﻿103 
  

  

  NOTES 
  ON 
  THE 
  COCONUT 
  BEETLE 
  {ORYCTES 
  MONOCEROS, 
  OL.) 
  

  

  IN 
  KENYA 
  COLONY. 
  

  

  By 
  F. 
  W. 
  Dry. 
  

  

  The 
  present 
  notes 
  are 
  a 
  short 
  account 
  of 
  work 
  of 
  a 
  preliminary 
  nature 
  on 
  the 
  

   Coast 
  of 
  Kenya 
  Colony, 
  mostly 
  between 
  August 
  1920 
  and 
  February 
  1921, 
  at 
  the 
  end 
  

   of 
  a 
  tour 
  of 
  service, 
  and 
  may 
  serve 
  to 
  indicate 
  some 
  of 
  the 
  chief 
  points 
  calling 
  for 
  

   investigation. 
  They 
  are 
  concerned 
  with 
  the 
  life-history 
  of 
  the 
  insect 
  and 
  with 
  some 
  

   field 
  observations. 
  The 
  life-history 
  work 
  was 
  carried 
  out 
  in 
  tents 
  shaded 
  by 
  a 
  large 
  

   mango 
  tree, 
  on 
  land 
  kindly 
  lent 
  by 
  Sheik 
  Ali 
  bin 
  Salim, 
  on 
  the 
  north 
  side 
  of 
  Mombasa 
  

   Island. 
  The 
  field 
  work 
  was 
  done 
  on 
  the 
  island 
  and 
  on 
  the 
  neighbouring 
  mainland. 
  

   For 
  records 
  of 
  the 
  numbers 
  of 
  beetles 
  captured 
  on 
  European 
  plantations 
  I 
  am 
  

   indebted 
  to 
  three 
  gentlemen 
  owning 
  or 
  managing 
  them. 
  

  

  The 
  Life-history 
  of 
  the 
  Coconut 
  Beetle. 
  

  

  The 
  Egg. 
  — 
  For 
  thirty 
  records 
  of 
  the 
  length 
  of 
  the 
  egg 
  stage 
  the 
  average 
  time 
  was 
  

   15 
  days, 
  the 
  minimum 
  being 
  12 
  days 
  and 
  the 
  maximum 
  20. 
  Of 
  the 
  eggs 
  deposited 
  

   in 
  confinement 
  two-thirds 
  did 
  not 
  hatch. 
  Eggs 
  have 
  not 
  been 
  laid 
  by 
  the 
  beetles 
  

   in 
  captivity 
  at 
  all 
  readily. 
  In 
  the 
  field 
  the 
  beetles 
  feed 
  on 
  the 
  " 
  cabbage 
  " 
  at 
  the 
  

   top 
  of 
  the 
  palm, 
  so 
  that 
  laboratory 
  conditions 
  were 
  necessarily 
  unnatural, 
  the 
  beetles 
  

   being 
  kept 
  in 
  two-pound 
  biscuit 
  tins, 
  a 
  pair 
  in 
  each. 
  The 
  tins 
  were 
  about 
  a 
  third 
  

   filled 
  with 
  the 
  powdery 
  material 
  from 
  the 
  inside 
  of 
  decaying 
  coconut 
  logs, 
  in 
  which 
  

   eggs 
  are 
  mostly 
  laid 
  in 
  the 
  field. 
  The 
  beetles 
  were 
  kept 
  provided 
  with 
  pieces 
  of 
  the 
  

   husk 
  of 
  unripe 
  coconuts 
  or 
  with 
  bits 
  of 
  sugar-cane, 
  on 
  both 
  of 
  which 
  they 
  were 
  found 
  

   to 
  feed 
  readily. 
  The 
  powdery 
  substance 
  was 
  searched 
  through 
  daily. 
  The 
  largest 
  

   number 
  of 
  eggs 
  obtained 
  from 
  one 
  female, 
  an 
  insect 
  bred 
  in 
  the 
  laboratory 
  and 
  kept 
  

   provided 
  throughout 
  life 
  with 
  a 
  mate, 
  was 
  30 
  ; 
  she 
  died 
  after 
  an 
  adult 
  life 
  of 
  111 
  

   days. 
  The 
  next 
  largest 
  number 
  was 
  15, 
  from 
  a 
  female 
  brought 
  in 
  from 
  the 
  field, 
  

   and 
  similarly 
  kept 
  provided 
  with 
  a 
  mate. 
  Quite 
  a 
  number 
  of 
  females 
  that 
  passed 
  

   their 
  whole 
  adult 
  life 
  in 
  the 
  laboratory 
  lived 
  a 
  long 
  time, 
  some 
  more 
  than 
  a 
  hundred 
  

   days, 
  without 
  laying 
  as 
  many 
  as 
  fifteen 
  eggs. 
  When 
  eggs 
  were 
  laid, 
  it 
  was 
  usual 
  

   to 
  find 
  several 
  deposited 
  the 
  same 
  day, 
  frequently 
  as 
  many 
  as 
  seven, 
  and 
  sometimes 
  

   nine, 
  ten 
  or 
  eleven. 
  In 
  the 
  field 
  during 
  the 
  Short 
  Rains 
  (October 
  to 
  December) 
  

   eggs 
  were 
  plentiful. 
  It 
  was 
  quite 
  common 
  to 
  find 
  a 
  single 
  female 
  beetle 
  in 
  a 
  log 
  

   with 
  fifty 
  or 
  more 
  eggs, 
  and 
  though 
  there 
  is 
  no 
  proof 
  that 
  these 
  had 
  all 
  been 
  laid 
  by 
  

   the 
  one 
  individual, 
  eggs 
  were 
  sufficiently 
  abundant 
  in 
  the 
  field 
  to 
  suggest 
  that 
  under 
  

   natural 
  conditions 
  the 
  beetles 
  lay 
  many 
  more 
  eggs 
  than 
  they 
  did 
  in 
  the 
  laboratory. 
  

  

  The 
  Larva. 
  — 
  The 
  grub 
  was 
  the 
  most 
  difficult 
  stage 
  of 
  the 
  beetle 
  to 
  work 
  with, 
  

   the 
  mortality 
  always 
  being 
  high. 
  The 
  literature 
  on 
  0. 
  rhinoceros, 
  L., 
  would 
  seem 
  

   to 
  suggest 
  that 
  the 
  same 
  difficulty 
  has 
  been 
  experienced 
  with 
  fhat 
  insect. 
  At 
  first 
  

   grubs 
  were 
  kept, 
  singly 
  or 
  a 
  few 
  together, 
  in 
  small 
  tins, 
  the 
  food 
  being 
  changed 
  fre- 
  

   quently 
  and 
  the 
  grubs 
  examined 
  daily 
  to 
  see 
  if 
  they 
  had 
  moulted. 
  Afterwards 
  the 
  

   grubs 
  were 
  handled 
  less 
  often, 
  and 
  greater 
  care 
  was 
  taken 
  to 
  give 
  food 
  not 
  containing 
  

   many 
  grub 
  faeces. 
  From 
  grubs 
  treated 
  in 
  this 
  way 
  some 
  information 
  was 
  obtained 
  

   about 
  moults, 
  but 
  of 
  these 
  grubs 
  not 
  a 
  single 
  one 
  hatched 
  in 
  the 
  laboratory 
  survived 
  

   to 
  pupate. 
  Moults 
  at 
  three 
  different 
  sizes 
  were 
  observed, 
  namely, 
  when 
  the 
  breadth 
  

   of 
  the 
  head 
  capsule 
  was 
  2\ 
  mm., 
  5-6 
  mm., 
  and 
  10-11 
  mm. 
  The 
  breadth 
  of 
  the 
  

   head 
  capsule 
  of 
  a 
  large 
  number 
  of 
  grubs 
  brought 
  in 
  from 
  the 
  field 
  was 
  measured, 
  

   but 
  none 
  were 
  found 
  with 
  measurements 
  intermediate 
  between 
  those 
  three 
  sizes. 
  

   Besides, 
  a 
  considerable 
  number 
  of 
  grubs 
  with 
  head 
  capsules 
  of 
  the 
  largest 
  size 
  

  

  