﻿the 
  Hessian 
  Fly. 
  339 
  

  

  coarctate 
  larva. 
  Careful 
  dissections 
  and 
  removal 
  of 
  the 
  

   outer 
  skin 
  reveals 
  the 
  larva 
  in 
  its 
  final 
  larval 
  stage 
  ; 
  the 
  

   smooth 
  shuttle-sha]3e 
  remains, 
  but 
  has 
  no 
  connexion 
  

   with 
  the 
  enclosed 
  larva, 
  which 
  has 
  shrunk 
  away 
  from 
  its 
  

   former 
  covering, 
  jms;( 
  as 
  a 
  ripe 
  nut 
  does 
  from 
  its 
  shell, 
  and 
  

   is 
  now 
  somewhat 
  flattened 
  and 
  much 
  wrinkled 
  in 
  form, 
  

   with 
  blunt 
  ends 
  ; 
  the 
  head, 
  which 
  in 
  the 
  feeding 
  larva 
  

   was 
  decidedly 
  turned 
  so 
  that 
  it 
  was 
  on 
  the 
  side, 
  has 
  now 
  

   recovered 
  its 
  primary 
  position 
  at 
  the 
  end, 
  and 
  imme- 
  

   diately 
  below 
  this, 
  in 
  front, 
  on 
  the 
  second 
  segment, 
  is 
  

   the 
  anchor-process, 
  a 
  photograph 
  of 
  which 
  I 
  will 
  now 
  

   throw 
  upon 
  the 
  screen 
  (Plate 
  XVI., 
  fig. 
  6). 
  From 
  this 
  

   front 
  view 
  you 
  will 
  observe 
  that 
  the 
  fixed 
  part 
  of 
  the 
  

   apparatus 
  lies 
  partially 
  embedded, 
  the 
  tips 
  just 
  projecting 
  

   beyond 
  the 
  top 
  of 
  the 
  segment. 
  

  

  Though 
  my 
  endeavours 
  to 
  catch 
  a 
  larva 
  in 
  the 
  act 
  of 
  

   turning 
  round 
  were 
  not 
  successful, 
  I 
  made 
  some 
  valuable 
  

   observations 
  from 
  the 
  contortions 
  of 
  the 
  disturbed 
  larvge, 
  

   the 
  most 
  important 
  being 
  that, 
  by 
  a 
  powerful 
  contraction 
  

   of 
  the 
  muscles 
  attached 
  to 
  the 
  lower 
  part 
  of 
  the 
  anchor- 
  

   process, 
  the 
  larva 
  was 
  enabled 
  to 
  draw 
  the 
  apparatus 
  in 
  

   at 
  the 
  base 
  until 
  it 
  was 
  at 
  right 
  angles 
  to 
  the 
  normal 
  

   position 
  ; 
  the 
  head, 
  too, 
  was 
  drawn 
  quite 
  in, 
  so 
  that 
  the 
  

   forked 
  end 
  of 
  the 
  anchor-process 
  projected 
  to 
  its 
  fullest 
  

   extent, 
  and 
  whilst 
  in 
  this 
  naked 
  condition 
  it 
  is 
  thrust 
  

   into 
  the 
  inside 
  walls 
  of 
  the 
  coarctate 
  larva 
  ; 
  the 
  muscles 
  

   are 
  relaxed, 
  and 
  the 
  ventral 
  surface 
  brought 
  into 
  contact 
  

   with 
  the 
  inside 
  ventral 
  surface 
  of 
  the 
  coarctate 
  larva. 
  

   Then 
  other 
  muscles 
  appear 
  to 
  move 
  a 
  portion 
  of 
  the 
  

   dorsal 
  surface 
  of 
  the 
  body 
  downwards 
  and 
  round 
  towards 
  

   the 
  bottom 
  or 
  head-end 
  of 
  the 
  coarctate 
  larva 
  ; 
  the 
  tips 
  

   are 
  then 
  withdrawn, 
  the 
  base 
  contracted 
  again, 
  and 
  a 
  

   hold 
  taken 
  by 
  the 
  tips 
  being 
  driven 
  in 
  a 
  little 
  higher 
  up 
  ; 
  

   again 
  the 
  muscles 
  bring 
  a 
  tiny 
  portion 
  of 
  the 
  body 
  

   further 
  round 
  and 
  down, 
  and 
  so 
  this 
  leverage 
  goes 
  on 
  

   until 
  the 
  larva 
  has 
  completed 
  its 
  task, 
  reversed 
  its 
  

   position, 
  and 
  rests 
  with 
  its 
  head 
  up 
  and 
  anchor-process 
  

   outwards; 
  the 
  spines 
  on 
  the 
  skin 
  of 
  the 
  larva, 
  all 
  of 
  

   which 
  point 
  down 
  towards 
  the 
  base, 
  assist 
  it 
  materially 
  

   in 
  obtaining 
  a 
  firm 
  hold 
  on 
  the 
  inside 
  of 
  the 
  coarctate 
  

   larva, 
  preventing 
  it 
  from 
  slipping 
  back. 
  

  

  On 
  July 
  31st, 
  1889, 
  I 
  received 
  from 
  Mr. 
  Stewart 
  

   a 
  number 
  of 
  pieces 
  of 
  the 
  common 
  reed 
  grass 
  

   {Digraphis 
  arundinacea) 
  ; 
  on 
  the 
  outside 
  of 
  the 
  stems 
  

  

  TRANS. 
  ENT. 
  SOC. 
  LOND. 
  1891. 
  PART 
  II. 
  (jUNE.) 
  2 
  A 
  

  

  