﻿28 
  CONTAGIOUS 
  DISEASES 
  OF 
  THE 
  CHINCH-BUG. 
  

  

  EMPUSA 
  APHIDIS. 
  

  

  As 
  before 
  stated, 
  Empusa 
  aphidis 
  was 
  first 
  noticed 
  in 
  our 
  infection 
  case 
  

   June 
  28. 
  There 
  were 
  8 
  or 
  10 
  bugs 
  found 
  covered 
  with 
  a 
  vigorous 
  growth 
  

   of 
  this 
  fungus. 
  This 
  disease 
  had 
  probably 
  been 
  sent 
  in 
  from 
  some 
  field 
  where 
  

   it 
  naturally 
  existed. 
  Empusa 
  continued 
  to 
  multiply 
  in 
  the 
  infection 
  cases, 
  

   and 
  by 
  July 
  12th 
  it 
  rivaled 
  Sporotrichum 
  in 
  the 
  number 
  of 
  its 
  victims. 
  Bugs 
  

   without 
  external 
  signs 
  of 
  disease 
  in 
  the 
  afternoon 
  would 
  be 
  found 
  hanging 
  to 
  

   the 
  wheat 
  blades 
  the 
  following 
  morning 
  covered 
  with 
  a 
  vigorous 
  growth 
  of 
  

   Empusa. 
  When 
  the 
  conditions 
  remain 
  favorable 
  the 
  fungus 
  keeps 
  on 
  grow- 
  

   ing 
  at 
  the 
  expense 
  of 
  the 
  tissues 
  of 
  the 
  bug, 
  until 
  nothing 
  is 
  left 
  save 
  bits 
  of 
  

   the 
  chitinous 
  integument. 
  

  

  Attempts 
  were 
  made 
  to 
  obtain 
  pure 
  cultures 
  of 
  Empusa, 
  but 
  without 
  suc- 
  

   cess. 
  At 
  first 
  bugs 
  covered 
  with 
  Empusa 
  were 
  placed 
  on 
  the 
  surface 
  of 
  the 
  

   culture 
  medium 
  in 
  the 
  hope 
  that 
  the 
  spores 
  would 
  be 
  thrown, 
  as 
  is 
  the 
  habit 
  

   with 
  this 
  fungus, 
  and 
  the 
  growth 
  of 
  these 
  spores 
  would 
  give 
  a 
  pure 
  culture. 
  

   The 
  spores 
  were 
  thrown 
  in 
  a 
  ring 
  about 
  the 
  bug 
  to 
  a 
  distance 
  of 
  a 
  quarter 
  of 
  

   an 
  inch, 
  but 
  a 
  rapid 
  growth 
  of 
  bacteria 
  from 
  the 
  bug 
  broke 
  down 
  the 
  culture 
  

   medium, 
  and 
  the 
  Empusa 
  spores 
  did 
  not 
  develop. 
  

  

  To 
  keep 
  the 
  bacteria 
  from 
  reaching 
  the 
  medium, 
  a 
  cover 
  glass 
  was 
  heated 
  

   over 
  a 
  Bunsen 
  burner 
  until 
  it 
  became 
  very 
  much 
  convexed. 
  This 
  was 
  then 
  

   placed 
  on 
  the 
  culture 
  medium, 
  convex 
  side 
  up, 
  and 
  upon 
  this 
  were 
  placed 
  

   three 
  bugs 
  covered 
  with 
  Empusa. 
  A 
  mycelial 
  growth 
  was 
  obtained 
  in 
  this 
  

   way 
  un 
  contaminated 
  with 
  bacteria 
  ; 
  but 
  no 
  spores 
  were 
  produced. 
  We 
  have 
  

   been 
  unable, 
  then, 
  to 
  attempt 
  the 
  inoculation 
  of 
  chinch-bugs 
  with 
  pure 
  cult- 
  

   ures 
  of 
  Empusa. 
  That 
  the 
  fungus 
  has 
  power 
  to 
  rapidly 
  spread 
  from 
  one 
  bug 
  

   to 
  another, 
  the 
  experiments 
  in 
  our 
  infection 
  cases 
  have 
  clearly 
  shown. 
  

  

  A 
  chinch-bug 
  covered 
  with 
  Empusa 
  seems 
  to 
  be 
  studded 
  with 
  minute 
  gray 
  

   beads. 
  A 
  thin 
  section 
  cut 
  through 
  the 
  body 
  of 
  a 
  bug 
  in 
  this 
  condition 
  shows 
  

   the 
  body 
  cavity 
  to 
  be 
  crowded 
  with 
  the 
  mycelial 
  growth, 
  and 
  protruding 
  

   through 
  the 
  integument 
  are 
  vast 
  numbers 
  of 
  broad 
  conidiophores, 
  each 
  bear- 
  

   ing 
  a 
  single 
  conidium 
  (Plate 
  III, 
  fig. 
  1). 
  

  

  It 
  is 
  by 
  the 
  sudden 
  rupture 
  of 
  the 
  conidiophore, 
  due 
  to 
  turgescence, 
  that 
  

   the 
  conidia 
  are 
  thrown 
  to 
  some 
  distance. 
  

  

  Where 
  the 
  fungus 
  continues 
  its 
  growth 
  to 
  the 
  complete 
  destruction 
  of 
  the 
  

   chinch-bug, 
  the 
  whole 
  mycelial 
  mass 
  breaks 
  up 
  into 
  bodies 
  varying 
  from 
  

   16x29 
  micromillimeters 
  to 
  23.5 
  x 
  27.4 
  micromillimeters 
  (Plate 
  III, 
  figs. 
  2 
  

   to 
  7). 
  

  

  In 
  one 
  instance 
  resting 
  spores, 
  apparently, 
  were 
  found. 
  These 
  were 
  round 
  

   bodies 
  with 
  granular 
  contents 
  and 
  thick 
  walls, 
  and 
  varying 
  in 
  diameter 
  from 
  

   21 
  to 
  25 
  micromillimeters. 
  Plate 
  III, 
  fig. 
  7, 
  shows 
  such 
  a 
  spore 
  apparently 
  

   in 
  situ. 
  These 
  spores, 
  however, 
  are 
  smaller 
  than 
  the 
  published 
  measurements 
  

   of 
  the 
  resting 
  spores 
  of 
  Empusa 
  aphidis, 
  and 
  were 
  only 
  few 
  in 
  number, 
  in- 
  

   stead 
  of 
  filling 
  the 
  body 
  of 
  the 
  insect 
  as 
  is 
  the 
  habit 
  of 
  this 
  fungus. 
  Dr. 
  

   Thaxter 
  thinks 
  these 
  the 
  resting 
  spores 
  of 
  an 
  accidental 
  fungus. 
  

  

  