﻿710 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  i 
  

  

  Sometimes 
  the 
  larva 
  descends 
  to 
  the 
  ground 
  and 
  molts 
  there. 
  Harris 
  j 
  

   states 
  that 
  ' 
  it 
  is 
  shorter, 
  somewhat 
  flattened, 
  and 
  more 
  obtuse 
  than 
  

  

  before, 
  and 
  is 
  of 
  a 
  deeper 
  yellow 
  color, 
  with, 
  an 
  oblong 
  greenish 
  spot 
  in 
  I 
  

   the 
  middle 
  of 
  the 
  body, 
  in 
  tbis 
  state, 
  which 
  is 
  intermediate 
  between 
  

  

  the 
  larva 
  and 
  pupa 
  states, 
  which 
  has, 
  by 
  l)r. 
  Fitch, 
  been 
  termed 
  the 
  1 
  

  

  "embryo-pupa" 
  and 
  by 
  us 
  "semi-pupa," 
  the 
  insect 
  spins 
  a 
  minute 
  i 
  

  

  silken 
  cocoon, 
  which, 
  according 
  to 
  Dr. 
  Fitch, 
  is 
  smaller 
  than 
  a 
  mustard 
  i 
  

  

  seed, 
  and 
  remains 
  in 
  the 
  ground 
  through 
  the 
  winter, 
  situated 
  at 
  the 
  I 
  

  

  depth 
  of 
  an 
  inch 
  beneath 
  the 
  surface. 
  In 
  the 
  next 
  June 
  they 
  are 
  trans- 
  s 
  

  

  formed 
  to 
  pupoe, 
  with 
  the 
  limbs 
  free. 
  When 
  about 
  to 
  assume 
  the 
  adult 
  i 
  

  

  state, 
  the 
  pupa 
  works 
  its 
  way 
  to 
  the 
  surface 
  in 
  June 
  and 
  July.' 
  " 
  ' 
  

  

  Descrqytion. 
  — 
  The 
  eggs 
  of 
  the 
  wheat-midge 
  are 
  long, 
  oval-cylindrical, 
  and 
  tinged 
  

   with 
  pale 
  red. 
  When 
  the 
  larva 
  is 
  at 
  rest 
  it 
  is 
  oval, 
  flattened 
  on 
  the 
  under 
  side, 
  deep 
  

   yellow, 
  and 
  0.08 
  inch 
  long. 
  The 
  female 
  fly 
  is 
  nearly 
  one-tenth 
  of 
  an 
  inch 
  long, 
  bright 
  

   orange 
  or 
  lemon-yellow, 
  and 
  tarnished 
  or 
  slightly 
  smoky 
  on 
  the 
  back 
  forward 
  of 
  the 
  

   wings, 
  the 
  latter 
  clear, 
  with 
  a 
  small 
  cross-vein 
  near 
  their 
  base 
  ; 
  the 
  antennae 
  are 
  about 
  

   as 
  long 
  as 
  the 
  body, 
  and 
  composed 
  of 
  twelve 
  oblong 
  joints, 
  which 
  are 
  narrower 
  in 
  

   their 
  middles 
  and 
  separated 
  by 
  short 
  pedicels. 
  In 
  the 
  males 
  the 
  antennte 
  are 
  remark- 
  

   ably 
  long, 
  slender, 
  and 
  delicate, 
  and 
  consist 
  of 
  twenty-four 
  globular 
  joints; 
  it 
  is 
  ( 
  

   smaller, 
  but 
  in 
  other 
  respects 
  agrees'with 
  the 
  female. 
  — 
  (Fitch.) 
  j 
  

  

  Farasites. 
  — 
  Dr. 
  Fitch 
  has 
  shown 
  that 
  when 
  the 
  midges 
  increase 
  or 
  di- 
  ' 
  

   minish 
  in 
  numbers 
  its 
  parasites 
  increase 
  or 
  diminish 
  in 
  the 
  same 
  ratio, 
  

   "the 
  same 
  as 
  the 
  Hessian 
  fly, 
  once 
  so 
  frightfully 
  destructive 
  to 
  our 
  wheat- 
  

   crops 
  here 
  in 
  America, 
  has 
  become 
  subdued 
  by 
  its 
  parasites, 
  whereby 
  it 
  is 
  

   seldom 
  noticed 
  now 
  or 
  known 
  to 
  be 
  present 
  in 
  our 
  country, 
  although 
  it 
  

   can 
  be 
  found 
  almost 
  every 
  year 
  in 
  our 
  wheat-fields, 
  showing 
  it 
  is 
  still 
  

   with 
  us, 
  everywhere 
  ready 
  to 
  again 
  increase 
  and 
  become 
  destructive 
  [ 
  

   were 
  it 
  not 
  constantly 
  repressed 
  and 
  kept 
  down 
  by 
  its 
  parasitic 
  foes." 
  

   Mr. 
  Curtis 
  is 
  quoted 
  as 
  saying 
  that 
  in 
  Europe 
  " 
  these 
  parasites 
  so 
  effect- 
  

   ually 
  execute 
  their 
  mission, 
  that 
  it 
  has 
  often 
  happened 
  a 
  year 
  or 
  two 
  

   after 
  the 
  midges 
  were 
  in 
  excess 
  not 
  a 
  specimen 
  could 
  be 
  found." 
  Its 
  il 
  

   destructiveness 
  in 
  this 
  country 
  is 
  due 
  to 
  the 
  fact 
  that 
  we 
  have 
  no 
  native 
  1 
  

   parasites 
  to 
  keep 
  it 
  within 
  xjroper 
  limits, 
  and 
  Dr. 
  Fitch 
  urges 
  that 
  the 
  i 
  

   parasites 
  be 
  imported 
  from 
  Europe. 
  

  

  Gkain-Aphis, 
  Jj)Ms 
  avence 
  Fabricius. 
  — 
  Multitudes 
  of 
  dark 
  plant-lice, 
  clustering 
  on 
  

   the 
  heads 
  of 
  wheat 
  in 
  August, 
  blackening 
  the 
  fields 
  of 
  grain, 
  and, 
  by 
  sucking 
  the 
  ker- 
  

   nels, 
  causing 
  them 
  to 
  shrink 
  in 
  size 
  and 
  diminish 
  in 
  weight. 
  

  

  We 
  will 
  suppose 
  a 
  number 
  of 
  eggs 
  to 
  hatch 
  out 
  their 
  wingless 
  females 
  ; 
  

   with 
  an 
  occasional 
  winged 
  individual 
  there 
  are 
  as 
  yet 
  no 
  males 
  in 
  exist- 
  

   ence, 
  and 
  yet 
  these 
  virgin 
  aphides, 
  or 
  plant-lice, 
  every 
  few 
  days 
  produce 
  

   hundreds 
  of 
  young 
  alive; 
  each 
  of 
  which 
  in 
  turn 
  come 
  to 
  maturity 
  and 
  

   produce 
  their 
  young 
  alive. 
  Hence, 
  by 
  the 
  end 
  of 
  summer 
  we 
  have 
  mill- 
  

   ions 
  of 
  lice 
  overrunning 
  our 
  wheat- 
  fields, 
  the 
  very 
  youngest 
  as 
  well 
  as 
  > 
  

   the 
  oldest 
  as 
  if 
  for 
  their 
  lives 
  sucking 
  in 
  the 
  sap 
  from 
  the 
  ear 
  of 
  the 
  I 
  

   grain. 
  For 
  by 
  a 
  marvelous 
  adaptation 
  to 
  their 
  mode 
  of 
  life, 
  what 
  in 
  

   beetles 
  are 
  jaws 
  for 
  biting 
  are 
  here 
  lengthened 
  out 
  and 
  joined 
  together 
  

   to 
  form 
  a 
  tube, 
  with 
  a 
  sucking- 
  stomach 
  at 
  the 
  base. 
  This 
  tube 
  the 
  louse 
  

   forces 
  into 
  the 
  root 
  of 
  the 
  ear, 
  and 
  thus 
  anchored 
  by 
  their 
  jaws, 
  whole 
  

   groups 
  cluster 
  head 
  downward 
  on 
  the 
  heads 
  of 
  grain, 
  and 
  by 
  their 
  

   numbers 
  color 
  a 
  whole 
  field. 
  But 
  the 
  supply 
  of 
  liquid 
  food 
  is 
  greater 
  

   than 
  the 
  aphides 
  can 
  manage, 
  hence 
  two 
  tubes 
  open 
  out 
  from 
  the 
  hind 
  

   part 
  of 
  the 
  abdomen, 
  from 
  which 
  exudes 
  a 
  sweet 
  sticky 
  fluid 
  called 
  

   "honey-dew." 
  Ants 
  come 
  to 
  eat 
  it 
  as 
  it 
  falls 
  on 
  the 
  leaves, 
  or 
  lap 
  it 
  

   from 
  the 
  honey-tubes 
  of 
  the 
  aphis, 
  and 
  as 
  the 
  supply 
  lessens, 
  they 
  gently 
  

   strike 
  the 
  aphis 
  with 
  their 
  anteunoe 
  to 
  make 
  them 
  yield 
  more. 
  

  

  At 
  the 
  approach 
  of 
  cold 
  weather, 
  when 
  the 
  whole 
  race 
  of 
  aphides 
  

  

  