﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [23]^ 
  

  

  either 
  by 
  an 
  accelerating 
  or 
  retarding 
  influence 
  upon 
  the 
  duration 
  of 
  

   development, 
  our 
  liy 
  will 
  show 
  certain 
  deviations 
  under 
  different 
  lati- 
  

   tudes. 
  The 
  followiug 
  holds 
  for 
  the 
  district 
  of 
  Fulda 
  (50.p 
  North 
  

   Latitude): 
  The 
  eggs 
  out 
  of 
  w^hich 
  the 
  maggots 
  hibernating 
  on 
  stubbles 
  

   are 
  produced 
  are 
  de[)osited 
  in 
  May; 
  the 
  perfect 
  insects 
  appear 
  the 
  fol- 
  

   lowing 
  year 
  in 
  April 
  and 
  May 
  ; 
  the 
  metamorphosis 
  of 
  these 
  flies 
  therefore 
  

   requires 
  a 
  ^yhole 
  year. 
  On 
  the 
  other 
  hand, 
  the 
  flies 
  issuing 
  just 
  before 
  

   the 
  beginning 
  of 
  winter 
  undergo 
  two 
  generations 
  in 
  one 
  year. 
  So 
  we 
  

   have 
  a 
  single 
  and 
  a 
  double 
  generation, 
  which 
  will 
  probably 
  also 
  hold 
  

   for 
  the 
  gieater 
  part 
  of 
  northern 
  Germany. 
  Further 
  on 
  toward 
  the 
  

   north, 
  owing 
  to 
  the 
  earlier 
  appearance 
  of 
  winter, 
  the 
  hibernation 
  of 
  the 
  

   summer 
  generation 
  becomes 
  more 
  and 
  more 
  frequent; 
  finally, 
  near 
  the 
  

   polar 
  districts 
  of 
  Qur 
  cereals, 
  the 
  coming 
  out 
  in 
  fall 
  becomes 
  impossible, 
  

   so 
  that 
  there 
  will 
  occur 
  but 
  one 
  single 
  generation. 
  On 
  the 
  other 
  hand, 
  

   in 
  the 
  south 
  there 
  might 
  be 
  observed 
  but 
  one 
  donble 
  generation 
  long 
  be- 
  

   fore 
  reaching 
  the 
  equatorial 
  limits 
  of 
  our 
  cereals. 
  

  

  That 
  the 
  maggots 
  also 
  hibernate 
  on 
  stubble 
  of 
  the 
  other 
  cereals 
  har- 
  

   boring 
  our 
  insect 
  nobody 
  will 
  question. 
  For 
  gathering 
  maggots 
  in 
  

   spring 
  it 
  is 
  well 
  to 
  choose 
  fields 
  with 
  young 
  clover, 
  because 
  the 
  stubble, 
  

   under 
  the 
  protection 
  of 
  the 
  wild 
  mustard 
  is 
  then 
  longer 
  preserved 
  ; 
  

   furthermore, 
  as 
  it 
  is 
  well 
  known 
  that 
  wheat 
  straw 
  has 
  more 
  resistance 
  

   against 
  the 
  weathei" 
  than 
  the 
  straw 
  of 
  rye, 
  and 
  esxjecially 
  barley, 
  wheat 
  

   stubbles 
  again 
  deserve 
  attention. 
  

  

  § 
  4. 
  Summer 
  aENEHATioN. 
  

  

  The 
  metamorphoses 
  of 
  the 
  summer 
  generation 
  take, 
  favored 
  by 
  the 
  

   warm 
  season, 
  a 
  rai)id 
  course. 
  The 
  flies 
  issuing 
  in 
  Ai)ril 
  and 
  May 
  find 
  

   plenty 
  of 
  the 
  food-plants 
  for 
  their 
  ottspring. 
  Those 
  of 
  them 
  which 
  passed 
  

   through 
  the 
  earlier 
  stages 
  on 
  winter 
  cereals 
  ovii)osit 
  again 
  on 
  the 
  same 
  

   kind 
  of 
  crop 
  which 
  had 
  already 
  raised 
  a 
  brood 
  ; 
  but 
  as 
  the 
  basal 
  leaves 
  be- 
  

   gin 
  to 
  decay, 
  the 
  female 
  now 
  chooses 
  stalked 
  ones 
  for 
  her 
  eggs 
  ; 
  but 
  those 
  

   flies 
  which 
  hibernate 
  as 
  maggots 
  on 
  barley 
  aftergrowth 
  or 
  on 
  stubbles 
  are 
  

   compelled 
  to 
  seek 
  new 
  breeding 
  localities, 
  in 
  which 
  desire 
  they 
  strongly 
  

   incline 
  to 
  winter 
  wheat. 
  Only 
  when 
  the 
  latter 
  is 
  wanting 
  in 
  the 
  neigh- 
  

   borhood 
  do 
  they 
  content 
  themselves 
  with 
  spring 
  cereals, 
  which 
  for 
  

   the 
  purpose 
  of 
  the 
  fly 
  are 
  sufdciently 
  advanced 
  in 
  May. 
  The 
  hatching- 
  

   young 
  maggots, 
  as 
  in 
  fall, 
  creep 
  to 
  the 
  base 
  of 
  the 
  blade, 
  where 
  they 
  

   find 
  all 
  the 
  requirements 
  for 
  further 
  development. 
  According 
  to 
  the, 
  at 
  

   this 
  time, 
  more 
  or 
  less 
  advanced 
  plant, 
  the 
  maggots 
  afterwards 
  occur 
  

   on 
  the 
  lower 
  stalk 
  nodules, 
  or 
  immediately 
  above 
  the 
  root 
  stock. 
  The 
  

   spring 
  cereals 
  usually 
  overcome 
  the 
  attacks 
  of 
  the 
  worms 
  by 
  a 
  luxuii- 
  

   ant, 
  rapid 
  growth, 
  as 
  they, 
  in 
  spite 
  of 
  the 
  worms, 
  a<lvauce 
  on 
  fertile 
  

   soil. 
  Toward 
  the 
  20th 
  of 
  June 
  the 
  majority 
  of 
  the 
  maggots 
  are 
  full 
  

   grown, 
  some 
  of 
  them 
  being 
  then 
  already 
  in 
  the 
  pseudo-pupal 
  state. 
  

  

  As 
  the 
  maggot 
  lives 
  on 
  the 
  juice 
  of 
  the 
  plant, 
  remaining 
  in 
  its 
  first 
  

   chosen 
  dwelling, 
  this 
  spot 
  becomes 
  so 
  much 
  loosened 
  by 
  extraction 
  of 
  

   juices 
  that 
  it 
  shrivels, 
  and 
  the 
  stalk, 
  too 
  weak 
  to 
  bear 
  the 
  ear, 
  bends 
  

   over 
  at 
  the 
  first 
  wind. 
  

  

  It 
  happens, 
  when 
  a 
  strong 
  stalk, 
  that 
  one 
  or 
  several 
  maggots 
  imbed 
  

   themselves, 
  on 
  account 
  of 
  their 
  sedentary 
  habits, 
  in 
  the 
  soft, 
  yielding 
  

   substance 
  deeply 
  into 
  the 
  cavity 
  of 
  the 
  stalk; 
  if 
  the 
  spot 
  then 
  heals, 
  

   i. 
  e., 
  makes 
  it 
  possible 
  by 
  luxuriant 
  growth, 
  that 
  the 
  wound 
  regenerates 
  

   by 
  new 
  cell-formation, 
  externally 
  all 
  traces 
  of 
  the 
  wound 
  afterwards 
  dis- 
  

   api)ear. 
  Whoever 
  follows 
  this 
  process 
  in 
  nature 
  will 
  not 
  wonder, 
  when 
  

   he 
  finds 
  the 
  i)seudo-pup2e 
  in 
  the 
  interior 
  of 
  the 
  stalk, 
  close 
  to 
  the 
  upper 
  

  

  