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  BRITISH 
  LEPIDOPTEEA. 
  

  

  or 
  any 
  other 
  similar 
  view, 
  several 
  facts 
  with 
  respect 
  to 
  the 
  assumed 
  

   sterility 
  of 
  hybrids, 
  e.g., 
  the 
  unequal 
  fertility 
  of 
  hybrids 
  produced 
  from 
  

   reciprocal 
  crosses, 
  or 
  the 
  " 
  increased 
  sterility 
  in 
  those 
  hybrids 
  which 
  

   occasionally 
  and 
  exceptionally 
  resemble 
  closely 
  either 
  pure 
  parent." 
  

   We 
  have 
  no 
  facts 
  among 
  the 
  recorded 
  experiments 
  relating 
  to 
  hybrid 
  

   lepidoptera 
  to 
  show 
  that 
  the 
  latter 
  statement 
  is 
  true, 
  but, 
  as 
  to 
  the 
  

   unequal 
  fertility 
  of 
  reciprocal 
  crosses, 
  it 
  is 
  amply 
  illustrated 
  by 
  the 
  ease 
  

   with 
  which 
  fertile 
  eggs 
  of 
  Smerinthushyhv. 
  hybridus 
  (ocellata 
  $ 
  x 
  populi 
  

  

  2 
  ) 
  are 
  obtained 
  compared 
  with 
  the 
  difficulty 
  of 
  obtaining 
  those 
  of 
  

   Amorpha 
  hybr. 
  inversa 
  (populi 
  g 
  x 
  ocellata 
  2 
  ). 
  Bacot 
  offers 
  (Ent. 
  Bee, 
  

   x., 
  p. 
  190) 
  two 
  possible 
  explanations 
  of 
  the 
  peculiarities 
  as 
  noticed 
  in 
  

   these 
  hybrids 
  ; 
  (1) 
  The 
  small 
  size 
  of 
  the 
  eggs 
  of 
  Smerinthus 
  ocellata 
  would 
  

   prevent, 
  or 
  prematurely 
  stop, 
  the 
  development 
  of 
  the 
  embryonic 
  larva 
  (if 
  

   the 
  $ 
  parent 
  were 
  Amorpha 
  populi 
  a 
  species 
  which 
  produces 
  a 
  much 
  

   larger 
  embryonic 
  larva). 
  (2) 
  The 
  $ 
  being 
  the 
  more 
  conservative 
  

   sex, 
  has 
  a 
  larger 
  portion 
  of 
  ancestral 
  determinants 
  than 
  tbe 
  $ 
  ; 
  so 
  

   that, 
  when 
  the 
  more 
  progressive 
  g 
  of 
  the 
  less 
  specialised 
  species 
  

   (Smerinthus 
  ocellata) 
  pairs 
  with 
  the 
  conservative 
  2 
  of 
  the 
  more 
  

   highly 
  developed 
  species 
  (Amorpha 
  populi), 
  the 
  cross 
  is 
  between 
  

   individuals 
  that 
  are 
  more 
  nearly 
  related 
  as 
  regards 
  the 
  constituents 
  of 
  

   the 
  germ-plasm 
  than 
  would 
  be 
  the 
  case 
  were 
  the 
  sexes 
  reversed, 
  and 
  

   there 
  is, 
  therefore, 
  a 
  far 
  greater 
  likelihood 
  of 
  fertile 
  ova 
  resulting. 
  

  

  One 
  of 
  the 
  most 
  remarkable 
  facts 
  relating 
  to 
  hybridity 
  is 
  the 
  

   tendency 
  observed 
  for 
  the 
  hybrid 
  imagines 
  to 
  emerge 
  more 
  quickly 
  

   than 
  either 
  of 
  the 
  parent 
  species. 
  We 
  have 
  illustrated 
  this 
  point 
  at 
  

   length 
  with 
  regard 
  to 
  Smerinthus 
  hybr. 
  hybridus 
  (anted, 
  iii., 
  p. 
  459), 
  

   the 
  imagines 
  of 
  which 
  largely 
  emerge 
  in 
  the 
  autumn, 
  after 
  a 
  pupal 
  period 
  

   of 
  about 
  three 
  weeks". 
  Pungeler 
  notes 
  (Standfuss' 
  RandbucJi, 
  etc., 
  p. 
  56) 
  

   a 
  similar 
  result 
  in 
  Fumea 
  hybr. 
  pungeleri 
  and 
  F. 
  hybr. 
  inrersa, 
  stating 
  

   that 
  males 
  only 
  were 
  bred, 
  and 
  that 
  these 
  emerged 
  in 
  the 
  autumn 
  with- 
  

   out 
  the 
  larva? 
  hybernating, 
  whilst 
  the 
  pure 
  larva? 
  of 
  both 
  species 
  (F. 
  casta 
  

   and 
  F. 
  affinis) 
  hybernated, 
  some 
  of 
  those 
  of 
  F. 
  afjinis, 
  indeed, 
  going 
  

   over 
  two 
  winters. 
  The 
  same 
  peculiarity 
  is 
  well 
  illustrated 
  by 
  Stand- 
  

   fuss 
  (Entom., 
  xxxiv., 
  pp. 
  78-80), 
  who, 
  in 
  the 
  spring 
  of 
  1897, 
  crossed 
  

   Clostera 
  curtula 
  $ 
  x 
  anachoreta 
  $ 
  , 
  and 
  the 
  fertile 
  eggs, 
  hatching- 
  

   simultaneously, 
  produced 
  larva?, 
  the 
  greater 
  number 
  of 
  which 
  rapidly 
  

   attained 
  full 
  growth, 
  pupated 
  and 
  produced 
  imagines 
  (hybr. 
  raeschkei) 
  

   before 
  the 
  end 
  of 
  June 
  — 
  all 
  J 
  s, 
  whilst 
  the 
  smaller 
  number 
  fed 
  on 
  

   slowly. 
  In 
  the 
  meantime, 
  the 
  3 
  raeschkei 
  paired 
  with 
  $> 
  C. 
  anachoreta, 
  

   and, 
  by 
  the 
  beginning 
  of 
  August, 
  had 
  produced 
  another 
  generation 
  of 
  

   imagines 
  — 
  again 
  all 
  $ 
  s 
  (hybr. 
  facilis). 
  These 
  in 
  turn 
  were 
  paired 
  

   with 
  ? 
  C. 
  anachoreta, 
  and 
  the 
  larva? 
  of 
  this 
  cross 
  were 
  feeding 
  contem- 
  

   poraneously 
  with 
  the 
  spring 
  larva? 
  (their 
  grand-aunts), 
  two 
  of 
  which 
  

   finally 
  pupated 
  on 
  August 
  21st 
  and 
  23rd, 
  and 
  produced 
  imagines 
  in 
  

   October. 
  In 
  the 
  meantime, 
  the 
  larva? 
  of 
  the 
  early 
  August 
  cross 
  (facilis 
  

  

  X 
  anachoreta) 
  fed 
  up, 
  pupated, 
  and 
  later 
  in 
  the 
  autumn 
  produced 
  imagines 
  

   — 
  yet 
  again 
  all 
  $ 
  s 
  (hybr. 
  approximata). 
  Relative 
  to 
  this, 
  Standfuss 
  

  

  * 
  Newman 
  (of 
  Bexley) 
  reared 
  many 
  S. 
  hybr. 
  hybridus 
  in 
  1901 
  and 
  1902. 
  Certain 
  

   individuals 
  of 
  these 
  are 
  noted 
  by 
  Adkinand 
  Clark 
  (Proc. 
  Sth. 
  Lond. 
  Ent. 
  Soc, 
  1902, 
  

   pp. 
  110-111) 
  as 
  emerging 
  from 
  pupse 
  of 
  the 
  year, 
  whilst, 
  on 
  the 
  other 
  hand, 
  Adkin 
  

   records 
  another 
  example 
  (op. 
  cit., 
  1903, 
  p. 
  70) 
  tbat 
  emerged 
  July 
  10th, 
  1903, 
  from 
  

   a 
  larva 
  reared 
  in 
  1901, 
  the 
  pupal 
  stage 
  having 
  lasted 
  one 
  year 
  and 
  eleven 
  months. 
  

  

  