﻿PARASITES 
  OF 
  THE 
  HESSIAN 
  FLY. 
  219 
  

  

  the 
  foregoing 
  parasites, 
  but 
  it 
  was. 
  evolved 
  later 
  in 
  the 
  -year. 
  Her- 
  

   rick 
  adds 
  that 
  all 
  the 
  parasites 
  m^^ntioned 
  " 
  are 
  likewise 
  evolved 
  in 
  the 
  

   spring 
  from 
  the 
  Hessian 
  Fly 
  pupai 
  of 
  the 
  summer 
  previous." 
  

  

  The 
  iiith 
  parasite 
  has 
  quite 
  different 
  habits. 
  It 
  was 
  said 
  by 
  Herri 
  ck 
  

   to 
  deposit 
  its 
  eggs 
  in 
  those 
  of 
  the 
  Hessian 
  Fly. 
  Herrick, 
  its 
  first 
  dis- 
  

   coverer, 
  thus 
  speaks 
  of 
  it 
  : 
  

  

  The 
  insect 
  is 
  abiindant 
  in 
  tlie 
  autumn. 
  I 
  first 
  saw 
  it 
  September 
  23, 
  1833, 
  in 
  the 
  act 
  

   'of 
  depositing 
  its 
  eggs 
  in 
  the 
  eggs 
  of 
  the 
  Hessian 
  Fly. 
  From 
  subsequent 
  observations 
  

   it 
  appears 
  that 
  four 
  or 
  live 
  eggs 
  are 
  laid 
  in 
  a 
  single 
  egg 
  of 
  the 
  Hessian 
  Fly. 
  The 
  lat- 
  

   ter 
  egg 
  hatches, 
  and 
  the 
  animal 
  advances 
  to 
  the 
  pupa 
  state 
  as 
  usual, 
  but 
  from 
  the 
  

   puparium 
  no 
  Hessian 
  Fly 
  ever 
  comes 
  forth. 
  This 
  parasite 
  forms 
  within 
  the 
  puparinm 
  

   ii 
  silky 
  cocoon 
  of 
  a 
  brownish 
  color. 
  

  

  It 
  is 
  probable 
  that 
  it 
  is 
  the 
  species 
  first 
  discovered 
  by 
  Herrick 
  in 
  Con- 
  

   necticut 
  which 
  Professor 
  Cook 
  has 
  detected 
  ovipositing 
  in 
  the 
  eggs 
  of 
  

   the 
  Hessian 
  Fly."^ 
  

  

  It 
  is 
  black 
  and 
  looks 
  not 
  unlike 
  a 
  tiny 
  gnat. 
  The 
  female 
  feels 
  for 
  the 
  egg 
  with 
  her 
  

   antenna, 
  and 
  when 
  found 
  intrudes 
  the 
  fatal 
  egg, 
  which, 
  I 
  find, 
  takes 
  three-fourths 
  of 
  

   a 
  minute 
  ; 
  full 
  three 
  times 
  as 
  long 
  as 
  it 
  takes 
  the 
  Hessian 
  Fly. 
  The 
  little 
  parasite 
  is 
  

   much 
  longer, 
  too, 
  in 
  finding 
  the 
  eggs 
  than 
  is 
  the 
  fly 
  in 
  laying 
  them. 
  I 
  find 
  that 
  each 
  

   egg 
  receives 
  one, 
  two, 
  or 
  three 
  of 
  the 
  i)arasite's 
  eggs. 
  The 
  eggs 
  of 
  these 
  latter 
  are 
  

   tardy 
  in 
  hatching, 
  so 
  that 
  the 
  larva 
  of 
  the 
  parasite 
  may 
  feed 
  on 
  the 
  maggot 
  of 
  the 
  

   Hessian 
  Fly, 
  not 
  her 
  eggs. 
  These 
  pupate 
  in 
  the 
  puparium 
  of 
  the 
  fly. 
  

  

  Flatygaster 
  error 
  Fitch! 
  — 
  Having 
  received 
  one 
  of 
  these 
  egg-parasites 
  

   from 
  Professor 
  Cook, 
  I 
  find 
  it 
  to 
  be 
  so 
  much 
  like 
  the 
  Flatygaster 
  error 
  

  

  11- 
  Onr 
  attention 
  has 
  been 
  called 
  by 
  Mr. 
  Howard 
  to 
  the 
  fact 
  that 
  as 
  a 
  rule 
  to 
  which 
  

   there 
  is 
  no 
  known 
  exception, 
  egg-parasites 
  issue 
  as 
  adults 
  froui 
  the 
  eggs 
  of 
  their 
  host; 
  

   and 
  on 
  reflection 
  it 
  seems 
  to 
  us 
  that 
  the 
  Flatygaster 
  in 
  question 
  is 
  entirely 
  too 
  large 
  

   to 
  be 
  regarded 
  as 
  a 
  true 
  egg 
  parasite, 
  those 
  known 
  to 
  be 
  such 
  being 
  of 
  minute 
  size. 
  

   Fresh 
  and 
  very 
  careful 
  observations 
  are 
  therefore 
  needed 
  on 
  this 
  point, 
  and 
  it 
  is 
  pos- 
  

   sible 
  that 
  both 
  Herrick 
  and 
  Cook 
  have 
  been 
  in 
  error, 
  and 
  that 
  the 
  eggs 
  were 
  in- 
  

   serted 
  in 
  freshly 
  hatched 
  larvui 
  when 
  little 
  larger 
  than 
  the 
  eggs. 
  We 
  append 
  Mr. 
  

   Howard's 
  criticism 
  : 
  

  

  " 
  Fitch's 
  description 
  of 
  Flatygaster 
  error 
  (which 
  name 
  you 
  apply 
  to 
  the 
  so-called 
  ' 
  egg- 
  

   parasite' 
  in 
  Bulletin 
  4) 
  is 
  so 
  general 
  that 
  it 
  will 
  apply 
  to 
  almost 
  any 
  species 
  of 
  the 
  

   genus. 
  And 
  now 
  a 
  word 
  as 
  to 
  the 
  egg-parasite. 
  So 
  contrary 
  is 
  it 
  to 
  all 
  analogy 
  in 
  

   the 
  whole 
  group 
  of 
  parasitic 
  Hymenoptera, 
  to 
  saynothingof 
  the 
  well-known 
  habits 
  of 
  

   the 
  genus 
  Flatygaster, 
  that 
  a 
  parasitic 
  egg 
  should 
  be 
  deposited 
  within 
  the 
  egg 
  of 
  a 
  

   host 
  and 
  not 
  hatch 
  until 
  the 
  larva 
  of 
  the 
  latter 
  has 
  issued, 
  that 
  I 
  look 
  upon 
  the 
  re- 
  

   ported 
  observations 
  of 
  Herrick, 
  and 
  especially 
  of 
  Cook, 
  as 
  in 
  the 
  highest 
  degree 
  im- 
  

   probable. 
  

  

  " 
  1. 
  No 
  other 
  case 
  is 
  on 
  record, 
  to 
  my 
  knowledge, 
  where 
  an 
  egg-parasite 
  does 
  not 
  

   issue 
  as 
  an 
  adult 
  from 
  the 
  egg 
  of 
  its 
  host. 
  

  

  " 
  2. 
  European 
  species 
  of 
  Flatygaster 
  are 
  known 
  to 
  lay 
  their 
  eggs 
  in 
  larvae 
  of 
  Ceci- 
  

   dorayidae 
  only, 
  

  

  *' 
  3. 
  The 
  difficulties 
  in 
  the 
  way 
  of 
  making 
  such 
  an 
  observation 
  as 
  Cook 
  records 
  are 
  

   practically 
  insurmountable. 
  

  

  ''The 
  second 
  point 
  alone 
  would, 
  in 
  my 
  judgment, 
  settle 
  the 
  matter, 
  as 
  the 
  geueric 
  

   habits 
  of 
  parasites 
  are 
  very 
  uniform." 
  

   Respectfully, 
  yours, 
  

  

  L. 
  O. 
  HOWARD. 
  

  

  