﻿471 
  

  

  of 
  galls, 
  which 
  appear 
  later 
  on 
  the 
  spot 
  attacked, 
  though 
  whether 
  

   these 
  are 
  laid 
  by 
  one 
  or 
  more 
  females 
  is 
  unknown. 
  The 
  egg, 
  which 
  is 
  

   described 
  and 
  figured, 
  produces 
  a 
  larva 
  in 
  10 
  to 
  14 
  days 
  ; 
  the 
  young 
  

   larvae 
  are 
  found 
  as 
  early 
  as 
  the 
  middle 
  of 
  June, 
  and 
  adult 
  larvae 
  in 
  

   the 
  first 
  half 
  of 
  July. 
  Only 
  two 
  moults 
  were 
  observed, 
  but 
  it 
  is 
  thought 
  

   that 
  there 
  are 
  more. 
  Like 
  the 
  larvae 
  of 
  I. 
  inquilinum, 
  those 
  of 
  /. 
  rossi- 
  

   cum 
  change 
  their 
  appearance 
  during 
  growth, 
  the 
  later 
  stages 
  losing 
  

   the 
  cone-like 
  appendix 
  which 
  covers 
  the 
  head 
  of 
  the 
  newly-hatched 
  

   larva. 
  The 
  larvae 
  remain 
  in 
  this 
  stage 
  for 
  about 
  two 
  or 
  three 
  days 
  

   without 
  feeding, 
  and 
  after 
  moulting, 
  the 
  appendix 
  on 
  the 
  head 
  is 
  

   replaced 
  by 
  a 
  small 
  blunt 
  projection. 
  The 
  larva 
  moults 
  again 
  in 
  

   five 
  or 
  six 
  days 
  and 
  attains 
  its 
  final 
  form. 
  The 
  galls 
  caused 
  by 
  

   oviposition, 
  which 
  are 
  of 
  a 
  green 
  or 
  yellow 
  colour, 
  are 
  usually 
  situated 
  

   behind 
  the 
  leaf-sheath, 
  so 
  that 
  it 
  is 
  necessary 
  to 
  turn 
  back 
  the 
  latter 
  

   to 
  discover 
  them, 
  though 
  where 
  there 
  is 
  a 
  large 
  number 
  of 
  galls 
  the 
  

   nodes 
  are 
  visibly 
  swollen. 
  The 
  author 
  has 
  found 
  such 
  galls 
  mostly 
  

   on 
  rye 
  and 
  very 
  seldom 
  on 
  wheat 
  ; 
  on 
  the 
  latter 
  plant 
  the 
  single 
  galls 
  

   usually 
  overlap 
  each 
  other, 
  forming 
  a 
  common 
  gall 
  in 
  which 
  the 
  several 
  

   larvae 
  are 
  situated 
  in 
  separate 
  chambers, 
  the 
  leaf-sheath 
  being 
  

   involved 
  in 
  the 
  galls. 
  In 
  the 
  first 
  half 
  of 
  July, 
  when 
  the 
  larvae 
  are 
  

   adult, 
  they 
  cease 
  feeding 
  and 
  remain 
  dormant 
  until 
  they 
  pupate 
  in 
  

   the 
  middle 
  of 
  the 
  following 
  May, 
  the 
  pupal 
  stage 
  lasting 
  from 
  two 
  to 
  

   three 
  weeks. 
  The 
  life-history 
  and 
  the 
  character 
  of 
  the 
  galls 
  of 
  /. 
  

   rossicum 
  are 
  similar 
  to 
  those 
  of 
  I. 
  hordei, 
  Harris, 
  and 
  /. 
  tritici, 
  Fitch, 
  

   which 
  attack 
  barley 
  and 
  wheat. 
  

  

  Isosowa 
  noxiale, 
  Portch., 
  described 
  and 
  figured 
  by 
  the 
  author, 
  appears 
  

   in 
  its 
  adult 
  stage 
  in 
  the 
  middle 
  of 
  May. 
  The 
  eggs 
  are 
  deposited 
  on 
  

   summer-sown, 
  as 
  well 
  as 
  on 
  winter-sown 
  wheat 
  and 
  are 
  laid 
  in 
  the 
  

   third 
  and 
  fourth 
  internodes, 
  one 
  egg 
  being 
  deposited 
  in 
  each. 
  The 
  larvae 
  

   live 
  inside 
  the 
  stalks 
  of 
  the 
  wheat, 
  feeding 
  on 
  their 
  walls, 
  principally 
  

   in 
  the 
  lower 
  third 
  of 
  the 
  internode. 
  The 
  young 
  larvae 
  appear 
  from 
  

   the 
  middle 
  of 
  June 
  onwards, 
  and 
  having 
  become 
  adult, 
  pass 
  into 
  the 
  

   node 
  and 
  build 
  there 
  a 
  cylindrical 
  cell 
  in 
  which 
  they 
  remain, 
  head 
  down- 
  

   wards, 
  for 
  about 
  9 
  or 
  10 
  months, 
  pupation 
  taking 
  place 
  in 
  May 
  and 
  

   lasting 
  about 
  a 
  fortnight. 
  

  

  Isosoma 
  inquilinmn, 
  sp. 
  n., 
  in 
  its 
  adult 
  stage 
  is 
  very 
  similar 
  to 
  

   7. 
  noxiale 
  ; 
  it 
  appears 
  in 
  the 
  fields 
  simultaneously 
  w^ith 
  I. 
  rossicum, 
  and 
  

   oviposits 
  on 
  the 
  same 
  plants, 
  so 
  that 
  usually, 
  on 
  opening 
  the 
  galls 
  

   of 
  the 
  latter, 
  larvae 
  of 
  /. 
  rossicum, 
  in 
  their 
  first 
  stage, 
  and 
  from 
  one 
  

   to 
  four 
  eggs 
  of 
  I. 
  inquilinum, 
  are 
  found 
  together. 
  The 
  eggs 
  of 
  I. 
  inquil- 
  

   inum 
  are 
  of 
  a 
  clear 
  grey 
  colour, 
  while 
  those 
  of 
  all 
  other 
  Isosoma 
  are 
  

   white. 
  Like 
  those 
  of 
  7. 
  rossicum, 
  the 
  larvae 
  of 
  7. 
  inquilinum 
  als 
  

   present 
  marked 
  differences 
  of 
  form 
  in 
  their 
  three 
  stages. 
  The 
  larvae 
  

   of 
  the 
  first 
  stage 
  attack 
  and 
  kill 
  those 
  of 
  7. 
  rossicum 
  in 
  their 
  first 
  or 
  

   second 
  stage. 
  If 
  several 
  eggs 
  of 
  7. 
  inquilinum 
  are 
  laid 
  in 
  one 
  gall 
  

   of 
  7. 
  rossicum 
  only 
  one 
  larva 
  survives 
  ; 
  after 
  the 
  first 
  moult 
  the 
  larvae 
  

   become 
  ph}i:ophagous. 
  The 
  author 
  refers 
  to 
  a 
  similar 
  case 
  described 
  

   by 
  Nielsen, 
  in 
  which 
  the 
  larva 
  of 
  a 
  species 
  of 
  Euryfoma 
  feeds 
  first 
  on 
  

   the 
  larvae 
  of 
  Cryptocampus 
  angustus, 
  and 
  afterwards 
  becomes 
  phyto- 
  

   phagous. 
  

  

  Isosoma 
  eremitum, 
  Portch. 
  ; 
  the 
  author 
  describes 
  this 
  species 
  and 
  

   points 
  out 
  that 
  it 
  is 
  impossible 
  to 
  accept 
  the 
  statement 
  of 
  Ashmead 
  

   that 
  it 
  belongs 
  to 
  the 
  genus 
  Philachyra, 
  Hal. 
  These 
  insects 
  appear 
  

  

  