﻿188 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  numerous, 
  much 
  thicker, 
  and 
  shorter 
  than 
  the 
  cuticular 
  hairs. 
  They 
  

   have 
  rounded 
  apices, 
  and 
  are 
  inclined 
  backward. 
  They 
  do 
  not 
  seem 
  

   to 
  correspond 
  in 
  any 
  way 
  to 
  the 
  hairs, 
  for 
  they 
  do 
  not 
  rest 
  over 
  pores, 
  

   nor 
  have 
  I 
  seen 
  any 
  specially 
  modified 
  cells 
  underlying 
  them. 
  As 
  

   far 
  as 
  I 
  have 
  observed, 
  they 
  are 
  mere 
  local 
  irregularities, 
  each 
  nodule 
  

   being 
  apparently 
  supported 
  by 
  some 
  four 
  or 
  six 
  unmodified 
  epidermal 
  

   cells. 
  230 
  The 
  cones 
  in 
  those 
  specimens 
  I 
  have 
  examined 
  are 
  entirely 
  want- 
  

   ing 
  in 
  the 
  ventral 
  arch, 
  in 
  the 
  upper 
  portion 
  of 
  the 
  dorsal 
  arch, 
  but 
  on 
  

   the 
  sides 
  of 
  the 
  dorsal 
  arches 
  they 
  are 
  of 
  considerably 
  greater 
  dimensions 
  

   than 
  upon 
  the 
  spiracular 
  membrane, 
  and 
  finally 
  they 
  are 
  larger 
  and 
  more 
  

   numerous 
  on 
  the 
  anterior 
  than 
  on 
  the 
  posterior 
  abdominal 
  segments. 
  

   I 
  have 
  not, 
  however, 
  attempted 
  to 
  follow 
  out 
  the 
  distribution 
  of 
  these 
  

   structures 
  in 
  greater 
  detail. 
  

  

  Second, 
  the 
  whole 
  of 
  the 
  cuticula 
  except 
  the 
  cones 
  just 
  described 
  and 
  

   the 
  hairs, 
  is 
  divided 
  into 
  numerous 
  minute 
  fields 
  (Figs. 
  63 
  and 
  65), 
  each 
  

   of 
  which 
  corresponds 
  to 
  a 
  single 
  cell 
  of 
  the 
  underlying 
  epidermis. 
  Each 
  

   field 
  is 
  bounded 
  by 
  a 
  distinct 
  polygonal 
  outline, 
  and 
  its 
  surface 
  is 
  either 
  

   covered 
  by 
  a 
  large 
  number 
  of 
  extremely 
  minute 
  projecting 
  points 
  (Fig. 
  

   65), 
  as 
  on 
  the 
  dorsal 
  arch, 
  or 
  is 
  smooth 
  as 
  upon 
  the 
  articular 
  membrane 
  

   and 
  ventral 
  arch. 
  Upon 
  the 
  sides 
  of 
  the 
  dorsal 
  arch 
  and 
  upon 
  the 
  spirac- 
  

   ular 
  membrane 
  each 
  field 
  has 
  a 
  projecting 
  spine 
  or 
  sometimes 
  two 
  or 
  even 
  

   three. 
  Fig. 
  65 
  represents 
  a 
  surface 
  view 
  of 
  part 
  of 
  the 
  side 
  of 
  one 
  of 
  the 
  

   dorsal 
  arches. 
  Upon 
  the 
  articular 
  cuticula 
  each 
  spine 
  springs 
  from 
  a 
  

   short 
  basal 
  collar. 
  Fig. 
  63 
  represents 
  a 
  surface 
  view 
  of 
  the 
  upper 
  and 
  

   anterior 
  part 
  of 
  the 
  dorsal 
  arch. 
  The 
  fine 
  sculpture 
  is 
  drawn 
  only 
  on 
  

   a 
  few 
  of 
  the 
  fields, 
  none 
  of 
  which 
  have 
  spines. 
  The 
  figure 
  is 
  intended 
  

   to 
  show 
  that 
  from 
  the 
  smooth 
  circular 
  area 
  around 
  the 
  base 
  of 
  the 
  hairs, 
  

   7i, 
  the 
  fine 
  points 
  of 
  the 
  sculpturing 
  appear 
  to 
  radiate, 
  while 
  elsewhere 
  

   they 
  are 
  only 
  irregularly 
  distributed. 
  I 
  have 
  been 
  unable 
  to 
  determine 
  

   how 
  this 
  radiating 
  appearance 
  is 
  caused. 
  

  

  The 
  ventral 
  arch 
  has 
  a 
  quite 
  smooth 
  surface 
  and 
  but 
  few 
  hairs. 
  The 
  

   articular 
  membrane 
  has 
  few 
  hairs, 
  a 
  number 
  of 
  broad 
  cones, 
  and 
  sculp- 
  

   tured 
  fields, 
  bearing 
  spines, 
  which 
  have 
  a 
  thick 
  collar 
  around 
  their 
  

   bases. 
  The 
  dorsal 
  arch 
  resembles 
  this 
  membrane 
  generally, 
  but 
  differs 
  

   from 
  it 
  by 
  the 
  simpler 
  character 
  of 
  its 
  spines, 
  by 
  their 
  absence 
  from 
  its 
  

   upper 
  portions, 
  and 
  by 
  its 
  brownish 
  tinge. 
  The 
  cuticula 
  between 
  the 
  

   segments 
  resembles 
  the 
  spiracular 
  membrane. 
  

  

  The 
  cuticula 
  forms 
  also 
  the 
  stigmata 
  or 
  openings 
  of 
  the 
  tracheal 
  sys- 
  

   tem. 
  Immediately 
  around 
  each 
  opening 
  the 
  cuticula 
  is 
  perfectly 
  smooth, 
  

   while 
  to 
  form 
  the 
  stigmata 
  it 
  undergoes 
  various 
  modifications, 
  which 
  I 
  

   have 
  not 
  studied. 
  The 
  cuticula 
  of 
  the 
  thorax, 
  head, 
  and 
  limbs 
  I 
  have 
  not 
  

   examined. 
  

  

  Epidermis. 
  — 
  The 
  cuticula 
  is 
  secreted 
  by 
  an 
  underlying 
  layer 
  of 
  cells, 
  

   the 
  epidermis 
  proper, 
  often 
  called 
  the 
  matrix 
  or 
  hypodermis, 
  but 
  inas- 
  

  

  180 
  1 
  think 
  it 
  possible 
  that 
  the 
  examination 
  of 
  sections, 
  which 
  the 
  imperfect 
  preservation 
  of 
  the 
  parts 
  

   prevented 
  my 
  making, 
  will 
  show 
  that 
  the 
  cones 
  are 
  after 
  all 
  really 
  produced 
  by 
  specialized 
  cells. 
  The 
  

   •nrface 
  views 
  I 
  have 
  obtained 
  are 
  none 
  of 
  them 
  thoroughly 
  satisfactory 
  in 
  this 
  respect. 
  

  

  