﻿404 
  

  

  AN 
  INTERESTING 
  PRINCIPLE 
  IN 
  ECONOMIC 
  ENTOMOLOGY 
  AND 
  SOME 
  

  

  USEFUL 
  APPLICATIONS. 
  

  

  By 
  K. 
  Kunhikannan, 
  M.A., 
  Ph.D., 
  F.E.S. 
  

  

  In 
  the 
  course 
  of 
  my 
  investigation 
  of 
  the 
  serious 
  pest 
  of 
  palms, 
  Oryctes 
  rhinoceros, 
  

   it 
  was 
  observed 
  that 
  a 
  great 
  proportion 
  of 
  the 
  larvae 
  work 
  their 
  way 
  several 
  inches 
  

   below 
  the 
  floor 
  of 
  the 
  manure 
  pit 
  in 
  which 
  they 
  thrive, 
  for 
  pupation 
  ; 
  and 
  it 
  occurred 
  

   to 
  the 
  writer 
  that 
  attempts 
  should 
  be 
  made 
  to 
  prevent 
  the 
  return 
  journey 
  by 
  ,b.e 
  

   insects 
  as 
  adults. 
  Now 
  the 
  larvae 
  and 
  adults 
  are 
  of 
  about 
  equal 
  girth, 
  but 
  as 
  . 
  ie 
  

   former 
  are 
  soft-bodied 
  they 
  can 
  squeeze 
  themselves 
  through 
  holes 
  which 
  are 
  im- 
  

   passable 
  for 
  the 
  rigid-bodied 
  adult. 
  A 
  sheet 
  of 
  expanded 
  metal 
  with 
  meshes 
  

   12 
  by 
  24 
  mm. 
  will 
  let 
  the 
  larvae 
  through 
  but 
  not 
  the 
  adults, 
  and 
  therefore 
  should 
  

   prevent 
  the 
  escape 
  of 
  beetles 
  from 
  manure 
  pits 
  in 
  which 
  the 
  floor 
  has 
  been 
  carefully 
  

   covered 
  with 
  this 
  metal. 
  How 
  far 
  the 
  idea 
  will 
  be 
  of 
  practical 
  application 
  in 
  the 
  

   control 
  of 
  the 
  pest 
  under 
  the 
  varying 
  conditions 
  in 
  which 
  manure 
  is 
  stored 
  remains 
  

   to 
  be 
  seen, 
  but 
  this 
  preliminary 
  note 
  is 
  written 
  to 
  draw 
  attention 
  not 
  to 
  any 
  remedy 
  

   but 
  to 
  the 
  principle 
  itself, 
  which 
  is 
  important 
  and 
  has 
  a 
  wider 
  application 
  than 
  to 
  

   the 
  insect 
  from 
  the 
  study 
  of 
  which 
  it 
  was 
  first 
  derived. 
  It 
  has 
  been 
  found, 
  for 
  example, 
  

   that 
  it 
  operates 
  in 
  the 
  case 
  of 
  flies 
  also, 
  the 
  holes 
  through 
  which 
  the 
  maggots 
  may 
  

   be 
  able 
  to 
  pass 
  being 
  impassable 
  for 
  the 
  adults. 
  In 
  the 
  case 
  of 
  the 
  house-fly 
  a 
  per- 
  

   forated 
  zinc 
  sheet 
  will 
  let 
  the 
  maggots 
  through, 
  but 
  not 
  the 
  adults, 
  and 
  a 
  trap 
  is 
  

   under 
  trial 
  in 
  which 
  the 
  flies 
  are 
  attracted 
  to 
  suitable 
  material 
  and 
  the 
  maggots 
  

   resulting 
  from 
  oviposition 
  have 
  to 
  pass 
  for 
  pupation 
  through 
  a 
  perforated 
  zinc 
  sheet 
  

   into 
  a 
  chamber 
  from 
  which 
  the 
  flies 
  cannot 
  escape. 
  The 
  success 
  of 
  this 
  trap 
  as 
  

   well 
  as 
  of 
  the 
  lines 
  of 
  attack 
  now 
  opened 
  up 
  against 
  Oryctes 
  rhinoceros 
  remains 
  to 
  

   be 
  seen, 
  but 
  the 
  principle 
  is, 
  I 
  believe, 
  of 
  sufficient 
  importance 
  for 
  early 
  attention 
  

   to 
  be 
  drawn 
  to 
  it 
  in 
  the 
  pages 
  of 
  this 
  journal. 
  

  

  