﻿ENTOMOLOGICAL 
  ASPECTS 
  OF 
  AN 
  OUTBREAK 
  OF 
  SLEEPING 
  SICKNESS. 
  359 
  

  

  Such 
  clear 
  areas 
  in 
  the 
  Mwanza 
  district 
  and 
  the 
  smallish 
  open 
  spaces 
  that 
  carry 
  

   cattle 
  surrounded 
  by 
  fly 
  offer 
  abundant 
  proof 
  that 
  clearing 
  of 
  the 
  bush 
  effectively 
  

   banishes 
  tsetse. 
  But 
  wholesale 
  clearing 
  by 
  means 
  of 
  paid 
  labour 
  resembles 
  wholesale 
  

   game 
  destruction 
  by 
  the 
  same 
  means 
  in 
  being 
  prohibitively 
  expensive. 
  Can 
  we 
  

   divert 
  any 
  natural 
  agencies 
  to 
  this 
  work 
  ? 
  

  

  Open 
  ground 
  in 
  the 
  African 
  bush 
  is 
  due 
  (a) 
  to 
  seasonal 
  flooding 
  or 
  swampiness 
  ; 
  

   (b) 
  temporarily, 
  to 
  clearing 
  by 
  natives 
  for 
  cultivating 
  or 
  for 
  firewood 
  and 
  building 
  

   material, 
  and 
  (c) 
  temporarily, 
  to 
  browsing 
  by 
  game 
  and 
  such 
  intensive 
  grazing 
  by 
  

   cattle 
  as 
  leads 
  to 
  browsing 
  by 
  the 
  latter 
  ; 
  it 
  is 
  also 
  (d) 
  maintained, 
  and 
  in 
  many 
  

   places 
  is 
  capable 
  of 
  being 
  gradually 
  brought 
  about, 
  by 
  regular 
  late 
  grass-burning. 
  

   I 
  will 
  discuss 
  these 
  factors, 
  though 
  not 
  in 
  this 
  order. 
  

  

  Clearing 
  by 
  Flooding. 
  — 
  This 
  would 
  in 
  most 
  cases 
  entail 
  engineering 
  and 
  expenditure, 
  

   but 
  opportunities 
  to 
  flood 
  cheaply 
  should 
  be 
  watched 
  for. 
  The 
  dead 
  trees 
  standing 
  

   in 
  the 
  overflow 
  " 
  lake 
  " 
  of 
  Kidete 
  on 
  the 
  Central 
  Railway 
  show 
  what 
  its 
  effect 
  would 
  

   be 
  on 
  the 
  existing 
  bush, 
  and 
  its 
  ultimate 
  drying 
  out 
  would 
  remove 
  the 
  attraction 
  

   to 
  tsetse 
  that 
  the 
  damp 
  margins 
  of 
  the 
  flooded 
  area 
  might 
  temporarily 
  constitute. 
  

   I 
  am 
  not 
  aware 
  at 
  present 
  that 
  cheap 
  seasonal 
  flooding 
  is 
  applicable 
  to 
  any 
  part 
  of 
  

   the 
  Usukuma 
  fly-belt. 
  

  

  Gradual 
  Clearing 
  of 
  Bush 
  by 
  the 
  Annual 
  Grass 
  Fires. 
  — 
  Simultaneous 
  grass-burning 
  

   on 
  a 
  great 
  scale 
  in 
  an 
  unevacuated 
  sleeping 
  sickness 
  area, 
  or 
  in 
  a 
  famine 
  area 
  in 
  which 
  

   game 
  is 
  not 
  present 
  in 
  sufficient 
  numbers, 
  may 
  conceivably 
  be 
  dangerous. 
  Our 
  

   observations 
  on 
  the 
  Simiyu 
  showed 
  that 
  some 
  species, 
  at 
  least, 
  of 
  the 
  morsitans 
  group, 
  

   will 
  concentrate 
  and 
  maintain 
  themselves 
  continuously 
  on 
  man 
  when 
  other 
  foods 
  

   fail, 
  and 
  special 
  observation 
  is 
  now 
  needed 
  to 
  show 
  whether 
  such 
  fires 
  are 
  less 
  

   or 
  more 
  dangerous 
  than 
  the 
  ordinary 
  early 
  fires 
  that 
  (themselves 
  expelling 
  game) 
  

   leave 
  patches 
  of 
  shelter 
  dotted 
  everywhere 
  in 
  which 
  the 
  flies 
  can 
  maintain 
  existence 
  

   better 
  than 
  in 
  well-burned 
  areas 
  and 
  from 
  which 
  they 
  concentrate 
  on 
  passing 
  man. 
  

   Pending 
  the 
  result, 
  we 
  might 
  omit 
  areas 
  of 
  this 
  kind 
  from 
  any 
  scheme 
  of 
  large 
  

   simultaneous 
  burning. 
  

  

  For 
  other 
  places 
  with 
  sufficient 
  grass, 
  late 
  burning 
  and 
  (within 
  strict 
  limits) 
  

   simultaneous 
  burning 
  will 
  be 
  especially 
  useful, 
  and 
  it 
  is 
  particularly 
  necessary 
  in 
  

   the 
  evacuated 
  Simiyu-Duma 
  block. 
  This 
  lends 
  itself 
  well 
  to 
  grass 
  fires, 
  the 
  growth 
  

   of 
  the 
  grass, 
  except 
  in 
  places 
  (as 
  near 
  Nasa), 
  being 
  very 
  fair. 
  Also 
  it 
  especially 
  

   demands 
  late 
  burning, 
  for 
  everywhere 
  amongst 
  the 
  grass 
  are 
  now 
  present 
  numbers 
  

   of 
  young 
  thorn 
  trees 
  of 
  several 
  species, 
  some 
  of 
  which 
  are 
  already 
  growing 
  up 
  and 
  

   forming 
  thickets 
  admirably 
  suited 
  to 
  the 
  apparent 
  needs 
  of 
  the 
  fly, 
  while 
  others 
  are 
  

   still 
  young 
  enough 
  for 
  this 
  to 
  be 
  prevented 
  by 
  late 
  burning 
  (cf. 
  p. 
  323). 
  The 
  fly 
  

   breeds 
  greatly 
  in 
  the 
  thickets, 
  and 
  to 
  this 
  extent 
  late 
  grass 
  fires 
  may 
  gradually 
  attack 
  

   the 
  pupae 
  ; 
  but 
  where 
  these 
  are 
  deposited 
  under 
  the 
  rocks 
  of 
  the 
  kopjes 
  they 
  are 
  

   protected 
  from 
  the 
  fires. 
  Also 
  it 
  is 
  a 
  measure 
  the 
  carrying 
  out 
  of 
  which 
  does 
  not 
  

   necessitate 
  the 
  presence 
  of 
  large 
  numbers 
  of 
  natives 
  in 
  the 
  infected 
  area. 
  

  

  The 
  one 
  real 
  difficulty 
  is 
  the 
  administrative 
  one. 
  I 
  drew 
  attention 
  to 
  this 
  

   difficulty 
  (which 
  has 
  been 
  overcome 
  in 
  the 
  past) 
  in 
  my 
  report 
  to 
  the 
  Mozambique 
  

   Government 
  in 
  1918 
  (Bull. 
  Ent. 
  Res., 
  ix, 
  pt. 
  iv, 
  p. 
  384). 
  A 
  method 
  of 
  fixing 
  

   responsibility 
  in 
  order 
  to 
  control 
  the 
  fishers, 
  hunters 
  and 
  honey-seekers 
  who 
  fire 
  the 
  

   grass 
  is 
  necessary. 
  

  

  Clearing 
  by 
  Native 
  Settlement. 
  — 
  It 
  will 
  be 
  noted 
  that 
  I 
  have 
  included 
  in 
  the 
  map 
  

   figures 
  representing 
  (as 
  I 
  understand) 
  only 
  the 
  taxable 
  males 
  of 
  each 
  Sultanate 
  in 
  

   Usukuma, 
  as 
  given 
  me 
  by 
  the 
  Senior 
  Commissioner. 
  It 
  will 
  be 
  seen 
  that 
  the 
  popu- 
  

   lation 
  of 
  this 
  kind 
  of 
  the 
  Sultanates 
  west 
  of 
  Usmao 
  and 
  Nung-hu, 
  inclusive, 
  totals 
  

   341,806, 
  in 
  an 
  area 
  of 
  about 
  3,115 
  square 
  miles, 
  or 
  roughly 
  109-7 
  to 
  the 
  square 
  mile, 
  

   and 
  that 
  this 
  country, 
  except 
  for 
  a 
  margin 
  on 
  the 
  Simiyu, 
  is 
  practically 
  all 
  cleared 
  

   of 
  bush. 
  It 
  will 
  be 
  seen, 
  further, 
  that 
  the 
  population 
  (of 
  this 
  kind) 
  of 
  the 
  eastern 
  

   Sultanates 
  totals 
  only 
  100,720 
  in 
  an 
  area 
  of 
  about 
  8,762 
  square 
  miles, 
  or 
  11 
  -5 
  to 
  the 
  

  

  