﻿332 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  as 
  in 
  Agrion 
  ; 
  those 
  of 
  the 
  metapleurum 
  are 
  much 
  as 
  in 
  the 
  meso-, 
  but 
  

   a 
  well-marked 
  suture 
  separates 
  the 
  meso-epimerum 
  from 
  the 
  meta-epi- 
  

   sternum, 
  and 
  the 
  latter 
  is 
  much 
  wider 
  towards 
  the 
  insertion 
  of 
  the 
  wing 
  

   than 
  next 
  to 
  the 
  coxa. 
  

  

  In 
  the 
  prothorax 
  of 
  ^schna 
  the 
  epi 
  sternum 
  is 
  very 
  small, 
  and 
  sub- 
  

   divided 
  into 
  several 
  pieces 
  j 
  the 
  epimerum 
  is 
  larger 
  and 
  not 
  divided; 
  it 
  

   is 
  about 
  as 
  long 
  as 
  broad, 
  and 
  posteriorly 
  submembranous. 
  

  

  The 
  coxa 
  is 
  very 
  large, 
  being 
  much 
  enlarged 
  within, 
  meeting 
  the 
  

   opposite 
  coxa 
  on 
  the 
  median 
  line. 
  

  

  Mesopleurum 
  (Fig. 
  1) 
  enormous, 
  and 
  forming 
  a 
  large 
  part 
  of 
  the 
  dor- 
  

   sal 
  region 
  of 
  the 
  thorax. 
  The 
  episternum 
  is 
  enormous, 
  forming 
  wiih 
  

   its 
  fellow 
  on 
  the 
  opposite 
  side 
  a 
  large 
  proportion 
  of 
  the 
  front 
  and 
  meso- 
  

   notum; 
  the 
  foramen 
  leading 
  into 
  the 
  prothorax 
  is 
  situated 
  very 
  low, 
  

   the 
  mesostigmata 
  being 
  situated 
  on 
  the 
  upper 
  side 
  of 
  the 
  opening. 
  

   The 
  two 
  meso-episterna 
  unite 
  to 
  form 
  the 
  front 
  of 
  the 
  mesothorax 
  and 
  

   also 
  the 
  anterior 
  fourth 
  or 
  third 
  of 
  the 
  dorsal 
  region 
  of 
  the 
  entire 
  thorax. 
  

   Dorsally 
  there 
  is 
  on 
  the 
  united 
  episterna 
  a 
  high 
  median 
  ridge 
  becom- 
  

   ing 
  forked 
  behind, 
  with 
  two 
  lateral 
  diverging 
  transverse 
  ridges. 
  The 
  

   ridge 
  originates 
  in 
  front 
  from 
  the 
  hinder 
  border 
  of 
  a 
  transverse 
  cres- 
  

   cent-shaped 
  area 
  directly 
  above 
  the 
  foramen 
  leading 
  into 
  the 
  pro- 
  

   thorax. 
  A 
  straight, 
  distinct 
  suture 
  separates 
  the 
  episternum 
  from 
  the 
  

   epimerum. 
  Between 
  the 
  episternum 
  and 
  the 
  trochantine 
  is 
  a 
  sclerite, 
  the 
  

   nature 
  of 
  which 
  is 
  uncertain 
  ; 
  by 
  its 
  close 
  relation 
  to 
  the 
  sternum 
  it 
  may 
  

   be 
  the 
  infra- 
  episternum 
  and 
  probably 
  not 
  the 
  coxa, 
  the 
  latter 
  ax)pearing 
  

   to 
  be 
  obsolete. 
  

  

  The 
  epimerum 
  is 
  large, 
  broad, 
  oblique, 
  and 
  below 
  in 
  front 
  of 
  the 
  meta- 
  

   stigma 
  separated 
  by 
  suture 
  from 
  the 
  meta-episternum, 
  but 
  above 
  there 
  

   is 
  no 
  suture, 
  only 
  a 
  broad, 
  valley 
  -like 
  depression. 
  

  

  Metapleurum. 
  The 
  episternum 
  is 
  about 
  one-half 
  as 
  wide 
  as 
  the 
  large, 
  

   swollen, 
  smooth 
  epimerum, 
  which 
  composes 
  the 
  posterior 
  third 
  of 
  the 
  

   pleurum 
  of 
  the 
  thorax. 
  Below 
  the 
  metastigma 
  is 
  a 
  square 
  sclerite, 
  

   directly 
  over 
  the 
  trochantine, 
  which 
  is 
  probably 
  the 
  infra-episternum, 
  

   there 
  apparently 
  being 
  no 
  coxaj 
  the 
  trochantine 
  as 
  in 
  the 
  prothorax. 
  

  

  Sternum. 
  

  

  In 
  Agrion 
  the 
  prosternum 
  is 
  small, 
  triangular, 
  longer 
  than 
  broad, 
  

   with 
  the 
  apex 
  acute. 
  

  

  Mesosternum 
  a 
  little 
  larger 
  and 
  broader 
  than 
  the 
  prosternum, 
  but 
  

   still 
  small. 
  

  

  Metasternum. 
  What 
  I 
  am 
  disposed 
  to 
  regard 
  as 
  this 
  sclerite 
  is 
  a 
  very 
  

   large, 
  elongated, 
  polygonal 
  area, 
  which 
  is 
  semi-membranous 
  and 
  flat. 
  

  

  In 
  Calopteryx 
  the 
  sternites 
  are 
  as 
  in 
  Agrion, 
  but 
  the 
  metasternum 
  is 
  

   broader 
  and 
  shorter, 
  with 
  an 
  anterior 
  deeply 
  impressed 
  median 
  line. 
  

  

  In 
  ^schna 
  the 
  mesosternum 
  is 
  small, 
  broad, 
  irregular 
  j 
  while 
  the 
  

   metasternum 
  is 
  much 
  smaller, 
  nearly 
  obsolete 
  in 
  front 
  of 
  tlie 
  legs, 
  

  

  