﻿186 
  

  

  BRITISH 
  LEPIDOPTERA. 
  

  

  Imago. 
  — 
  20mm. 
  -24mm. 
  Head, 
  thorax, 
  and 
  abdomen 
  same 
  tint 
  as 
  

   the 
  ground-colour 
  of 
  the 
  wings. 
  The 
  anterior 
  wings 
  with 
  the 
  apex 
  

   comparatively 
  blunt, 
  the 
  ground-colour 
  clayey, 
  pale 
  greyish-ochreous, 
  

   or 
  ochreous-brown, 
  more 
  grey 
  in 
  the 
  central 
  area 
  and 
  along 
  the 
  inner 
  

   margin, 
  with 
  a 
  more 
  or 
  less 
  indistinctly 
  denned 
  triangular 
  blotch 
  placed 
  

   on 
  the 
  costa 
  just 
  before 
  the 
  fissure 
  ; 
  a 
  dark 
  conspicuous 
  discal 
  lunule 
  ; 
  

   the 
  outer 
  margin 
  darker 
  than 
  the 
  ground-colour, 
  the 
  darker 
  band 
  edged 
  

   internally 
  by 
  a 
  paler 
  line 
  parallel 
  to 
  the 
  outer 
  margin, 
  and 
  crossing 
  

   both 
  lobes 
  ; 
  fringes 
  pale 
  greyish. 
  Posterior 
  wings 
  divided 
  into 
  three 
  

   plumules 
  ; 
  greyish-brown, 
  mottled 
  with 
  darker 
  scales, 
  especially 
  along 
  

   margins 
  ; 
  fringes 
  paler; 
  the 
  third 
  plumule 
  with 
  some 
  black 
  scales, 
  but 
  

   not 
  forming 
  so 
  distinct 
  a 
  tuft 
  as 
  they 
  do 
  in 
  gonodactyla. 
  

  

  Sexual 
  dimorphism. 
  — 
  The 
  females 
  average 
  rather 
  larger, 
  and 
  are 
  

   decidedly 
  darker 
  (i.e., 
  more 
  fuscous) 
  than 
  the 
  males 
  (Bankes). 
  

  

  Variation. 
  — 
  Hofmann 
  notes 
  that 
  this 
  insect 
  is 
  " 
  distinguished 
  

   from 
  all 
  the 
  allied 
  species 
  by 
  its 
  peculiar 
  clayey 
  coloration, 
  and 
  by 
  the 
  

   costal 
  mark 
  over 
  the 
  fissure 
  bping 
  either 
  entirely 
  absent, 
  or 
  represented 
  

   by 
  a 
  dark 
  straight 
  dash 
  extending 
  towards 
  the 
  base 
  of 
  the 
  wing." 
  In 
  

   size, 
  there 
  appears 
  to 
  be 
  a 
  considerable 
  difference 
  in 
  the 
  specimens 
  of 
  

   the 
  two 
  broods, 
  those 
  of 
  the 
  second 
  brood 
  being, 
  on 
  the 
  whole, 
  dis- 
  

   tinctly 
  smaller 
  than 
  those 
  of 
  the 
  first 
  brood. 
  Barrett 
  considered 
  that 
  

   this 
  was 
  largely 
  due 
  to 
  a 
  difference 
  in 
  the 
  temperature 
  at 
  which 
  the 
  

   larvae 
  fed 
  up, 
  noting 
  that, 
  in 
  August, 
  18^0, 
  the 
  second 
  brood 
  was 
  very 
  

   abundant 
  at 
  Pembroke, 
  and 
  that 
  the 
  individuals 
  were 
  much 
  smaller 
  

   than 
  those 
  of 
  the 
  spring 
  brood. 
  This 
  difference 
  might 
  be 
  best 
  remem- 
  

   bered 
  by 
  calling 
  the 
  autumnal 
  brood 
  : 
  — 
  

  

  Var. 
  gen. 
  2 
  aestiva, 
  n. 
  var. 
  Isodactylus 
  var., 
  Barrt., 
  " 
  Lep. 
  Brit. 
  Isles, 
  xi.,'' 
  

   p. 
  351, 
  pi. 
  413, 
  fig. 
  4/> 
  (1904). 
  — 
  Variable 
  in 
  size, 
  but 
  the 
  autumnal 
  specimens 
  

   distinctly 
  smaller 
  than 
  those 
  on 
  the 
  wing 
  in 
  June, 
  and 
  far 
  paler 
  in 
  colour, 
  often 
  

   dull 
  drab 
  or 
  whitish-drab 
  (Barrett). 
  

  

  Barrett 
  says 
  that 
  the 
  autumnal 
  specimens 
  are 
  often 
  little 
  more 
  than 
  

   one-half 
  the 
  size 
  of 
  those 
  captured 
  in 
  spring; 
  but 
  Bankes 
  observes 
  

   that, 
  "judging 
  from 
  a 
  few 
  caught, 
  and 
  a 
  large 
  number 
  of 
  bred 
  

   specimens 
  of 
  both 
  broods, 
  the 
  approximate 
  average 
  wing-expanse 
  of 
  

   the 
  first 
  brood 
  appears 
  to 
  be 
  — 
  J 
  , 
  22-5mm. 
  ; 
  ? 
  , 
  24mm. 
  ; 
  and 
  of 
  the 
  

   second 
  brood 
  to 
  be 
  — 
  $ 
  , 
  20mm. 
  ; 
  $ 
  , 
  21mm. 
  The 
  largest 
  $ 
  and 
  ? 
  

   examined, 
  both 
  belonging 
  to 
  the 
  first 
  brood, 
  but 
  hardly 
  larger 
  than 
  

   some 
  others 
  reared 
  with 
  them, 
  expand, 
  respectively, 
  25mm. 
  and 
  26mm., 
  

   while 
  the 
  smallest 
  representatives 
  of 
  each 
  sex, 
  but 
  little 
  smaller 
  

   than 
  a 
  few 
  others 
  of 
  the 
  second 
  generation 
  to 
  which 
  they 
  belong, 
  

   measure 
  only 
  17mm. 
  in 
  the 
  $ 
  , 
  and 
  16mm. 
  in 
  the 
  2 
  • 
  The 
  wing- 
  

   expanse 
  of 
  one 
  dwarf 
  $ 
  of 
  the 
  first 
  brood 
  is 
  just 
  18mm." 
  Of 
  

   the 
  colour 
  variation 
  Bankes 
  writes 
  (in 
  Hit.) 
  : 
  As 
  a 
  rule 
  the 
  examples 
  

   of 
  the 
  second 
  generation 
  are, 
  in 
  both 
  sexes, 
  much 
  smaller 
  and 
  

   paler 
  than 
  those 
  of 
  the 
  first, 
  although, 
  very 
  occasionally, 
  individuals 
  

   belonging 
  to 
  the 
  latter 
  may 
  be 
  bred 
  identical 
  in 
  size 
  and 
  colour 
  with 
  

   normal 
  representatives 
  of 
  the 
  former, 
  and, 
  in 
  exceptional 
  cases, 
  second- 
  

   brood 
  specimens 
  are 
  so 
  large 
  and 
  dark 
  that, 
  were 
  their 
  history 
  un- 
  

   known, 
  one 
  would 
  have 
  unhesitatingly 
  referred 
  them 
  to 
  the 
  earlier 
  

   brood. 
  The 
  following 
  is 
  an 
  attempt 
  to 
  classify 
  the 
  various 
  forms 
  : 
  — 
  

  

  1. 
  Fore 
  wing 
  pale 
  whitish-grey, 
  hardly, 
  or 
  but 
  slightly, 
  clouded 
  with 
  darker 
  

  

  = 
  ab. 
  pallidus, 
  n. 
  ab. 
  

  

  2. 
  Forewing 
  whitish-grey, 
  somewhat 
  clouded 
  with 
  darker 
  = 
  ab. 
  canus, 
  n. 
  ab. 
  

  

  3. 
  Forewing 
  browniah-ochreous, 
  clouded 
  with 
  fuscous 
  = 
  isodactylus, 
  Z. 
  The 
  

  

  type 
  specimen 
  was 
  a 
  3 
  (teste 
  Zeller). 
  

  

  