﻿PACKAUD.J 
  PARASITES 
  OF 
  NORTHERN 
  ARMY-WORM. 
  707 
  

  

  distiugiiishable, 
  bas 
  two 
  little 
  flattened 
  plates 
  that 
  were 
  the 
  breathing- 
  

   pores 
  in 
  the 
  larva. 
  The 
  two 
  first 
  segments 
  are 
  partially 
  split 
  off, 
  and 
  

   ruptured 
  across 
  the 
  end, 
  where 
  the 
  fly 
  burst 
  out. 
  The 
  fly 
  appeared 
  the 
  

   20th 
  of 
  September. 
  

  

  " 
  The 
  eggs," 
  Mr. 
  Walsh 
  says, 
  " 
  are 
  much 
  the 
  shape 
  and 
  color 
  of 
  those 
  

   of 
  the 
  flesh-fly. 
  The 
  fly 
  fastens 
  its 
  eggs 
  by 
  an 
  insoluble 
  cement 
  on 
  the 
  

   upper 
  surface 
  of 
  the 
  two 
  or 
  three 
  first 
  rings 
  of 
  the 
  body. 
  Instinct 
  ap- 
  

   pears 
  to 
  teach 
  the 
  mother-fly 
  that 
  if 
  she 
  places 
  her 
  eggs 
  further 
  back, 
  

   the 
  little 
  maggots, 
  as 
  they 
  hatch 
  out 
  and 
  begin 
  to 
  penetrate 
  the 
  flesh, 
  

   ■will 
  be 
  felt 
  by 
  the 
  victim 
  and 
  seized 
  by 
  its 
  powerful 
  jaws, 
  as 
  I 
  have 
  seen 
  

   wood-feeding 
  caterpillars 
  seize 
  and 
  worry 
  like 
  a 
  dog 
  ants 
  that 
  attacked 
  

   them." 
  

  

  Mr. 
  Walsh 
  had 
  fifty 
  or 
  sixty 
  worms, 
  of 
  which 
  all 
  but 
  two 
  had 
  their- 
  

   eggs, 
  from 
  one 
  to 
  six 
  iu 
  number, 
  fastened 
  on 
  their 
  upper 
  side. 
  From 
  

   these 
  he 
  bred 
  fifty-four 
  Tachinas 
  and 
  two 
  moths. 
  " 
  Now 
  these 
  army- 
  

   worms 
  averaged 
  about 
  three 
  eggs 
  apiece, 
  and 
  consequently 
  two-thirds 
  

   of 
  the 
  eggs 
  of 
  the 
  TacJiina 
  must 
  have 
  perished 
  without 
  arriving 
  at 
  ma- 
  

   turity." 
  

  

  " 
  My 
  TacJima 
  eggs, 
  so 
  far 
  as 
  I 
  noticed, 
  did 
  not 
  hatch 
  till 
  the 
  larva 
  

   had 
  gone 
  under 
  ground 
  ; 
  but 
  from 
  information 
  received 
  from 
  Mr. 
  Emery, 
  

   I 
  have 
  reason 
  to 
  believe 
  that, 
  under 
  certain 
  circumstances, 
  this, 
  or 
  an 
  

   allied 
  species, 
  hatches 
  out 
  above 
  ground, 
  adhering 
  externally, 
  and 
  ' 
  grow- 
  

   ing 
  rapidly, 
  while 
  its 
  victim 
  decreases 
  in 
  size.' 
  They 
  uniformly 
  devoured 
  

   the 
  larva 
  before 
  it 
  transformed 
  into 
  the 
  pupa 
  state. 
  The 
  time 
  for 
  the 
  

   entire 
  transformation 
  of 
  such 
  as 
  I 
  experimented 
  upon 
  from 
  egg 
  to 
  fly, 
  

   was 
  from 
  fifteen 
  to 
  nineteen 
  days." 
  * 
  * 
  * 
  " 
  Jefferson 
  Eussell, 
  an 
  in- 
  

   telligent 
  farmer, 
  had 
  repeatedly, 
  on 
  damp, 
  cloudy 
  mornings, 
  watched 
  a 
  

   large, 
  bluish-green 
  fly, 
  about 
  the 
  size 
  of 
  a 
  blow-fly, 
  attacking 
  the 
  army- 
  

   worm, 
  and 
  depositing 
  its 
  eggs 
  on 
  the 
  shoulders 
  of 
  the 
  victim, 
  as 
  he 
  as- 
  

   certained 
  by 
  a 
  double 
  lens. 
  As 
  they 
  were 
  attacked, 
  the 
  army-worms 
  

   kept 
  dropping 
  to 
  the 
  ground 
  and 
  gathering 
  in 
  clusters, 
  or 
  hiding 
  under 
  

   clods, 
  until 
  finally 
  the 
  wheat 
  on 
  which 
  they 
  occurred 
  was 
  entirely 
  free 
  

   from 
  them." 
  Mr. 
  Eiley 
  says 
  that 
  in 
  1875 
  fully 
  80 
  per 
  cent, 
  of 
  the 
  army- 
  

   worms 
  which 
  he 
  noticed 
  were 
  attacked 
  hy 
  the 
  Tachina 
  Hies. 
  "They 
  

   never 
  abound 
  or 
  travel 
  from 
  one 
  field 
  to 
  another, 
  but 
  they 
  are 
  accom- 
  

   panied 
  by 
  a 
  number 
  of 
  two-winged 
  flies, 
  w^hich 
  are 
  often 
  so 
  numerous 
  

   that 
  their, 
  buzzing 
  reminds 
  one 
  of 
  a 
  swarm 
  of 
  bees." 
  — 
  (Eighth 
  Eeport.) 
  

   This 
  fact 
  supports 
  the 
  opinion 
  of 
  Wagner 
  (see 
  p. 
  ) 
  that 
  insect-para- 
  

   sites 
  usually 
  increase 
  in 
  proportion 
  to 
  their 
  hosts. 
  

  

  Egg. 
  — 
  When 
  first 
  laid, 
  spherical, 
  0.02 
  inch 
  in 
  diameter, 
  smooth, 
  opaque 
  'uhite 
  ; 
  cov- 
  

   ered 
  with 
  a 
  glistening, 
  adhesive 
  fluid 
  ; 
  shell 
  delicate, 
  becoming 
  faintly 
  irridesceut 
  and 
  

   more 
  sordid 
  before 
  hatching. 
  — 
  (Riley.) 
  

  

  Larva. 
  — 
  When 
  first 
  hatched, 
  1.7 
  

   millemeter 
  in 
  length; 
  dull 
  white, 
  

   and 
  a 
  large 
  dark 
  head. 
  

  

  In 
  the 
  first 
  and 
  second 
  stages, 
  

   the 
  two 
  front 
  jiairs 
  of 
  abdominal 
  

   legs 
  are 
  atrophied 
  so 
  as 
  to 
  necessi- 
  

   tate 
  a 
  looping 
  gait. 
  In 
  the 
  third 
  

   stage 
  the 
  looping 
  habit 
  is 
  lost, 
  but 
  

   the 
  front 
  abdominal 
  legs 
  are 
  still 
  

   somewhat 
  the 
  smallest. 
  In 
  the 
  Fig. 
  6.— 
  Pupa 
  

   fourth 
  stage, 
  the 
  color 
  is 
  dull, 
  dark 
  ^J^ 
  Cbrysa- 
  

   FiG. 
  5.— 
  Full-grown 
  Northern 
  Arm.y-tvorm. 
  green, 
  and 
  the 
  chameleonitic 
  brown 
  ^®' 
  

  

  lines 
  appear. 
  — 
  (Riley.) 
  

   The 
  mature 
  larva 
  is 
  about 
  an 
  inch 
  and 
  a 
  half 
  long. 
  Its 
  cylindrical 
  body, 
  divided 
  

   into 
  thirteen 
  rings, 
  becomes 
  more 
  contracted 
  and 
  wrinkled 
  at 
  each 
  end, 
  and 
  is 
  spai'sely 
  

   covered 
  with 
  short 
  hairs. 
  The 
  head 
  is 
  covered 
  by 
  a 
  net-work 
  of 
  confluent 
  spots, 
  while 
  

   along 
  the 
  middle 
  of 
  the 
  face 
  run 
  two 
  lines 
  diverging 
  at 
  each 
  end. 
  A 
  light-colored 
  waved 
  

   line, 
  just 
  above 
  the 
  legs, 
  is 
  succeeded 
  by 
  a 
  dark 
  one 
  ; 
  then 
  a 
  light 
  one, 
  edged 
  with 
  two 
  

  

  