﻿472 
  

  

  exclusively 
  oil 
  rye, 
  and 
  are 
  on 
  the 
  wing 
  during 
  May 
  and 
  the 
  first 
  half 
  

   of 
  June. 
  The 
  eggs 
  are 
  mostly 
  laid 
  on 
  the 
  4tli 
  internode, 
  and 
  usually 
  

   singly. 
  The 
  larvae 
  of 
  /. 
  eremituni, 
  var. 
  nodale, 
  are 
  of 
  a 
  paler 
  colour 
  

   than 
  those 
  of 
  the 
  typical 
  form 
  and 
  resemble 
  those 
  of 
  Philachyra 
  

   apterum. 
  They 
  also 
  pass 
  into 
  the 
  nodes 
  and 
  there 
  form 
  a 
  plug 
  of 
  

   gnawed 
  particles, 
  while 
  the 
  larvae 
  of 
  the 
  typical 
  form 
  remain 
  in 
  the 
  

   internodes. 
  The 
  great 
  majority 
  of 
  larvae 
  observed 
  by 
  the 
  author 
  

   belonged 
  to 
  the 
  var. 
  nodale, 
  but 
  the 
  adults 
  obtained 
  from 
  the 
  two 
  

   varieties 
  were 
  identical. 
  The 
  pupation 
  of 
  both 
  varieties 
  takes 
  place 
  

   in 
  the 
  first 
  half 
  of 
  May 
  in 
  the 
  following 
  year. 
  

  

  Philachyra 
  apterum 
  has 
  two 
  distinct 
  generations 
  during 
  the 
  year 
  ; 
  

   a 
  spring 
  variety, 
  having 
  wings 
  which 
  are 
  scarcely 
  visible 
  to 
  the 
  naked 
  

   eye, 
  and 
  a 
  summer 
  winged 
  variety, 
  about 
  15 
  per 
  cent, 
  of 
  w^hich, 
  how- 
  

   ever, 
  also 
  have 
  more 
  or 
  less 
  shortened 
  wings. 
  This 
  insect 
  bears 
  some 
  

   resemblance 
  to 
  the 
  American 
  species 
  P. 
  grande, 
  Riley. 
  The 
  adults 
  

   of 
  the 
  spring 
  generation 
  appear 
  in 
  the 
  fields 
  after 
  the 
  middle 
  of 
  April 
  ; 
  

   the 
  second 
  generation 
  early 
  in 
  June, 
  the 
  insects 
  remaining 
  on 
  the 
  wing 
  

   till 
  the 
  second 
  half 
  of 
  the 
  month. 
  The 
  females 
  of 
  this 
  generation 
  

   oviposit 
  in 
  the 
  internodes 
  of 
  summer 
  and 
  winter-sown 
  wheat. 
  The 
  

   adult 
  larvae 
  resemble 
  those 
  of 
  I. 
  eremitum 
  var. 
  nodale, 
  and 
  their 
  life- 
  

   history 
  and 
  the 
  damage 
  they 
  do 
  are 
  similar. 
  This 
  insect 
  differs 
  from 
  

   all 
  species 
  of 
  Isosoma 
  in 
  that 
  the 
  larvae 
  of 
  the 
  winged 
  generation 
  do 
  

   not 
  hibernate, 
  but 
  pupate 
  at 
  the 
  end 
  of 
  summer 
  and 
  in 
  autumn. 
  

  

  Two 
  synoptical 
  tables 
  for 
  the 
  identification 
  of 
  the 
  imagines 
  and 
  

   larvae 
  of 
  these 
  species 
  of 
  Isosoma 
  are 
  given. 
  

  

  No 
  parasites 
  of 
  the 
  imagines 
  are 
  known, 
  but 
  the 
  larval 
  stage 
  has 
  many 
  

   enemies, 
  parasitic 
  and 
  fungoid, 
  various 
  fungoid 
  diseases 
  being 
  respon- 
  

   sible 
  for 
  the 
  destruction 
  of 
  about 
  15 
  per 
  cent. 
  Several 
  species 
  of 
  

   Chalcidoidea 
  are 
  ectoparasites 
  of 
  Isosoma, 
  especially 
  Homojjonis 
  

   fidviventris. 
  Walker, 
  fam. 
  Pteromalidae, 
  which 
  is 
  found 
  in 
  North 
  

   and 
  Central 
  Europe, 
  and 
  has 
  two 
  generations 
  a 
  year. 
  The 
  first 
  

   generation 
  is 
  on 
  the 
  wing 
  in 
  the 
  first 
  half 
  of 
  July 
  and 
  oviposits 
  in 
  

   the 
  internodes 
  of 
  wheat, 
  where 
  larvae 
  of 
  Philachyra 
  apterum 
  are 
  

   present. 
  In 
  August, 
  the 
  larvae 
  of 
  the 
  parasite 
  having 
  destroyed 
  

   their 
  host, 
  pupate 
  in 
  the 
  cells 
  prepared 
  by 
  it, 
  the 
  pupal 
  stage 
  lasting 
  

   from 
  10 
  to 
  12 
  days, 
  and 
  the 
  imago 
  gnaws 
  a 
  hole 
  in 
  the 
  stem 
  of 
  the 
  

   wheat 
  in 
  order 
  to 
  escape. 
  The 
  second 
  generation 
  attacks 
  the 
  larvae 
  

   of 
  P. 
  apterum 
  which 
  remain 
  in 
  the 
  fields 
  in 
  the 
  stubble, 
  and 
  winters 
  

   in 
  the 
  larval 
  stage, 
  pupating 
  in 
  May. 
  

  

  Homoporus 
  luniger, 
  Nees, 
  has 
  two 
  or 
  three 
  generations 
  a 
  year. 
  The 
  

   first 
  flies 
  in 
  May 
  and 
  June, 
  ovipositing 
  in 
  galls 
  of 
  I. 
  rossicum, 
  and 
  also, 
  

   but 
  less 
  often, 
  in 
  those 
  of 
  P. 
  apterum. 
  The 
  second 
  generation 
  appears 
  

   in 
  July 
  and 
  the 
  larvae 
  in 
  the 
  first 
  half 
  of 
  August. 
  Some 
  of 
  these 
  

   winter 
  and 
  pupate 
  in 
  the 
  spring, 
  but 
  the 
  majority 
  pupate 
  in 
  the 
  

   second 
  half 
  of 
  August 
  and 
  produce 
  a 
  third 
  generation, 
  the 
  further 
  

   fate 
  of 
  which 
  is 
  unknown. 
  

  

  Eupelmus 
  atropurpureus, 
  Dalm. 
  (Eupelmidae) 
  attacks 
  P. 
  apterum, 
  

   I. 
  rossicum, 
  I. 
  eremitum, 
  I. 
  inquilinum 
  and 
  also 
  Homoporus 
  luniger, 
  

   being 
  a 
  hyperparasite 
  of 
  the 
  latter. 
  Eupielmus 
  degeeri, 
  Dalm., 
  of 
  

   which 
  only 
  females 
  were 
  found, 
  is 
  parasitic 
  on 
  P. 
  apterum 
  and 
  on 
  

   various 
  other 
  insects. 
  Decatoma 
  mellea. 
  Walk. 
  (Eurytomidae), 
  

   attacks 
  /. 
  rossicum. 
  

  

  Homoporus 
  (?) 
  vassilievi, 
  Ashm. 
  Kurdjumov 
  considers 
  that 
  this 
  

  

  