﻿410 
  W. 
  F. 
  FISKE. 
  

  

  VI 
  (/). 
  Long-shore 
  Range 
  and 
  Density 
  of 
  Fly 
  as 
  determined 
  by 
  Food 
  Supply 
  on 
  

   Victoria 
  Nyanza. 
  

  

  Glossina 
  must, 
  of 
  course, 
  have 
  food, 
  and 
  no 
  other 
  food 
  than 
  the 
  blood 
  of 
  vertebrates 
  

   is 
  required 
  by 
  flies 
  in 
  confinement. 
  If 
  any 
  other 
  sort 
  is 
  ever 
  taken, 
  evidence 
  or 
  

   indication 
  that 
  it 
  is 
  required 
  by 
  the 
  flies 
  is 
  entirely 
  lacking. 
  

  

  Evidence 
  is 
  abundant 
  and 
  conclusive 
  that 
  the 
  four 
  most 
  common 
  of 
  the 
  large 
  

   shore-loving 
  or 
  amphibious 
  animals 
  found 
  in 
  this 
  region 
  are 
  all 
  favoured 
  hosts 
  

   (crocodile, 
  Varanus, 
  situtunga 
  and 
  hippo). 
  Evidence 
  with 
  respect 
  to 
  common 
  

   game 
  animals 
  of 
  the 
  mainland 
  (bush-buck, 
  bush-pig, 
  water-buck 
  and 
  buffalo) 
  is 
  

   negative 
  or 
  conflicting, 
  but 
  it 
  would 
  probably 
  be 
  a 
  conservative 
  estimate 
  that 
  the 
  

   four 
  favoured 
  hosts 
  first 
  mentioned 
  provide 
  95 
  per 
  cent, 
  of 
  the 
  food 
  taken 
  by 
  Glossina 
  

   palpal/is 
  on 
  the 
  mainland 
  and 
  98 
  or 
  99 
  per 
  cent, 
  of 
  its 
  food 
  on 
  the 
  islands 
  (excepting 
  

   the 
  islands 
  of 
  Bunjako 
  and 
  Binga, 
  where 
  bush-buck, 
  etc., 
  occur, 
  and 
  Bukassa, 
  where 
  

   pig 
  is 
  a 
  factor). 
  

  

  If 
  this 
  is 
  correct, 
  it 
  might 
  be 
  assumed 
  that 
  complete 
  extermination 
  of 
  the 
  four 
  

   principle 
  hosts 
  would 
  — 
  in 
  the 
  absence 
  of 
  man 
  and 
  domestic 
  animals 
  — 
  cause 
  reduc- 
  

   tion 
  in 
  density 
  of 
  infestation 
  by 
  95 
  to 
  99 
  per 
  cent. 
  I 
  think 
  this 
  would 
  undoubtedly 
  

   follow, 
  if 
  the 
  extermination 
  of 
  the 
  hosts 
  was 
  complete, 
  for 
  there 
  are 
  several 
  reaches 
  

   of 
  mainland 
  shore 
  in 
  the 
  district 
  of 
  Buddu 
  where 
  absence 
  of 
  all 
  host 
  animals 
  of 
  favoured 
  

   species 
  from 
  points 
  within 
  range 
  or 
  reach 
  of 
  tsetse 
  from 
  good 
  shelter 
  and 
  good 
  

   breeding 
  places 
  is 
  specifically 
  correlated 
  with 
  absence 
  of 
  fly. 
  The 
  best 
  case 
  of 
  this 
  

   sort 
  is 
  illustrated 
  by 
  figure 
  6 
  and 
  the 
  explanatory 
  note 
  accompanying 
  it. 
  Another 
  

   striking 
  case 
  is 
  the 
  Mujuzi 
  colony, 
  which 
  is 
  remarkable 
  in 
  so 
  many 
  ways, 
  and 
  which 
  

   is 
  illustrated 
  by 
  fig. 
  5 
  (p. 
  388). 
  This 
  colony 
  centres 
  conspicuously 
  at 
  the 
  point 
  

   (45 
  in 
  graph) 
  where 
  alone 
  food 
  is 
  plentiful. 
  North 
  of 
  the 
  colony 
  centre 
  (points 
  

   46 
  and 
  47) 
  there 
  are 
  good 
  breeding 
  grounds 
  and 
  good 
  shelter, 
  but 
  the 
  falling 
  off 
  

   in 
  density, 
  coupled 
  with 
  the 
  uniquely 
  high 
  female 
  percentage 
  (p. 
  373), 
  left 
  no 
  

   doubt 
  that 
  absence 
  of 
  food 
  explained 
  scarcity 
  of 
  fly 
  away 
  from 
  the 
  colony 
  

   centre. 
  

  

  It 
  is 
  absolutely 
  necessary, 
  however, 
  that 
  adequate 
  protection 
  in 
  the 
  form 
  of 
  

   both 
  shelter 
  and 
  breeding 
  grounds 
  shall 
  be 
  provided 
  for 
  the 
  insect 
  within 
  reach 
  

   of 
  food 
  ; 
  otherwise 
  the 
  most 
  abundant 
  supply 
  of 
  the 
  most 
  preferred 
  food 
  is 
  valueless 
  

   to 
  the 
  species. 
  These 
  conditions 
  occur 
  in 
  many 
  localities, 
  and 
  are 
  described 
  in 
  some 
  

   detail 
  in 
  discussions 
  on 
  the 
  effect 
  of 
  shelter 
  and 
  breeding 
  grounds 
  on 
  range 
  and 
  

   density 
  of 
  fly. 
  Small 
  islets, 
  like 
  that 
  south 
  of 
  Dziru 
  or 
  that 
  east 
  of 
  Bubembe 
  

   (p. 
  429), 
  may 
  fairly 
  swarm 
  with 
  crocodile 
  and 
  Varanus, 
  and, 
  in 
  addition, 
  provide 
  

   breeding 
  places 
  of 
  the 
  very 
  best, 
  but 
  if 
  devoid 
  of 
  adequate 
  massive 
  shelter 
  they 
  are 
  

   fly 
  free, 
  or 
  infested 
  only 
  by 
  stragglers 
  from 
  elsewhere. 
  

  

  It 
  is 
  wholly 
  impracticable 
  to 
  attempt 
  a 
  presentation 
  of 
  general 
  data 
  concerning 
  

   environmental 
  conditions 
  at 
  the 
  many 
  points 
  on 
  the 
  mainland 
  and 
  on 
  the 
  more 
  

   than 
  70 
  islands 
  that 
  were 
  wholly 
  or 
  in 
  part 
  surveyed. 
  (It 
  would 
  require 
  not 
  less 
  

   that 
  150 
  pages 
  of 
  descriptive 
  matter 
  apart 
  from 
  tables 
  and 
  graphs.) 
  The 
  selected 
  

   cases 
  cited 
  in 
  various 
  connections 
  must 
  suffice, 
  together 
  with 
  the 
  conclusions 
  drawn 
  

   from 
  a 
  thorough 
  study 
  of 
  original 
  data 
  in 
  the 
  field 
  (November-December 
  1914), 
  

   followed 
  by 
  extensive 
  fly 
  surveys 
  (Sesse 
  Islands 
  and 
  the 
  Buddu 
  and 
  Mawakota 
  shores) 
  

  

  