﻿66 
  BRITISH 
  LEPIDOPTERA. 
  

  

  experiments 
  noted 
  in 
  more 
  detail, 
  bearing 
  on 
  this 
  phase 
  of 
  the 
  subject, 
  

   are 
  as 
  follows 
  : 
  — 
  

  

  1. 
  Mimas 
  tille 
  g 
  x 
  obsoleta 
  2. 
  — 
  Two 
  broods. 
  The 
  first 
  brood 
  

   gave 
  72 
  imagines, 
  all 
  normal 
  ; 
  the 
  second, 
  65 
  moths, 
  all 
  normal 
  

   (Standfuss, 
  Insekten 
  Borse, 
  xix., 
  p. 
  163). 
  

  

  2. 
  Mimas 
  obsoleta 
  $ 
  x 
  tllee 
  2 
  . 
  — 
  Three 
  broods. 
  First 
  produced 
  

   69 
  moths, 
  68 
  normal, 
  and 
  1 
  2 
  slightly 
  aberrant 
  ; 
  the 
  second 
  gave 
  52 
  

   moths, 
  51 
  typical, 
  and 
  1 
  2 
  of 
  the 
  obsoleta 
  form 
  ; 
  the 
  third 
  resulted 
  in 
  

   81 
  imagines, 
  77 
  being 
  normal, 
  1 
  $ 
  and 
  1 
  2 
  of 
  the 
  obsoleta 
  form, 
  and 
  

   1 
  $ 
  and 
  1 
  2 
  intermediate 
  (Standfuss, 
  Insekten 
  Borse, 
  xix., 
  p. 
  163). 
  

  

  3. 
  Abraxas 
  ulmata 
  (?) 
  $ 
  x 
  suffusa 
  2 
  . 
  — 
  [The 
  $ 
  may 
  also 
  have 
  

   been 
  suffusa. 
  Eggs 
  obtained 
  1897 
  (Ent. 
  Bee, 
  ix., 
  p. 
  301).] 
  (a) 
  70 
  imag- 
  

   ines 
  bred 
  — 
  67 
  typical, 
  3 
  slightly 
  suffused, 
  none 
  followed 
  § 
  . 
  The 
  colour 
  

   of 
  ab. 
  suffusa 
  is 
  due 
  to 
  an 
  extension 
  of 
  the 
  bluish-grey 
  scales 
  over 
  the 
  

   whole 
  wing 
  area 
  ; 
  there 
  are 
  no 
  melanic 
  scales. 
  The 
  aberrations 
  

   appear 
  to 
  be 
  caused 
  by 
  disease, 
  or 
  perhaps 
  by 
  certain 
  meteorological 
  

   conditions 
  acting 
  on 
  pupa? 
  with 
  deficient 
  vitality 
  (Biding, 
  Ent 
  Bee, 
  

   x., 
  pp. 
  263-264). 
  (j8) 
  The 
  experiment 
  was 
  repeated 
  in 
  1898, 
  and 
  40 
  

   imagines 
  were 
  bred 
  from 
  suffusa 
  $ 
  xsuff'usa 
  2 
  parentage. 
  All 
  these 
  

   were 
  typical 
  ulmata, 
  not 
  one 
  resembled 
  the 
  2 
  parent. 
  There 
  were 
  

   not 
  even 
  unusual 
  blotches 
  on 
  any 
  of 
  the 
  specimens 
  (Ent. 
  Bee, 
  xi., 
  

   p. 
  290). 
  

  

  VII. 
  Dimorphism 
  in 
  one 
  sex. 
  

  

  Although 
  rather 
  outside 
  the 
  scope 
  of 
  this 
  chapter, 
  we 
  may 
  note 
  

   that 
  information 
  is 
  badly 
  needed 
  of 
  the 
  percentages 
  of 
  dimorphic 
  

   progeny 
  in 
  those 
  species 
  in 
  which 
  the 
  dimorphism 
  is 
  confined 
  to 
  one 
  

   sex. 
  The 
  problem 
  involving 
  the 
  cause 
  of 
  the 
  maintenance 
  of 
  this 
  

   dimorphism 
  in 
  one 
  sex, 
  might 
  also, 
  in 
  some 
  cases 
  at 
  least, 
  with 
  

   sufficient 
  experimental 
  trials, 
  be 
  more 
  or 
  less 
  satisfactorily 
  solved. 
  In 
  

   Spilosoma 
  mendica, 
  this 
  dimorphism 
  is 
  confined 
  to 
  the 
  J 
  s 
  in 
  which 
  

   there 
  are 
  two 
  forms 
  — 
  mendica 
  (dark), 
  and 
  rustica 
  (light), 
  but 
  rarely 
  

   occurring 
  in 
  the 
  same 
  locality, 
  that 
  is, 
  it 
  is 
  racial, 
  whilst 
  in 
  Dryas 
  

   paphia 
  it 
  is 
  the 
  2 
  that 
  is 
  dimorphic 
  — 
  paphia 
  (brown), 
  and 
  valesina 
  

   (greenish-black), 
  and 
  in 
  Colias 
  edusa 
  also 
  the 
  dimorphism 
  is 
  in 
  the 
  2 
  

   — 
  edusa 
  (orange), 
  helice 
  (white) 
  , 
  and 
  in 
  these 
  the 
  dimorphic 
  forms 
  occur 
  

   together, 
  i.e., 
  the 
  dimorphism 
  is 
  aberrational. 
  But 
  we 
  have 
  few 
  detailed 
  

   experiments 
  giving 
  useful 
  information 
  on 
  the 
  various 
  points 
  arising 
  out 
  

   of 
  a 
  study 
  of 
  this 
  dimorphism. 
  At 
  present 
  we 
  can 
  only 
  find 
  the 
  

   following 
  : 
  — 
  

  

  1. 
  Colias 
  edusa 
  $ 
  x 
  helice 
  2 
  .—(a) 
  Four 
  2 
  s 
  laid 
  between 
  850 
  

   and 
  900 
  eggs 
  in 
  August, 
  1900. 
  Larva? 
  fed 
  up 
  quickly, 
  and 
  pupation 
  

   took 
  place 
  in 
  September. 
  The 
  imagines 
  emerged 
  in 
  October, 
  and 
  

   totalled 
  302 
  g 
  s 
  and 
  235 
  2s 
  = 
  537 
  of 
  both 
  sexes. 
  Tabulated, 
  these 
  

   worked 
  out 
  as 
  follows 
  : 
  — 
  

  

  Total 
  specimens.. 
  <? 
  s 
  302 
  50-2% 
  

  

  typical. 
  . 
  ? 
  s 
  125 
  1 
  9q 
  _ 
  23-3% 
  

  

  helice. 
  . 
  ? 
  s 
  110/ 
  " 
  d0 
  20-5% 
  

  

  537 
  100-0 
  

  

  Female 
  results 
  . 
  . 
  typical 
  125 
  53-2% 
  

  

  helice 
  110 
  46-8% 
  

  

  235 
  100-0 
  

  

  (Frohawk, 
  Entom., 
  xxxiv., 
  pp. 
  3-5.) 
  

  

  