﻿TSETSE 
  PLY 
  IN 
  SOUTHERN 
  RHOBESTA, 
  1918. 
  83 
  

  

  These 
  figures 
  are 
  more 
  or 
  less 
  in 
  accordance 
  with 
  Lloyd's 
  results, 
  and 
  they 
  also 
  

   suggest 
  that 
  baboons 
  may 
  constitute 
  an 
  efficient 
  substitute 
  for 
  game 
  as 
  a 
  food- 
  

   supply 
  for 
  tsetse. 
  It 
  should 
  be 
  noted 
  that 
  all 
  the 
  collections, 
  except 
  that 
  near 
  the 
  

   Gorai 
  river 
  in 
  April 
  1911, 
  were 
  made 
  during 
  the 
  season 
  when 
  the 
  fly 
  is 
  concentrated, 
  

   and 
  that 
  the 
  collection 
  referred 
  to 
  is 
  the 
  only 
  one 
  showing 
  extreme 
  disparity 
  in 
  the 
  

   proportion 
  of 
  the 
  sexes. 
  During 
  the 
  period 
  of 
  concentration 
  there 
  is 
  no 
  scope 
  for 
  

   the 
  females 
  to 
  separate 
  from 
  the 
  males, 
  whilst 
  during 
  the 
  remainder 
  of 
  the 
  year 
  

   they 
  have 
  a 
  considerable 
  extent 
  of 
  forest 
  at 
  their 
  disposal. 
  This 
  fact 
  may 
  have 
  

   some 
  bearing 
  on 
  the 
  result. 
  

  

  (2) 
  The 
  fact 
  that 
  a 
  material 
  percentage 
  of 
  the 
  game 
  survived 
  the 
  rinderpest 
  is 
  

   an 
  obstacle 
  in 
  the 
  way 
  of 
  accepting 
  the 
  theory 
  that 
  the 
  reduction 
  of 
  the 
  game 
  at 
  this 
  

   period 
  was 
  the 
  sole 
  cause 
  of 
  the 
  immense 
  reduction 
  of 
  the 
  fly. 
  We 
  are, 
  however, 
  

   in 
  the 
  same 
  difficulty 
  with 
  regard 
  to 
  the 
  disappearance 
  of 
  fly 
  from 
  many 
  belts 
  in 
  

   South 
  Africa, 
  following 
  the 
  wholesale 
  destruction 
  of 
  game 
  by 
  hunters, 
  for 
  in 
  neither 
  

   case 
  was 
  the 
  removal 
  of 
  the 
  animals 
  complete. 
  It 
  is 
  in 
  this 
  connection 
  that 
  further 
  

   evidence 
  as 
  to 
  the 
  question 
  whether 
  the 
  hot 
  months 
  preceding 
  the 
  rains 
  are 
  of 
  

   maximum 
  importance 
  to 
  the 
  fly 
  or 
  not 
  is 
  required. 
  Supposing 
  this 
  to 
  be 
  the 
  case, 
  the 
  

   change 
  in 
  the 
  habits 
  of 
  game 
  consequent 
  on 
  persecution 
  might 
  have 
  a 
  very 
  consider- 
  

   able 
  effect, 
  The 
  most 
  favoured 
  haunts 
  of 
  the 
  fly 
  during 
  the 
  season 
  of 
  concentration 
  

   are 
  the 
  edges 
  of 
  vleis, 
  and 
  under 
  natural 
  conditions 
  this 
  places 
  them 
  in 
  a 
  position 
  

   to 
  secure 
  more 
  or 
  less 
  regular 
  meals 
  ; 
  for, 
  as 
  is 
  known 
  to 
  all 
  hunters 
  in 
  Africa, 
  the 
  

   game 
  comes 
  regularly 
  to 
  graze 
  on 
  the 
  green 
  grass 
  in 
  these 
  vleis 
  in 
  the 
  afternoon 
  during 
  

   the 
  hot 
  dry 
  months 
  and 
  must 
  necessarily 
  pass 
  through 
  the 
  haunts 
  of 
  the 
  fly. 
  Under 
  

   persecution 
  game 
  develops 
  a 
  habit 
  of 
  visiting 
  the 
  vleis 
  at 
  night 
  and 
  leaving 
  at 
  dawn, 
  

   so 
  that 
  the 
  fly 
  does 
  not 
  get 
  the 
  same 
  opportunities 
  for 
  feeding. 
  It 
  is 
  conceivable 
  

   that 
  the 
  great 
  losses 
  amongst 
  the 
  game 
  during 
  the 
  rinderpest 
  may 
  have 
  produced 
  a 
  

   similar 
  shyness, 
  which, 
  supplementing 
  the 
  undeniably 
  immense 
  reduction 
  in 
  numbers 
  

   of 
  the 
  animals, 
  might 
  account 
  for 
  a 
  practical 
  cessation 
  of 
  breeding, 
  during 
  what 
  may 
  

   be 
  the 
  most 
  important 
  period. 
  During 
  the 
  wet 
  season 
  the 
  presence 
  of 
  only 
  a 
  fraction 
  

   of 
  the 
  usual 
  food-supply 
  scattered 
  throughout 
  the 
  forest 
  would 
  in 
  any 
  case 
  have 
  a 
  

   very 
  deleterious 
  effect. 
  

  

  Some 
  of 
  the 
  more 
  vigorous 
  opponents 
  of 
  the 
  game 
  and 
  fly 
  theory 
  appear 
  to 
  think 
  

   it 
  necessary 
  to 
  suppose 
  that 
  every 
  fly 
  was 
  starved 
  at 
  the 
  time 
  of 
  the 
  rinderpest 
  if 
  the 
  

   lack 
  of 
  food 
  is 
  to 
  account 
  for 
  the 
  fly's 
  disappearance, 
  but 
  this 
  is 
  obviously 
  quite 
  unneces- 
  

   sary. 
  A 
  practical 
  cessation 
  of 
  breeding 
  would 
  produce 
  the 
  same 
  result 
  and 
  this 
  might 
  

   conceivably 
  be 
  brought 
  about 
  by 
  a 
  greatly 
  reduced 
  and 
  uncertain 
  food-supply. 
  We 
  

   know 
  little 
  enough 
  concerning 
  the 
  factors 
  that 
  induce 
  the 
  fly 
  to 
  breed, 
  but 
  we 
  do 
  

   know 
  that 
  regular 
  meals 
  are 
  necessary 
  to 
  the 
  insect 
  in 
  confinement, 
  and 
  it 
  seems 
  

   almost 
  probable 
  that 
  a 
  state 
  of 
  semi-starvation 
  in 
  nature 
  would 
  either 
  cause 
  the 
  

   insects 
  to 
  cease 
  breeding, 
  or 
  that 
  pregnant 
  females, 
  with 
  growing 
  larvae 
  draining 
  

   their 
  vitality, 
  would 
  tend 
  to 
  die 
  off 
  or 
  abort 
  in 
  such 
  circumstances. 
  Unfortunately 
  

   it 
  is 
  impossible 
  to 
  verify 
  such 
  facts 
  under 
  artificial 
  conditions. 
  

  

  The 
  most 
  striking 
  point 
  in 
  connection 
  with 
  the 
  controversy 
  is, 
  however, 
  that 
  not 
  

   a 
  single 
  alternative 
  suggestion 
  of 
  any 
  weight 
  has 
  been 
  made. 
  It 
  has 
  been 
  vaguely 
  

   suggested 
  that 
  climatic 
  conditions 
  may 
  have 
  been 
  accountable 
  or 
  that 
  the 
  fact 
  of 
  

  

  