﻿INVESTIGATIONS 
  INTO 
  THE 
  BIONOMICS 
  OF 
  GLOSSINA 
  PALPALIS. 
  435 
  

  

  Conditions 
  at 
  the 
  back 
  of 
  ancient, 
  permanently 
  anchored 
  fields 
  and 
  belts 
  of 
  sudd 
  

   are 
  somewhat 
  more 
  likely 
  to 
  be 
  favourable 
  to 
  the 
  existence 
  of 
  Glossina 
  palpalis 
  

   than 
  conditions 
  at 
  inland 
  points 
  generally, 
  because 
  there 
  is 
  apt 
  to 
  be 
  sandy 
  soil 
  

   sufficiently 
  well 
  watered 
  to 
  sustain 
  sheltering 
  vegetation. 
  But 
  it 
  is 
  improbable 
  

   that 
  the 
  necessary 
  combination 
  of 
  food, 
  shelter 
  and 
  breeding 
  places 
  would 
  exist 
  

   at 
  all 
  commonly 
  unless 
  the 
  sudd-belt 
  is 
  so 
  narrow 
  as 
  to 
  permit 
  landing 
  of 
  amphibious 
  

   animals. 
  

  

  It 
  is 
  a 
  safe 
  enough 
  presumption 
  that 
  a 
  sudd-belt 
  not 
  traversed 
  by 
  hippo 
  or 
  crocodile 
  

   trails 
  is 
  free 
  of 
  fly 
  on 
  its 
  landward 
  side, 
  but 
  narrow 
  belts 
  crossed 
  by 
  hippo 
  or 
  crocodile 
  

   trails 
  should 
  not 
  be 
  regarded 
  as 
  sufficient 
  protection 
  against 
  fly. 
  

  

  IX. 
  The 
  Inimical 
  Factors 
  in 
  the 
  Bionomics 
  of 
  Glossina 
  palpalis. 
  

  

  The 
  natural 
  enemies 
  and 
  other 
  inimical 
  factors 
  in 
  the 
  bionomics 
  of 
  Glossina 
  

   are 
  numerous 
  and 
  diverse. 
  For 
  this 
  very 
  reason 
  they 
  are 
  peculiarly 
  difficult 
  to 
  identify 
  

   and 
  study. 
  It 
  is 
  much 
  more 
  simple 
  and 
  practical 
  to 
  study 
  the 
  more 
  specific 
  and 
  

   easily 
  defined 
  protective 
  factors 
  than 
  the 
  more 
  numerous, 
  less 
  specific 
  and 
  less 
  

   easily 
  defined 
  destructive 
  and 
  otherwise 
  inimical 
  factors 
  against 
  which 
  they 
  afford 
  

   protection. 
  

  

  For 
  example, 
  shade 
  at 
  breeding 
  grounds 
  is 
  protective 
  against 
  the 
  destructive 
  

   effects 
  of 
  sun, 
  and 
  the 
  clean- 
  washed 
  deposits 
  of 
  sand 
  or 
  gravel 
  which 
  are 
  most 
  favoured 
  

   as 
  breeding 
  places 
  are 
  protection 
  against 
  many 
  different 
  species 
  of 
  parasitic 
  and 
  

   predatory 
  destructors 
  of 
  insects, 
  that 
  are 
  generally 
  distributed 
  and 
  common 
  in 
  most 
  

   other 
  types 
  of 
  soil 
  than 
  these. 
  If 
  shade 
  at 
  the 
  breeding 
  grounds 
  is 
  destroyed, 
  the 
  

   puparia 
  in 
  these 
  are 
  quickly 
  killed 
  by 
  the 
  sun 
  ; 
  and 
  if 
  there 
  are 
  no 
  other 
  breeding 
  

   grounds 
  left 
  to 
  the 
  fly 
  in 
  that 
  district, 
  it 
  will 
  soon 
  be 
  exterminated, 
  either 
  through 
  

   lack 
  of 
  protection 
  or 
  through 
  the 
  operation 
  of 
  destructive 
  factors, 
  according 
  to 
  the 
  

   point 
  of 
  view. 
  But 
  though 
  shade 
  is 
  specifically 
  protective 
  against 
  a 
  specific 
  destructive 
  

   factor, 
  it 
  is 
  not 
  that 
  factor 
  which 
  operates 
  exterminatively 
  when 
  protection 
  against 
  

   it 
  is 
  destroyed 
  ; 
  it 
  is 
  the 
  parasitic 
  and 
  predatory 
  enemies 
  which 
  become 
  exterminative, 
  

   because 
  the 
  flies 
  will 
  most 
  certainly 
  not 
  deposit 
  their 
  young 
  in 
  unshaded 
  situations 
  

   to 
  be 
  destroyed 
  by 
  sun. 
  They 
  will 
  seek 
  shaded 
  places, 
  wherein 
  ants, 
  perhaps, 
  or 
  

   ground 
  beetles 
  or 
  beetle 
  larvae, 
  or 
  yet 
  other 
  predatory 
  creatures 
  will 
  be 
  the 
  destructive 
  

   agents, 
  according 
  to 
  the 
  particular 
  spot 
  that 
  they 
  select. 
  

  

  It 
  is 
  impossible 
  in 
  such 
  cases 
  to 
  specify 
  the 
  destructive 
  agents 
  actually 
  responsible 
  

   for 
  extermination 
  of 
  the 
  species. 
  The 
  breeding 
  grounds 
  are 
  a 
  protection 
  against 
  

   not 
  one 
  or 
  two 
  but 
  against 
  a 
  whole 
  coalition 
  of 
  enemies, 
  any 
  one 
  of 
  which 
  may 
  be 
  

   exterminative 
  if 
  the 
  flies 
  were 
  to 
  deposit 
  all 
  their 
  larvae 
  in 
  situations 
  exposed 
  to 
  that 
  

   particular 
  one, 
  and 
  all 
  of 
  which 
  are 
  impotent 
  to 
  destroy 
  if 
  the 
  one 
  specific 
  form 
  of 
  

   protection 
  is 
  provided 
  and 
  utilised 
  by 
  the 
  flies. 
  

  

  Moreover 
  it 
  is 
  difficult 
  to 
  see 
  how 
  knowledge 
  of 
  the 
  inimical 
  factors 
  can 
  be 
  made 
  

   of 
  practical 
  application. 
  If 
  we 
  have 
  a 
  knowledge 
  of 
  the 
  protective 
  factors, 
  they 
  

   can 
  be 
  utilised, 
  for 
  by 
  depriving 
  the 
  insect 
  of 
  its 
  protection 
  very 
  practical 
  utilisation 
  

   can 
  be 
  made 
  of 
  its 
  destructors. 
  But 
  knowledge 
  of 
  the 
  destructors 
  is 
  valueless 
  unless 
  

   it 
  includes 
  knowledge 
  of 
  the 
  protection 
  which 
  serves 
  the 
  species 
  against 
  them. 
  It 
  

  

  