﻿330 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  vertex. 
  As 
  the 
  eyes 
  are 
  enormous 
  and 
  meet 
  on 
  th« 
  median 
  line 
  of 
  tlie 
  

   head, 
  the 
  eijicranium 
  is 
  divided 
  by 
  them 
  into 
  three 
  portions 
  : 
  1, 
  a 
  nar- 
  

   row 
  orbito-gular 
  area, 
  not 
  seen 
  from 
  abovej 
  2, 
  an 
  ocello-antennal, 
  very 
  

   small, 
  subtriangular 
  area 
  ; 
  and 
  3, 
  a 
  pre-antennal, 
  large 
  area, 
  correspond- 
  

   ing 
  to 
  the 
  small 
  ante-antennal 
  area 
  in 
  Agrion. 
  This 
  area, 
  with 
  the 
  

   dypeus, 
  forms 
  the 
  peculiar 
  shelf-like 
  projection 
  of 
  the 
  front 
  of 
  the 
  head. 
  

   The 
  area 
  is 
  divided 
  into 
  a 
  horizontal 
  broad 
  area 
  and 
  a 
  transverse 
  cres- 
  

   cent-shaped 
  subarea, 
  separated 
  from 
  the 
  horizontal 
  portion 
  by 
  a 
  sharp 
  

   ridge. 
  The 
  clypeus 
  is 
  very 
  large 
  and 
  full, 
  reaching 
  from 
  eye 
  to 
  eye, 
  

   and 
  nearly 
  as 
  long 
  as 
  broad. 
  It 
  is 
  separated 
  from 
  the 
  epicranium 
  by 
  a 
  

   well-marked 
  curvilinear 
  suture. 
  In 
  front 
  it 
  incloses 
  the 
  ante- 
  clypeus, 
  

   which 
  is 
  a 
  crescent-shaped 
  sclerite 
  no 
  wider 
  than 
  the 
  labrum, 
  and 
  sep- 
  

   arated 
  by 
  a 
  distinct 
  suture 
  from 
  the 
  clypeus 
  proper. 
  

   The 
  labrum 
  is 
  large 
  and 
  broad, 
  very 
  distinct 
  from 
  the 
  clypeus. 
  

  

  THE 
  THORAX. 
  

  

  Notum, 
  

  

  The 
  Odonata 
  are 
  characterized 
  by 
  the 
  unusual 
  development 
  of 
  the 
  

   I)leurites, 
  the 
  meso-episternum 
  forming 
  the 
  larger 
  part 
  of 
  the 
  dorsum 
  

   of 
  the 
  thorax, 
  the 
  meso- 
  and 
  metanotum 
  being 
  greatly 
  reduced 
  in 
  size, 
  

   owing 
  to 
  the 
  great 
  and 
  long-sustained 
  powers 
  of 
  flight 
  possessed 
  by 
  

   these 
  insects. 
  

  

  In 
  Agrion 
  the 
  pronotum 
  (PI. 
  XLVII, 
  fig. 
  10) 
  is 
  well 
  developed 
  com- 
  

   pared 
  with 
  the 
  meso- 
  and 
  metanotum; 
  somewhat 
  broader 
  than 
  long, 
  

   divided 
  into 
  three 
  areas, 
  being 
  emarginate 
  in 
  front 
  and 
  behind, 
  with 
  the 
  

   edges 
  turned 
  up, 
  while 
  the 
  large 
  central 
  area 
  has 
  two 
  lateral, 
  slightly 
  

   swollen 
  areas. 
  

  

  Mesonotum, 
  (Fig. 
  11.) 
  The 
  prsescutum 
  not 
  visible; 
  scutum 
  entire, 
  

   minute, 
  not 
  much 
  longer 
  than 
  wide. 
  The 
  scutellum 
  is 
  a 
  much 
  swollen 
  

   rounded 
  knob, 
  with 
  the 
  base 
  subtriangular, 
  not 
  much 
  smaller 
  than 
  the 
  

   scutum. 
  The 
  post 
  scutellum 
  appears 
  to 
  be 
  a 
  moderately 
  broad, 
  even, 
  

   two-ridged, 
  transverse 
  band. 
  

  

  The 
  metanotum 
  (Fig. 
  11) 
  repeats 
  the 
  general 
  appearance 
  of 
  the 
  meso- 
  

   notum 
  and 
  is 
  of 
  the 
  same 
  size, 
  the 
  wings 
  being 
  alike. 
  The 
  priescutum 
  

   is 
  not 
  visible. 
  The 
  scutum 
  is 
  deeply 
  divided 
  into 
  two 
  halves, 
  each 
  

   half 
  minute 
  and 
  much 
  swollen. 
  The 
  scutellum 
  as 
  in 
  mesonotum, 
  but 
  

   considerably 
  larger. 
  The 
  post-scutellum 
  is 
  ^ery 
  distinct, 
  forming 
  a 
  

   transversely-oblong 
  piece 
  no 
  wider 
  than 
  the 
  scutellum. 
  

  

  Calopteryx 
  (PI. 
  XL 
  VIII, 
  figs. 
  5-6) 
  is 
  substantially 
  as 
  in 
  Agrion, 
  as 
  

   regards 
  the 
  notum. 
  

  

  In 
  JEschna 
  Tieros 
  the 
  pronotum 
  is 
  small 
  and 
  narrow, 
  and 
  nearly 
  con- 
  

   cealed 
  from 
  above 
  by 
  the 
  head. 
  It 
  is 
  about 
  two-thirds 
  as 
  long 
  as 
  broad, 
  

   divided 
  into 
  a 
  short 
  transverse 
  ridge 
  and 
  a 
  posterior, 
  longer 
  portion 
  

   subtriangular 
  behind, 
  by 
  a 
  deep 
  constriction 
  or 
  impressed 
  line. 
  

  

  Mesonotum, 
  (PI. 
  XLYIII, 
  fig. 
  3.) 
  The 
  priescutum 
  obsolete, 
  not 
  visi- 
  

  

  