﻿462 
  

  

  W. 
  F. 
  FISKE. 
  

  

  Conditions 
  in 
  1906. 
  

  

  (Keport 
  of 
  Dr. 
  K. 
  Van 
  Someren.) 
  

  

  "Just 
  beyond 
  Dumo 
  there 
  is 
  again 
  a 
  

   forest 
  area 
  for 
  some 
  half 
  mile. 
  Where 
  

   the 
  forest 
  ceases 
  until 
  the 
  German 
  boun- 
  

   dary 
  there 
  is 
  no 
  fly 
  to 
  be 
  found. 
  

  

  Conditions 
  in 
  1915. 
  

  

  (Fly 
  Survey.) 
  

  

  The 
  fly 
  stops 
  at 
  a 
  point 
  only 
  100 
  yards 
  

   beyond 
  that 
  indicated 
  by 
  Dr. 
  Van 
  Someren. 
  

   But 
  there 
  are 
  several 
  colonies 
  south 
  of 
  the 
  

   point. 
  

  

  " 
  Of 
  the 
  flies 
  caught 
  in 
  this 
  area 
  187 
  

   were 
  males 
  and 
  72 
  females 
  ( 
  — 
  28 
  per 
  cent, 
  

   females). 
  

  

  " 
  At 
  Dumo 
  by 
  one 
  of 
  the 
  watering 
  places 
  

   I 
  caught 
  20 
  females 
  to 
  14 
  males 
  ( 
  = 
  59 
  

   per 
  cent, 
  females). 
  

  

  " 
  On 
  another 
  occasion 
  along 
  the 
  forest 
  

   up 
  to 
  the 
  Kirala 
  River 
  my 
  boys 
  caught 
  

   106 
  males 
  to 
  2 
  females 
  (=1*9 
  per 
  cent, 
  

   females). 
  This 
  is 
  of 
  interest 
  in 
  connection 
  

   with 
  the 
  physical 
  features. 
  Since 
  fibre 
  

   collecting 
  ceased 
  there 
  practically 
  no 
  one 
  

   visits 
  it. 
  

  

  The 
  total 
  catch 
  in 
  this 
  area 
  was 
  215 
  

   males 
  and 
  184 
  females, 
  making 
  46 
  per 
  cent, 
  

   females. 
  

  

  At 
  the 
  identical 
  watering 
  place 
  (the 
  

   only 
  one 
  in 
  the 
  fly 
  area) 
  two 
  catches 
  were 
  

   made 
  on 
  different 
  days 
  as 
  below 
  : 
  — 
  

  

  Males. 
  

   15 
  

   19 
  

  

  34 
  

  

  Females 
  

   41 
  

   57 
  

  

  98 
  

  

  Female 
  

  

  percentage. 
  

  

  73% 
  

  

  75% 
  

  

  74% 
  

  

  Along 
  the 
  forest 
  up 
  to 
  the 
  Kirala 
  River 
  

   the 
  catch 
  of 
  males 
  was 
  identical, 
  106, 
  but 
  

   that 
  of 
  females 
  was 
  86, 
  making 
  45 
  per 
  cent?. 
  

  

  Again 
  it 
  is 
  interesting 
  to 
  note 
  that 
  sex 
  ratio 
  shows 
  that 
  the 
  watering 
  place, 
  

   which 
  is 
  (or 
  was) 
  just 
  outside 
  the 
  " 
  belt 
  of 
  scrub 
  and 
  long 
  grass," 
  is 
  now, 
  as 
  it 
  was 
  

   in 
  1906, 
  unattractive 
  to 
  the 
  idle 
  males, 
  and 
  is 
  the 
  point 
  south 
  of 
  the 
  colony 
  centre 
  

   where 
  female 
  percentage 
  is 
  highest. 
  But 
  northward, 
  along 
  the 
  beach 
  where 
  

   " 
  practically 
  no 
  one 
  ' 
  : 
  ' 
  went 
  in 
  1906, 
  the 
  conditions 
  are 
  absolutely 
  changed. 
  

  

  The 
  foregoing 
  brings 
  out 
  clearly 
  the 
  need 
  for 
  eternal 
  vigilance 
  if 
  any 
  systematised 
  

   effort 
  is 
  ever 
  made 
  to 
  repopulate 
  the 
  riparian 
  zone 
  and 
  islands, 
  and 
  to 
  protect 
  the 
  

   population 
  against 
  recurrence 
  of 
  sleeping 
  sickness. 
  There 
  is 
  no 
  more 
  dangerous 
  

   reach 
  of 
  shore 
  in 
  Africa, 
  perhaps, 
  than 
  that 
  between 
  the 
  points 
  Sekwe 
  and 
  Bale, 
  

   yet 
  it 
  was 
  perfectly 
  safe 
  apparently 
  in 
  1906, 
  and 
  the 
  changes 
  have 
  been 
  wrought 
  

   by 
  the 
  falling 
  of 
  the 
  lake 
  level. 
  

  

  Wherever 
  the 
  shore 
  falls 
  gradually 
  into 
  the 
  lake, 
  similar 
  changes 
  are 
  likely 
  to 
  

   occur 
  at 
  any 
  time, 
  especially 
  if 
  there 
  is 
  much 
  sand 
  in 
  the 
  district. 
  The 
  danger 
  

   points 
  can 
  be 
  found 
  by 
  a 
  "fly 
  survey 
  ' 
  of 
  the 
  shore, 
  and 
  must 
  be 
  watched 
  to 
  

   preclude 
  the 
  chance 
  of 
  conditions 
  eminently 
  favourable 
  to 
  spread 
  of 
  the 
  human 
  

   parasite 
  coming 
  about 
  unknown 
  to 
  sanitary 
  or 
  administrative 
  officials. 
  

  

  XI 
  (d). 
  Causes 
  for 
  Fluctuation 
  in 
  Lake 
  Level. 
  

  

  Causes 
  for 
  the 
  irregular 
  fluctuation 
  in 
  level 
  of 
  Victoria 
  Nyanza 
  are, 
  in 
  part, 
  

   its 
  great 
  size 
  and 
  narrow 
  outlet. 
  From 
  so 
  great 
  an 
  area 
  loss 
  through 
  evaporation 
  

   must 
  be 
  enormous, 
  and 
  relatively 
  constant 
  as 
  compared 
  with 
  the 
  overflow. 
  The 
  

   latter 
  represents 
  the 
  surplus 
  of 
  rainfall 
  over 
  evaporation, 
  and 
  if 
  evaporation 
  is 
  a 
  

   relatively 
  constant 
  quantity, 
  any 
  variations 
  in 
  rainfall 
  are 
  likely 
  to 
  be 
  greatly 
  

   exaggerated. 
  The 
  surplus 
  not 
  being 
  so 
  very 
  large, 
  it 
  does 
  not 
  require 
  much 
  to 
  double 
  it. 
  

  

  