﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [25] 
  

  

  Dr. 
  Asa 
  Fitch 
  has 
  thoroughly 
  revised 
  what 
  has 
  been 
  stated 
  on 
  the 
  

   Hessian 
  fly 
  in 
  various 
  wc^rl^s 
  and 
  journals, 
  has 
  connected 
  the 
  most 
  im- 
  

   portant 
  facts 
  with 
  personal 
  observations, 
  and 
  has 
  worked 
  up 
  the 
  entire 
  

   material 
  known 
  about 
  this 
  insect 
  in 
  his 
  paper, 
  '' 
  The 
  Hessian 
  fly 
  j 
  its 
  his- 
  

   tory, 
  character, 
  transformations, 
  and 
  habits," 
  in 
  the 
  American 
  Journal 
  

   of 
  A-griculture 
  and 
  Science, 
  vols. 
  IV 
  and 
  V, 
  Albany, 
  1846. 
  After 
  sev- 
  

   eral 
  vain 
  endeavors 
  to 
  obtain 
  this 
  paper, 
  which 
  is 
  rare 
  in 
  Germany, 
  

   from 
  a 
  bookseller, 
  I 
  finally 
  received 
  it 
  from 
  Dr. 
  Dohrn, 
  in 
  Stettin. 
  

  

  Loew 
  compared 
  bis 
  rye 
  gall-gnat 
  with 
  Fitch's 
  Hessian 
  fly, 
  and 
  found 
  

   differences 
  partly 
  due 
  either 
  to 
  manner 
  of 
  life 
  or 
  to 
  a 
  knowledge 
  of 
  dif- 
  

   ferent 
  states 
  of 
  development 
  in 
  both 
  flies, 
  and 
  therefore 
  regarded 
  them 
  

   as 
  diflerent 
  species. 
  My 
  examinations 
  of 
  our 
  gall-gnat, 
  whose 
  identity 
  

   with 
  Loew's 
  0. 
  secalina 
  I 
  stated 
  in 
  the 
  preceding 
  paragraph, 
  enable 
  me 
  

   to 
  scrutinize 
  the 
  specific 
  diflerences 
  of 
  the 
  author 
  of 
  '^ 
  Die 
  neue 
  Korn- 
  

   made.'^ 
  

  

  Loew 
  says 
  : 
  " 
  That 
  the 
  whole 
  life-history 
  of 
  the 
  Hessian 
  fly 
  closely 
  

   agrees 
  with 
  that 
  of 
  our 
  rye 
  gall-gnat 
  is 
  obvious 
  ; 
  but 
  it 
  would 
  be 
  hasty 
  to 
  

   see 
  in 
  this 
  accordance, 
  which 
  in 
  so 
  closely 
  allied 
  species 
  cannot 
  be 
  ex- 
  

   pected 
  otherwise, 
  a 
  i^roof 
  of 
  the 
  identity 
  of 
  the 
  two 
  species. 
  Moreover, 
  

   we 
  find 
  some 
  trifling 
  diflerences. 
  Cecidomyia 
  destructor 
  almost 
  exclu- 
  

   sively 
  attacks 
  wheat 
  only; 
  our 
  rye 
  gall-gnat 
  has 
  hitherto 
  been 
  found 
  on 
  

   rye 
  only." 
  

  

  In 
  § 
  3, 
  2, 
  I 
  stated 
  that, 
  according 
  to 
  my 
  observations, 
  the 
  winter 
  gen- 
  

   eration 
  m 
  our 
  districts, 
  too, 
  besides 
  its 
  occurrence 
  on 
  barley 
  after- 
  

   growth, 
  could 
  be 
  found 
  on 
  rye 
  only. 
  This 
  is 
  explained 
  by 
  the 
  circum- 
  

   stance 
  that, 
  as 
  previously 
  mentioned, 
  the 
  sowing 
  of 
  winter 
  wheat 
  in 
  our 
  

   districts 
  is 
  done 
  when 
  the 
  swarming 
  time 
  of 
  the 
  insect 
  is 
  almost 
  past. 
  

   If 
  our 
  farmers 
  gave 
  up 
  the 
  hitherto 
  practised 
  late 
  sowing 
  of 
  winter 
  

   wheat, 
  the 
  fly 
  without 
  doubt 
  would 
  principally 
  choose 
  wheat 
  for 
  its 
  

   domicil, 
  such 
  being 
  -actually 
  the 
  case 
  in 
  the 
  neighboring 
  districts 
  of 
  the 
  

   Ehou 
  Mountains, 
  where 
  wheat 
  is 
  only 
  protected 
  against 
  the 
  cold 
  by 
  

   earlier 
  sowing. 
  In 
  America 
  wheat 
  is 
  attacked 
  by 
  the 
  insect 
  mainly 
  in 
  

   the 
  fall 
  ; 
  by 
  the 
  general 
  practice 
  of 
  early 
  sowing, 
  the 
  attacks 
  of 
  the 
  

   wheat-midge 
  {Cecidomyia 
  tritici^ 
  Kirby) 
  are 
  avoided. 
  The 
  fact 
  that 
  the 
  

   insect 
  infests 
  mainly 
  wheat 
  everywhere 
  under 
  the 
  same 
  conditions, 
  evi- 
  

   dently 
  shows 
  a 
  certain 
  fondness 
  of 
  the 
  fly 
  for 
  this 
  cereal, 
  on 
  account 
  of 
  

   which 
  wheat 
  must 
  be 
  considered 
  as 
  the 
  best 
  adapted 
  food-plant 
  for 
  the 
  

   maggot. 
  What 
  Loew 
  states 
  regarding 
  the 
  occurrence 
  and 
  life-history 
  

   of 
  the 
  summer 
  generation, 
  he 
  infers 
  by 
  analogy 
  with 
  the 
  Hessian 
  fly 
  

   and 
  other 
  gall-gnats 
  known 
  to 
  him, 
  hence 
  it 
  follows 
  that 
  at 
  that 
  time 
  he 
  

   was 
  not 
  yet 
  acquainted 
  with 
  this 
  sec^ond 
  generation. 
  I 
  am 
  therefore 
  

   inclined 
  to 
  believe 
  that 
  later 
  observations 
  led 
  him 
  to 
  the 
  conviction 
  

   that 
  the 
  sole 
  occurrence 
  in 
  rye, 
  purely 
  due 
  to 
  external 
  causes, 
  cannot 
  

   in 
  the 
  least 
  be 
  a 
  characteristic 
  point 
  by 
  which 
  the 
  formation 
  of 
  a 
  new 
  

   species 
  would 
  be 
  justified. 
  

  

  Further 
  on 
  Loew 
  says 
  : 
  ^' 
  The 
  maggots 
  and 
  pup^e 
  of 
  the 
  winter 
  gen- 
  

   eration 
  of 
  C. 
  destructor 
  are 
  said 
  to 
  occur 
  always 
  only 
  just 
  above 
  the 
  up- 
  

   per 
  end 
  of 
  the 
  root-stock 
  ; 
  those 
  of 
  the 
  rye 
  gall-gnat 
  are 
  usually 
  some- 
  

   what 
  higher 
  up." 
  

  

  From 
  what 
  has 
  been 
  said 
  above 
  about 
  the 
  domicil 
  of 
  the 
  maggots 
  and, 
  

   the 
  resting 
  place 
  of 
  the 
  pupse 
  in 
  general, 
  this 
  alleged 
  difl'erence 
  loses,' 
  

   as 
  a 
  matter 
  of 
  course, 
  all 
  meaning. 
  

  

  Concerning 
  the 
  imago, 
  Loew 
  says 
  : 
  

  

  Of 
  the 
  American 
  (Hessian) 
  fly, 
  I 
  have 
  not 
  yet 
  seen 
  any 
  specimens 
  ; 
  they 
  are 
  wanting 
  

   in 
  any 
  of 
  onr 
  entomological 
  musenm 
  collections, 
  nor 
  could 
  I 
  lincl 
  any 
  iu 
  private 
  col- 
  

   lections. 
  As 
  to 
  any 
  differences 
  between 
  our 
  rye 
  gall-gnat 
  and 
  the 
  Hessian 
  fly, 
  I 
  must, 
  

  

  