﻿AQUATIC 
  INSECTS 
  IN 
  THE 
  ADIRONDACKS 
  521 
  

  

  c 
  Tibiae 
  and 
  tarsi 
  yellow 
  externally 
  ; 
  tbe 
  black 
  of 
  tbe 
  abdominal 
  segments 
  

  

  tending 
  to 
  form 
  apical 
  rings 
  albifrons 
  

  

  CO 
  Tibiae 
  and 
  tarsi 
  wholly 
  black 
  ; 
  the 
  black 
  of 
  the 
  abdominal 
  tending 
  to 
  

   form 
  apical 
  lateral 
  triangles 
  

   d 
  Wings 
  with 
  the 
  basal 
  half 
  (or 
  somewhat 
  less) 
  flavescent 
  ; 
  branches 
  of 
  

   the 
  genital 
  hamule 
  of 
  the 
  male 
  inclosing 
  an 
  angular 
  notch; 
  vulvar 
  

   lamina 
  of 
  the 
  female 
  with 
  its 
  lobes 
  short 
  and 
  sharply 
  recurved 
  up- 
  

   ward, 
  their 
  apices 
  meeting 
  the 
  venter 
  of 
  the 
  ninth 
  segment 
  vertically 
  

  

  assimilatum 
  

  

  dd 
  Wings 
  flavescent 
  only 
  at 
  the 
  extreme 
  base 
  ; 
  branches 
  of 
  the 
  genital 
  

  

  hamule 
  of 
  the 
  male 
  inclosing 
  an 
  oval 
  or 
  a 
  rounded 
  notch 
  ; 
  vulvar 
  

  

  lamina 
  of 
  the 
  female 
  with 
  appressed 
  lobes 
  which 
  meet 
  the 
  venter 
  of 
  

  

  the 
  ninth 
  segment 
  naore 
  obliquely 
  

  

  e 
  Branches 
  of 
  the 
  genital 
  hamule 
  of 
  the 
  male 
  inclosing 
  an 
  oval 
  notch, 
  

  

  the 
  outer 
  about 
  twice 
  as 
  stout 
  as 
  the 
  inner, 
  about 
  equally 
  curved 
  ; 
  

  

  the 
  vulvar 
  lamina 
  of 
  the 
  female 
  with 
  its 
  sides 
  regularly 
  sloping 
  

  

  rubicundulum 
  

   ee 
  Branches 
  of 
  the 
  genital 
  hamule 
  of 
  the 
  male 
  inclosing 
  a 
  short 
  rounded 
  

   notch, 
  the 
  inner 
  branch 
  more 
  sharply 
  incurved, 
  the 
  outer 
  about 
  four 
  

   times 
  as 
  thick 
  as 
  the 
  inner 
  ; 
  the 
  vulvar 
  lamina 
  of 
  the 
  female 
  some- 
  

   what 
  contracted 
  at 
  about 
  midway 
  its 
  length, 
  the 
  sides 
  more 
  con- 
  

   vergent 
  in 
  the 
  basal 
  half 
  obtrusum 
  

  

  hh 
  Superior 
  abdominal 
  appendage 
  of 
  the 
  male 
  without 
  a 
  prominent 
  inferior 
  

   median 
  tooth, 
  but 
  only 
  with 
  small 
  inferior 
  denticles 
  of 
  about 
  equal 
  size 
  ; 
  

   vulvar 
  lamina 
  of 
  the 
  female 
  not 
  cleft 
  

  

  c 
  Wings 
  with 
  the 
  basal 
  half 
  flavescent 
  semicinctum 
  

  

  cc 
  Wings 
  flavescent 
  only 
  at 
  the 
  extreme 
  base 
  

  

  d 
  Femora 
  and 
  tibiae 
  entirely 
  yellow 
  vicinum 
  

  

  dd 
  Femora 
  and 
  tibiae 
  marked 
  with 
  black 
  on 
  the 
  sides 
  costiferum 
  

  

  a 
  Dorsal 
  hooks 
  of 
  abdominal 
  segments 
  6-8 
  long 
  and 
  sharp, 
  about 
  as 
  long 
  as 
  

   their 
  respective 
  segments 
  

   & 
  Lateral 
  spines 
  straight 
  on 
  both 
  outer 
  and 
  inner 
  margins 
  costiferum 
  

  

  1 
  The 
  nymphs 
  of 
  albifrons 
  and 
  corruptum 
  are 
  unknown; 
  that 
  of 
  the 
  former 
  species 
  Is 
  

   likely 
  to 
  be 
  of 
  the 
  type 
  of 
  the 
  nymph 
  of 
  rubicundulum. 
  I 
  give 
  a 
  figure 
  (pl. 
  25, 
  fig. 
  1) 
  of 
  a 
  

   nymph 
  from 
  southern 
  California 
  of 
  S. 
  illotum, 
  the 
  nearest 
  ally 
  of 
  corruptum. 
  The 
  nymph 
  

   of 
  corruptum 
  will 
  probably 
  be 
  of 
  this 
  type. 
  

  

  I 
  have 
  nymphs 
  of 
  rubicundulum 
  raised 
  at 
  Ithaca, 
  of 
  obtrusum, 
  raised 
  at 
  Lake 
  Forest 
  

   111., 
  and 
  of 
  assimilatum 
  raised 
  at 
  Saranac 
  Inn. 
  Between 
  the 
  nymphs 
  of 
  rubicundulum 
  

   and 
  obtrusum 
  I 
  find 
  only 
  a 
  scarcely 
  perceptible 
  difCerence 
  in 
  size, 
  that 
  of 
  obtrusum 
  being 
  a 
  

   little 
  smaller, 
  in 
  the 
  bred 
  specimens. 
  Both 
  these 
  are 
  a 
  very 
  little 
  smaller 
  than 
  assimilatum; 
  and 
  

   I 
  note 
  that 
  in 
  the 
  bred 
  specimens 
  the 
  dorsal 
  hooks 
  on 
  the 
  fourth 
  and 
  fifth 
  abdominal 
  segments 
  

   (hidden 
  between 
  the 
  wing 
  cases) 
  are 
  larger 
  and 
  more 
  nearly 
  equal 
  in 
  size 
  in 
  assimilatum, 
  

   smaller 
  and 
  more 
  unequal 
  in 
  size 
  and 
  paler 
  in 
  the 
  other 
  two. 
  These 
  differences 
  are 
  so 
  slight 
  and 
  

   have 
  been 
  studied 
  in 
  so 
  few 
  specimens 
  that 
  I 
  have 
  not 
  thought 
  best 
  to 
  introduce 
  them 
  as 
  yet 
  into 
  

   the 
  table. 
  

  

  As 
  to 
  the 
  imagos 
  of 
  these 
  three 
  nominal 
  species, 
  I 
  know 
  of 
  no 
  absolutely 
  constant 
  differences 
  

   either 
  in 
  size, 
  coloration, 
  structure, 
  distribution 
  or 
  habits 
  that 
  will 
  in 
  every 
  case 
  distinguish 
  be- 
  

   tween 
  them. 
  The 
  typical 
  rubicundulum 
  is 
  of 
  course, 
  intermediate 
  between 
  the 
  other 
  two. 
  I 
  

   have 
  examined 
  hundreds 
  of 
  specimens 
  of 
  each, 
  and 
  say 
  unhesitatingly 
  that 
  they 
  Intergrade 
  com- 
  

   pletely; 
  nevertheless. 
  It 
  is 
  convenient 
  to 
  recognize 
  the 
  three 
  forms, 
  and 
  practically, 
  there 
  is 
  little 
  

   difficulty 
  generally 
  in 
  distinguishing 
  between 
  them. 
  I 
  have 
  therefore 
  listed 
  them 
  separately. 
  

  

  