﻿AQUATIC 
  INSECTS 
  IN 
  THE 
  ADIRONDACKS 
  463 
  

  

  The 
  nymphs 
  are 
  known 
  for 
  a 
  larger 
  proportion 
  of 
  the 
  genera 
  than 
  in 
  

   any 
  other 
  subfamily. 
  They 
  are 
  climbers 
  among 
  green 
  plants, 
  over 
  tim- 
  

   bers, 
  on 
  swaying 
  roots, 
  etc., 
  preferring 
  the 
  border 
  of 
  open 
  water 
  or 
  the 
  

   edge 
  of 
  a 
  current. 
  They 
  are 
  slender, 
  active, 
  clean, 
  with 
  smooth 
  bodies 
  

   marked 
  with 
  a 
  color 
  pattern 
  of 
  greens 
  and 
  browns, 
  well 
  adapted 
  to 
  con- 
  

   cealment 
  in 
  the 
  midst 
  of 
  their 
  natural 
  environment. 
  They 
  will 
  eat 
  al- 
  

   most 
  any 
  living 
  animal 
  that 
  they 
  can 
  capture 
  and 
  hold, 
  and 
  they 
  eat 
  

   one 
  another 
  with 
  evident 
  rehsh. 
  

  

  The 
  nymphs 
  agree 
  in 
  the 
  possession 
  of 
  the 
  following 
  characters 
  : 
  Head 
  

   depressed; 
  antennae 
  (when 
  grown) 
  six 
  to 
  seven-jointed, 
  filiform 
  ; 
  eyes 
  

   -large, 
  very 
  prominent, 
  covering 
  the 
  anterolateral 
  angles 
  of 
  the 
  head; 
  

   labium 
  very 
  long, 
  reaching 
  between 
  the 
  bases 
  of 
  the 
  middle 
  legs, 
  men- 
  

   tum 
  flat, 
  not 
  covering 
  the 
  face, 
  median 
  lobe 
  with 
  a 
  minute 
  median 
  cleft, 
  

   lateral 
  lobe 
  denticulate 
  on 
  inner 
  side, 
  and 
  with 
  a 
  terminal 
  hook, 
  as 
  well 
  

   as 
  the 
  usual 
  movable 
  hook 
  ; 
  legs 
  slender, 
  fitted 
  for 
  climbing 
  and 
  cling- 
  

   ing; 
  tarsi 
  three-jointed; 
  prothorax 
  with 
  a 
  transverse, 
  dorsal, 
  flattened 
  

   area, 
  and 
  a 
  pair 
  of 
  conic 
  processes 
  above 
  each 
  coxa; 
  spiracles 
  large, 
  

   conspicuous 
  ; 
  abdomen 
  somewhat 
  spindle-shaped, 
  with 
  lateral 
  margins 
  

   becoming 
  acute 
  posteriorly; 
  lateral 
  spines 
  present 
  on 
  a 
  variable 
  number 
  

   of 
  the 
  segments 
  ; 
  inferior 
  abdominal 
  appendages 
  at 
  least 
  twice 
  as 
  long 
  

   as 
  the 
  lateral 
  appendages. 
  

  

  The 
  following 
  tables 
  will 
  enable 
  any 
  one 
  to 
  distinguish 
  the 
  members 
  

   of 
  our 
  few 
  genera. 
  

  

  KEY 
  TO 
  GENERA 
  

  

  Imagos 
  

   a 
  The 
  radial 
  sector 
  (Rs., 
  fig. 
  9) 
  simple 
  

  

  & 
  But 
  two 
  cubito-anal 
  cross 
  veins; 
  vein 
  M^ 
  undulate; 
  supratriangle 
  with- 
  

   out 
  cross 
  veins 
  ; 
  but 
  onecross 
  vein 
  under 
  the 
  stigma.-Gom 
  phaeschna 
  

   && 
  With 
  three 
  or 
  more 
  cnbito-anal 
  cross 
  veins 
  ; 
  vein 
  M2 
  not 
  undulate 
  ; 
  supra- 
  

   triangle 
  divided 
  by 
  cross 
  veins 
  ; 
  several 
  cross 
  veins 
  under 
  the 
  stigma 
  

  

  c 
  Basal 
  space 
  traversed 
  by 
  crossveins 
  Boyeri 
  a 
  

  

  cc 
  Basal 
  space 
  open 
  ; 
  Basiaeschna 
  

  

  aa 
  Radial 
  sector 
  bearing 
  an 
  apical 
  fork 
  

   & 
  Sectors 
  of 
  the 
  arculus 
  (veins 
  M1-3 
  and 
  M4 
  ) 
  separating 
  from 
  the 
  arculas 
  at 
  or 
  

   below 
  its 
  middle 
  

  

  c 
  The 
  radial 
  sector 
  symmetrically 
  forked, 
  between 
  it 
  and 
  the 
  supplementary 
  

   vein 
  below 
  it, 
  one 
  or 
  two 
  rows 
  of 
  cells 
  

  

  (Z 
  Face 
  strongly 
  produced 
  above, 
  the 
  upper 
  margin 
  of 
  the 
  frons 
  very 
  acute 
  ; 
  

   the 
  veins 
  Mi 
  and 
  M2 
  parallel 
  to 
  the 
  level 
  of 
  the 
  stigma; 
  radial 
  sector 
  

   and 
  the 
  supplementary 
  vein 
  below 
  it 
  separated 
  by 
  a 
  single 
  row 
  of 
  cells 
  

  

  Nasi 
  a 
  e 
  sch 
  n 
  a 
  

   M 
  Face 
  vertical, 
  not 
  sharply 
  angulate 
  at 
  upper 
  edge 
  of 
  frons 
  ; 
  veins 
  Mi 
  

   and 
  M2 
  approximated 
  at 
  the 
  stigma 
  ; 
  the 
  radial 
  sector 
  and 
  the 
  supple- 
  

   mentary 
  vein 
  below 
  it 
  separated 
  by 
  two 
  rows 
  of 
  cells 
  

  

  E 
  p 
  i 
  a 
  eschn 
  a 
  

  

  cc 
  The 
  radial 
  sector 
  strongly 
  deflected 
  toward 
  the 
  stigma 
  at 
  the 
  base 
  of 
  its 
  

  

  fork, 
  unsymmetric; 
  between 
  it 
  and 
  the 
  supplementary 
  vein 
  below 
  it, 
  

  

  three 
  to 
  seven 
  rows 
  of 
  cells 
  Aeschna 
  

  

  &6 
  Sectors 
  of 
  the 
  arculus 
  springing 
  from 
  above 
  the 
  middle 
  of 
  the 
  arculus.Anax 
  

  

  