﻿254 
  D. 
  d'emmerez 
  de 
  charmoy. 
  

  

  In 
  general 
  the 
  relationship 
  existing 
  between 
  the 
  host 
  and 
  the 
  parasite 
  are 
  so 
  well 
  

   balanced 
  that 
  the 
  mere 
  presence 
  of 
  the 
  parasite 
  points 
  to 
  the 
  existence 
  of 
  the 
  host, 
  

   although 
  in 
  most 
  cases 
  it 
  is 
  extremely 
  difficult 
  to 
  find 
  the 
  latter. 
  

  

  The 
  habits 
  of 
  this 
  Scoliid 
  present 
  no 
  peculiarities 
  apart 
  from 
  the 
  fact 
  that 
  it 
  

   exhibits 
  a 
  marked 
  partiality 
  for 
  certain 
  plants, 
  like 
  Scolia 
  oryctophaga 
  and 
  some 
  

   other 
  species. 
  In 
  Pamplemousses, 
  where 
  the 
  flowers 
  are 
  varied, 
  this 
  wasp 
  visits 
  

   almost 
  exclusively 
  Cordia 
  interrupta 
  (Herbe 
  Conde), 
  whilst 
  at 
  Reduit, 
  where 
  this 
  plant 
  

   does 
  not 
  exist, 
  it 
  visits 
  Lantana 
  and 
  Convolvulus, 
  exhibiting 
  a 
  preference 
  for 
  the 
  latter. 
  

  

  Though 
  the 
  females 
  are 
  on 
  the 
  wing 
  in 
  varying 
  numbers 
  at 
  any 
  time 
  during 
  the 
  

   day, 
  it 
  is 
  between 
  11 
  a.m. 
  and 
  3 
  p.m. 
  that 
  they 
  are 
  met 
  with 
  most 
  frequently. 
  The 
  

   males 
  do 
  not 
  go 
  underground, 
  but 
  they 
  have 
  a 
  curious 
  habit, 
  common 
  to 
  many 
  solitary 
  

   Hymenoptera, 
  of 
  collecting 
  in 
  considerable 
  numbers 
  at 
  night 
  on 
  the 
  same 
  twig, 
  

   forming 
  thereby 
  compact 
  swarms 
  of 
  several 
  hundred 
  insects. 
  

  

  This 
  species 
  varies 
  in 
  size. 
  Plate 
  viii, 
  fig. 
  6, 
  shows 
  the 
  limits 
  of 
  this 
  variation 
  in 
  

   males 
  and 
  females 
  respectively. 
  

  

  The 
  life-cycle 
  varies 
  but 
  little 
  from 
  that 
  of 
  Scolia 
  oryctophaga, 
  the 
  chief 
  difference 
  

   being 
  in 
  the 
  duration 
  of 
  the 
  pupal 
  stage, 
  which 
  has 
  never 
  been 
  found 
  to 
  exceed 
  three 
  

   months, 
  the 
  development 
  of 
  the 
  egg 
  and 
  larva 
  lasting 
  5 
  and 
  12 
  days 
  respectively. 
  

  

  This 
  insect 
  thrives 
  fairly 
  well 
  in 
  captivity 
  and 
  can 
  be 
  reared 
  just 
  like 
  S. 
  oryctophaga 
  

   in 
  pots, 
  but 
  requires 
  a 
  deeper 
  layer 
  of 
  soil, 
  8 
  in. 
  deep 
  at 
  least. 
  The 
  parasitised 
  beetle 
  

   larvae 
  are 
  found 
  4 
  in. 
  to 
  6 
  in. 
  underground, 
  and 
  are 
  never 
  enclosed 
  in 
  cells. 
  

  

  The 
  Results 
  of 
  the 
  Introduction. 
  

  

  It 
  is 
  difficult 
  at 
  the 
  present 
  time 
  to 
  give 
  precise 
  information 
  concerning 
  the 
  results 
  

   of 
  this 
  importation, 
  in 
  view 
  of 
  the 
  conditions 
  under 
  which 
  the 
  liberation 
  of 
  the 
  Scoliids 
  

   was 
  effected. 
  Lack 
  of 
  a 
  precise 
  knowledge 
  of 
  the 
  habits 
  of 
  these 
  insects 
  at 
  the 
  outset 
  

   prevented 
  preliminary 
  preparation 
  or 
  the 
  grouping 
  together 
  of 
  conditions 
  likely 
  to 
  

   induce 
  the 
  gathering 
  of 
  insects 
  at 
  particular 
  spots 
  where 
  they 
  had 
  been 
  liberated, 
  

   thereby 
  excluding 
  the 
  possibility 
  of 
  following 
  closely 
  the 
  progress 
  of 
  their 
  

   acclimatisation. 
  

  

  The 
  absence 
  of 
  flowers 
  at 
  some 
  of 
  the 
  spots 
  where 
  Scolia 
  oryctophaga 
  were 
  liberated 
  

   resulted 
  in 
  the 
  rapid 
  dispersion 
  of 
  these 
  insects. 
  On 
  the 
  day 
  following 
  their 
  liberation 
  

   only 
  two 
  or 
  three 
  insects 
  were 
  to 
  be 
  observed 
  hovering 
  over 
  the 
  place 
  where 
  they 
  were 
  

   originally 
  set 
  free, 
  and 
  three 
  days 
  afterwards 
  not 
  one 
  was 
  to 
  be 
  found. 
  There 
  is 
  no 
  

   reason 
  to 
  believe 
  that 
  they 
  had 
  all 
  perished 
  in 
  so 
  short 
  a 
  time, 
  inasmuch 
  as 
  females 
  

   coming 
  from 
  the 
  same 
  importation 
  lived 
  in 
  captivity 
  for 
  several 
  weeks 
  after 
  having 
  

   parasitised 
  larvae 
  of 
  Oryctes 
  tarandus. 
  In 
  August 
  1918, 
  i.e., 
  one 
  year 
  later, 
  a 
  female 
  

   was 
  found 
  at 
  Riche 
  Bois 
  and 
  another 
  at 
  Reduit, 
  and 
  in 
  September 
  of 
  the 
  same 
  

   year 
  another 
  female 
  was 
  found 
  at 
  Riche 
  Bois. 
  

  

  Observations 
  showed 
  that 
  this 
  Scoliid 
  in 
  the 
  free 
  state 
  had 
  parasitised 
  Oryctes 
  

   tarandus. 
  There 
  is 
  ground, 
  therefore, 
  for 
  believing 
  that 
  the 
  insect 
  has 
  acclimatised 
  

   itself 
  in 
  Mauritius, 
  although 
  a 
  considerable 
  time 
  must 
  elapse 
  before 
  it 
  can 
  control 
  to 
  

   an 
  appreciable 
  extent 
  the 
  damage 
  done 
  by 
  the 
  Oryctes. 
  So 
  far 
  as 
  concerns 
  the 
  other 
  

   species 
  imported 
  at 
  the 
  same 
  time 
  as 
  Scolia 
  oryctophaga, 
  there 
  is 
  no 
  indication 
  as 
  yet 
  

   that 
  they 
  have 
  established 
  themselves 
  in 
  the 
  island. 
  

  

  Now 
  that 
  sufficient 
  data 
  have 
  been 
  acquired 
  as 
  to 
  methods 
  and 
  requirements, 
  

   it 
  is 
  proposed 
  to 
  make 
  further 
  importations 
  of 
  these 
  insects 
  at 
  a 
  convenient 
  time 
  in 
  

   the 
  future. 
  

  

  