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  development. 
  It 
  has 
  not 
  been 
  established 
  whether 
  the 
  larva 
  feeds 
  

   during 
  this 
  earher 
  stage, 
  but 
  the 
  author 
  is 
  inchned 
  to 
  doubt 
  it. 
  The 
  

   central 
  leaf 
  withers 
  three 
  or 
  four 
  days 
  after 
  the 
  larva 
  has 
  entered 
  the 
  

   stalk 
  ; 
  the 
  upper 
  part, 
  which 
  projects 
  from 
  the 
  sheath, 
  finally 
  drops 
  

   off 
  ; 
  the 
  remainder 
  becomes 
  soft 
  and 
  flabby 
  and 
  furnishes 
  the 
  dead 
  

   tissues 
  on 
  which 
  the 
  larva 
  feeds. 
  The 
  larvae 
  are 
  also 
  able 
  to 
  infest 
  

   two 
  stalks 
  ; 
  when 
  one 
  of 
  them 
  is 
  too 
  weak 
  to 
  allow 
  the 
  larva 
  to 
  com- 
  

   plete 
  its 
  development, 
  it 
  passes 
  to 
  another 
  one. 
  In 
  some 
  cases 
  the 
  

   lirva 
  was 
  unable 
  to 
  get 
  into 
  the 
  second 
  stalk, 
  the 
  tissue 
  having 
  become 
  

   tough, 
  but 
  it 
  then 
  proceeded 
  to 
  eat 
  into 
  the 
  tillering 
  knot 
  till 
  the 
  

   stalk 
  withered 
  and 
  fell 
  off. 
  When 
  passing 
  to 
  other 
  stalks 
  the 
  larvae 
  

   feed 
  on 
  the 
  hve 
  tissues 
  of 
  the 
  latter. 
  It 
  is 
  estimated 
  that 
  about 
  40 
  

   per 
  cent, 
  of 
  the 
  larvae 
  damage 
  two 
  stalks 
  in 
  this 
  way 
  ; 
  it 
  has 
  never 
  

   been 
  observed 
  that 
  one 
  larva 
  could 
  damage 
  three 
  stalks 
  of 
  the 
  same 
  

   plant. 
  An 
  experiment 
  undertaken 
  at 
  the 
  Station 
  shows 
  that 
  the 
  

   lar\^ae 
  do 
  not 
  pass 
  from 
  one 
  plant 
  to 
  another. 
  

  

  It 
  is 
  only 
  when 
  the 
  plants 
  have 
  been 
  infested 
  very 
  early 
  in 
  their 
  

   growth 
  and 
  when 
  the 
  larva 
  damages 
  the 
  tillering 
  knot, 
  that 
  the 
  whole 
  

   plant 
  perishes 
  ; 
  normally 
  a 
  plant 
  is 
  able 
  to 
  tiller 
  and 
  to 
  recover. 
  It 
  

   is 
  not 
  considered 
  that 
  the 
  damage 
  done 
  to 
  winter 
  wheat 
  is 
  considerable, 
  

   as 
  usually 
  the 
  larvae 
  injure 
  only 
  the 
  side-shoots, 
  which 
  give 
  no 
  ears 
  

   in 
  that 
  case. 
  With 
  regard 
  to 
  summer 
  wheat, 
  special 
  investigations 
  

   have 
  been 
  conducted 
  at 
  the 
  Station, 
  the 
  results 
  of 
  which 
  are 
  illustrated 
  

   by 
  tables, 
  figures, 
  etc. 
  At 
  the 
  time 
  when 
  the 
  larvae 
  pass 
  into 
  the 
  leaf 
  

   tube 
  the 
  infested 
  plants 
  show 
  a 
  greater 
  tillering, 
  resulting 
  in 
  the 
  

   formation 
  of 
  new 
  stalks, 
  which, 
  however, 
  do 
  not 
  develop 
  properly 
  ; 
  

   the 
  length 
  of 
  the 
  stalks 
  and 
  the 
  weight 
  of 
  the 
  material 
  in 
  them 
  shows 
  

   a 
  decrease 
  as 
  compared 
  with 
  healthy 
  plants. 
  At 
  the 
  moment 
  of 
  

   earing, 
  the 
  diseased 
  plants 
  show 
  a 
  decrease 
  in 
  tillering 
  and 
  a 
  still 
  greater 
  

   decrease 
  in 
  plants 
  giving 
  ears, 
  while 
  the 
  weight 
  of 
  the 
  material 
  of 
  the 
  

   plants 
  is 
  also 
  smaller 
  At 
  the 
  time 
  of 
  ripening, 
  the 
  number 
  of 
  grains 
  in 
  

   the 
  ears 
  of 
  diseased 
  plants 
  is 
  15*5 
  per 
  cent 
  less 
  than 
  that 
  of 
  healthy 
  

   plants, 
  and 
  the 
  absolute 
  weight 
  of 
  the 
  grains 
  is 
  3*4: 
  per 
  cent, 
  lower 
  ; 
  

   the 
  number 
  of 
  ears 
  is 
  also 
  less, 
  most 
  of 
  the 
  diseased 
  plants 
  having 
  

   one, 
  or 
  a 
  maximum 
  of 
  two 
  ears, 
  but 
  never 
  three 
  ; 
  further, 
  the 
  ripening 
  

   of 
  the 
  grains 
  of 
  the 
  diseased 
  plants 
  requires 
  more 
  time. 
  The 
  general 
  

   result 
  of 
  these 
  investigations 
  is 
  to 
  show 
  that 
  Adia 
  genitalis 
  decreases 
  

   the 
  harvest 
  of 
  the 
  diseased 
  plants 
  by 
  40 
  per 
  cent. 
  This 
  fly 
  injures 
  

   summer 
  and 
  winter 
  wheat, 
  and 
  sometimes 
  rye, 
  but 
  does 
  not 
  injure 
  oats 
  

   or 
  barley. 
  An 
  experiment 
  conducted 
  at 
  the 
  Station 
  shows 
  that 
  the 
  

   insects 
  do 
  not 
  oviposit 
  on 
  either 
  of 
  the 
  last-named 
  plants. 
  Rye 
  

   ripens 
  quicker 
  than 
  winter 
  wheat, 
  and 
  at 
  the 
  moment 
  when 
  the 
  flies 
  

   appear 
  it 
  has 
  already 
  grown 
  sufficiently 
  to 
  resist 
  attack. 
  The 
  author 
  

   gives 
  several 
  tables 
  showing 
  the 
  infestation 
  of 
  winter 
  and 
  summer 
  

   wheat 
  during 
  the 
  last 
  two 
  years 
  ; 
  late 
  winter 
  wheat 
  (sown 
  in 
  Sept- 
  

   ember) 
  is 
  more 
  injured 
  than 
  that 
  sown 
  early, 
  the 
  former 
  beginning 
  to 
  

   tiUer 
  only 
  in 
  spring, 
  while 
  the 
  latter 
  has 
  completed 
  the 
  tillering 
  in 
  the 
  

   previous 
  autumn. 
  Early 
  summer 
  wheat 
  was 
  the 
  most 
  seriously 
  

   injured 
  grain. 
  The 
  author 
  calculates 
  that 
  the 
  damage 
  done 
  yearly 
  by 
  

   the 
  insect 
  in 
  the 
  government 
  of 
  Poltava 
  may 
  be 
  put 
  at 
  over 
  £200,000. 
  

   It 
  is 
  spread 
  over 
  many 
  parts 
  of 
  the 
  government 
  and 
  must 
  be 
  considered 
  

   a 
  very 
  serious 
  pest. 
  No 
  parasites 
  of 
  A. 
  genitalis 
  have 
  yet 
  been 
  dis- 
  

   covered. 
  Control 
  measures 
  must 
  be 
  directed 
  against 
  the 
  puparia, 
  

  

  