions 
  as 
  to 
  the 
  relative 
  wariness 
  of 
  the 
  

   different 
  species. 
  With 
  A. 
  ludlowi 
  and 
  A. 
  subpictus 
  var. 
  malayensis 
  a 
  rapid 
  advance 
  

   towards 
  the 
  basins 
  containing 
  them 
  was 
  detected 
  instantly, 
  the 
  larvae 
  diving 
  at 
  once, 
  

   so 
  that 
  on 
  arrival 
  not 
  a 
  single 
  one 
  was 
  to 
  be 
  seen 
  at 
  the 
  surface. 
  All 
  would 
  be 
  resting 
  

  

  