﻿186 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  few 
  of 
  the 
  tracheae, 
  2V., 
  and 
  in 
  Fig. 
  2 
  the 
  muscle 
  r. 
  m., 
  to 
  which 
  I 
  shall 
  

   refer 
  later. 
  

  

  In 
  brief, 
  the 
  grasshopper 
  is 
  built 
  up, 
  1, 
  of 
  the 
  outer 
  body 
  wall; 
  2, 
  oi 
  

   the 
  inner 
  tube, 
  digestive 
  canal; 
  and, 
  3, 
  of 
  the 
  organs 
  which 
  intervene 
  

   between 
  the 
  two 
  first. 
  Accordingly, 
  I 
  shall 
  describe, 
  1st, 
  the 
  outer 
  

   body 
  wall; 
  2d, 
  the 
  intervening 
  tissue 
  (mesoderm); 
  3d, 
  the 
  digestive 
  

   canal 
  and 
  its 
  appendages. 
  226 
  

  

  Before 
  entering 
  into 
  the 
  special 
  subjects, 
  I 
  would 
  remark 
  that 
  the 
  

   Orthoptera, 
  and 
  indeed 
  all 
  insects, 
  are, 
  it 
  seems 
  to 
  me, 
  remarkably 
  fa- 
  

   vorable 
  objects 
  for 
  histological 
  investigations. 
  As 
  regards 
  Caloptenus 
  

   and 
  (Edvpoda, 
  it 
  may 
  be 
  mentioned 
  in 
  general 
  that 
  the 
  cellular 
  elements 
  

   of 
  their 
  bodies 
  are 
  particularly 
  large, 
  and 
  the 
  nuclei 
  of 
  the 
  cells 
  distin- 
  

   guished 
  by 
  being, 
  for 
  the 
  most 
  part, 
  strikingly 
  granulated 
  and 
  seldom 
  

   exhibiting 
  distinct 
  nucleoli. 
  

  

  ECTODERM. 
  

  

  Cuticula.— 
  -It 
  is 
  well 
  known 
  that 
  insects 
  have 
  an 
  external 
  crust 
  or 
  

   shell, 
  the 
  cuticula, 
  which 
  is 
  supposed 
  to 
  always 
  consist 
  mainly 
  of 
  a 
  pe- 
  

   culiar 
  substance, 
  chitine, 
  often 
  mingled 
  with 
  earthy 
  salts, 
  such 
  as 
  car- 
  

   bonate 
  of 
  lime 
  and 
  magnesia. 
  

  

  In 
  both 
  locusts 
  and 
  crickets 
  the 
  abdominal 
  segments 
  present 
  differ- 
  

   ences 
  in 
  the 
  characteristics 
  of 
  the 
  cuticula 
  of 
  different 
  regions. 
  There 
  

   are 
  at 
  least 
  three 
  distinct 
  modifications— 
  first, 
  upon 
  the 
  dorsal 
  arch; 
  

   second, 
  on 
  the 
  spiracular 
  or 
  articular 
  fold, 
  which 
  intervenes 
  between 
  

   the 
  two 
  main 
  arches 
  ; 
  and, 
  third, 
  the 
  main 
  portion 
  of 
  the 
  ventral 
  arch- 
  

   but 
  in 
  the 
  locusts 
  the 
  dorsal 
  and 
  ventral 
  portions 
  are 
  very 
  similar. 
  The 
  

   dorsal 
  arch, 
  as 
  seen 
  in 
  transverse 
  sections 
  (Fig. 
  3 
  d), 
  is 
  much 
  the 
  larger, 
  

   covering 
  the 
  back 
  and 
  sides 
  of 
  the 
  body, 
  and 
  the 
  articular 
  membrane, 
  

   art, 
  is 
  a 
  comparatively 
  narrow 
  band. 
  Upon 
  the 
  living 
  locust, 
  or 
  one 
  

   recently 
  killed, 
  it 
  is 
  easy 
  to 
  observe 
  that 
  the 
  dorsal 
  and 
  ventral 
  arches 
  

   are 
  movable 
  upon 
  one 
  another 
  in 
  consequence 
  of 
  the 
  extreme 
  elasticity 
  

   and 
  flexibility 
  of 
  the 
  articular 
  membrane 
  (Fig. 
  6, 
  art). 
  Both 
  the 
  dorsal 
  

   and 
  ventral 
  portions 
  of 
  the 
  cuticula 
  are 
  rigid, 
  and, 
  in 
  the 
  locusts 
  at 
  least, 
  

   present 
  a 
  faint 
  striation 
  parallel 
  to 
  the 
  circumference 
  of 
  the 
  section. 
  

   This 
  striation 
  may 
  indicate 
  a 
  fibrillar 
  structure. 
  The 
  inner 
  surface 
  of 
  the 
  

   cuticula 
  presents 
  certain 
  peculiarities 
  in 
  the 
  distribution 
  of 
  a 
  reddish- 
  

   brown 
  pigment, 
  probably 
  part 
  of 
  the 
  matrix, 
  but 
  otherwise 
  this 
  surface 
  

   appears 
  quite 
  smooth, 
  while 
  the 
  external 
  surface 
  is 
  somewhat 
  roughened, 
  

   and 
  is 
  beautifully 
  sculptured 
  in 
  Anabrus, 
  as 
  I 
  will 
  shortly 
  describe. 
  

   The 
  thickness 
  of 
  the 
  cuticula 
  is 
  about 
  the 
  same 
  in 
  both 
  arches; 
  it 
  has 
  a 
  

   yellowish 
  tinge, 
  shading 
  off 
  into 
  brown 
  at 
  the 
  posterior 
  edges 
  of 
  the 
  

   abdominal 
  segments. 
  The 
  rigid 
  portions 
  of 
  the 
  cuticula 
  are 
  further 
  

   characterized 
  by 
  the 
  pores 
  (Poren-canalchen) 
  and 
  hairs. 
  The 
  pores 
  are 
  

   quite 
  large 
  in 
  diameter 
  (see 
  Fig. 
  4 
  p), 
  and 
  are 
  wid 
  ened 
  at 
  e 
  achjmdj 
  

  

  ^For 
  t^^a^^Tt^^ts 
  the 
  reader 
  m^so 
  consult 
  chapter 
  IX 
  of 
  the 
  First 
  Annual 
  Report 
  

   of 
  the 
  Commission, 
  pp. 
  257-272. 
  

  

  