﻿AQUATIC 
  INSECTS 
  IN 
  THE 
  ADIRONDACKS 
  423 
  

  

  Abdomen 
  black 
  and 
  white 
  ; 
  segments 
  2-5 
  pure 
  white 
  (in 
  old 
  males) 
  

   with 
  black 
  spiracles; 
  segment 
  6 
  yellowish; 
  segments 
  7-10 
  black, 
  paler 
  

   below. 
  

  

  Male 
  subimago 
  (undescribed). 
  Differs 
  only 
  in 
  having 
  the 
  setae 
  

   about 
  5 
  mm 
  long 
  (as 
  in 
  the 
  female) 
  ; 
  and 
  in 
  lacking 
  strongly 
  contrasting 
  

   black 
  and 
  white 
  colors 
  on 
  the 
  abdomen, 
  all 
  the 
  colors 
  being 
  duller, 
  the 
  

   wings 
  merely 
  translucent, 
  with 
  a 
  fine 
  fringe 
  of 
  hairs. 
  

  

  Female 
  imago. 
  Length 
  3-5 
  mm, 
  setae 
  5 
  mm. 
  Color 
  reddish 
  

   brown, 
  darker 
  on 
  the 
  thorax 
  and 
  paler 
  beneath 
  the 
  body; 
  discoloring 
  

   badly 
  when 
  pinned. 
  Head 
  and 
  thorax 
  brownish 
  with 
  ocelli 
  paler 
  and 
  

   €yes 
  black. 
  Thoracic 
  dorsum 
  brown, 
  darker 
  on 
  the 
  ridges, 
  with 
  a 
  pair 
  

   of 
  oblique 
  pale 
  stripes 
  extending 
  from 
  the 
  hind 
  angles 
  of 
  the 
  prothorax 
  

   to 
  the 
  wings, 
  and 
  a 
  pair 
  of 
  narrow, 
  submedian, 
  longitudinal 
  stripes 
  on 
  the 
  

   mesothorax. 
  

  

  Abdomen 
  reddish 
  brown, 
  apical 
  segments 
  paler. 
  

  

  Female 
  subimago. 
  Differs 
  in 
  obscurer 
  coloration; 
  on 
  the 
  top 
  of 
  

   the 
  mesothorax 
  there 
  is 
  a 
  single 
  wide 
  middorsal 
  longitudinal 
  stripe. 
  

  

  Known 
  only 
  from 
  the 
  St 
  Lawrence 
  river 
  and 
  Saranac 
  Inn. 
  Specimens 
  

   are 
  deposited 
  at 
  Cambridge 
  in 
  the 
  Museum 
  of 
  comparative 
  zoology 
  and 
  in 
  

   the 
  New 
  York 
  state 
  museum. 
  

  

  Nymph. 
  Measures 
  4-5 
  mm; 
  setae 
  2.3-2.5 
  mm 
  additional; 
  anten- 
  

   nae 
  2.2 
  mm. 
  

  

  Body 
  slender, 
  graceful, 
  smooth, 
  clean; 
  brownish 
  above, 
  yellowish 
  

   beneath 
  and 
  on 
  the 
  sutures; 
  a 
  narrow 
  middorsal 
  yellowish 
  line, 
  dilated 
  

   on 
  the 
  middle 
  of 
  the 
  mesothorax, 
  and 
  expanded 
  again 
  into 
  a 
  quadrate 
  

   spot 
  at 
  the 
  front 
  of 
  the 
  prothorax; 
  paired 
  yellowish 
  markings 
  beside 
  this 
  

   line, 
  and 
  numerous 
  small 
  yellowish 
  spots 
  nearer 
  the 
  sides 
  ; 
  legs 
  and 
  

   antennae 
  yellowish. 
  Setae 
  with 
  a 
  brownish 
  shade 
  near 
  the 
  bare 
  tip; 
  all 
  

   fringes 
  short; 
  the 
  two 
  outer 
  setae 
  fringed 
  only 
  on 
  the 
  inner 
  side. 
  

  

  Gills 
  present 
  on 
  abdominal 
  segments 
  1-7. 
  small, 
  separate, 
  widely 
  

   extended 
  and 
  fully 
  exposed 
  ; 
  each 
  leaf 
  obovate, 
  a 
  little 
  oblique, 
  with 
  a 
  

   chitinous 
  thickened 
  inferior 
  border, 
  this 
  border, 
  short 
  on 
  the 
  foremost 
  gill 
  

   leaf, 
  reaches 
  the 
  apex 
  on 
  the 
  sixth 
  one, 
  and 
  comprises 
  the 
  greater 
  part 
  of 
  

   the 
  narrow, 
  reduced 
  seventh 
  one. 
  

  

  The 
  face 
  is 
  vertical, 
  with 
  the 
  ocelli 
  in 
  front, 
  somewhat 
  as 
  in 
  Siphlurus. 
  

  

  The 
  nymph 
  is 
  an 
  exceedingly 
  agile, 
  little 
  fellow, 
  darting 
  hither 
  and 
  

   thither 
  with 
  astonishing 
  speed 
  when 
  one 
  tries 
  to 
  pick 
  it 
  up. 
  

  

  A 
  few 
  specimens 
  of 
  a 
  larger, 
  undetermined 
  species 
  of 
  B 
  a 
  e 
  t 
  i 
  s 
  were 
  

   taken 
  at 
  the 
  hatchery 
  windows. 
  

  

  Siphlurus 
  alternatus 
  Say 
  

  

  Plate 
  11, 
  figure 
  7 
  

   1824 
  Baetis 
  alter 
  n 
  at 
  ns 
  Say, 
  Grodman's 
  western 
  quart, 
  reporter, 
  2 
  : 
  304 
  

   1859 
  Baetis 
  alternatus 
  Leconte 
  (ed.), 
  Complete 
  writings 
  T. 
  Say, 
  1 
  : 
  204 
  

  

  1861 
  Baetis 
  alternatus 
  Hageu, 
  Synopsis 
  Neur. 
  N. 
  Am. 
  p. 
  49 
  

  

  1862 
  Baetis 
  alternatus 
  Wnlsh, 
  Acad. 
  nat. 
  sci. 
  Phil. 
  Proc. 
  p. 
  369 
  

  

  1863 
  Baetis 
  alternatus 
  Hagen, 
  Ent. 
  soc. 
  Phil. 
  Proc. 
  2 
  : 
  169 
  

  

  