﻿28 
  ROBERT 
  VEITCH. 
  

  

  living 
  vegetable 
  matter, 
  being 
  most 
  destructive 
  in 
  January, 
  February 
  and 
  March, 
  

   of 
  the 
  next 
  year, 
  by 
  which 
  time 
  they 
  are 
  nearly 
  full-grown. 
  They 
  pupate 
  in 
  April 
  

   and 
  May 
  in 
  earthern 
  cells 
  at 
  a 
  depth 
  of 
  6 
  to 
  18 
  inches, 
  and 
  after 
  31 
  days 
  or 
  so 
  in 
  

   the 
  pupal 
  stage 
  the 
  beetles 
  appear. 
  The 
  adults 
  do 
  not 
  leave 
  the 
  soil 
  immediately 
  

   after 
  their 
  transformation, 
  but 
  rest 
  in 
  the 
  earthern 
  cells 
  for 
  a 
  week 
  or 
  two, 
  and 
  then 
  

   emerge 
  to 
  feed 
  and 
  mate 
  and 
  repeat 
  the 
  life-cycle. 
  There 
  is 
  only 
  one 
  generation 
  

   in 
  a 
  vear. 
  

  

  This 
  pest 
  is 
  very 
  destructive 
  on 
  sandy 
  soils, 
  in 
  which 
  it 
  attacks 
  cane 
  of 
  all 
  ages. 
  

   Fields 
  replanted 
  in 
  January, 
  February 
  and 
  March 
  almost 
  invariably 
  suffer 
  severely, 
  

   as 
  the 
  grubs 
  at 
  that 
  time 
  are 
  well 
  grown 
  and 
  immediately 
  attack 
  the 
  young 
  plants, 
  

   destroying 
  the 
  roots, 
  or 
  eating 
  the 
  young 
  shoots 
  at 
  the 
  base 
  and 
  thus 
  severing 
  them 
  

   from 
  the 
  set 
  and 
  the 
  root 
  system. 
  Many 
  of 
  the 
  attacked 
  plants 
  die, 
  but 
  others 
  

   survive, 
  although, 
  more 
  or 
  less 
  crippled, 
  the 
  older 
  cane 
  being 
  better 
  able 
  to 
  with- 
  

   stand 
  the 
  attacks, 
  as 
  its 
  recuperative 
  powers 
  are 
  greater, 
  but 
  even 
  such 
  crops 
  are 
  

   frequently 
  severely 
  checked. 
  

  

  The 
  following 
  natural 
  enemies 
  take 
  a 
  heavy 
  toll 
  of 
  the 
  white 
  grubs 
  of 
  this 
  species. 
  

   The 
  wireworms 
  of 
  Monocrepidius 
  pallipes, 
  Esch., 
  attack 
  and 
  destroy 
  the 
  grubs 
  

   in 
  large 
  numbers, 
  and 
  the 
  Scoliid 
  wasp, 
  Discolia 
  ovalauensis, 
  Sauss., 
  parasitises 
  

   very 
  many 
  of 
  them. 
  An 
  unidentified 
  species 
  of 
  mite 
  attacks 
  the 
  grubs 
  in 
  considerable 
  

   numbers 
  when 
  kept 
  in 
  captivity, 
  and 
  the 
  attacked 
  individuals 
  generally 
  die. 
  In 
  

   the 
  field 
  conditions 
  do 
  not 
  seem 
  to 
  be 
  so 
  favourable 
  to 
  the 
  mite, 
  and 
  it 
  is 
  only 
  rarely 
  

   that 
  one 
  there 
  finds 
  grubs 
  as 
  badly 
  infested 
  as 
  in 
  the 
  laboratory. 
  Minah 
  birds 
  

   destroy 
  large 
  numbers 
  of 
  grubs 
  during 
  cultivation 
  operations, 
  and 
  are 
  undoubtedly 
  

   of 
  great 
  assistance 
  in 
  minimising 
  the 
  losses 
  from 
  this 
  pest. 
  

  

  Fields 
  known 
  to 
  be 
  badly 
  infested 
  by 
  white 
  grubs 
  should 
  not 
  be 
  planted 
  until 
  

   April, 
  as 
  by 
  that 
  time 
  most 
  of 
  the 
  grubs 
  will 
  be 
  in 
  the 
  pupal 
  or 
  prepupal 
  stage, 
  

   and 
  so 
  the 
  crop 
  will 
  be 
  free 
  from 
  serious 
  attack 
  until 
  December 
  or 
  January, 
  when 
  

   the 
  cane 
  will 
  be 
  well 
  established 
  and 
  so 
  better 
  able 
  to 
  resist 
  the 
  grub 
  attacks. 
  The 
  

   collection 
  and 
  destruction 
  of 
  beetles 
  and 
  grubs 
  is 
  also 
  of 
  assistance 
  in 
  controlling 
  

   this 
  pest, 
  while 
  the 
  frequent 
  ploughing 
  of 
  infested 
  fields 
  will 
  expose 
  many 
  grubs 
  

   to 
  destruction 
  by 
  minahs. 
  

  

  The 
  White 
  Grub 
  of 
  Alluvial 
  and 
  Red 
  Hill 
  Soils 
  (Rhopaea 
  subnitida, 
  Arrow) 
  (fig. 
  3). 
  

   The 
  cane 
  grub 
  of 
  sandy 
  soils 
  has 
  been 
  dealt 
  with 
  in 
  considerable 
  detail 
  in 
  the 
  

   preceding 
  paragraphs, 
  but 
  a 
  much 
  briefer 
  reference 
  will 
  suffice 
  for 
  the 
  less 
  destructive 
  

   species, 
  R. 
  subnitida, 
  partly 
  because 
  it 
  is 
  of 
  less 
  importance, 
  partly 
  because 
  less 
  

   detail 
  is 
  required 
  owing 
  to 
  the 
  similarity 
  between 
  the 
  life-histories 
  of 
  the 
  two 
  

   species, 
  and 
  partly 
  because 
  it 
  has 
  been 
  less 
  closely 
  studied 
  than 
  R. 
  vestita. 
  

  

  The 
  seasonal 
  occurrence 
  of 
  the 
  two 
  species 
  is 
  practically 
  the 
  same, 
  and 
  so 
  far 
  

   the 
  writer 
  has 
  not 
  observed 
  any 
  difference 
  in 
  feeding 
  habits. 
  The 
  beetles 
  eat 
  

   acacia, 
  coconut, 
  cane 
  and 
  guava 
  leaves, 
  but 
  the 
  amount 
  of 
  food 
  consumed 
  is 
  small. 
  

  

  The 
  beetle, 
  pupa, 
  grub 
  and 
  egg 
  of 
  R. 
  subnitida 
  are 
  each 
  larger 
  than 
  the 
  corres- 
  

   ponding 
  stages 
  of 
  R. 
  vestita. 
  The 
  beetle 
  of 
  the 
  latter 
  species 
  can 
  always 
  be 
  readily 
  

   identified 
  by 
  the 
  presence 
  of 
  a 
  smooth 
  median 
  area 
  on 
  the 
  pygidium, 
  which 
  in 
  the 
  

   former 
  is 
  setose 
  all 
  over. 
  The 
  writer 
  cannot 
  distinguish 
  between 
  the 
  pupae 
  and 
  

  

  