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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  adhering 
  to 
  the 
  body 
  wall 
  through 
  the 
  region 
  of 
  the 
  stomach. 
  In 
  a 
  

   well-fed 
  caterpillar 
  the 
  cells 
  of 
  the 
  fat 
  body 
  (fig. 
  16, 
  A) 
  are 
  full 
  of 
  

   small 
  drops 
  of 
  a 
  liquid 
  that 
  looks 
  and 
  acts 
  like 
  oil. 
  Two 
  physiologi- 
  

   cal 
  tests 
  for 
  fat 
  are 
  that 
  it 
  stains 
  black 
  in 
  a 
  weak 
  solution 
  of 
  osinic 
  

   acid 
  and 
  red 
  in 
  a 
  solution 
  called 
  " 
  Soudan 
  III." 
  The 
  oily 
  drops 
  

   in 
  the 
  fat 
  body 
  of 
  the 
  tent 
  caterpillar 
  sustain 
  both 
  of 
  these 
  tests, 
  

   and 
  thus 
  show 
  that 
  they 
  contain 
  fat. 
  In 
  a 
  caterpillar 
  that 
  has 
  been 
  

   starved 
  for 
  several 
  days 
  the 
  fat 
  body 
  is 
  reduced 
  to 
  a 
  few 
  small 
  strands 
  

   of 
  cells 
  on 
  the 
  crop, 
  but 
  each 
  of 
  these 
  cells 
  contains 
  as 
  much 
  fat 
  as 
  

   do 
  those 
  of 
  the 
  normal 
  fat 
  body. 
  

  

  Another 
  substance 
  stored 
  in 
  the 
  caterpillar's 
  body 
  for 
  future 
  use 
  

   is 
  glycogen 
  or 
  animal 
  starch, 
  and 
  it, 
  too, 
  is 
  contained 
  in 
  the 
  cells 
  of 
  

   the 
  fat 
  body. 
  The 
  fat 
  body 
  is, 
  therefore, 
  a 
  sort 
  of 
  liver 
  to 
  the 
  insect, 
  

   since 
  the 
  storage 
  of 
  glycogen 
  is 
  one 
  of 
  the 
  important 
  functions 
  of 
  

   the 
  liver 
  in 
  vertebrate 
  animals. 
  Glycogen 
  is 
  used 
  up 
  in 
  the 
  produc- 
  

   tion 
  of 
  energy, 
  and 
  both 
  it 
  and 
  the 
  stored 
  

   fat 
  are 
  consumed 
  during 
  the 
  next 
  stage 
  

   of 
  the 
  insect, 
  when 
  the 
  caterpillar 
  under- 
  

   goes 
  the 
  alterations 
  that 
  produce 
  from 
  it. 
  

   a 
  moth. 
  

  

  During 
  these 
  alterations, 
  however, 
  busi- 
  

  

  Fig. 
  16.— 
  A, 
  fat 
  cells 
  of 
  a 
  cat- 
  , 
  ° 
  ' 
  -_ 
  ' 
  „ 
  , 
  . 
  

  

  erpiiiar 
  u 
  inches 
  long 
  as 
  ness 
  does 
  not 
  go 
  on 
  as 
  usual. 
  Many 
  oi 
  the 
  

   they 
  look 
  when 
  stained 
  with 
  \ft 
  f 
  unc 
  tions 
  are 
  discontinued 
  and 
  physio- 
  

  

  osmic 
  acid; 
  B, 
  fat 
  cells 
  of 
  a 
  , 
  . 
  , 
  . 
  . 
  . 
  

  

  male 
  moth 
  just 
  out 
  of 
  the 
  logical 
  processes 
  come 
  into 
  action 
  that 
  

   cocoon. 
  The 
  clear 
  spaces 
  are 
  would 
  be 
  impossible 
  in 
  an 
  active 
  animal. 
  

  

  filled 
  with 
  an 
  oily 
  liquid. 
  „, 
  „ 
  .. 
  . 
  . 
  . 
  . 
  , 
  

  

  lnereiore 
  the 
  insect 
  goes 
  into 
  a 
  special 
  

   inactive 
  stage 
  called 
  the 
  pupa, 
  and 
  some 
  of 
  the 
  details 
  of 
  its 
  reorgani- 
  

   zation, 
  called 
  metamorphosis, 
  will 
  now 
  be 
  described. 
  

  

  HOW 
  THE 
  CATERPILLAR 
  BECOMES 
  A 
  MOTH. 
  

  

  When 
  the 
  caterpillar 
  ceases 
  feeding 
  its 
  body 
  contains 
  an 
  abun- 
  

   dance 
  of 
  fat, 
  and 
  its 
  silk 
  glands 
  are 
  more 
  distended 
  than 
  at 
  any 
  time 
  

   before. 
  When 
  it 
  begins 
  to 
  spin 
  its 
  cocoon 
  its 
  alimentary 
  canal 
  con- 
  

   tains 
  no 
  remains 
  of 
  food, 
  the 
  crop 
  is 
  contracted 
  to 
  a 
  narrow 
  cylinder 
  

   and 
  the 
  stomach 
  is 
  shrunken 
  and 
  flabby. 
  But 
  the 
  latter 
  contains 
  a 
  

   soft, 
  orange-brown 
  substance, 
  composed, 
  not 
  of 
  plant 
  tissue, 
  but 
  of 
  

   animal 
  cells. 
  It 
  is, 
  in 
  fact, 
  the 
  dissolving 
  cellular 
  lining 
  of 
  the 
  

   stomach 
  itself 
  which 
  has 
  already 
  been 
  shed 
  into 
  the 
  cavity 
  of 
  the 
  

   stomach, 
  and 
  is 
  apparently 
  in 
  the 
  process 
  of 
  being 
  digested 
  by 
  the 
  

   new 
  wall 
  that 
  is 
  taking 
  its 
  place. 
  This 
  marks 
  the 
  beginning 
  of 
  the 
  

   dismantling 
  of 
  the 
  caterpillar 
  preparatory 
  to 
  the 
  process 
  of 
  reforma- 
  

   tion 
  that 
  is 
  to 
  take 
  place 
  — 
  the 
  beginning 
  of 
  metamorphosis. 
  

  

  After 
  the 
  caterpillar 
  has 
  completed 
  its 
  cocoon, 
  its 
  life 
  as 
  a 
  cater- 
  

   pillar 
  is 
  almost 
  ended. 
  Its 
  external 
  appearance 
  is 
  already 
  much 
  al- 
  

   tered 
  by 
  the 
  shortening 
  of 
  its 
  body 
  and 
  the 
  loss 
  of 
  its 
  furry 
  covering, 
  

  

  