﻿EPHEMERINA. 
  333 
  

  

  and 
  behind 
  is 
  a 
  broad, 
  sternal, 
  large 
  area, 
  broader 
  and 
  shorter 
  than 
  in 
  

   Agrion. 
  

  

  It 
  should 
  be 
  observed 
  that 
  in 
  Odonata 
  the 
  middle 
  and 
  hind 
  legs 
  are 
  

   close 
  together. 
  

  

  THE 
  ABDOMEN. 
  

  

  In 
  Agrion 
  (PI. 
  L, 
  figs. 
  4-6) 
  there 
  are 
  ten 
  uromeres. 
  The 
  first 
  tergite 
  is 
  

   well-developed, 
  the 
  second 
  one-half 
  as 
  long 
  as 
  the 
  five 
  succeeding 
  tergites. 
  

   JSTo 
  pleurites, 
  the 
  tergites 
  overlapping 
  the 
  urosternites, 
  which 
  are 
  very 
  

   narrow. 
  The 
  tenth 
  urosome 
  shorter 
  than 
  broad. 
  The 
  claspers 
  possibly 
  

   represent 
  an 
  eleventh 
  urosome, 
  as 
  such 
  a 
  segment 
  is 
  developed 
  in 
  the 
  

   embryo, 
  but 
  in 
  the 
  adult 
  the 
  claspers 
  appear 
  to 
  be 
  appendages 
  (cer- 
  

   copoda) 
  of 
  the 
  tenth 
  urosome. 
  Oalopteryx 
  closely 
  resembles 
  Agrion 
  as 
  

   to 
  its 
  abdomen. 
  

  

  In 
  ^schna 
  (PI. 
  XLIX, 
  L. 
  figs. 
  1-3) 
  there 
  are 
  ten 
  uromeres; 
  and 
  the 
  

   rudiments 
  of 
  an 
  eleventh 
  urosternitej 
  the 
  cercopoda 
  (c) 
  are 
  long 
  and 
  

   spatulate. 
  

  

  Suborder 
  3 
  EPHEMERmA. 
  Plates 
  XLY, 
  XLYI. 
  

  

  THE 
  HEAD. 
  

  

  EpJiemeva. 
  — 
  It 
  has 
  been 
  difficult 
  with 
  the 
  material 
  at 
  my 
  command 
  to 
  

   properly 
  describe 
  the 
  external 
  anatomy 
  of 
  any 
  member 
  of 
  this 
  group. 
  

   The 
  species 
  examined 
  was 
  our 
  commonest 
  Ephemera 
  in 
  Rhode 
  Island, 
  

   identified 
  by 
  Dr. 
  Hagen 
  as 
  probably 
  U. 
  cupida 
  (Leptophlebia) 
  Walk., 
  

   and 
  also 
  aspecies 
  of 
  Palingenia. 
  There 
  is 
  a 
  great 
  deal 
  of 
  variation 
  in 
  

   the 
  form 
  of 
  the 
  thorax 
  and 
  head 
  in 
  the 
  genera 
  of 
  this 
  suborder, 
  which 
  

   is 
  as 
  much 
  specialized 
  in 
  its 
  way 
  as 
  the 
  Odonata 
  is 
  in 
  its. 
  

  

  In 
  examining 
  the 
  under 
  side 
  of 
  the 
  head 
  of 
  an 
  alcoholic 
  Ephemera, 
  

   the 
  subject 
  of 
  the 
  drawing 
  made 
  by 
  Dr. 
  Grissler 
  (Fig. 
  2), 
  there 
  is 
  a 
  cav- 
  

   ernous 
  area, 
  at 
  the 
  bottom 
  of 
  which 
  I 
  can 
  discover 
  what 
  appear 
  to 
  be 
  

   the 
  rudiments 
  of 
  the 
  maxillse 
  and 
  labium. 
  There 
  are 
  certainly 
  no 
  rudi- 
  

   ments 
  of 
  the 
  mandibles. 
  The 
  gular 
  region 
  and 
  the 
  mentum 
  can 
  be 
  dis- 
  

   tinguished, 
  and 
  I 
  think 
  I 
  can 
  detect 
  the 
  labial 
  palpi 
  and 
  lingua 
  j 
  con- 
  

   cerning 
  the 
  maxillge 
  I 
  am 
  less 
  certain. 
  The 
  drawing 
  was 
  made 
  by 
  Dr. 
  

   Gissler 
  from 
  but 
  one 
  specimen, 
  and 
  while 
  correct 
  in 
  most 
  respects 
  he 
  

   regards 
  the 
  sketch 
  of 
  the 
  mouth-parts 
  as 
  provisional. 
  The 
  general 
  

   relations 
  of 
  the 
  under 
  side 
  of 
  the 
  head 
  are 
  as 
  he 
  drew 
  them, 
  with 
  one 
  or 
  

   two 
  corrections 
  made 
  by 
  the 
  writer. 
  

  

  In 
  an 
  alcoholic 
  specimen 
  of 
  Palingenig, 
  MUneata 
  (perhaps 
  a 
  subimago) 
  

   I 
  can 
  discover 
  no 
  certain 
  rudiments 
  of 
  any 
  of 
  the 
  mouth-parts. 
  The 
  

   under 
  side 
  of 
  the 
  head 
  forms 
  a 
  deep 
  hollow, 
  and 
  the 
  mouth 
  region 
  is 
  a 
  

   deep 
  pit, 
  bounded 
  by 
  a 
  high, 
  thin 
  wall 
  in 
  front 
  — 
  the 
  lower 
  edge 
  of 
  the 
  

   clypeus. 
  This 
  pit 
  is 
  open 
  to 
  the 
  roof 
  of 
  the 
  mouth 
  or 
  clypeus. 
  It 
  is 
  

   impossible 
  to 
  distinguish 
  the 
  rudiments 
  of 
  any 
  of 
  the 
  mouth 
  parts, 
  and 
  

   practically 
  they 
  appear 
  to 
  be 
  wholly 
  obsolete. 
  

  

  