﻿284 
  KEPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  to 
  the 
  Study 
  of 
  Insects" 
  (p. 
  20) 
  we 
  have 
  given 
  a 
  tabular 
  view 
  of 
  the 
  four 
  

   segments 
  of 
  the 
  head 
  and 
  the 
  appendages 
  they 
  bear. 
  This 
  view 
  is 
  fully 
  

   confirmed 
  by 
  our 
  studies 
  on 
  the 
  embryology 
  of 
  the 
  locust. 
  If 
  the 
  reader 
  

   will 
  turn 
  to 
  Plate 
  XYIIIj 
  Fig. 
  2, 
  he 
  will 
  see 
  the 
  order 
  of 
  succession 
  of 
  the 
  

   antennsB 
  and 
  mouth-parts. 
  It 
  will 
  be 
  seen 
  that 
  the 
  antennae 
  and 
  mouth- 
  

   parts 
  are 
  outgrowths 
  budding 
  out 
  from 
  the 
  four 
  primitive 
  segments 
  of 
  

   the 
  head 
  5 
  that 
  the 
  antennae 
  grow 
  out 
  (compare 
  also 
  PI. 
  XYIII, 
  Fig. 
  4) 
  

   from 
  the 
  under 
  side 
  of 
  the 
  procephalic 
  lobes, 
  and 
  that 
  these 
  should 
  there- 
  

   fore 
  receive 
  the 
  name 
  of 
  antennal 
  lobes. 
  In 
  like 
  manner 
  the 
  mandibles 
  

   and 
  first 
  and 
  second 
  maxillae 
  arise 
  respectively 
  from 
  the 
  three 
  succeeding 
  

   segments. 
  The 
  figures 
  by 
  Kowalevsky 
  and 
  Bobretsky 
  and 
  by 
  other 
  

   observers, 
  as 
  well 
  as 
  those 
  of 
  the 
  earliest 
  stages 
  of 
  Diplax, 
  Pulex, 
  and 
  

   Attelabus 
  which 
  we 
  have 
  published, 
  show 
  that 
  the 
  cephalic 
  segments 
  

   are 
  first 
  indicated, 
  and 
  that 
  subsequently 
  the 
  appendages 
  bud 
  out 
  from 
  

   the 
  under 
  side 
  at 
  a 
  point 
  situated 
  on 
  each 
  side 
  of 
  the 
  sternal 
  or 
  median 
  

   line 
  of 
  the 
  body. 
  It 
  appears 
  that 
  the 
  appendages 
  arise 
  between 
  the 
  

   sternal 
  and 
  pleural 
  portions 
  of 
  the 
  segment. 
  

  

  There, 
  however, 
  remains 
  a 
  portion 
  of 
  the 
  head 
  in 
  front 
  of 
  the 
  procephalic 
  

   or 
  antennal 
  lobes, 
  which 
  afterwards 
  becomes 
  the 
  clypeus 
  and 
  labrum 
  

   or 
  upper 
  lip. 
  Do 
  these 
  parts 
  belong 
  to 
  the 
  antennal 
  segment, 
  or 
  are 
  

   they 
  rudimentary 
  portions 
  of 
  a 
  segment 
  situated 
  in 
  front 
  of 
  our 
  first 
  

   segment? 
  This 
  lobe 
  or 
  outgrowth 
  is 
  evidently 
  a 
  single 
  unpaired 
  lobe 
  

   which 
  grows 
  out 
  in 
  front 
  of 
  the 
  antennal 
  lobes, 
  and 
  is 
  seen 
  to 
  form 
  the 
  

   front 
  or 
  upper 
  wall 
  of 
  the 
  mouth. 
  We 
  regard 
  it 
  as 
  the 
  tergal 
  portion 
  

   of 
  the 
  antennal 
  segment, 
  and 
  the 
  procephalic 
  lobes 
  as 
  probably 
  forming 
  

   the 
  pleural 
  portion 
  of 
  the 
  segment. 
  The 
  procephalic 
  lobes, 
  then, 
  bear- 
  

   ing 
  the 
  antennae 
  below, 
  and 
  higher 
  up 
  on 
  the 
  sides 
  the 
  eyes 
  and 
  ocelli, 
  

   become 
  the 
  epicrauium 
  of 
  the 
  larval 
  and 
  adult 
  insect. 
  It 
  follows, 
  there- 
  

   fore, 
  that 
  the 
  head 
  of 
  larval 
  and 
  adult 
  insects 
  is 
  made 
  up 
  mostly 
  of 
  the 
  

   first 
  or 
  antennal 
  segment, 
  and 
  that 
  the 
  epicrauium 
  is 
  the 
  pleural 
  portion 
  

   of 
  this 
  segment, 
  and 
  the 
  clypeus, 
  and 
  its 
  offshoot 
  the 
  labrum, 
  is 
  the 
  

   dorsal 
  or 
  tergal 
  f)ortion 
  of 
  this 
  segment. 
  

  

  The 
  only 
  other 
  portion 
  of 
  the 
  head 
  of 
  certain 
  adult 
  insects 
  w^hich 
  

   remains 
  to 
  be 
  accounted 
  for 
  is 
  the 
  so-called 
  ''occiput." 
  This 
  forms 
  the 
  

   base 
  of 
  the 
  head 
  of 
  Oorydalis, 
  a 
  Neuropterous 
  insect, 
  which, 
  however, 
  is 
  

   more 
  distinct 
  in 
  the 
  larva. 
  In 
  most 
  other 
  insects 
  the 
  occiput 
  is 
  either 
  

   obsolete 
  or 
  soldered 
  to 
  the 
  hind 
  part 
  of 
  the 
  epicrauium, 
  We 
  have 
  traced 
  

   the 
  history 
  of 
  this 
  piece 
  (sclerite) 
  in 
  Diplax, 
  a 
  dragon 
  fly, 
  and 
  have 
  found 
  

   that 
  it 
  represents 
  the 
  tergal 
  portion 
  of 
  the 
  fourth 
  or 
  labial 
  segment. 
  In 
  

   our 
  memoir 
  on 
  the 
  development 
  of 
  this 
  dragon 
  fly, 
  PI. 
  2, 
  Fig. 
  9 
  (com- 
  

   l^are 
  also 
  Fig. 
  — 
  in 
  text), 
  the 
  head 
  of 
  the 
  embryo 
  is 
  seen 
  to 
  be 
  divided 
  

   into 
  two 
  regions, 
  the 
  anterior, 
  formed 
  of 
  the 
  first 
  three 
  segments, 
  and 
  

   the 
  posterior, 
  formed 
  of 
  the 
  fourth 
  or 
  labial 
  segment. 
  This 
  postoral 
  

   segment 
  at 
  first 
  appears 
  to 
  be 
  one 
  of 
  the 
  thoracic 
  segments, 
  but 
  is 
  often 
  

   added 
  to 
  the 
  head. 
  A. 
  Brandt's 
  figure 
  of 
  Galopteryx 
  virgo, 
  PI. 
  II, 
  Fig. 
  19, 
  

   represents 
  an 
  embr^-^o 
  of 
  a 
  stage 
  similar 
  to 
  ours, 
  where 
  the 
  postoral 
  or 
  

  

  