﻿b 
  W. 
  A. 
  LAMBORX. 
  

  

  The 
  entire 
  absence 
  of 
  A. 
  aconitas, 
  except 
  for 
  two 
  individuals, 
  in 
  a 
  collection 
  

   numbering 
  10,549 
  and 
  comprising 
  five 
  other 
  species, 
  as 
  shown 
  in 
  Table 
  II, 
  offers 
  a 
  

   most 
  striking 
  contrast 
  to 
  its 
  relative 
  proportions 
  in 
  the 
  parallel 
  collections, 
  as 
  shown 
  in 
  

   Table 
  I, 
  in 
  which 
  out 
  of 
  a 
  total 
  of 
  20,605 
  larvae, 
  including 
  six 
  other 
  species, 
  no 
  fewer 
  

   than 
  11,938 
  were 
  those 
  of 
  this 
  Anopheline. 
  To 
  what 
  causes 
  can 
  its 
  absence 
  be 
  due 
  ? 
  

   To 
  what 
  is 
  due 
  the 
  overwhelming 
  abundance 
  of 
  this 
  species 
  elsewhere 
  ? 
  If 
  due 
  to 
  

   differences 
  in 
  the 
  nature 
  of 
  the 
  breeding-places, 
  in 
  what 
  do 
  these 
  consist 
  ? 
  

  

  The 
  mere 
  presence 
  of 
  reeds, 
  affording 
  a 
  measure 
  of 
  shade, 
  would 
  hardly 
  seem 
  to 
  

   account 
  for 
  it, 
  as 
  the 
  larvae 
  were 
  obtainable 
  elsewhere 
  in 
  situations 
  entirely 
  free 
  from 
  

   such 
  growth 
  and 
  exposed 
  to 
  the 
  overhead 
  sun. 
  The 
  difference 
  in 
  size 
  of 
  the 
  ponds 
  and 
  

   the 
  depth 
  of 
  the 
  water 
  has 
  also 
  no 
  bearing 
  on 
  the 
  matter 
  : 
  one 
  knows 
  of 
  other 
  breeding- 
  

   places 
  equal 
  in 
  point 
  of 
  size 
  and 
  depth 
  of 
  water, 
  in 
  some 
  of 
  which 
  the 
  larvae 
  of 
  

   A. 
  aconituS 
  are 
  found 
  though 
  absent 
  in 
  others. 
  

  

  For 
  further 
  study 
  of 
  the 
  question 
  of 
  selection 
  of 
  breeding-place, 
  a 
  little 
  group 
  of 
  

   four 
  other 
  small 
  ponds 
  and 
  one 
  little 
  reedy 
  swamp 
  on 
  the 
  outskirts 
  of 
  another 
  quarter 
  

   of 
  the 
  town 
  were 
  selected 
  in 
  March 
  1921 
  . 
  The 
  relative 
  position 
  of 
  these 
  is 
  shown 
  on 
  the 
  

   accompanying 
  map 
  (fig. 
  1). 
  

  

  Feet 
  looo 
  500 
  o 
  

  

  ..i.i.i 
  I 
  

  

  I 
  Furlonq 
  

  

  Scs/e.- 
  3 
  inches 
  to 
  One 
  M/'/e. 
  

  

  3000 
  4000 
  

  

  1000 
  

  

  i 
  

  

  2000 
  

  

  I 
  

  

  5000 
  5280 
  Feet. 
  

  

  

  J 
  /4 
  

  

  I 
  Mile. 
  

  

  Fig. 
  1. 
  Sketch-map 
  to 
  show 
  the 
  relative 
  positions 
  of 
  the 
  ponds 
  examined 
  

  

  for 
  Anopheles 
  larvae. 
  

  

  