﻿TENT 
  CATERPILLAR 
  — 
  SNODGRASS. 
  

  

  349 
  

  

  The 
  sac 
  (Pr) 
  , 
  into 
  which 
  the 
  ducts 
  of 
  the 
  silk 
  gland 
  opens, 
  is 
  called 
  

   the 
  silk 
  press, 
  because 
  its 
  thick 
  walls 
  are 
  supposed 
  to 
  squeeze 
  the 
  

   silk 
  into 
  a 
  thread 
  varying 
  in 
  form 
  and 
  thickness 
  according 
  to 
  the 
  

   pressure 
  exerted 
  on 
  it. 
  The 
  cut 
  end 
  of 
  the 
  press, 
  given 
  at 
  E, 
  shows 
  

   the 
  crescent 
  form 
  of 
  its 
  cavity 
  (Lum) 
  in 
  cross 
  section, 
  and 
  the 
  

   thickening 
  in 
  its 
  roof 
  (Rph), 
  called 
  the 
  raphe. 
  Muscles 
  (Mcls) 
  

   inserted 
  on 
  the 
  raphe 
  and 
  the 
  sides 
  of 
  the 
  press 
  serve 
  to 
  enlarge 
  

   the 
  interior 
  of 
  the 
  

   press 
  by 
  lifting 
  the 
  

   roof 
  and 
  spread- 
  

   ing 
  the 
  walls. 
  The 
  

   four 
  sets 
  of 
  these 
  

   muscles 
  are 
  shown 
  

   from 
  above 
  at 
  C. 
  

   The 
  opening 
  of 
  

   the 
  press 
  cavity 
  

   probably 
  sucks 
  the 
  

   si-Ik 
  liquid 
  into 
  it 
  

   from 
  the 
  reser- 
  

   voirs, 
  and 
  when 
  the 
  

   muscles 
  relax 
  the 
  

   elastic 
  roof 
  springs 
  

   back 
  and 
  forces 
  

   the 
  silk 
  through 
  

   the 
  spinneret. 
  The 
  

   continuous 
  pas- 
  

   sage 
  from 
  the 
  

   ducts 
  into 
  the 
  

   press 
  and 
  from 
  the 
  

   press 
  into 
  the 
  spin- 
  

   neret 
  is 
  shown 
  

   from 
  the 
  side 
  at 
  D. 
  

  

  The 
  silk 
  liquid 
  

   is 
  very 
  gummy 
  

   and 
  adheres 
  tightly 
  

   to 
  whatever 
  it 
  touches, 
  while 
  at 
  the 
  same 
  time 
  it 
  hardens 
  rapidly 
  and 
  

   becomes 
  a 
  tough, 
  inelastic 
  thread 
  as 
  it 
  is 
  drawn 
  out 
  of 
  the 
  spinneret 
  

   when 
  the 
  caterpillar 
  swings 
  its 
  head 
  away 
  from 
  the 
  point 
  of 
  

   attachment. 
  

  

  The 
  mouth 
  of 
  the 
  caterpillar 
  is 
  between 
  the 
  jaws 
  and 
  the 
  lips. 
  

   It 
  opens 
  into 
  a 
  short 
  gullet 
  or 
  oesophagus, 
  which 
  is 
  the 
  first 
  part 
  of 
  

   the 
  alimentary 
  canal 
  (fig. 
  14, 
  CE). 
  The 
  rest 
  of 
  the 
  canal 
  is 
  a 
  wide 
  

   tube 
  occupying 
  most 
  of 
  the 
  space 
  within 
  the 
  caterpillar's 
  body 
  and 
  

   is 
  divided 
  into 
  the 
  crop 
  {Or), 
  the 
  stomach 
  or 
  ventriculus 
  (Vent), 
  

   and 
  the 
  intestine 
  (Int). 
  The 
  crop 
  is 
  a 
  sac 
  for 
  receiving 
  the 
  food 
  

  

  Fig. 
  13. 
  — 
  The 
  silk 
  glands 
  and 
  spinning 
  organs. 
  A, 
  the 
  silk 
  

   glands 
  (01), 
  their 
  reservoirs 
  (Res), 
  and 
  ducts 
  (Dct) 
  open- 
  

   ing 
  into 
  the 
  silk 
  press 
  (Pr). 
  G-lf, 
  glands 
  of 
  Filippi 
  opening 
  

   into 
  the 
  ducts. 
  

  

  B, 
  side 
  view 
  of 
  maxilla 
  (Mx) 
  and 
  tip 
  of 
  lahlum 
  (Lb) 
  

   carrying 
  the 
  spinneret 
  (Spn) 
  showing 
  the 
  silk 
  press 
  (Pr) 
  

   in 
  place 
  and 
  the 
  ducts 
  (Dct) 
  entering 
  it. 
  

  

  C, 
  upper 
  side 
  of 
  the 
  silk 
  press 
  (Pr), 
  showing 
  the 
  4 
  sets 
  

   of 
  muscles 
  (Mcls) 
  inserted 
  on 
  its 
  walls 
  and 
  on 
  the 
  rod-like 
  

   raphe 
  (Rph) 
  in 
  its 
  roof. 
  

  

  D, 
  side 
  view 
  of 
  the 
  press, 
  ducts, 
  spinneret, 
  raphe, 
  and 
  

   muscles. 
  

  

  E, 
  cross 
  section 
  of 
  the 
  press, 
  showing 
  its 
  cavity 
  or 
  lumen 
  

   (Lum), 
  which 
  is 
  enlarged 
  when 
  the 
  muscles 
  lift 
  up 
  the 
  

   collapsed 
  roof. 
  

  

  