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  XX. 
  On 
  some 
  cases 
  of 
  Dimorphism 
  and 
  Polymorphism 
  

   among 
  Palcearctic 
  Lepidoptera. 
  By 
  Serge 
  Alphe- 
  

   RAKY, 
  of 
  St. 
  Petersburg. 
  Communicated 
  by 
  Henry 
  

   John 
  Elwes, 
  F.L.S., 
  F.Z.S., 
  &e. 
  

  

  [Eead 
  August 
  5th, 
  1891.] 
  

  

  Many 
  authentic 
  instances 
  of 
  dimorphism, 
  or 
  even 
  poly- 
  

   morphism, 
  in 
  the 
  female 
  sex 
  of 
  various 
  species 
  of 
  

   Lepidoptera 
  are 
  known 
  to 
  exist, 
  but 
  only 
  a 
  few 
  such 
  

   cases 
  are 
  generally 
  acknowledged 
  for 
  the 
  male 
  sex. 
  It 
  

   is 
  rather 
  strange 
  that, 
  when 
  in 
  certain 
  species 
  the 
  males 
  

   are 
  of 
  one 
  form 
  [monomorphic] 
  , 
  but 
  the 
  females 
  dimor- 
  

   phic 
  (whether 
  the 
  different 
  forms 
  are 
  found 
  together 
  or 
  

   in 
  different 
  localities 
  widely 
  apart), 
  nobody 
  seems 
  to 
  

   wonder 
  at 
  the 
  fact 
  ; 
  whereas, 
  if 
  females 
  of 
  supposed 
  

   distinct 
  species 
  are 
  absolutely 
  identical 
  in 
  appearance, 
  

   but 
  their 
  males 
  dimorphic, 
  such 
  males 
  are 
  mostly 
  treated 
  

   as 
  belonging 
  to 
  separate 
  species. 
  

  

  Let 
  us 
  take, 
  as 
  an 
  example, 
  Cleogene 
  Niveata, 
  Sc. 
  

   (= 
  Illibaria, 
  Hb.), 
  from 
  the 
  Carniola 
  and 
  Styrian 
  Alps, 
  

   where 
  both 
  males 
  and 
  females 
  are 
  white, 
  and 
  the 
  

   Pyrenean 
  Cleogene 
  Peletieraria, 
  Dup., 
  which 
  differs, 
  

   from 
  the 
  first, 
  only 
  in 
  the 
  male 
  being 
  of 
  a 
  dark 
  slate- 
  

   colour, 
  and 
  a 
  trifle 
  larger, 
  as 
  a 
  rule. 
  

  

  The 
  females 
  of 
  Niveata 
  and 
  Peletieraria 
  are 
  identical. 
  

   We 
  shall 
  find 
  but 
  a 
  small 
  number 
  of 
  lepidopterists 
  

   inclined 
  to 
  recognise 
  in 
  these 
  two 
  forms 
  mere 
  varieties 
  of 
  

   one 
  and 
  the 
  same 
  moth, 
  which 
  they 
  most 
  decidedly 
  are. 
  

  

  It 
  would 
  have 
  been 
  still 
  more 
  difficult 
  to 
  have 
  their 
  

   specific 
  identity 
  admitted 
  if 
  both 
  forms 
  inhabited 
  the 
  

   same 
  locality, 
  as 
  in 
  some 
  other 
  cases, 
  where 
  dimorphic 
  

   forms 
  really 
  do 
  fly 
  together. 
  

  

  Of 
  generally 
  acknowledged 
  instances 
  of 
  dimorphism 
  in 
  

   the 
  male 
  sex 
  there 
  are 
  but 
  few, 
  and 
  these 
  are 
  of 
  such 
  

   an 
  unmistakable 
  and 
  obvious 
  character 
  that 
  no 
  place 
  for 
  

   the 
  slightest 
  doubt 
  is 
  left, 
  even 
  for 
  the 
  most 
  obstinate 
  

   species 
  separator. 
  Among 
  such 
  cases 
  it 
  is 
  enough 
  to 
  

  

  trans, 
  ent. 
  soc. 
  lond. 
  1891. 
  — 
  part 
  iv. 
  (dec.) 
  

  

  