﻿202 
  

  

  CONTAGIOUS 
  DISEASES 
  OF 
  THE 
  CHINCH-BUG. 
  

  

  remainder, 
  with 
  the 
  dried 
  remains 
  received 
  from 
  Professor 
  Snow, 
  being 
  scattered 
  

   about 
  over 
  a 
  small 
  area 
  of 
  young 
  wheat 
  sown 
  for 
  experiment, 
  and 
  also 
  swarming 
  with 
  

   young 
  chinch-bugs. 
  The 
  hills 
  of 
  corn 
  on 
  which 
  the 
  bugs 
  had 
  been 
  placed 
  were 
  iso- 
  

   lated 
  from 
  others, 
  equally 
  badly 
  infested, 
  by 
  narrow 
  frames 
  of 
  boards 
  placed 
  on 
  the 
  

   ground, 
  and 
  the 
  upper 
  edges 
  covered 
  with 
  tar. 
  This 
  last 
  precaution 
  was 
  taken 
  in 
  

   order 
  to 
  prevent 
  communication 
  with 
  other 
  hills, 
  intended 
  as 
  checks 
  on 
  those 
  used 
  

   directly 
  in 
  the 
  experiment. 
  The 
  area 
  of 
  young 
  wheat 
  over 
  which 
  infected 
  bugs 
  had 
  

   been 
  placed 
  was 
  not 
  inclosed, 
  but 
  its 
  limits 
  carefully 
  marked. 
  Five 
  days 
  after, 
  July 
  

   27th, 
  a 
  single 
  bug 
  was 
  found 
  on 
  one 
  of 
  the 
  isolated 
  hills 
  of 
  corn, 
  which 
  had 
  very 
  evi- 
  

   dently 
  died 
  from 
  -the 
  effects 
  of 
  Entomophthora, 
  and 
  by 
  the 
  30th 
  enough 
  others 
  were 
  

   found 
  to 
  show 
  that 
  the 
  fungus 
  had 
  fully 
  established 
  itself, 
  and 
  the 
  barriers 
  about 
  the 
  

   isolated 
  hills 
  were 
  removed. 
  

  

  On 
  August 
  2d, 
  dead 
  bugs 
  covered 
  with 
  Entomophthora 
  were 
  found 
  in 
  considerable 
  

   numbers 
  about 
  hills 
  of 
  corn 
  25 
  feet 
  from 
  where 
  the 
  original 
  colonies 
  had 
  been 
  placed, 
  

   and 
  also 
  throughout 
  and 
  even 
  55 
  feet 
  beyond 
  the 
  area 
  of 
  young 
  wheat 
  over 
  which 
  

   dead 
  and 
  affected 
  bugs 
  had 
  been 
  distributed. 
  Daily 
  observations 
  were 
  now 
  made, 
  

   but 
  the 
  progress 
  of 
  the 
  disease 
  seemed 
  to 
  come 
  to 
  a 
  stand-still. 
  From 
  the 
  5th 
  of 
  

   August 
  up 
  to 
  the 
  9th, 
  it 
  was 
  almost 
  impossible 
  to 
  get 
  sufficient 
  material, 
  outside, 
  to 
  

   enable 
  me 
  to 
  carry 
  on 
  laboratory 
  experiments. 
  August 
  13th 
  the 
  spread 
  of 
  Ento- 
  

   mophthora 
  appeared 
  to 
  have 
  taken 
  on 
  new 
  life, 
  and 
  diseased 
  bugs 
  were 
  becoming 
  

   much 
  more 
  numerous. 
  August 
  15th 
  found 
  diseased 
  bugs 
  172 
  feet 
  from 
  any 
  place 
  

   where 
  they 
  had 
  been 
  previously 
  observed. 
  August 
  20th 
  diseased 
  bugs 
  were 
  very 
  

   abundant 
  over 
  all 
  of 
  the 
  area 
  where 
  disease 
  had 
  been 
  distributed, 
  and 
  two 
  days 
  later 
  

   examples 
  were 
  found 
  a 
  quarter 
  of 
  a 
  mile 
  from 
  the 
  starting-point 
  of 
  the 
  disease. 
  Im- 
  

   mediately 
  after 
  this, 
  however, 
  came 
  another 
  halt, 
  both 
  in 
  the 
  intensity 
  of 
  attack 
  and 
  

   rapidity 
  with 
  which 
  it 
  spread, 
  due 
  either 
  to 
  the 
  dry 
  weather 
  or 
  to 
  the 
  fact 
  that 
  the 
  

   bugs 
  had 
  now 
  reached 
  the 
  adult 
  stage 
  and 
  had 
  become 
  diffused 
  over 
  the 
  country, 
  no 
  

   longer 
  congregating 
  together. 
  From 
  either 
  one 
  or 
  the 
  other, 
  or 
  both 
  of 
  these 
  causes, 
  

   I 
  lost 
  track 
  of 
  Entomophthora, 
  and 
  was 
  not 
  able 
  to 
  again 
  find 
  it 
  in 
  the 
  fields. 
  It 
  seems 
  

   proper 
  to 
  state 
  here 
  that 
  chinch-bugs 
  were 
  not 
  at 
  any 
  time 
  excessively 
  abundant. 
  

   The 
  greatest 
  numbers 
  were 
  in 
  the 
  exact 
  localities 
  where 
  the 
  disease 
  was 
  first 
  distrib- 
  

   uted, 
  the 
  congregating 
  at 
  these 
  places 
  being 
  brought 
  about 
  by 
  the 
  close 
  proximity 
  

   to 
  a 
  large 
  number 
  of 
  small 
  experimental 
  plats 
  of 
  wheat; 
  and 
  when 
  this 
  was 
  harvested 
  

   the 
  bugs 
  collected 
  en 
  masse 
  on 
  the 
  corn 
  and 
  young 
  wheat. 
  In 
  connection 
  with 
  these 
  

   facts, 
  it 
  is 
  also 
  interesting 
  to 
  note 
  that 
  from 
  July 
  15 
  to 
  August 
  31 
  there 
  were 
  10 
  

   days 
  on 
  which 
  rain 
  fell. 
  The 
  dates 
  of 
  these 
  rains 
  and 
  the 
  amount 
  of 
  precipitation 
  

   are 
  given 
  below: 
  

  

  July 
  17 
  

   July 
  19 
  

   July 
  22 
  

   July 
  23 
  

   July 
  26 
  

  

  Precip- 
  

   itation 
  

   (inches). 
  

  

  .02 
  

   1.25 
  

   .20 
  

   .04 
  

   .13 
  

  

  July 
  29 
  . 
  

   July 
  30 
  . 
  

   Aug. 
  9 
  

   Aug. 
  13 
  

   Aug. 
  14 
  

  

  Precip- 
  

   itation 
  

  

  (inches). 
  

  

  .78 
  

   .50 
  

   3.36 
  

   .15 
  

   .02 
  

  

  With 
  a 
  view 
  of 
  learning 
  whether 
  or 
  not 
  there 
  was 
  any 
  difference 
  as 
  regards 
  sus- 
  

   ceptibility 
  to 
  the 
  attack 
  of 
  Entomophthora 
  between 
  bugs 
  in 
  different 
  stages 
  of 
  de- 
  

   velopment, 
  a 
  series 
  of 
  experiments 
  was 
  begun, 
  as 
  follows: 
  

  

  Young 
  plants 
  of 
  Setaria 
  glauca 
  were 
  transplanted 
  to 
  a 
  box, 
  and 
  upon 
  each 
  plant 
  

   was 
  placed 
  a 
  dead 
  bug 
  covered 
  with 
  the 
  fungus, 
  and 
  also 
  healthy 
  larvse; 
  larvje 
  just 
  

   on 
  the 
  point 
  of 
  pupation; 
  pupas 
  just 
  prior 
  to 
  reaching 
  the 
  adult 
  stage; 
  and 
  fully- 
  

   developed 
  adults, 
  each 
  stage 
  being 
  placed 
  on 
  separate 
  plants, 
  and 
  each 
  covered 
  with 
  

   a 
  small 
  inverted 
  glass 
  vial 
  numbered 
  by 
  lettering. 
  As 
  checks, 
  another 
  series 
  was 
  

  

  