﻿INVESTIGATIONS 
  INTO 
  THE 
  BIONOMICS 
  OF 
  GLOSSINA 
  PALPALIS. 
  351 
  

  

  of 
  fly, 
  and 
  various 
  others 
  to 
  which 
  the 
  original 
  fly 
  surveys 
  had 
  accorded 
  only 
  in- 
  

   cidental 
  attention 
  or 
  had 
  left 
  out 
  of 
  consideration 
  entirely. 
  Reduction 
  in 
  density 
  

   of 
  fly 
  is 
  one 
  object 
  ; 
  reduction 
  in 
  the 
  injuriousness 
  or 
  injurious 
  status 
  of 
  fly 
  is, 
  in 
  

   actuality, 
  a 
  totally 
  different 
  object, 
  and 
  methods 
  of 
  study 
  must 
  vary 
  accordingly. 
  

  

  Finally, 
  it 
  was 
  disclosed 
  that 
  the 
  question 
  of 
  paramount 
  importance 
  was 
  one 
  

   that 
  required 
  yet 
  different 
  methods 
  of 
  study. 
  It 
  is 
  to 
  define 
  the 
  extent 
  to 
  which 
  

   frequency 
  of 
  contact 
  between 
  flies 
  and 
  persons 
  inhabiting 
  a 
  given 
  region 
  must 
  be 
  

   reduced 
  in 
  order 
  to 
  bring 
  human 
  trypanosomiasis 
  under 
  effective 
  and 
  satisfactory 
  

   control. 
  It 
  is 
  a 
  question 
  which 
  can 
  only 
  be 
  answered 
  by 
  measuring 
  the 
  frequency 
  

   of 
  contact 
  and 
  the 
  coincidence 
  of 
  trypanosome 
  infection 
  in 
  the 
  population. 
  It 
  

   is, 
  I 
  regret 
  to 
  say, 
  impossible 
  for 
  me 
  to 
  carry 
  on 
  investigations 
  along 
  this 
  most 
  

   necessary 
  line 
  unaided. 
  It 
  is 
  for 
  the 
  entomologist 
  to 
  measure 
  density 
  of 
  fly 
  and 
  

   frequency 
  of 
  contact 
  between 
  flies 
  and 
  men, 
  and 
  to 
  identify 
  and 
  study 
  the 
  factors 
  

   in 
  control, 
  but 
  unless 
  he 
  is 
  specifically 
  trained 
  to 
  diagnose 
  and 
  detect 
  trypanosome 
  

   infection, 
  his 
  studies 
  are 
  incomplete 
  and 
  of 
  relatively 
  little 
  value. 
  

  

  Every 
  effort 
  was 
  made 
  in 
  1915 
  to 
  secure 
  the 
  co-operation 
  of 
  a 
  Medical 
  Officer 
  

   for 
  a 
  tour 
  along 
  the 
  coast 
  and 
  islands 
  of 
  Nyanza 
  Province 
  (British 
  East 
  Africa), 
  

   where 
  the 
  riparian 
  populations 
  had 
  not 
  been 
  removed 
  ; 
  but, 
  on 
  account 
  of 
  the 
  

   War, 
  nothing 
  could 
  be 
  done. 
  Some 
  little 
  information 
  on 
  this 
  point 
  was 
  gleaned 
  

   from 
  old 
  (manuscript) 
  reports 
  of 
  Medical 
  Officers 
  employed 
  on 
  " 
  Sleeping 
  Sickness 
  

   Extended 
  Investigations 
  " 
  in 
  Uganda, 
  which, 
  as 
  far 
  as 
  it 
  went, 
  strongly 
  confirmed 
  

   the 
  presumption 
  that 
  the 
  disease 
  is 
  incapable 
  of 
  spreading 
  unless 
  there 
  is 
  excessive 
  

   breadth 
  of 
  contact 
  between 
  fly 
  and 
  population 
  — 
  in 
  excess, 
  for 
  example, 
  of 
  that 
  

   encountered 
  in 
  the 
  survey 
  of 
  the 
  Buddu 
  shore 
  in 
  the 
  Bukakata 
  District 
  — 
  and 
  a 
  few 
  

   other 
  scraps 
  of 
  information 
  have 
  been 
  found 
  in 
  literature 
  — 
  for 
  example, 
  in 
  Todd 
  

   and 
  Wolbach's 
  survey 
  for 
  human 
  trypanosomiasis 
  in 
  the 
  Gambia, 
  which 
  contains 
  

   a 
  few 
  brief 
  references 
  to 
  prevailing 
  density 
  of 
  fly 
  and 
  frequency 
  of 
  contact 
  — 
  but 
  

   it 
  is 
  a 
  line 
  of 
  investigation 
  which 
  has 
  yet 
  to 
  be 
  systematically 
  followed. 
  

  

  I. 
  Disparity 
  between 
  the 
  Sexes 
  of 
  Glossina 
  palpalis. 
  

  

  When 
  any 
  considerable 
  number 
  of 
  flies 
  of 
  this 
  species 
  of 
  Glossina 
  are 
  caught, 
  it 
  

   is 
  unusual 
  to 
  find 
  the 
  sexes 
  evenly 
  represented. 
  Although 
  they 
  are 
  produced 
  in 
  

   equal 
  or 
  approximately 
  equal 
  numbers, 
  they 
  are 
  caught 
  in 
  unequal 
  numbers.* 
  

  

  This 
  disparity 
  between 
  the 
  sexes 
  of 
  Glossina 
  palpalis 
  is 
  an 
  extremely 
  variable 
  

   quantity, 
  ranging 
  in 
  different 
  localities 
  (in 
  catches 
  of 
  100 
  flies 
  or 
  more) 
  from 
  1 
  *9 
  per 
  

   cent, 
  to 
  85 
  - 
  per 
  cent, 
  of 
  females 
  or 
  from 
  15*0 
  per 
  cent, 
  to 
  98*1 
  per 
  cent, 
  of 
  males. 
  

   Females 
  never 
  predominate 
  to 
  quite 
  the 
  extent 
  of 
  males, 
  and 
  most 
  frequently 
  the 
  

   males 
  are 
  in 
  excess. 
  

  

  Various 
  hypothetical 
  explanations 
  for 
  this 
  phenomenon 
  have 
  been 
  proposed 
  by 
  

   Medical 
  Officers 
  and 
  Entomologists 
  who 
  have 
  observed 
  it, 
  and 
  prior 
  to 
  the 
  inception 
  

   of 
  these 
  investigations 
  all 
  these 
  explanations 
  presupposed 
  that 
  " 
  caught 
  flies 
  are 
  

   hungry 
  flies 
  " 
  (attracted 
  to 
  their 
  captor 
  through 
  desire 
  to 
  feed 
  on 
  his 
  person), 
  therefore 
  

  

  *" 
  Thus 
  of 
  1,400 
  flies 
  bred 
  from 
  pupae 
  obtained 
  on 
  Damba 
  Island 
  the 
  proportions 
  were 
  

   $ 
  : 
  $ 
  :: 
  48 
  : 
  52. 
  Whereas 
  of 
  5,000 
  flies 
  caugh 
  ] 
  during 
  the 
  period 
  in 
  which 
  the 
  pupae 
  were 
  

   co 
  lected 
  the 
  proportions 
  were 
  $ 
  : 
  $ 
  :: 
  78*6 
  : 
  21-4." 
  Carpenter: 
  Bepts. 
  of 
  the 
  S.S.Comm. 
  

   of 
  the 
  Royal 
  Soc, 
  xii, 
  p. 
  105. 
  

  

  