﻿TENT 
  CATERPILLAR 
  — 
  SNODGRASS. 
  355 
  

  

  In 
  the 
  case 
  of 
  the 
  mandibles 
  the 
  condition 
  is 
  reversed 
  — 
  the 
  new 
  

   organs 
  shrink 
  to 
  such 
  an 
  extent 
  that 
  they 
  leave 
  the 
  old 
  ones 
  almost 
  

   empty. 
  From 
  this 
  we 
  see, 
  however, 
  that 
  the 
  parts 
  of 
  the 
  head 
  of 
  the 
  

   propupa 
  are 
  derived 
  from 
  those 
  of 
  the 
  caterpillar, 
  just 
  as 
  are 
  the 
  

   parts 
  in 
  any 
  one 
  stage 
  of 
  the 
  caterpillar, 
  except 
  the 
  first, 
  derived 
  

   from 
  those 
  of 
  the 
  preceding 
  stage, 
  and 
  are 
  disclosed 
  when 
  the 
  skin 
  

   is 
  shed. 
  The 
  change 
  of 
  form 
  in 
  the 
  propupa 
  is 
  but 
  a 
  detail, 
  for 
  in 
  

   some 
  species 
  changes 
  take 
  place 
  during 
  the 
  molt 
  between 
  stages 
  of 
  

   the 
  caterpillar. 
  

  

  The 
  legs 
  of 
  the 
  propupa 
  are 
  so 
  much 
  longer 
  than 
  those 
  of 
  the 
  

   caterpillar 
  that 
  only 
  the 
  terminal 
  part 
  of 
  each, 
  the 
  tarsus 
  (fig. 
  17, 
  

   G, 
  Tar), 
  can 
  develop 
  inside 
  the 
  corresponding 
  caterpillar 
  leg 
  (F) 
  ; 
  

   the 
  rest 
  of 
  the 
  leg 
  folds 
  upward 
  within 
  the 
  skin 
  against 
  the 
  side 
  of 
  

   the 
  body, 
  just 
  as 
  the 
  antennae 
  fold 
  back 
  against 
  the 
  sides 
  of 
  the 
  head 
  

   to 
  find 
  space 
  for 
  their 
  increasing 
  bulk. 
  This 
  does 
  not 
  mean, 
  there- 
  

   fore, 
  that 
  the 
  caterpillar 
  leg 
  represents 
  only 
  the 
  tarsal 
  part 
  of 
  the 
  

   adult 
  leg, 
  though 
  it 
  has 
  often 
  been 
  so 
  interpreted. 
  

  

  The 
  case 
  of 
  the 
  wings 
  appears 
  to 
  be 
  different, 
  for 
  the 
  caterpillar 
  

   has 
  no 
  external 
  wings 
  at 
  all, 
  not 
  even 
  rudiments 
  in 
  which 
  the 
  pro- 
  

   pupal 
  wings 
  could 
  start 
  their 
  growth. 
  Consequently 
  the 
  wing 
  buds 
  

   are 
  forced 
  to 
  grow 
  internally. 
  They 
  can 
  be 
  found 
  inside 
  the 
  skin 
  

   of 
  the 
  caterpillar 
  as 
  little 
  sacs 
  turned 
  outside 
  in. 
  When 
  the 
  cater- 
  

   pillar 
  skin 
  is 
  loosened 
  over 
  that 
  of 
  the 
  propupa 
  the 
  wing 
  sacs 
  are 
  

   everted 
  and 
  quickly 
  take 
  their 
  normal 
  place 
  on 
  the 
  outside 
  of 
  the 
  

   body 
  as 
  small 
  external 
  lobes 
  (fig. 
  17, 
  C, 
  W 
  2 
  , 
  W 
  s 
  ). 
  

  

  The 
  propupa 
  remains 
  within 
  the 
  caterpillar 
  skin 
  for 
  three 
  or 
  four 
  

   days 
  and 
  then 
  the 
  latter 
  splits 
  open 
  along 
  the 
  back 
  of 
  the 
  first 
  two 
  

   body 
  segments, 
  over 
  the 
  top 
  of 
  the 
  head 
  and 
  down 
  the 
  right 
  side 
  

   of 
  the 
  frontal 
  triangle 
  to 
  the 
  base 
  of 
  the 
  right 
  jaw. 
  The 
  creature 
  

   within 
  now 
  quickly 
  wriggles 
  out 
  of 
  the 
  skin 
  and 
  pushes 
  it 
  over 
  the 
  

   rear 
  end 
  of 
  its 
  body 
  and 
  into 
  the 
  end 
  of 
  the 
  cocoon, 
  where 
  it 
  remains 
  

   as 
  a 
  hairy 
  wad, 
  the 
  last 
  evidence 
  of 
  the 
  caterpillar. 
  

  

  The 
  propupa 
  (fig. 
  17, 
  C) 
  very 
  clearly 
  started 
  out 
  to 
  be 
  a 
  moth 
  

   (E), 
  but 
  the 
  thing 
  that 
  appears 
  (D) 
  when 
  the 
  caterpillar 
  skin 
  is 
  

   shed 
  does 
  not 
  at 
  all 
  resemble 
  a 
  moth. 
  The 
  propupa, 
  in 
  fact, 
  has 
  

   changed 
  to 
  a 
  pupa, 
  and 
  this 
  (D) 
  is 
  a 
  cylindrical 
  hard-shelled 
  crea- 
  

   ture, 
  rounded 
  at 
  the 
  head 
  end, 
  tapering 
  at 
  the 
  other, 
  with 
  all 
  of 
  its 
  

   appendages 
  glued 
  down 
  fast 
  to 
  the 
  body 
  wall. 
  Its 
  size 
  is 
  much 
  

   less 
  than 
  that 
  of 
  the 
  propupa 
  (C) 
  and 
  its 
  length 
  only 
  about 
  one-third 
  

   that 
  of 
  the 
  original 
  caterpillar 
  (A). 
  The 
  only 
  motion 
  it 
  can 
  make 
  

   is 
  a 
  rotary, 
  wriggling 
  movement 
  of 
  the 
  rear 
  end 
  of 
  the 
  body. 
  A 
  

   pupa 
  of 
  this 
  sort 
  is 
  characteristic 
  of 
  moths 
  and 
  butterflies 
  and 
  is 
  

   called 
  a 
  chrysalis. 
  It 
  is 
  a 
  specialized 
  stage 
  in 
  the 
  insect's 
  life, 
  which, 
  

   by 
  its 
  compact 
  form 
  and 
  shell-like 
  skin, 
  affords 
  greater 
  safety 
  for 
  

  

  