﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [37] 
  

  

  6. 
  Flowing 
  under, 
  burning, 
  rolling 
  of 
  the 
  stubbles. 
  

  

  Fitcli 
  is 
  very 
  much 
  opposed 
  to 
  these 
  remedies 
  of 
  destruction. 
  Loew 
  

   partly 
  recommends 
  them. 
  The 
  destruction 
  of 
  the 
  pupae 
  hidden 
  in 
  stub- 
  

   bles 
  appears 
  to 
  him 
  in 
  years 
  of 
  great 
  frequency 
  of 
  their 
  parasites 
  as 
  

   a 
  remedy 
  of 
  doubtful 
  value, 
  while 
  he 
  advocates 
  it 
  in 
  years 
  when 
  the 
  

   latter 
  are 
  less 
  numerous. 
  All 
  reports 
  from 
  America 
  agree 
  in 
  that 
  the 
  

   fly 
  visits 
  a 
  certain 
  district 
  only 
  for 
  a 
  number 
  of 
  years 
  ; 
  then 
  disappears, 
  

   to 
  reappear 
  after 
  a 
  longer 
  or 
  shorter 
  time. 
  The 
  devastations 
  caused 
  by 
  

   the 
  insect 
  in 
  itij 
  first 
  year 
  of 
  api)earance 
  are 
  but 
  little, 
  gradually 
  reach- 
  

   ing 
  their 
  point 
  of 
  culmination 
  after 
  three 
  or 
  four 
  yearns 
  increase. 
  At 
  

   the 
  same 
  time 
  the 
  parasites 
  multiply 
  also, 
  not 
  in 
  the 
  same 
  degree, 
  but 
  in 
  

   a 
  ratio 
  of 
  geometrical 
  i)rogression, 
  so 
  that 
  in 
  the 
  very 
  same 
  year 
  in 
  

   which 
  the 
  flies 
  are 
  extremely 
  numerous 
  they 
  become 
  overwhelmed 
  by 
  

   the 
  parasites; 
  hence 
  but 
  few 
  flies 
  appear 
  in 
  the 
  following 
  year. 
  That 
  

   we 
  in 
  Germany 
  may 
  make 
  the 
  same 
  observations 
  with 
  the 
  fly 
  and 
  its 
  

   parasites 
  cannot 
  be 
  doubted. 
  Certain 
  practical 
  inferences 
  will 
  be 
  that 
  in 
  

   a 
  given 
  year 
  we 
  may 
  always 
  know 
  whether 
  to 
  bring 
  the 
  one 
  or 
  the 
  other 
  

   remedy 
  into 
  application 
  or 
  not. 
  It 
  requires 
  but 
  little 
  consideration 
  to 
  

   see 
  that 
  already, 
  with 
  50 
  per 
  cent, 
  of 
  parasites, 
  the 
  plowing 
  under, 
  burn- 
  

   ing, 
  or 
  rolling 
  over 
  the 
  stubbles 
  will 
  cause 
  a 
  prolongation 
  of 
  the 
  feeding 
  

   cycle, 
  therefore 
  doing 
  damage. 
  We 
  can 
  assume 
  with 
  certainty 
  in 
  all 
  

   cases 
  that 
  but 
  few 
  parasites 
  occur 
  at 
  the 
  beginning 
  of 
  a 
  feeding 
  cycle. 
  

   The 
  above-mentioned 
  remedies 
  therefore 
  should 
  be 
  applied. 
  

  

  Eolling 
  of 
  the 
  crops 
  has 
  been 
  done 
  successfully 
  in 
  America. 
  That 
  in 
  

   this 
  way 
  many 
  eggs 
  and 
  maggots 
  are 
  destroyed 
  I 
  doubt, 
  since 
  the 
  

   eggs 
  in 
  the 
  furrows 
  of 
  the 
  leaves 
  are 
  protected 
  against 
  the 
  pressure 
  of 
  

   the 
  roller 
  and 
  the 
  maggots 
  are 
  situated 
  very 
  deep 
  in 
  the 
  young 
  sprouts. 
  

   A 
  good 
  effect 
  could 
  only 
  be 
  obtained 
  by 
  a 
  very 
  heavy 
  roller, 
  and 
  such 
  

   wonld 
  also 
  damage 
  the 
  crops. 
  

  

  For 
  the 
  destruction 
  of 
  the 
  spring 
  brood 
  Fitch 
  proposes 
  moiving 
  of 
  the 
  

   wheat, 
  stating 
  an 
  experiment 
  made 
  with 
  wheat 
  two 
  feet 
  high, 
  and 
  where- 
  

   from 
  it 
  resulted 
  that 
  the 
  wheat 
  at 
  this 
  stage 
  can 
  be 
  cut 
  without 
  loss 
  

   of 
  producti^'eness. 
  I 
  have 
  had 
  similar 
  experience 
  on 
  rich 
  soil, 
  the 
  root- 
  

   stock 
  soon 
  producing 
  new 
  stalks 
  not 
  at 
  all 
  diminished 
  in 
  strength. 
  But 
  

   this 
  occurs 
  exceptionally; 
  the 
  ears 
  never 
  attain 
  the 
  full 
  size, 
  remaining 
  

   smaller, 
  and 
  in 
  continual 
  drought 
  the 
  experiment 
  is 
  altogether 
  a 
  fail- 
  

   ure. 
  We 
  therefore 
  consider 
  mowing 
  off 
  too 
  risky 
  for 
  recommendation. 
  

   Several 
  people 
  haverei)orted 
  that 
  whole 
  "swarms" 
  of 
  our 
  gall-gnat 
  had 
  

   alighted 
  on 
  cereals 
  for 
  oviposition. 
  Last 
  fall 
  and 
  again 
  this 
  spring 
  I 
  

   often 
  went 
  on 
  much-infested 
  fields 
  during 
  swarming 
  time 
  at 
  different 
  

   hours 
  of 
  the 
  day 
  and 
  have 
  gathered 
  flies 
  here 
  as 
  well 
  as 
  on 
  neighboring- 
  

   fields, 
  but 
  never 
  found 
  them 
  gregariously 
  accumulated 
  • 
  on 
  the 
  contrary, 
  

   they 
  appeared 
  singly. 
  I 
  therefore 
  altogether 
  doubt 
  that 
  it 
  is 
  peculiar 
  

   to 
  the 
  insect 
  to 
  collect 
  in 
  swarms. 
  Those 
  observations 
  on 
  the 
  gregarious 
  

   appearances 
  of 
  our 
  fly 
  are 
  either 
  exaggerations 
  or 
  illusions. 
  If 
  our 
  in- 
  

   sects 
  had 
  really 
  social 
  habits 
  it 
  would 
  be 
  not 
  out 
  of 
  place 
  to 
  catch 
  them 
  

   with 
  a 
  net. 
  According 
  to 
  my 
  own 
  observations 
  the 
  catching 
  with 
  a 
  net 
  

   amounts 
  to 
  nothing 
  at 
  all. 
  

  

  I 
  will 
  now 
  dwell 
  on 
  indirect 
  remedies. 
  To 
  those 
  belongs 
  every 
  remedy 
  

   which 
  gives 
  the 
  plants 
  greater 
  resistance 
  against 
  their 
  attacks, 
  whereby 
  

   the 
  flies 
  are 
  more 
  or 
  less 
  restricted. 
  

  

  7. 
  Bich 
  soil. 
  

  

  The 
  importance 
  of 
  this 
  remedy 
  we 
  have 
  already 
  recognized 
  when 
  

   speaking 
  of 
  pasturing; 
  it 
  becomes 
  still 
  more 
  evident 
  if 
  we 
  recall 
  the 
  de- 
  

  

  