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  CONTAGIOUS 
  DISEASES 
  OF 
  THE 
  CHINCH- 
  BUG. 
  

  

  enough, 
  the 
  disease 
  in 
  question 
  is 
  strictly 
  confined 
  to 
  the 
  whorl 
  of 
  coeca 
  above 
  de- 
  

   scribed, 
  and 
  in 
  them 
  has 
  finally 
  the 
  effect 
  to 
  completely 
  destroy 
  the 
  secreting 
  epi- 
  

   thelium, 
  the 
  cells 
  of 
  which 
  break 
  down 
  and 
  disappear, 
  leaving 
  the 
  delicate 
  tubules 
  

   filled 
  with 
  a 
  vast 
  mass 
  of 
  microbes, 
  with 
  some 
  small 
  intermixture 
  of 
  droplets 
  of 
  fat 
  

   and 
  a 
  little 
  nondescript 
  debris, 
  the 
  result 
  of 
  cellular 
  decomposition. 
  The 
  bacterial 
  

   mass 
  is 
  always 
  a 
  perfectly 
  pure 
  culture 
  of 
  Micrococcus 
  insectorum 
  Burrill, 
  described 
  

   in 
  1883 
  from 
  the 
  alimentary 
  canal 
  of 
  the 
  chinch-bug, 
  and 
  not 
  since 
  encountered 
  else- 
  

   where. 
  

  

  In 
  slightly-affected 
  bugs 
  it 
  is 
  found 
  within 
  the 
  cells 
  of 
  the 
  coeca, 
  the 
  nuclei 
  of 
  

   which 
  may 
  become 
  crammed 
  with 
  it; 
  but 
  even 
  after 
  the 
  complete 
  degeneration 
  of 
  

   this 
  epithelium 
  the 
  other 
  cells 
  of 
  the 
  alimentary 
  tract 
  are 
  almost 
  absolutely 
  free 
  

   from 
  it, 
  a 
  fact 
  which 
  can 
  only 
  be 
  explained 
  on 
  the 
  supposition 
  that 
  it 
  is 
  select 
  in 
  

   its 
  conditions 
  of 
  growth. 
  In 
  bad 
  cases 
  it 
  may 
  be 
  found 
  free 
  in 
  the 
  fluids 
  of 
  the 
  

   posterior 
  part 
  of 
  the 
  canal, 
  but 
  not 
  in 
  number 
  to 
  compare 
  with 
  those 
  in 
  the 
  coeca. 
  

   In 
  the 
  first 
  and 
  second 
  stomachs 
  I 
  have 
  rarely 
  seen 
  it 
  at 
  all. 
  In 
  the 
  third 
  stomach 
  

   it 
  may 
  occasionally 
  appear, 
  but 
  there 
  it 
  never 
  attacks 
  the 
  epithelium. 
  In 
  the 
  fluids 
  

   of 
  the 
  body 
  cavity, 
  in 
  the 
  fatty 
  bodies, 
  in 
  the 
  Malpighian 
  tubules, 
  in 
  the 
  muscles, 
  

   and 
  in 
  the 
  nervous 
  masses, 
  it 
  is 
  totally 
  wanting, 
  even 
  in 
  the 
  specimens 
  worst 
  dis- 
  

   eased. 
  Perfect 
  slides 
  of 
  this 
  bacterial 
  species 
  may 
  be 
  made 
  by 
  smearing 
  diseased 
  

   coeca 
  on 
  a 
  cover 
  glass, 
  and 
  staining 
  and 
  mounting 
  by 
  the 
  usual 
  methods. 
  

  

  The 
  effect 
  on 
  the 
  insect 
  is 
  not 
  remarkable, 
  beyond 
  a 
  slowly-increasing 
  lethargy, 
  

   clumsiness, 
  and 
  weakness, 
  usually 
  but 
  not 
  always 
  accompanied 
  by 
  a 
  swelling 
  of 
  the 
  

   abdomen 
  and 
  a 
  greenish 
  hue 
  of 
  the 
  under 
  side 
  of 
  the 
  body, 
  due 
  to 
  the 
  tint 
  of 
  the 
  

   fatty 
  bodies 
  within. 
  In 
  the 
  latter 
  stages, 
  chinch-bugs 
  placed 
  upon 
  their 
  backs 
  can- 
  

   not 
  right 
  themselves, 
  but 
  can 
  only 
  feebly 
  move 
  their 
  legs. 
  Death 
  by 
  this 
  disease 
  is 
  

   not 
  followed 
  by 
  decay 
  or 
  by 
  any 
  post 
  mortem 
  development 
  of 
  fungus 
  growths. 
  The 
  

   attack 
  is 
  most 
  likely 
  to 
  appear 
  in 
  the 
  growing 
  insect, 
  and 
  in 
  the 
  stage 
  next 
  preced- 
  

   ing 
  the 
  adult, 
  just 
  previous 
  to 
  the 
  last 
  moult 
  — 
  a 
  period 
  of 
  extraordinary 
  suscepti- 
  

   tibility 
  in 
  insects 
  generally 
  ; 
  but 
  adults 
  are 
  often 
  seriously 
  and 
  even 
  fatally 
  affected. 
  

   Although 
  the 
  disease 
  is 
  to 
  all 
  appearance 
  contagious, 
  and 
  occasionally 
  destroys 
  vast 
  

   numbers 
  of 
  these 
  insects 
  together, 
  strict 
  proof 
  of 
  its 
  transmission 
  is 
  yet 
  wanting. 
  

   Attempts 
  at 
  cultures 
  made 
  previous 
  to 
  the 
  last 
  few 
  weeks 
  have 
  been 
  only 
  doubtfully 
  

   successful, 
  owing 
  to 
  the 
  evident 
  sensitiveness 
  of 
  this 
  Micrococcus 
  to 
  culture 
  condi- 
  

   tions, 
  and 
  to 
  the 
  difficulty 
  experienced 
  of 
  getting 
  a 
  pure 
  infection 
  material. 
  By 
  

   isolating 
  the 
  alimentary 
  canal 
  of 
  chinch-bugs 
  by 
  dissection, 
  and 
  separating 
  the 
  

   coeca 
  and 
  transferring 
  them 
  entire 
  to 
  culture 
  tubes 
  of 
  agar, 
  beef 
  broth, 
  and 
  the 
  like, 
  

   I 
  have 
  lately 
  succeeded, 
  in 
  conjunction 
  with 
  Professor 
  Burrill, 
  in 
  making 
  perfectly 
  

   pure 
  cultures 
  in 
  considerable 
  number 
  in 
  both 
  animal 
  and 
  vegetable 
  media, 
  in 
  both 
  

   fluid 
  and 
  solid 
  states. 
  As 
  a 
  result 
  of 
  the 
  infection 
  by 
  this 
  method, 
  of 
  16 
  culture 
  tubes 
  

   containing 
  respectively 
  beef 
  broth 
  and 
  infusions 
  of 
  corn 
  stalks 
  and 
  potato, 
  each 
  

   medium 
  being 
  represented 
  by 
  perfectly 
  neutral, 
  by 
  acid, 
  and 
  by 
  alkaline 
  tubes, 
  we 
  

   have 
  obtained 
  successful 
  cultures 
  in 
  all 
  the 
  neutral 
  and 
  alkaline 
  fluids 
  and 
  in 
  none 
  

   of 
  the 
  acid 
  ones, 
  and 
  from 
  these 
  fluid 
  cultures 
  have 
  made 
  transfer 
  cultures 
  on 
  solid 
  

   agar 
  with 
  entire 
  success. 
  

  

  The 
  sensitiveness 
  of 
  this 
  Micrococcus 
  to 
  acid 
  in 
  its 
  culture 
  fluid 
  is 
  probably 
  the 
  

   cause 
  of 
  its 
  strict 
  limitation 
  to 
  the 
  coeca 
  of 
  the 
  insect 
  intestine, 
  since 
  these 
  coeca 
  do 
  

   not 
  contain 
  any 
  portion 
  of 
  the 
  food, 
  but 
  serve 
  only 
  as 
  a 
  secreting 
  gland. 
  The 
  se- 
  

   cretion 
  must 
  be 
  neutral 
  or 
  alkaline, 
  while 
  the 
  partly 
  digested 
  food 
  is 
  probably 
  acid. 
  

   As 
  the 
  excretion 
  of 
  the 
  Malpighian 
  tubules 
  is 
  acid, 
  the 
  immunity 
  of 
  these 
  structures 
  

   has 
  a 
  similar 
  explanation. 
  It 
  is 
  a 
  point 
  of 
  special 
  entomological 
  interest, 
  that 
  we 
  

   have 
  in 
  this 
  microbe 
  a 
  possible 
  test 
  of 
  the 
  chemical 
  character 
  and 
  physiological 
  

   action 
  of 
  the 
  fluid 
  secretions 
  of 
  the 
  coeca 
  of 
  insects 
  — 
  a 
  matter 
  yet 
  in 
  controversy. 
  

  

  