﻿21 
  

  

  Returning 
  to 
  Lyda, 
  there 
  can 
  be 
  seen 
  iying 
  directly 
  beneath 
  the 
  

   parts 
  and 
  in 
  the 
  center, 
  the 
  distal 
  end 
  of 
  the 
  labrum-epipharynx 
  

   (Ir-ep). 
  This 
  is 
  shown 
  dissected 
  out 
  in 
  Plate 
  I, 
  figure 
  2. 
  The 
  

   so-called 
  "braces" 
  of 
  the 
  labrum 
  are 
  in 
  the 
  form 
  of 
  two 
  distinct 
  

   bars. 
  

  

  Plate 
  II, 
  with 
  the 
  exception 
  of 
  figure 
  6, 
  represents 
  the 
  parts 
  of 
  

   Lygaeonematus 
  erichsonii 
  dissected 
  out. 
  These 
  parts 
  are 
  not 
  

   drawn 
  to 
  scale 
  for 
  the 
  great 
  difiference 
  in 
  size 
  does 
  not 
  make 
  this 
  

   feasible. 
  Figures 
  i 
  and 
  2 
  show, 
  respectively, 
  the 
  left 
  and 
  right 
  

   mandibles. 
  They 
  are 
  articulated 
  to 
  the 
  head 
  by 
  a 
  condyle, 
  shown 
  

   in 
  the 
  figures. 
  The 
  mandibles 
  are 
  further 
  connected 
  to 
  the 
  head 
  

   by 
  mandibular 
  ligaments, 
  not 
  well 
  shown 
  in 
  the 
  drawings 
  of 
  this 
  

   saw-fly, 
  but 
  well 
  seen 
  in 
  a 
  species 
  of 
  the 
  family 
  Formicidae, 
  

   genus 
  Aphaenogaster, 
  here 
  presented 
  for 
  that 
  purpose 
  

   (Plate 
  II, 
  figure 
  6.) 
  The 
  mandibles, 
  as 
  in 
  Lyda, 
  are 
  separate 
  

   from 
  the 
  other 
  parts. 
  They 
  are 
  folded 
  together 
  when 
  at 
  rest, 
  

   the 
  difiference 
  in 
  the 
  structure 
  of 
  their 
  inner 
  margins 
  making 
  

   this 
  possible. 
  

  

  The 
  labium 
  (Plate 
  II, 
  figure 
  3) 
  is 
  drawn 
  from 
  a 
  dorsal 
  or 
  

   inner 
  aspect. 
  Here 
  is 
  seen 
  a 
  hypopharynx 
  (hyp). 
  In 
  the 
  mem- 
  

   brane 
  below 
  occurs 
  what 
  has 
  been 
  called 
  the 
  sub-mentum 
  {sm). 
  

   Beneath 
  the 
  hypopharynx 
  and 
  lymg 
  beneath 
  its 
  curving 
  edges, 
  is 
  

   the 
  mentum 
  {m). 
  From 
  it 
  arise, 
  as 
  in 
  Lyda, 
  the 
  glossa, 
  the 
  para- 
  

   glossa, 
  and 
  the 
  four-lobed 
  labial 
  palpi. 
  The 
  maxilla, 
  shown 
  in 
  

   figure 
  4, 
  has 
  already 
  been 
  described. 
  Attention 
  should 
  be 
  called, 
  

   however, 
  to 
  the 
  connecting 
  membrane 
  which 
  unites 
  it 
  to 
  the 
  la- 
  

   bium. 
  

  

  Plate 
  II, 
  figure 
  5, 
  shows 
  the 
  labrum-epipharynx. 
  It 
  possesses 
  

   that 
  peculiar 
  chitinized 
  portion 
  extending 
  in 
  the 
  membrane 
  to 
  the 
  

   other 
  parts. 
  This 
  structure 
  is 
  common 
  to 
  all 
  saw-flies 
  studied. 
  

   It 
  is 
  called 
  the 
  "brace 
  of 
  the 
  labrum," 
  and 
  has 
  already 
  been 
  re- 
  

   ferred 
  to. 
  It 
  varies 
  from 
  a 
  structure 
  consisting 
  of 
  two 
  distinct 
  

   bars 
  to 
  one 
  where 
  the 
  two 
  have 
  become 
  fused 
  into 
  one 
  solid 
  

   part. 
  In 
  Lyda 
  (Plate 
  I, 
  figure 
  2) 
  this 
  "brace" 
  is 
  seen 
  as 
  two 
  

   bars 
  connected 
  near 
  the 
  labrum. 
  In 
  Lygaeonematus 
  erichsonii 
  

   (Plate 
  II, 
  figure 
  5) 
  there 
  is 
  noticeable 
  a 
  tendency 
  towards 
  sep- 
  

   aration 
  and 
  also 
  in 
  Dolerus 
  arveruis 
  (Plate 
  I, 
  figure 
  6). 
  In 
  

   Tenthredo 
  rufopectus 
  (Plate 
  I, 
  figure 
  5) 
  the 
  "brace" 
  occurs 
  as 
  

  

  