﻿AQUATIC 
  INSECTS 
  IN 
  THE 
  ADIRONDACKS 
  419 
  

  

  GENERA 
  OF 
  EPHEMERID 
  NYMPHS 
  IN 
  EASTERN 
  UNITED 
  STATES 
  

  

  ■41 
  Body 
  flat, 
  widest 
  across 
  the 
  rear 
  of 
  the 
  head 
  ; 
  eyes 
  dorsal 
  ; 
  legs 
  depressed 
  ; 
  

   adapted 
  for 
  clinging 
  closely 
  to 
  flat 
  surfaces. 
  (Imagos 
  have 
  five 
  freely 
  

   movable 
  segments 
  to 
  the 
  hind 
  tarsi) 
  

  

  (Heptageninae) 
  Heptagenia, 
  sens. 
  lat. 
  

  

  4ia 
  Head 
  not 
  so 
  wide 
  as 
  succeeding 
  parts 
  of 
  the 
  body; 
  eyes 
  lateral; 
  (imago 
  

  

  with 
  but 
  three 
  or 
  four 
  freely 
  movable 
  segments 
  to 
  the 
  hind 
  tarsi, 
  the 
  basal 
  

  

  segment 
  at 
  least 
  coherent 
  with 
  the 
  tibia) 
  

  

  b 
  Body 
  widest 
  across 
  the 
  mesothorax; 
  legs 
  of 
  the 
  first 
  and 
  second 
  pairs 
  

  

  about 
  equidistant 
  at 
  the 
  base. 
  (Imagos 
  have 
  the 
  cubitus 
  and 
  the 
  first 
  

  

  aual 
  vein 
  nearly 
  parallel 
  toward 
  the 
  base) 
  (Baetinae) 
  

  

  c 
  Gills 
  completely 
  concealed 
  under 
  the 
  enormously 
  enlarged, 
  conspicuously 
  

  

  four 
  spined 
  raesonotum 
  Baetisca 
  

  

  <;c 
  Gills 
  exposed 
  ; 
  mesouotum 
  normal 
  

   4 
  Outer 
  caudal 
  setae 
  fringed 
  only 
  on 
  the 
  inner 
  sides 
  ; 
  gills 
  on 
  abdominal 
  

   segments 
  1-7; 
  agile 
  swimmers 
  

   e 
  Gills 
  simple 
  

  

  / 
  Gills 
  oval 
  in 
  outline, 
  obtuse 
  at 
  the 
  apex 
  Baetis 
  

  

  /f 
  Gills 
  lanceolate 
  in 
  outline, 
  acute 
  at 
  the 
  apex.. 
  Centroptilum 
  

   ■ee 
  Gills 
  double, 
  at 
  least 
  the 
  anterior 
  pairs 
  

  

  / 
  Antennae 
  hardly 
  longer 
  than 
  the 
  head 
  ; 
  the 
  thin 
  lateral 
  margin 
  of 
  

   the 
  eighth 
  abdominal 
  segment 
  produced 
  posteriorly 
  in 
  a 
  very 
  

  

  large 
  flat 
  tooth; 
  ocelli 
  on 
  the 
  face 
  Siphlurus 
  

  

  ff 
  Antennae 
  longer 
  than 
  half 
  the 
  body; 
  the 
  posterolateral 
  angles 
  of 
  

   the 
  eighth 
  abdominal 
  segment 
  not 
  forming 
  a 
  conspicuous 
  tooth 
  ; 
  

   ocelli 
  generally 
  on 
  the 
  top 
  of 
  the 
  head 
  

   (f 
  Antennae 
  shorter 
  than 
  the 
  body; 
  gill 
  tracheae 
  pinnately 
  branched 
  

  

  Callibaetis 
  

   gg 
  Antennae 
  longer 
  than 
  the 
  body 
  ; 
  gill 
  tracheae 
  palmately 
  branched 
  

  

  Cloeon 
  

   dd 
  Outer 
  setae 
  fringed 
  on 
  both 
  sides 
  

  

  e 
  Gills 
  on 
  abdominal 
  segments 
  1-7, 
  double, 
  similar 
  

  

  / 
  Divisions 
  of 
  the 
  gills 
  narrowly 
  linear 
  Leptophlebia 
  

  

  ff 
  Divisions 
  of 
  the 
  gills 
  leaflike, 
  each 
  with 
  a 
  terminal 
  filament 
  

  

  Bl 
  as 
  t 
  uru 
  s 
  

  

  ee 
  Gills 
  absent 
  Irom 
  one 
  or 
  more 
  of 
  abdominal 
  segments 
  1-7, 
  one 
  pair 
  

  

  more 
  or 
  less 
  elytroid, 
  covering 
  those 
  behind 
  it 
  

  

  f 
  Gills 
  present 
  on 
  the 
  seventh 
  abdominal 
  segment, 
  elytroid 
  on 
  the 
  

  

  third 
  or 
  fourth 
  segment; 
  a 
  pair 
  of 
  minute 
  tubercles 
  at 
  the 
  apical 
  

  

  margin 
  of 
  each 
  abdominal 
  segment 
  beside 
  the 
  median 
  line 
  

  

  Eph 
  e 
  m 
  erell 
  a 
  

  

  ff 
  Gills 
  absent 
  from 
  the 
  seventh 
  abdominal 
  segment, 
  elytroid 
  on 
  the 
  

  

  second 
  segment 
  : 
  no 
  dorsal 
  abdominal 
  tubercles 
  ....... 
  Caenis 
  

  

  1)1) 
  Body 
  somewhat 
  compressed, 
  widest 
  across 
  the 
  base 
  of 
  the 
  abdomen; 
  legs 
  

   of 
  the 
  first 
  pair 
  much 
  more 
  closely 
  approximated 
  at 
  the 
  base 
  than 
  those 
  of 
  

   the 
  second 
  pair; 
  all 
  the 
  legs 
  appressed 
  against 
  the 
  sides 
  of 
  the 
  body 
  and 
  

   adapted 
  for 
  burrowing; 
  mandibles 
  nsnally 
  produced 
  anteriorly 
  in 
  a 
  long, 
  

   curved 
  tusk. 
  (Imagos 
  have 
  the 
  cubitus 
  and 
  the 
  first 
  aual 
  vein 
  strongly 
  

   divergent 
  toward 
  the 
  base) 
  Ephemerinae 
  

   € 
  Head 
  without 
  frontal 
  prominence 
  ; 
  gill 
  rudiment 
  on 
  the 
  first 
  abdominal 
  

   segment 
  simple 
  Polymitarcys 
  

  

  