﻿INVESTIGATIONS 
  INTO 
  THE 
  BIONOMICS 
  OF 
  GLOSSINA 
  PALPALIS. 
  379 
  

  

  Under 
  entirely 
  natural 
  conditions 
  swarms 
  had 
  been 
  seen 
  on 
  Varanus, 
  situtunga, 
  

   crocodile, 
  hippopotamus, 
  pig 
  (of 
  domestic 
  stock, 
  but 
  run 
  wild) 
  and 
  tortoise, 
  and 
  

   most 
  freely 
  of 
  all 
  on 
  Varanus. 
  The 
  fact 
  that 
  repeated 
  attempts 
  to 
  induce 
  one 
  

   to 
  form 
  on 
  Varanus 
  which 
  were 
  held 
  in 
  constraint 
  all 
  failed, 
  excepting 
  only 
  the 
  first 
  

   (see 
  Sect. 
  VI 
  (c), 
  experiment 
  4), 
  convinced 
  one 
  that 
  something 
  more 
  than 
  the 
  mere 
  

   presence 
  of 
  a 
  host 
  animal 
  of 
  a 
  favoured 
  species 
  is 
  necessary, 
  and 
  failure 
  is 
  believed 
  

   to 
  be 
  due 
  to 
  the 
  impatience 
  of 
  these 
  animals 
  under 
  restraint. 
  In 
  other 
  words, 
  a 
  

   host 
  must 
  be 
  complacent 
  under 
  attack 
  as 
  well 
  as 
  of 
  a 
  favoured 
  species 
  or 
  it 
  will 
  not 
  

   be 
  favoured 
  by 
  tsetse 
  to 
  the 
  extent 
  of 
  attracting 
  a 
  " 
  following 
  swarm." 
  

  

  The 
  final 
  experiments 
  with 
  Varanus, 
  sheep 
  and 
  oxen 
  are 
  described 
  in 
  Sect. 
  VI 
  (c), 
  

   experiment 
  3. 
  They 
  led 
  to 
  the 
  conclusion 
  that 
  a 
  host 
  to 
  be 
  " 
  favoured," 
  must 
  

   always 
  be 
  complacent, 
  and 
  suggested 
  that 
  perhaps 
  almost 
  any 
  of 
  the 
  larger 
  animals, 
  

   including 
  man, 
  might 
  be 
  favoured, 
  even 
  to 
  the 
  extent 
  of 
  collecting 
  a 
  " 
  following 
  

   swarm," 
  if 
  it 
  were 
  in 
  them 
  to 
  sutler 
  the 
  attacks 
  of 
  Glossina 
  without 
  sign 
  of 
  protest. 
  

  

  ■V. 
  The 
  Effect 
  of 
  Open 
  Water 
  and 
  Humid 
  Conditions 
  upon 
  the 
  Range 
  

  

  of 
  Glossina 
  palpalis. 
  

  

  No 
  factor 
  in 
  the 
  bionomics 
  of 
  Glossina 
  palpalis 
  is 
  more 
  obviously 
  correlated 
  with 
  

   the 
  range 
  or 
  distribution 
  of 
  this 
  species 
  than 
  open 
  water. 
  It 
  is 
  a 
  riparian 
  species, 
  

   and 
  its 
  occurrence 
  far 
  from 
  shores 
  of 
  lakes 
  or 
  banks 
  of 
  streams 
  is 
  a 
  subject 
  for 
  remark 
  

   whenever 
  observed. 
  

  

  Exceptional 
  dispersion 
  inland, 
  however, 
  is 
  not 
  at 
  all 
  rare, 
  and 
  many 
  cases 
  of 
  it 
  

   were 
  encountered 
  and 
  studied. 
  In 
  all 
  cases 
  the 
  explanation 
  was 
  the 
  same, 
  and 
  

   involved, 
  as 
  virtually 
  every 
  topic 
  in 
  Glossina 
  bionomics 
  seems 
  bound 
  to 
  involve, 
  

   the 
  subject 
  of 
  hosts 
  and 
  host 
  preferences. 
  The 
  two 
  topics 
  are 
  inseparable 
  in 
  field 
  

   work 
  and 
  cannot 
  well 
  be 
  separated 
  in 
  discussing 
  and 
  recounting 
  field 
  work. 
  

  

  These 
  studies 
  were 
  more 
  convincing 
  to 
  the 
  observer 
  than 
  it 
  is 
  feared 
  they 
  may 
  

   prove 
  to 
  the 
  reader, 
  that 
  the 
  correlation 
  in 
  question 
  is 
  purely 
  coincidental 
  ; 
  that 
  water 
  

   or 
  humid 
  conditions 
  are 
  not 
  of 
  direct 
  benefit 
  to 
  the 
  insect, 
  nor 
  required 
  by 
  it 
  ; 
  but 
  

   that 
  a 
  proper 
  combination 
  of 
  food, 
  shelter 
  and 
  breeding 
  places 
  which 
  is 
  requisite 
  

   to 
  its 
  existence 
  occurs 
  so 
  infrequently 
  away 
  from 
  the 
  shores 
  of 
  lakes 
  or 
  banks 
  of 
  

   larger 
  streams 
  that 
  it 
  is 
  perforce 
  riparian 
  in 
  habit. 
  

  

  V 
  (a). 
  Range 
  of 
  Fly 
  inland 
  from 
  Lake 
  Shore. 
  

  

  Ordinarily 
  the 
  range 
  of 
  fly 
  inland 
  from 
  the 
  lake 
  shore 
  is 
  extremely 
  limited 
  ; 
  at 
  

   50 
  yards 
  there 
  will 
  usually 
  be 
  a 
  sharp 
  reduction 
  in 
  density 
  ; 
  beyond 
  100 
  to 
  200 
  yards 
  

   flies 
  will 
  appear 
  only 
  as 
  stragglers 
  ; 
  and 
  at 
  300 
  to 
  500 
  yards 
  they 
  will 
  disappear, 
  

   or, 
  at 
  least, 
  density 
  will 
  drop 
  below 
  any 
  figure 
  that 
  can 
  be 
  conveniently 
  measured. 
  

   If 
  range 
  inland 
  is 
  more 
  extensive 
  than 
  this, 
  some 
  special 
  cause 
  for 
  it 
  must 
  exist. 
  

  

  Attempts 
  to 
  measure 
  the 
  ordinary 
  inland 
  range 
  of 
  fly 
  were 
  limited 
  to 
  a 
  single 
  

   experiment 
  on 
  the 
  island 
  of 
  Kitobo 
  in 
  December 
  1913, 
  which 
  resulted 
  as 
  follows 
  — 
  

   the 
  catch 
  being 
  made 
  at 
  the 
  base 
  of 
  a 
  slope 
  that 
  rose 
  rather 
  steeply 
  to 
  a 
  plateau 
  with 
  

   abandoned 
  plantations. 
  

   (659) 
  c 
  

  

  