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  INSECTS 
  INJURIOUS 
  TO 
  ECONOMIC 
  CROPS 
  IN 
  THE 
  ZANZIBAR 
  

  

  PROTECTORATE. 
  

   By 
  W. 
  Mansfield-Aders, 
  

  

  Government 
  Economic 
  Biologist, 
  Zanzibar. 
  

   (Plates 
  XIII-XV.) 
  

  

  The 
  following 
  notes 
  on 
  the 
  various 
  insects 
  injurious 
  to 
  the 
  economic 
  crops 
  of 
  the 
  

   Zanzibar 
  Protectorate 
  are 
  based 
  on 
  investigations 
  made 
  during 
  the 
  last 
  few 
  years. 
  

  

  The 
  chief 
  economic 
  products 
  of 
  the 
  two 
  islands 
  (Zanzibar 
  and 
  Pemba) 
  are 
  cloves 
  

   and 
  coconuts, 
  the 
  former 
  being 
  of 
  greater 
  importance. 
  

  

  INSECTS 
  AFFECTING 
  CLOVES. 
  

  

  Fortunately 
  no 
  insect 
  pests 
  of 
  the 
  clove 
  tree 
  (Eugenia 
  caryophyllata) 
  have 
  been 
  

   discovered, 
  but 
  it 
  is 
  apparent 
  in 
  many 
  plantations 
  that 
  a 
  number 
  of 
  trees 
  are 
  

   unthrifty 
  and 
  die. 
  The 
  cause 
  of 
  death 
  still 
  remains 
  uncertain, 
  but 
  most 
  of 
  the 
  

   evidence 
  points 
  to 
  some 
  physiological 
  condition, 
  such 
  as 
  waterlogging 
  of 
  the 
  roots 
  

   near 
  swamps, 
  denudation 
  of 
  alluvial 
  soil 
  on 
  slopes, 
  or 
  the 
  tap-root 
  reaching 
  an 
  

   impervious 
  layer 
  of 
  stone. 
  The 
  bark 
  of 
  certain 
  unhealthy 
  trees 
  is 
  attacked 
  by 
  

   termites 
  (Termes 
  bellicosus) 
  and 
  dead 
  branches 
  are 
  infested 
  with 
  various 
  species 
  

   of 
  Bostrychid 
  beetles. 
  Some 
  young 
  clove 
  trees 
  from 
  Pemba 
  had 
  been 
  killed 
  by 
  

   T. 
  bellicosus 
  feeding 
  on 
  the 
  bark 
  of 
  the 
  lateral 
  roots. 
  

  

  The 
  adults 
  of 
  a 
  large 
  Tenebrionid 
  beetle, 
  Pycnocerus 
  passerinii, 
  Bertol., 
  have 
  

   been 
  found 
  on 
  several 
  occasions 
  lurking 
  under 
  dead 
  bark 
  on 
  clove 
  trees, 
  while 
  

   larvae 
  and 
  pupae 
  occur 
  in 
  deep 
  tree-holes 
  filled 
  with 
  decomposing 
  vegetation 
  ; 
  

   I 
  am 
  of 
  opinion 
  that 
  they 
  do 
  no 
  actual 
  damage, 
  but 
  only 
  feed 
  on 
  dead 
  bark, 
  etc. 
  

  

  Several 
  experiments 
  have 
  been 
  undertaken 
  to 
  test 
  whether 
  various 
  omnivorous 
  

   Lepidopterous 
  larvae, 
  such 
  as 
  those 
  of 
  Euproctis 
  producta, 
  would 
  feed 
  on 
  clove 
  

   trees 
  when 
  deprived 
  of 
  other 
  food, 
  but 
  all 
  died. 
  

  

  INSECTS 
  AFFECTING 
  COCONUTS. 
  

  

  Oryctes 
  monoceros 
  and 
  0. 
  boas. 
  These 
  two 
  rhinoceros 
  beetles 
  are 
  common 
  through- 
  

   out 
  the 
  two 
  islands 
  and 
  are 
  a 
  serious 
  menace 
  to 
  the 
  coconut 
  industry, 
  the 
  former 
  

   being 
  the 
  commoner 
  species. 
  The 
  damage 
  done 
  to 
  young 
  trees 
  is 
  often 
  very 
  serious 
  ; 
  

   in 
  some 
  plantations 
  more 
  than 
  half 
  of 
  the 
  trees 
  from 
  2J 
  to 
  3 
  years 
  old 
  are 
  killed, 
  

   while 
  others 
  are 
  stunted 
  and 
  their 
  productiveness 
  much 
  reduced. 
  A 
  certain 
  number 
  

   of 
  trees 
  survive 
  initial 
  attacks, 
  but 
  as 
  their 
  growth 
  is 
  retarded, 
  they 
  take 
  a 
  long 
  

   time 
  to 
  reach 
  maturity. 
  Mature 
  trees 
  rarely 
  succumb 
  to 
  the 
  attacks 
  of 
  the 
  beetles, 
  

   although 
  a 
  number 
  of 
  felled 
  trees 
  were 
  found 
  to 
  harbour 
  the 
  insects. 
  

  

  The 
  following 
  record 
  of 
  the 
  life-history 
  of 
  Oryctes 
  monoceros 
  has 
  been 
  obtained 
  : 
  — 
  

   Eggs 
  found 
  in 
  dead 
  coconut 
  trunk 
  . 
  . 
  . 
  . 
  . 
  . 
  11. 
  viii. 
  1917. 
  

  

  Eggs 
  hatched 
  

  

  Larvae 
  started 
  to 
  build 
  pupal 
  cell 
  

   Pupal 
  cell 
  completed 
  and 
  pupa 
  formed 
  

   Adults 
  emerged 
  

  

  19. 
  viii. 
  1917. 
  

  

  5. 
  xii. 
  1917. 
  

  

  10. 
  xii. 
  1917. 
  

  

  28. 
  xii. 
  1917. 
  

  

  (C605) 
  e2 
  

  

  