﻿ENTOMOLOGICAL 
  ASPECTS 
  OF 
  AN 
  OUTBREAK 
  OF 
  SLEEPING 
  SICKNESS. 
  329 
  

  

  The 
  main 
  area 
  occupied 
  by 
  this 
  fly 
  in 
  East 
  Mwanza 
  would 
  appear 
  to 
  coincide 
  

   with 
  that 
  of 
  the 
  main 
  acacia 
  woodland 
  area 
  shown 
  in 
  the 
  attached 
  rough 
  map. 
  In 
  

   the 
  north 
  it 
  occurred 
  in 
  the 
  strips 
  of 
  mhali-Combretiim-Grewia 
  wooding 
  at 
  the 
  immediate 
  

   foot 
  of 
  Mount 
  Baridi 
  (Ushashi 
  escarpment) 
  and 
  its 
  pupae 
  under 
  the 
  lower 
  boulders 
  

   of 
  the 
  mosaic 
  that 
  covers 
  this 
  hillside 
  ; 
  and 
  the 
  same 
  fly, 
  taken 
  again 
  in 
  numbers 
  

   by 
  two 
  of 
  my 
  natives, 
  has 
  been 
  sent 
  to 
  me 
  by 
  Mr. 
  Turnbull 
  from 
  the 
  mainland 
  of 
  

   Ukerewe 
  since 
  I 
  came 
  to 
  England. 
  Dr. 
  Maclean 
  took 
  it 
  an 
  hour 
  east 
  of 
  Chamliho. 
  

  

  In 
  these 
  circumstances 
  it 
  would 
  seem 
  likely 
  that 
  it 
  is 
  the 
  chief 
  fly 
  that 
  occurs 
  

   about 
  Ikoma 
  and 
  northwards 
  as 
  far 
  as 
  Bwasi 
  — 
  also 
  that 
  it 
  is 
  the 
  fly 
  that 
  is 
  said 
  to 
  

   infest 
  the 
  bush 
  in 
  the 
  centre 
  of 
  Ukerewe, 
  though 
  my 
  native 
  collectors 
  iailed 
  to 
  find 
  

   fly 
  there. 
  With 
  reference 
  to 
  the 
  area 
  about 
  Lake 
  £}'asi 
  that 
  is 
  shown 
  green 
  in 
  the 
  

   map, 
  Mr. 
  E. 
  D. 
  Browne, 
  the 
  Senior 
  Commissioner 
  of 
  the 
  Arusha 
  District, 
  wrote 
  to 
  

   me 
  in 
  a 
  letter, 
  dated 
  10th 
  September 
  1921, 
  " 
  I 
  am 
  well 
  acquainted 
  with 
  the 
  area 
  in 
  

   different 
  seasons. 
  I 
  believe 
  that 
  only 
  Glossina 
  morsitans 
  infests 
  the 
  Yaida 
  Valley 
  

   and 
  is 
  of 
  course 
  rampant 
  to 
  Eyasi 
  and 
  probably 
  all 
  round 
  this 
  lake, 
  except 
  possibly 
  

   at 
  the 
  extreme 
  north-east 
  corner, 
  and 
  even 
  there 
  I 
  am 
  doubtful 
  of 
  its 
  absence 
  at 
  all 
  

   seasons." 
  It 
  becomes 
  doubtful 
  now 
  if 
  the 
  fly 
  referred 
  to 
  and 
  that 
  on 
  the 
  Manyonga 
  

   River 
  (where 
  "and," 
  in 
  the 
  map, 
  should 
  read 
  "area") 
  is 
  actually 
  G. 
  morsitans 
  or 
  

   if 
  it 
  is 
  G. 
  swynnertoni. 
  The 
  latter 
  species, 
  as 
  I 
  have 
  said, 
  is 
  present 
  in 
  the 
  

   Chinyanga-Seke 
  belt, 
  which 
  is 
  separated 
  from 
  the 
  area 
  known 
  to 
  be 
  infected 
  only 
  

   by 
  the 
  comparatively 
  narrow 
  populated 
  strip 
  of 
  Nung-hu 
  and 
  by 
  a 
  strip 
  of 
  thin 
  

   thornland, 
  as 
  to 
  the 
  infestation 
  of 
  which 
  I 
  have 
  at 
  present 
  no 
  information 
  (v. 
  map). 
  

  

  Its 
  belts, 
  then, 
  would 
  appear 
  as 
  at 
  least 
  two 
  compact 
  areas 
  of 
  Acacia, 
  one 
  large, 
  

   one 
  small, 
  which 
  have 
  been 
  split 
  off 
  by 
  mbugas 
  and 
  population 
  from 
  the 
  great 
  

   western 
  fly-belt 
  of 
  Brachystegia 
  inhabited 
  by 
  morsitans. 
  From 
  the 
  Mbarangeti 
  and 
  

   Ikoma 
  northwards 
  the 
  larger 
  is 
  broken 
  into 
  blocks 
  by 
  open 
  mbugas, 
  cleared 
  areas 
  of 
  

   heavy 
  population, 
  and 
  such 
  uninfested 
  wooding 
  as 
  that 
  behind 
  Musoma, 
  the 
  latter 
  

   being 
  free 
  perhaps 
  through 
  having 
  been 
  surrounded 
  since 
  it 
  was 
  last 
  a 
  cleared 
  area 
  

   by 
  fly-proof 
  barriers. 
  The 
  smaller 
  belt, 
  at 
  Chinyanga, 
  consists 
  of 
  at 
  least 
  one 
  con- 
  

   siderable 
  " 
  island 
  "in 
  the 
  inhabited 
  country 
  between 
  the 
  main 
  belt 
  and 
  the 
  morsitans 
  

   belt. 
  

  

  The 
  fly 
  is 
  completely 
  absent 
  from 
  the 
  continuously 
  cleared 
  areas, 
  though 
  individuals 
  

   are 
  carried 
  in 
  for 
  some 
  distance, 
  and 
  the 
  villages 
  within 
  half 
  a 
  mile 
  or 
  a 
  mile 
  of 
  the 
  

   bush 
  would 
  occasionally 
  receive 
  invasions 
  of 
  half 
  a 
  dozen 
  or 
  a 
  dozen 
  at 
  a 
  time 
  travelling 
  

   on 
  people 
  who 
  have 
  been 
  hunting, 
  fishing 
  or 
  wood-cutting. 
  Cases 
  of 
  nagana 
  occur 
  

   in 
  herds 
  living 
  beside 
  the 
  bush 
  or 
  habitually 
  driven 
  through 
  a 
  piece 
  of 
  it 
  to 
  water. 
  

  

  6. 
  Glossina 
  morsitans, 
  Westw. 
  

  

  No 
  other 
  tsetse 
  than 
  G. 
  morsitans 
  has 
  to 
  my 
  knowledge 
  been 
  taken 
  in 
  the 
  

   strongly 
  infested 
  Brachystegia 
  area, 
  the 
  margin 
  of 
  which, 
  very 
  roughly 
  indicated, 
  is 
  

   shown 
  brown 
  in 
  the 
  map. 
  The 
  genitalia 
  of 
  the 
  flies 
  there 
  taken 
  show 
  sometimes 
  

   the 
  morsitans, 
  sometimes 
  the 
  submorsitans 
  characters. 
  The 
  margins 
  and 
  outlying 
  

   patches 
  of 
  the 
  area 
  do 
  not 
  always 
  contain 
  Brachystegia, 
  and 
  nearer 
  Lake 
  Tanganyika 
  

   this 
  great 
  Brachystegia 
  area 
  is 
  divided 
  by 
  the 
  acacia-dominated 
  formation 
  of 
  the 
  

   northern 
  part 
  of 
  the 
  Rukwa 
  depression. 
  Yet 
  in 
  this 
  also 
  I 
  took 
  nothing 
  (in 
  

   December 
  1921) 
  but 
  G. 
  morsitans, 
  and 
  this 
  fly 
  inhabits 
  extensive 
  acacia-formations 
  

   elsewhere 
  in 
  the 
  Territory 
  also, 
  as 
  in 
  the 
  Morogoro 
  District. 
  So 
  that 
  while 
  morsitans 
  

   is, 
  I 
  think, 
  probably 
  par 
  excellence 
  on 
  this 
  side 
  of 
  Africa 
  a 
  Brachystegia 
  fly, 
  it 
  cannot 
  

   be 
  merely 
  the 
  domination 
  of 
  Acacia 
  which 
  excludes 
  it 
  from 
  the 
  Chinyanga-Usukuma 
  

   fly-belt. 
  Similar 
  considerations 
  apply 
  to 
  G. 
  pallidipes, 
  which 
  in 
  some 
  belts 
  occurs 
  

   with 
  G. 
  morsitans 
  and 
  in 
  some 
  separately, 
  and 
  it 
  would 
  appear 
  to 
  require 
  merely 
  a 
  

   little 
  intensive 
  oecological 
  work 
  of 
  a 
  comparative 
  nature 
  to 
  show 
  us 
  the 
  essential 
  

   requirement 
  of 
  each 
  of 
  the 
  three 
  species. 
  

  

  