﻿INVESTIGATIONS 
  INTO 
  THE 
  BIONOMICS 
  OF 
  GLOSSINA 
  PALPALIS. 
  375 
  

  

  It 
  was 
  found 
  by 
  experiment, 
  details 
  of 
  which 
  need 
  not 
  be 
  given, 
  that 
  flies 
  will 
  cross 
  

   open 
  channels 
  up 
  to 
  at 
  least 
  300 
  yards 
  in 
  width, 
  but 
  that 
  they 
  do 
  not 
  cross 
  them 
  

   very 
  freely. 
  It 
  is 
  certain 
  that 
  the 
  width 
  of 
  the 
  channel 
  likely 
  to 
  be 
  crossed 
  is 
  dependent 
  

   on 
  the 
  character 
  of 
  the 
  farther 
  shore. 
  Certainly 
  they 
  do 
  not 
  cross 
  much 
  wider 
  channels 
  

   than 
  300 
  to 
  500 
  yards 
  at 
  all 
  freely, 
  for 
  from 
  the 
  beginning 
  evidence 
  of 
  their 
  doing 
  

   so 
  was 
  carefully 
  sought, 
  and 
  no 
  shred 
  of 
  it 
  secured. 
  

  

  It 
  is 
  the 
  movements 
  of 
  fly 
  along 
  shore, 
  or 
  along 
  the 
  border 
  line 
  between 
  sunlight 
  

   and 
  shadow, 
  with 
  which 
  we 
  are 
  principally 
  concerned, 
  and 
  these 
  studies 
  have 
  shown 
  

   how 
  the 
  flies 
  tend 
  to 
  congregate 
  in 
  attractively 
  sheltered 
  localities, 
  where, 
  in 
  conse- 
  

   quence, 
  density 
  of 
  males 
  is 
  high 
  and 
  percentage 
  of 
  females 
  low, 
  and 
  how, 
  pressed 
  

   by 
  hunge 
  , 
  both 
  sexes, 
  but 
  more 
  especially 
  the 
  females, 
  tend 
  to 
  disperse 
  from 
  these 
  

   centres 
  of 
  greater 
  density 
  and 
  range 
  along 
  the 
  lake 
  shore 
  or 
  other 
  favoured 
  route 
  

   in 
  search 
  of 
  the 
  sluggish 
  amphibian 
  animals 
  on 
  which 
  they 
  principally 
  feed, 
  thus 
  

   accounting 
  for 
  the 
  extraordinary 
  preponderance 
  of 
  females 
  amongst 
  caught 
  flies 
  

   in 
  repulsively 
  sheltered 
  localities. 
  

  

  IV. 
  The 
  Assembling 
  Habits 
  op 
  Glossina 
  palpalis. 
  

  

  The 
  stimuli 
  which 
  keep 
  in 
  motion 
  the 
  streams 
  of 
  tsetse 
  described 
  in 
  the 
  preceding 
  

   section 
  are 
  known 
  to 
  include, 
  and 
  believed 
  in 
  all 
  ordinary 
  circumstances 
  to 
  be 
  

   limited, 
  to 
  the 
  following 
  : 
  — 
  

  

  (A) 
  Hunger. 
  Every 
  second 
  or 
  third 
  day 
  the 
  flies 
  of 
  both 
  sexes 
  undertake 
  

   food-hunting 
  flights. 
  These 
  are 
  relatively 
  rapid 
  and 
  easy 
  to 
  follow. 
  

  

  (B) 
  Self-protection. 
  At 
  the 
  close 
  of 
  each 
  period 
  of 
  activity 
  the 
  flies 
  of 
  both 
  

   sexes 
  are 
  moved 
  to 
  seek 
  massive 
  shelter, 
  where 
  they 
  remain 
  in 
  seclusion 
  

   during 
  periods 
  of 
  inactivity. 
  They 
  appear 
  very 
  unwilling 
  to 
  move 
  far 
  

   away 
  from 
  such 
  shelter 
  ; 
  hence 
  flights 
  in 
  search 
  of 
  it 
  are 
  usually 
  of 
  short 
  

   duration. 
  

  

  (C) 
  Maternal 
  Instinct. 
  At 
  intervals 
  of 
  eight 
  days, 
  or 
  longer, 
  the 
  females 
  are 
  

  

  stimulated 
  to 
  seek 
  breeding 
  grounds 
  wherein 
  to 
  deposit 
  their 
  young. 
  The 
  

   great 
  concentration 
  of 
  puparia 
  in 
  very 
  attractive 
  breeding 
  places 
  is 
  proof 
  

   that 
  flights 
  in 
  search 
  of 
  them 
  were 
  of 
  considerable 
  duration. 
  The 
  location 
  

   of 
  deposits 
  of 
  puparia 
  near 
  the 
  well-marked 
  courses 
  followed 
  by 
  food- 
  

   hunting 
  flies 
  is 
  proof 
  that 
  these 
  are 
  followed. 
  But 
  the 
  flights 
  themselves 
  

   are 
  very 
  hard 
  to 
  follow. 
  

  

  (D) 
  Masculine 
  Instinct. 
  Every 
  day, 
  if 
  the 
  weather 
  is 
  good, 
  the 
  males 
  appear 
  

  

  all 
  to 
  leave 
  shelter 
  to 
  undertake 
  assembling 
  flights. 
  These 
  are 
  readily 
  

   followed, 
  and 
  as 
  described 
  in 
  the 
  preceding 
  section, 
  are 
  relatively 
  slow. 
  

   The 
  insects 
  tend 
  to 
  congregate 
  or 
  to 
  loiter 
  at 
  points 
  or 
  along 
  courses 
  where 
  

   the 
  females 
  are 
  most 
  likely 
  to 
  congregate 
  or 
  to 
  pass. 
  It 
  is 
  these 
  special 
  

   activities 
  which 
  are 
  now 
  to 
  be 
  considered. 
  

   Several 
  points 
  in 
  connection 
  with 
  the 
  assembling 
  habits 
  of 
  Glossina 
  palpalis 
  in 
  

   addition 
  to 
  those 
  touched 
  upon 
  in 
  the 
  preceding 
  sections 
  are 
  discussed 
  in 
  the 
  sub- 
  

   sections 
  following. 
  The 
  topic 
  is 
  inter- 
  dependent 
  with 
  several 
  others, 
  including, 
  

   especially, 
  host 
  preferences 
  of 
  the 
  flies. 
  

  

  