﻿WAGNER 
  ON 
  THE 
  HESSIAN 
  FLY. 
  [19] 
  

  

  3. 
  The 
  pupa 
  or 
  chrysalis.* 
  (Fig. 
  14.) 
  

  

  During 
  the 
  winter 
  we 
  perceive 
  no 
  conspicuous 
  changes 
  in 
  the 
  envel- 
  

   oped 
  maggot 
  as 
  taught 
  by 
  an 
  examination 
  after 
  removing 
  the 
  shell. 
  

   The 
  severe 
  cold 
  has 
  reduced 
  its 
  life-functions 
  to 
  a 
  minimum, 
  recalling 
  

   its 
  life 
  as 
  an 
  egg, 
  until 
  the 
  vivifying 
  vernal 
  sun 
  penetrates 
  even 
  its 
  cofiiu- 
  

   like 
  prison, 
  awakening 
  it 
  from 
  the 
  long 
  apparent 
  death 
  to 
  iicav 
  activity. 
  

   The 
  insect 
  at 
  the 
  time 
  is 
  still 
  in 
  its 
  larval 
  state, 
  wliich, 
  however, 
  it 
  soon 
  

   discards, 
  entering 
  the 
  pupa 
  state, 
  by 
  which 
  change 
  the 
  larvarium 
  lie- 
  

   comes 
  immediately 
  a 
  puparium. 
  The 
  changes 
  which 
  the 
  insect 
  under- 
  

   goes 
  during 
  pupation 
  advance 
  rapidly 
  and 
  are 
  accompanied 
  by 
  impor- 
  

   tant 
  modifications. 
  The 
  prothoracic 
  stigmata 
  are 
  substituted 
  within 
  a 
  

   few 
  days 
  by 
  two 
  stigraaphora, 
  and 
  in 
  the 
  antennal 
  region 
  we 
  i)erceive 
  two 
  

   bristled 
  organs. 
  Simultaneously 
  the 
  rudiments 
  of 
  the 
  antennae, 
  wings 
  

   and 
  legs 
  j)wsh 
  forth. 
  The 
  color 
  of 
  the 
  insect 
  in 
  this 
  ])hase 
  is 
  still 
  a 
  

   white 
  one, 
  but 
  already, 
  after 
  a 
  few 
  days, 
  the 
  ventral 
  surface 
  assumes 
  a 
  

   reddish 
  hue, 
  which 
  intensifies 
  with 
  every 
  successive 
  day, 
  gradually 
  ad- 
  

   vancing 
  toward 
  the 
  dorsal 
  side. 
  The 
  red 
  veins 
  of 
  the 
  future 
  wings 
  are 
  

   especially 
  conspicuous. 
  All 
  body-parts 
  exhibit, 
  in 
  the 
  course 
  of 
  about 
  

   a 
  week, 
  a 
  blood-red 
  color. 
  Finally 
  the 
  white 
  pupa-shell 
  is 
  secreted, 
  

   through 
  which 
  now 
  the 
  more 
  { 
  2 
  ) 
  or 
  less 
  ( 
  $ 
  ) 
  red 
  body 
  can 
  be 
  traced. 
  

   The 
  middle 
  of 
  April 
  is 
  the 
  time 
  when 
  pui)ation 
  begins, 
  but 
  this 
  ti'ansition 
  

   from 
  the 
  larva 
  to 
  the 
  pupa 
  is 
  not 
  the 
  same 
  for 
  all 
  maggots, 
  but 
  com- 
  

   prises 
  a 
  term 
  of 
  several 
  weeks, 
  a 
  fact 
  which 
  should 
  not 
  sui^irise 
  us 
  if 
  

   we 
  consider 
  that 
  the 
  time 
  of 
  sw^arming 
  and 
  consequently 
  also 
  the 
  time 
  

   of 
  hatching 
  of 
  the 
  young 
  maggots 
  in 
  autumn 
  laste<l 
  over 
  a 
  month, 
  and 
  

   that 
  the 
  maggots 
  occur 
  in 
  the 
  early 
  part 
  of 
  winter 
  simultaneously 
  in 
  

   various 
  stages 
  of 
  development. 
  

  

  The 
  pupa-shell 
  is 
  the 
  substantially 
  modified 
  former 
  larval 
  skin 
  ; 
  we 
  

   therefore 
  shall 
  recognize 
  in 
  it 
  the 
  form 
  which 
  the 
  maggot 
  possessed 
  ; 
  

   some 
  time 
  after 
  attaining 
  the 
  maximum 
  of 
  growth 
  it 
  separated 
  itself 
  from 
  

   the 
  inclosing 
  membrane. 
  Its 
  length 
  is 
  sometijnes 
  scarcely 
  3"'^, 
  but 
  

   in 
  most 
  cases 
  from 
  4^"^" 
  to 
  5°^™. 
  Its 
  form 
  ai)proaches 
  that 
  of 
  a 
  cylin- 
  

   der 
  with 
  the 
  ventral 
  side 
  more 
  convex, 
  the 
  posterior 
  end 
  blunt, 
  conical, 
  

   and 
  the 
  rounded 
  anterior 
  end 
  somewhat 
  bent 
  downward. 
  This 
  bending 
  

   took 
  place 
  si 
  mult^meously 
  with 
  the 
  retraction 
  of 
  the 
  head. 
  The 
  ujiper 
  

   surface 
  is 
  smooth 
  ; 
  ver^' 
  small 
  irregularities, 
  seen 
  under 
  the 
  microscope, 
  

   obviously 
  originated 
  in 
  consequence 
  of 
  shrinking. 
  The 
  punctured 
  trans- 
  

   verse 
  lines 
  limiting 
  each 
  body-segment 
  are, 
  on 
  account 
  of 
  the 
  dark 
  chest- 
  

   nut 
  color, 
  seen 
  under 
  the 
  mi<*roscope 
  only. 
  The 
  punctures 
  of 
  the 
  trans- 
  

   verse 
  lines 
  produce 
  refle<^;tions 
  in 
  white 
  and 
  light 
  brown 
  larval 
  shells 
  

   after 
  the 
  removal 
  of 
  the 
  worm; 
  the 
  reflections 
  recall 
  the 
  passing 
  of 
  light 
  

   through 
  very 
  minute 
  oriiic<^s 
  ; 
  I 
  regard 
  them, 
  therefore, 
  as 
  real 
  pores. 
  

   The 
  color 
  of 
  the 
  protuberance, 
  being 
  the 
  remainder 
  of 
  the 
  sucking 
  

   mouth 
  of 
  the 
  free 
  larva, 
  may 
  be 
  brown, 
  yellow, 
  or 
  white. 
  The 
  shell 
  has 
  

   lost 
  its 
  original 
  membranous 
  structure, 
  becoming 
  so 
  brittle 
  as 
  to 
  break 
  

   under 
  light 
  pressure, 
  

  

  Now 
  in 
  this 
  shell 
  is 
  the 
  pupa 
  proper, 
  which 
  itself 
  is 
  again 
  enveloped 
  

   by 
  a 
  white, 
  membranous 
  skin. 
  Its 
  average 
  length 
  is 
  3™™. 
  As 
  in 
  

   the 
  Coleoptera 
  and 
  Hymenoptera 
  its 
  antennae, 
  wings, 
  and 
  legs 
  are 
  

   also 
  enveloped 
  in 
  separate 
  sheaths, 
  and 
  so 
  ingeniously 
  placed 
  that 
  a 
  

   glance 
  at 
  such 
  a 
  mummy 
  excites 
  in 
  a 
  mind 
  susce])tible 
  to 
  the 
  beautiful 
  

   not 
  mortal 
  fright, 
  but 
  admiration 
  and 
  pleasure. 
  The 
  wings, 
  folded 
  back- 
  

  

  *This 
  would 
  "be 
  the 
  proper 
  place 
  to 
  point 
  out 
  the 
  manner 
  of 
  pupation 
  occurinpin 
  diptera 
  in 
  pen- 
  

   ernl, 
  and 
  especially 
  in 
  gall-piuats. 
  Loew's 
  paper 
  mentioned 
  above 
  demonstrates 
  this 
  very 
  intelligently 
  ; 
  

   therefore 
  1 
  highly 
  recommend 
  his 
  paper 
  to 
  those 
  finding 
  special 
  interest 
  in 
  the 
  present 
  ioiatter. 
  

  

  