﻿38 
  ROBERT 
  VEITCH. 
  

  

  drains 
  and 
  roads 
  on 
  the 
  plantations. 
  If 
  the 
  upper 
  leaves 
  of 
  any 
  bean 
  plant 
  be 
  pushed 
  

   aside 
  the 
  bean 
  bug 
  can 
  often 
  be 
  found 
  in 
  such 
  numbers 
  that 
  the 
  stem 
  of 
  the 
  plant 
  is 
  

   literally 
  black 
  with 
  them. 
  

  

  The 
  bug 
  is 
  5 
  mm. 
  in 
  length 
  and 
  belongs 
  to 
  the 
  sub-family 
  Scutellerinae. 
  The 
  

   eggs 
  have 
  been 
  found 
  on 
  the 
  leaves 
  of 
  Mauritius 
  bean, 
  on 
  the 
  leaves 
  of 
  the 
  commoner 
  

   weeds 
  of 
  the 
  cane-field, 
  on 
  pieces 
  of 
  timber 
  lying 
  in 
  fields 
  and 
  even 
  on 
  the 
  doors 
  and 
  

   window-sills 
  of 
  bungalows. 
  The 
  eggs 
  are 
  laid 
  in 
  a 
  double 
  row, 
  the 
  number 
  in 
  each 
  

   set 
  varying 
  from 
  ten 
  to 
  thirty. 
  Each 
  egg 
  is 
  about 
  one 
  millimetre 
  in 
  length 
  and 
  is 
  

   an 
  extremely 
  neat 
  white 
  cylinder 
  with 
  a 
  little 
  lid 
  that 
  is 
  opened 
  when 
  the 
  young 
  bug 
  

   emerges 
  ; 
  in 
  most 
  cases 
  the 
  lid 
  falls 
  of! 
  when 
  the 
  bug 
  leaves 
  the 
  egg, 
  but 
  sometimes 
  

   it 
  remains 
  hanging 
  half 
  open 
  as 
  if 
  it 
  were 
  hinged 
  to 
  the 
  cylinder. 
  The 
  eggs 
  are 
  laid 
  

   end 
  to 
  end 
  in 
  a 
  double 
  row 
  with 
  the 
  lid 
  ends 
  directed 
  outwards. 
  They 
  hatch 
  out 
  

   after 
  an 
  incubation 
  period 
  of 
  six 
  or 
  seven 
  days. 
  

  

  The 
  newly 
  emerged 
  bugs 
  immediately 
  start 
  sucking 
  the 
  plant 
  sap. 
  They 
  moult 
  

   frequently, 
  but 
  the 
  exact 
  number 
  of 
  the 
  moults 
  and 
  the 
  intervals 
  between 
  them 
  have 
  

   not 
  yet 
  been 
  definitely 
  ascertained. 
  The 
  numbers 
  of 
  this 
  pest 
  are 
  often 
  so 
  great 
  that 
  

   they 
  considerably 
  retard 
  the 
  growth 
  of 
  the 
  green 
  crop, 
  but 
  the 
  damage 
  is 
  not 
  suffi- 
  

   ciently 
  serious 
  to 
  warrant 
  the 
  adoption 
  of 
  control 
  measures. 
  The 
  multiplication 
  of 
  

   the 
  bugs 
  is 
  checked 
  by 
  a 
  Chalcidid 
  egg-parasite 
  described 
  by 
  Mr. 
  J. 
  Waterston 
  as 
  

   Ooencyrtus 
  jpacificus, 
  and 
  an 
  important 
  fungous 
  enemy 
  is 
  an 
  unidentified 
  species 
  of 
  

   Isaria 
  which 
  attacks 
  the 
  nymph 
  and 
  imago. 
  

  

  The 
  Cane 
  Aleurodid 
  (Aleurodes 
  comata, 
  Mask.). 
  

  

  This 
  Aleurodid 
  is 
  occasionally 
  found 
  in 
  extremely 
  large 
  numbers 
  on 
  the 
  under 
  

   surface 
  of 
  cane 
  leaves, 
  but 
  as 
  a 
  rule 
  it 
  is 
  not 
  common, 
  and 
  even 
  in 
  its 
  worst 
  attacks 
  

   it 
  is 
  only 
  a 
  minor 
  pest. 
  

  

  The 
  pale 
  yellow 
  eggs 
  are 
  attached 
  to 
  the 
  leaves 
  and 
  are 
  usually 
  found 
  in 
  clusters 
  

   containing 
  sometimes 
  as 
  many 
  as 
  150 
  eggs. 
  The 
  various 
  stages 
  are 
  all 
  typical 
  of 
  

   this 
  family. 
  

  

  The 
  damage 
  to 
  the 
  cane 
  is 
  twofold 
  ; 
  for 
  in 
  the 
  first 
  place, 
  it 
  is 
  stunted 
  by 
  the 
  

   loss 
  of 
  sap 
  sucked 
  out 
  of 
  the 
  tissues 
  by 
  the 
  Aleurodid, 
  and 
  in 
  the 
  second 
  place, 
  

   a 
  sooty 
  fungus 
  grows 
  on 
  the 
  excreted 
  honey- 
  dew 
  and 
  interferes 
  with 
  the 
  process 
  of 
  

   photosynthesis. 
  

  

  The 
  most 
  effective 
  check 
  to 
  the 
  increase 
  of 
  this 
  pest 
  is 
  the 
  maggot 
  of 
  a 
  Syrphid 
  

   which 
  feeds 
  on 
  all 
  its 
  stages. 
  The 
  life-history 
  of 
  this 
  predator 
  has 
  been 
  worked 
  out 
  

   and 
  is 
  briefly 
  as 
  follows. 
  The 
  white 
  cylindrical 
  egg 
  of 
  the 
  Syrphid 
  is 
  firmly 
  cemented 
  

   to 
  the 
  underside 
  of 
  the 
  cane 
  leaf, 
  and 
  is 
  almost 
  invariably 
  laid 
  alongside 
  an 
  actively 
  

   ovipositing 
  Aleurodid. 
  The 
  young 
  maggot 
  hatches 
  out 
  in 
  three 
  days, 
  and 
  imme- 
  

   diately 
  starts 
  to 
  feed 
  voraciously, 
  attacking 
  all 
  stages 
  of 
  the 
  pest, 
  but 
  seeming 
  to 
  

   prefer 
  the 
  eggs 
  and 
  the 
  adults 
  to 
  the 
  larvae 
  and 
  pupae. 
  The 
  quantity 
  of 
  food 
  

   consumed 
  is 
  enormous, 
  as 
  is 
  illustrated 
  by 
  the 
  fact 
  that 
  a 
  single 
  maggot 
  has 
  been 
  

   observed 
  to 
  destroy 
  as 
  many 
  as 
  one 
  hundred 
  eggs 
  in 
  a 
  day, 
  as 
  well 
  as 
  a 
  considerable 
  

   number 
  of 
  adults 
  ; 
  while 
  another 
  was 
  seen 
  destroying 
  thirty 
  eggs 
  and 
  four 
  adults 
  

   in 
  twenty 
  minutes. 
  The 
  maggot 
  is 
  typical 
  of 
  the 
  Syrphid 
  family, 
  and 
  is 
  full-grown 
  

   in 
  seven 
  or 
  eight 
  days 
  ; 
  it 
  forms 
  a 
  greenish 
  pear-shaped 
  pupa, 
  from 
  which 
  the 
  adult 
  

   emerges 
  six 
  days 
  later. 
  This 
  Syrphid 
  is 
  an 
  unidentified 
  species 
  of 
  Xanthogramma. 
  

  

  