﻿334 
  C. 
  F. 
  M. 
  SWYNNERTON. 
  

  

  XII. 
  — 
  The 
  Following-distance 
  of 
  Female 
  Flies. 
  

  

  The 
  length 
  of 
  distance 
  that 
  a 
  female 
  tsetse 
  will 
  "follow," 
  travelling 
  on 
  man 
  or 
  

   on 
  animals, 
  is 
  a 
  most 
  important 
  question 
  in 
  relation 
  to 
  the 
  possibility 
  of 
  checking 
  

   the 
  advance 
  of 
  a 
  fly-belt 
  by 
  means 
  of 
  a 
  barrier 
  clearing. 
  

  

  In 
  my 
  past 
  experiments 
  (with 
  cattle 
  and 
  man 
  and 
  using 
  brevipalpis 
  and 
  pallidipes) 
  

   820 
  yards 
  was 
  the 
  greatest 
  distance 
  covered 
  by 
  any 
  female 
  fly. 
  It 
  was 
  obvious 
  from 
  

   an 
  early 
  date 
  that 
  the 
  present 
  fly 
  was 
  behaving 
  quite 
  differently, 
  and 
  that 
  considerable 
  

   " 
  followings 
  " 
  by 
  females 
  were 
  taking 
  place. 
  

  

  I 
  took 
  the 
  first 
  opportunity 
  to 
  test 
  this 
  view 
  by 
  awaiting 
  my 
  carriers 
  near 
  the 
  

   opposite 
  side 
  of 
  a 
  completely 
  open 
  mbuga 
  and 
  catching 
  and 
  sexing 
  the 
  flies 
  on 
  them 
  

   when 
  they 
  had 
  been 
  travelling 
  for 
  twelve 
  minutes 
  (half 
  a 
  mile) 
  in 
  the 
  mbuga. 
  Six 
  

   of 
  the 
  flies 
  were 
  females 
  — 
  resting 
  on 
  the 
  men's 
  backs, 
  not 
  feeding 
  — 
  and 
  ten 
  were 
  

   males. 
  

  

  Again, 
  at 
  Zagayu, 
  with 
  Mr. 
  Tully's 
  help, 
  marked 
  females 
  were 
  tried, 
  and 
  I 
  myself 
  

   saw 
  followings 
  of 
  a 
  mile 
  and 
  a 
  quarter 
  on 
  walkers 
  and 
  (one 
  marked 
  female) 
  on 
  a 
  

   carried 
  cloth 
  screen. 
  Mr. 
  Tully 
  obtained 
  a 
  considerably 
  longer 
  following 
  by 
  using 
  

   his 
  bicycle 
  for 
  part 
  of 
  the 
  way, 
  but 
  it 
  was 
  known 
  already 
  that 
  female 
  G. 
  morsitans, 
  

   at 
  any 
  rate, 
  will 
  travel 
  for 
  great 
  distances 
  on 
  fast-moving 
  cars 
  and 
  bicycles. 
  

  

  The 
  females 
  travelled 
  quietly, 
  without 
  (so 
  far 
  as 
  I 
  saw) 
  constantly 
  flying 
  off 
  the 
  

   walker's 
  back 
  and 
  returning 
  to 
  it 
  as 
  did 
  the 
  males, 
  and, 
  apart 
  from 
  size 
  and 
  colour, 
  

   it 
  seemed 
  possible 
  to 
  distinguish 
  the 
  sexes 
  in 
  this 
  way. 
  Also 
  they 
  usually 
  settled 
  

   down 
  to 
  feed 
  in 
  the 
  end, 
  which 
  the 
  males 
  did 
  not, 
  and 
  then 
  left 
  their 
  carrier. 
  It 
  

   may 
  have 
  been 
  a 
  coincidence, 
  or 
  it 
  may 
  not, 
  that 
  the 
  females 
  of 
  the 
  Zagayu 
  experi- 
  

   ments 
  tended 
  to 
  begin 
  to 
  feed 
  as 
  the 
  rest-house 
  and 
  huts, 
  the 
  first 
  conspicuous 
  object 
  

   since 
  leaving 
  the 
  bush, 
  were 
  approached. 
  

  

  The 
  full 
  distance 
  that 
  will 
  be 
  travelled 
  has 
  yet 
  to 
  be 
  ascertained, 
  but 
  a 
  barrier 
  

   of 
  a 
  mile 
  and 
  a 
  half 
  and 
  probably 
  very 
  much 
  more 
  would 
  have 
  to 
  be 
  cleared 
  to 
  obviate 
  

   the 
  likelihood 
  of 
  females 
  crossing 
  it, 
  even 
  on 
  natives 
  — 
  at 
  any 
  rate 
  when 
  the 
  fly 
  was 
  

   specially 
  feeding 
  on 
  natives, 
  as 
  it 
  seemed 
  to 
  be 
  doing 
  here. 
  The 
  experiment 
  was 
  

   useful 
  also 
  as 
  indicating 
  the 
  special 
  danger 
  of 
  leaving 
  patches 
  of 
  bush 
  standing 
  near 
  

   dwellings 
  or 
  segregation 
  camps 
  within 
  following 
  range. 
  

  

  A 
  point 
  best 
  mentioned 
  here, 
  though 
  it 
  follows 
  naturally 
  on 
  the 
  concluding 
  remarks 
  

   of 
  Section 
  X 
  (p. 
  332), 
  is 
  that 
  my 
  observations 
  on 
  this 
  safari 
  tended 
  to 
  convince 
  me 
  

   finally 
  that 
  while 
  many 
  tsetses 
  leave 
  a 
  party 
  entering 
  open 
  ground, 
  those 
  that 
  are 
  

   once 
  carried 
  well 
  out 
  into 
  unsuitable 
  country 
  do 
  not 
  readily 
  leave 
  their 
  carriers 
  till 
  

   cover 
  is 
  once 
  more 
  reached. 
  The 
  conclusion 
  extended 
  to 
  the 
  female 
  of 
  the 
  present 
  

   species, 
  and 
  is 
  of 
  importance 
  in 
  relation 
  to 
  the 
  idea 
  of 
  a 
  barrier 
  clearing. 
  

  

  XIII. 
  — 
  Distance 
  of 
  Attack 
  and 
  Protection 
  of 
  Roads. 
  

  

  The 
  provision 
  of 
  cleared 
  high 
  roads 
  at 
  the 
  points 
  where 
  these 
  are 
  most 
  required 
  

   was 
  one 
  of 
  the 
  most 
  urgently 
  needed 
  measures 
  for 
  the 
  protection 
  of 
  the 
  population 
  

   from 
  the 
  infected 
  fly. 
  Experiments 
  were 
  therefore 
  attempted 
  with 
  the 
  object 
  of 
  

   ascertaining 
  the 
  necessary 
  width 
  of 
  clearing. 
  In 
  order 
  that 
  the 
  work 
  should 
  not 
  

   be 
  wasted 
  and 
  that 
  no 
  additional 
  natives 
  should 
  be 
  exposed 
  to 
  possible 
  infection, 
  

   they 
  were 
  carried 
  out 
  on 
  a 
  piece 
  of 
  road 
  (Zagayu 
  to 
  Sengerema) 
  that 
  was 
  about 
  to 
  

   be 
  cleared 
  by 
  these 
  people 
  in 
  any 
  case 
  as 
  part 
  of 
  the 
  scheme 
  of 
  control. 
  

  

  Experiment 
  I. 
  — 
  Range 
  of 
  Attack 
  across 
  Cleared 
  Ground. 
  — 
  It 
  was 
  planned 
  to 
  

   clear 
  first 
  to 
  50 
  yards 
  on 
  each 
  side 
  of 
  the 
  road 
  and 
  test, 
  then 
  to 
  increase 
  the 
  width 
  

   .and 
  test 
  again, 
  and 
  so 
  on 
  till 
  a 
  conclusion 
  should 
  be 
  reached. 
  Owing 
  to 
  the 
  miserable 
  

   native 
  tools 
  it 
  was 
  impossible 
  to 
  complete 
  this 
  in 
  the 
  time 
  at 
  my 
  disposal, 
  and 
  the 
  

   actual 
  experiment 
  was 
  as 
  shown 
  in 
  the 
  text 
  figure. 
  

  

  From 
  A 
  to 
  B, 
  about 
  900 
  yards 
  through 
  lightly 
  infested 
  bushes, 
  was 
  cleared 
  to 
  a 
  

   width 
  of 
  30 
  yards 
  to 
  minimise 
  the 
  chance 
  of 
  picking 
  up 
  tsetses 
  in 
  travelling 
  to 
  the 
  

  

  