﻿282 
  REPORT 
  UNITED 
  STATES 
  EKTOMOLOGICAL 
  COMMISSION. 
  

  

  in 
  tlie 
  manner 
  seen 
  at 
  Fig. 
  a, 
  and 
  turn 
  around 
  for 
  half 
  an 
  hour 
  before 
  

   beginning 
  to 
  feed. 
  Fig. 
  9 
  h 
  represents 
  one 
  of 
  these 
  larvae 
  at 
  this 
  time. 
  

   Fig. 
  10 
  was 
  drawn 
  by 
  Dr. 
  Gissler 
  to 
  represent 
  the 
  end 
  of 
  the 
  body 
  of 
  

   one 
  of 
  these 
  larvae, 
  to 
  show 
  the 
  form 
  of 
  the 
  infra-nnal 
  sucker-like 
  ex- 
  

   tremity 
  of 
  the 
  last 
  abdominal 
  segment, 
  which 
  is 
  produced 
  and 
  soft 
  at 
  the 
  

   end, 
  with 
  perhaps 
  temporary 
  dermal 
  glands 
  to 
  secrete 
  an 
  adhesive 
  fluid. 
  

   The 
  anus 
  is 
  seen 
  to 
  project 
  above 
  and 
  beyond 
  this 
  sucker, 
  r 
  representing 
  

   the 
  rectum, 
  l 
  the 
  intestine, 
  and 
  st 
  the 
  pyloric 
  end 
  of 
  the 
  stomach. 
  

  

  The 
  general 
  mode 
  of 
  development 
  of 
  these 
  two 
  Scolytid 
  beetles 
  exactly 
  

   agrees 
  with 
  that 
  of 
  the 
  Gurculionidse 
  or 
  true 
  weevils, 
  as 
  described 
  and 
  

   figured 
  in 
  the 
  author's 
  note 
  on 
  the 
  development 
  of 
  Attelabus 
  rhois 
  in 
  his 
  

   Embryological 
  Studies 
  on 
  Hexapodous 
  Insects. 
  ^^ 
  

  

  lY. 
  THE 
  NUMBER 
  OF 
  SEGMENTS 
  IN 
  THE 
  HEAD 
  OF 
  WINGED 
  INSECTS. 
  

  

  By 
  a 
  study 
  of 
  the 
  structure 
  of 
  the 
  head 
  of 
  adult 
  insects 
  it 
  is 
  very 
  diffi- 
  

   cult, 
  if 
  not 
  impossible, 
  to 
  determine 
  the 
  number 
  of 
  segments 
  in 
  the 
  head 
  

   of 
  winged 
  insects. 
  The 
  number 
  as 
  given 
  by 
  different 
  authors 
  is 
  very 
  

   variable, 
  while 
  it 
  is 
  popularly 
  supposed 
  that 
  the 
  head 
  corresponds 
  to 
  a 
  

   single 
  segment, 
  and 
  that 
  the 
  different 
  pieces 
  are 
  simply 
  "subsegments." 
  

   We 
  will 
  quote 
  from 
  Newport, 
  article 
  Insecta^ 
  in 
  Todd's 
  Oyclopsedia 
  of 
  

   Anatomy 
  and 
  Physiology, 
  the 
  views 
  generally 
  entertained 
  on 
  this 
  sub- 
  

   ject. 
  

  

  "According 
  to 
  the 
  investigations 
  of 
  the 
  most 
  careful 
  observers, 
  Sa- 
  

   viguy, 
  Audouin, 
  Macleay, 
  Kirby, 
  Cams, 
  Strauss-Durckheim, 
  Newman, 
  

   and 
  others, 
  every 
  segment 
  of 
  the 
  ijerfect 
  insect 
  is 
  made 
  up 
  of 
  distinct 
  

   parts, 
  not 
  always 
  separable 
  from 
  each 
  other 
  or 
  developed 
  to 
  the 
  same 
  

   extent, 
  but 
  existing 
  primarily 
  in 
  all. 
  It 
  is 
  also 
  believed 
  that 
  the 
  head 
  

   itself 
  is 
  formed 
  of 
  two 
  or 
  more 
  segments, 
  but 
  the 
  exact 
  number 
  which 
  

   enter 
  into 
  its 
  composition 
  is 
  yet 
  a 
  question. 
  So 
  uncertain 
  are 
  the 
  opin- 
  

   ions 
  held 
  upon 
  this 
  subject, 
  that 
  while 
  Burmeister 
  recognizes 
  only 
  two 
  

   segments, 
  Caru^ 
  and 
  Audouin 
  believe 
  there 
  are 
  three, 
  Macleay 
  and 
  New- 
  

   man 
  four, 
  and 
  Strauss-Durckheim, 
  even 
  so 
  many 
  as 
  seven. 
  These 
  dif- 
  

   ferent 
  conclusions 
  of 
  the 
  most 
  able 
  investigators 
  appear 
  to 
  have 
  arisen 
  

   chiefly 
  from 
  too 
  exclusive 
  examinations 
  of 
  the 
  head 
  in 
  jjerfect 
  insects, 
  

   without 
  reference 
  to 
  the 
  corresponding 
  parts 
  in 
  larvai. 
  It 
  is 
  only 
  by 
  

   comparing 
  the 
  distinctly 
  indicated 
  j)arts 
  of 
  the 
  head 
  in 
  the 
  perfect 
  insect 
  

   with 
  similar 
  ones 
  in 
  the 
  larva 
  that 
  we 
  can 
  hiope 
  to 
  ascertain 
  the 
  exact 
  

   number 
  of 
  segments 
  of 
  which 
  it 
  is 
  composed. 
  In 
  the 
  head 
  of 
  the 
  perfect 
  

   insect 
  there 
  ought 
  to 
  be 
  found 
  some 
  traces 
  of 
  all 
  the 
  segments 
  which 
  

   exist 
  in 
  the 
  larvae 
  of 
  the 
  same 
  species, 
  and 
  in 
  that 
  of 
  the 
  more 
  perfectly, 
  

   developed 
  larvae 
  that 
  undergo 
  a 
  true 
  metamorphosis 
  there 
  ought 
  in 
  like 
  

   manner 
  to 
  be 
  found 
  the 
  rudiments 
  of 
  all 
  the 
  segments 
  in 
  the 
  least 
  

   perfectly 
  developed. 
  Now, 
  the 
  common 
  larva 
  of 
  the 
  Dipterous 
  insect, 
  

  

  »3s 
  Memoirs 
  of 
  the 
  Peabody 
  Academy 
  of 
  Science, 
  Salem, 
  Mass., 
  1872. 
  Pl.'lH. 
  

  

  