﻿REPORT 
  OF 
  TSETSE-FLY 
  INVESTIGATION 
  IN 
  NIGERIA. 
  381 
  

  

  IV. 
  — 
  The 
  Sex 
  Ratio 
  in 
  G. 
  tachinoides. 
  

  

  It 
  is 
  well 
  known 
  that 
  with 
  palpalis, 
  morsitans 
  and 
  brevipalpis 
  in 
  a 
  catch 
  of 
  fly 
  

   the 
  males 
  are 
  usually 
  greatly 
  in 
  excess 
  of 
  the 
  females. 
  When 
  the 
  natural 
  fauna 
  

   of 
  an 
  area 
  is 
  reduced 
  the 
  proportion 
  of 
  females 
  rises 
  to 
  50 
  per 
  cent., 
  or 
  even 
  higher, 
  

   with 
  palpalis 
  and 
  morsitans, 
  while 
  no 
  data 
  on 
  this 
  point 
  have 
  yet 
  been 
  collected 
  

   for 
  brevipalpis. 
  This 
  simply 
  means 
  that 
  the 
  majority 
  of 
  the 
  flies 
  which 
  investigate 
  

   man 
  are 
  males 
  seeking 
  mates 
  and 
  not 
  particularly 
  desirous 
  of 
  feeding, 
  but 
  that 
  

   when 
  natural 
  food 
  is 
  scarce 
  the 
  females 
  are 
  more 
  driven 
  to 
  him 
  in 
  a 
  search 
  for 
  food 
  

   —their 
  hunger 
  compelling 
  them 
  to 
  miss 
  no 
  chance 
  of 
  a 
  meal. 
  The 
  accumulated 
  

   males 
  which 
  accompany 
  moving 
  man 
  or 
  animals 
  are 
  known 
  as 
  " 
  following 
  swarms." 
  

   No 
  such 
  following 
  swarm 
  has 
  been 
  seen 
  with 
  tachinoides 
  about 
  either 
  man 
  or 
  domestic 
  

   animals, 
  and 
  every 
  fly 
  that 
  comes 
  seems 
  to 
  be 
  desirous 
  of 
  feeding. 
  Even 
  those 
  

   which 
  contain 
  recently 
  drawn 
  blood 
  are 
  quite 
  ready 
  to 
  imbibe 
  more 
  if 
  they 
  are 
  not 
  

   full 
  to 
  repletion. 
  At 
  the 
  same 
  time 
  there 
  is 
  no 
  general 
  preponderance 
  of 
  males 
  in 
  

   the 
  catches. 
  In 
  a 
  total 
  of 
  14,400 
  flies 
  examined 
  from 
  all 
  localities 
  the 
  female 
  per- 
  

   centage 
  is 
  46. 
  Of 
  these 
  12,000 
  were 
  taken 
  at 
  Mashiwashi 
  and 
  Maalo, 
  a 
  village 
  six 
  

   miles 
  further 
  west, 
  and 
  the 
  female 
  percentage 
  was 
  also 
  46. 
  In 
  the 
  latter 
  areas 
  the 
  

   population 
  is 
  scanty 
  and 
  there 
  is 
  a 
  large 
  natural 
  fauna, 
  so 
  that 
  if 
  tachinoides 
  behaved 
  

   like 
  the 
  other 
  species 
  the 
  female 
  percentage 
  should 
  be 
  low, 
  as 
  that 
  of 
  morsitans 
  is 
  

   in 
  the 
  same 
  areas 
  (exactly 
  10 
  per 
  cent, 
  females 
  in 
  364 
  flies 
  examined). 
  After 
  com- 
  

   paring 
  the 
  female 
  percentages 
  in 
  catches 
  taken 
  in 
  60 
  localities 
  with 
  the 
  food 
  available, 
  

   mammals 
  and 
  reptiles, 
  and 
  the 
  estimated 
  nutrition 
  of 
  the 
  fly 
  as 
  found 
  by 
  examination 
  

   of 
  the 
  gut 
  contents, 
  no 
  relation 
  between 
  varying 
  sex 
  proportions 
  and 
  the 
  hunger 
  

   of 
  the 
  fly 
  can 
  be 
  found. 
  There 
  would 
  be 
  no 
  useful 
  purpose 
  served 
  in 
  describing 
  

   special 
  cases, 
  as 
  the 
  figures 
  constantly 
  contradict 
  the 
  accepted 
  views 
  of 
  sex 
  pro- 
  

   portion 
  in 
  tsetses. 
  The 
  conclusions 
  which 
  may 
  be 
  drawn 
  are 
  : 
  — 
  (a) 
  the 
  mating 
  

   habits 
  of 
  these 
  flies 
  differ 
  from 
  those 
  of 
  the 
  other 
  species 
  whose 
  habits 
  are 
  known, 
  

   the 
  males 
  not 
  needing 
  to 
  make 
  a 
  following 
  swarm 
  in 
  order 
  to 
  secure 
  mates 
  ; 
  

   (b) 
  G. 
  tachinoides 
  likes 
  man 
  as 
  a 
  host 
  quite 
  as 
  well 
  as 
  any 
  other 
  animal, 
  and 
  this 
  

   conclusion 
  was 
  reached 
  from 
  another 
  point 
  of 
  view. 
  

  

  V. 
  — 
  Food 
  of 
  Tsetse-flies. 
  

   1 
  . 
  Glossina 
  palpalis. 
  

  

  In 
  the 
  dissection 
  of 
  552 
  recently 
  caught 
  flies 
  in 
  various 
  localities 
  it 
  was 
  found 
  

   that 
  96 
  contained 
  recognisable 
  blood 
  which 
  was 
  mammalian 
  in 
  75 
  (78 
  per 
  cent.) 
  

   and 
  non-mammalian 
  in 
  21 
  (22 
  per 
  cent.). 
  This 
  proportion 
  was 
  found 
  to 
  be 
  about 
  

   the 
  same 
  where 
  game 
  was 
  present 
  or 
  almost 
  absent 
  (see 
  Table 
  III). 
  As 
  in 
  Uganda, 
  

   the 
  source 
  of 
  the 
  nucleated 
  red 
  cells 
  was 
  probably 
  crocodiles 
  and 
  Varanus, 
  the 
  

   monitor 
  lizard, 
  the 
  latter 
  being 
  plentiful 
  in 
  most 
  of 
  the 
  palpalis 
  haunts. 
  The 
  

   catches 
  made 
  were 
  always 
  too 
  small 
  to 
  show 
  any 
  relation 
  between 
  the 
  female 
  per- 
  

   centage 
  and 
  a 
  natural 
  food 
  supplv 
  as 
  opposed 
  to 
  man 
  or 
  domestic 
  stock. 
  Out 
  of 
  

   21 
  localities, 
  in 
  which 
  at 
  least 
  15 
  flies 
  were 
  caught, 
  crocodiles 
  were 
  present 
  in 
  11 
  and 
  

   the 
  average 
  female 
  percentage 
  was 
  42 
  ; 
  game 
  animals 
  were 
  tolerably 
  plentiful 
  in 
  12 
  

   and 
  the 
  average 
  female 
  percentage 
  was 
  40 
  ; 
  there 
  was 
  close 
  contact 
  with 
  domestic 
  

   stock 
  in 
  8 
  and 
  the 
  average 
  female 
  percentage 
  was 
  40 
  ; 
  man 
  was 
  in 
  close 
  contact 
  

   with 
  the 
  fly 
  in 
  19 
  and 
  the 
  average 
  female 
  percentage 
  was 
  42. 
  These 
  figures 
  are 
  

   enough 
  to 
  show 
  that 
  generally 
  in 
  the 
  Northern 
  Provinces 
  the 
  fly 
  looks 
  to 
  man, 
  when 
  

   available, 
  for 
  a 
  proportion 
  of 
  its 
  food, 
  but 
  the 
  territory 
  is 
  on 
  the 
  outskirts 
  of 
  the 
  

   palpalis 
  country 
  and 
  atypical 
  conditions 
  are 
  therefore 
  not 
  surprising. 
  

  

  In 
  two 
  localities 
  where 
  palpalis 
  was 
  found, 
  cattle, 
  sheep 
  and 
  goats 
  were 
  grazing 
  

   to 
  such 
  an 
  extent 
  that 
  practically 
  all 
  other 
  mammalian 
  hosts 
  were 
  excluded, 
  these 
  

   being 
  (1) 
  from 
  Lemmi 
  to 
  Taura 
  on 
  the 
  northern 
  face 
  of 
  the 
  Banchi 
  Plateau, 
  a 
  large 
  

   stock-raisincr 
  district 
  ; 
  and 
  (2) 
  at 
  Tilde 
  Filani, 
  also 
  at 
  the 
  foot 
  of 
  the 
  plateau 
  but 
  

   more 
  to 
  the 
  S.E., 
  a 
  description 
  of 
  which 
  is 
  given 
  on 
  page 
  383. 
  

  

  