﻿118 
  

  

  spines 
  are 
  sometimes 
  found 
  behveen 
  the 
  girdles 
  of 
  spines 
  

   (Figs. 
  46,63). 
  In 
  the 
  first 
  stage 
  of 
  Steiniella 
  callida 
  (Figs. 
  

   54,64) 
  and 
  in 
  the 
  third 
  stage 
  of 
  Ocyptera 
  brassicaria 
  (Fig. 
  

   60) 
  there 
  are 
  chitinous 
  piates 
  in 
  the 
  integument. 
  

  

  With 
  regard 
  to 
  the 
  detailed 
  descriptions 
  of 
  the 
  larvæ 
  

   I 
  may 
  refer 
  to 
  the 
  Danish 
  and 
  to 
  the 
  explanations 
  of 
  the 
  

   figures. 
  

  

  2. 
  Biology. 
  

  

  The 
  relation 
  between 
  the 
  hosts 
  and 
  the 
  parasites 
  is 
  

   nearly 
  the 
  same 
  in 
  all 
  the 
  examined 
  species 
  parasitic 
  on 
  

   insect-larvæ. 
  As 
  type 
  I 
  have 
  dealt 
  in 
  detail 
  with 
  Ptycho- 
  

   myia 
  selecta 
  Meig., 
  a 
  species 
  which 
  is 
  parasitic 
  on 
  the 
  full- 
  

   grown 
  larva 
  of 
  Hyponomeuta 
  euonymella 
  Scop. 
  The 
  fly 
  

   deposits 
  its 
  eggs 
  in 
  June 
  and 
  July 
  irregularly 
  on 
  the 
  body 
  

   of 
  the 
  host 
  in 
  a 
  number 
  of 
  from 
  1 
  to 
  23. 
  ^) 
  The 
  parasites 
  

   penetrate 
  from 
  the 
  eggs 
  directly 
  through 
  the 
  integument 
  of 
  the 
  

   host 
  larva 
  (Fig. 
  47). 
  This 
  gives 
  rise 
  to 
  an 
  invagination 
  of 
  

   the 
  cuticula 
  of 
  the 
  host 
  round 
  the 
  margin 
  of 
  the 
  hole 
  of 
  

   entrance 
  (Fig. 
  1,2); 
  the 
  invagination 
  forms 
  a 
  funnel 
  (Fig. 
  

   47) 
  that 
  encloses 
  the 
  posterior 
  end 
  of 
  the 
  larva 
  which 
  

   respires 
  through 
  it. 
  On 
  the 
  outside 
  of 
  the 
  chitinous 
  funnel 
  

   is 
  found 
  a 
  coating 
  of 
  hypoderra-cells 
  (Fig. 
  2 
  ep.). 
  The 
  chi- 
  

   tinous 
  funnel 
  is 
  continued 
  by 
  a 
  sac-like 
  layer, 
  quite 
  enclo- 
  

   sing 
  the 
  parasite 
  (Fig. 
  1 
  s). 
  This 
  sac 
  consists 
  of 
  fat-cells, 
  

  

  ^) 
  It 
  is 
  very 
  conimon 
  to 
  find 
  on 
  the 
  hosts 
  of 
  the 
  parasitic 
  flies 
  a 
  

   considerably 
  greater 
  number 
  of 
  eggs 
  or 
  more 
  or 
  less 
  young 
  larvæ 
  

   than 
  the 
  host 
  can 
  support. 
  The 
  parasites 
  thus 
  penetrate 
  into 
  

   the 
  host, 
  but 
  a 
  greater 
  or 
  smaller 
  number 
  die 
  at 
  an 
  earlier 
  or 
  

   later 
  stage 
  of 
  development. 
  The 
  death 
  is 
  sometimes 
  caused 
  by 
  

   pressure 
  from 
  the 
  other 
  larvæ, 
  but 
  cases 
  are 
  commonly 
  found 
  in 
  

   which 
  the 
  death 
  has 
  not 
  arisen 
  from 
  mechanical 
  power 
  from 
  the 
  

   side 
  of 
  the 
  other 
  larvæ. 
  Similar 
  cases 
  occur 
  also 
  in 
  other 
  para- 
  

   sitic 
  insects 
  (cf. 
  p. 
  95 
  — 
  100 
  and 
  the 
  literature 
  here 
  cited.) 
  

  

  