﻿15 
  

  

  Variation 
  in 
  the 
  genus 
  Cerostoma 
  (auct). 
  

  

  By 
  Alfred 
  Sich, 
  F.E.S. 
  Read 
  August 
  8th, 
  1918. 
  

  

  The 
  species 
  forming 
  this 
  group 
  are 
  of 
  considerable 
  interest. 
  

   They 
  are 
  undoubtedly 
  closely 
  allied 
  but 
  show 
  certain 
  differences 
  in 
  

   structure 
  which 
  have 
  led 
  some 
  authorities 
  to 
  split 
  up 
  the 
  species 
  

   into 
  different 
  genera, 
  while 
  others 
  have 
  been 
  content 
  to 
  gather 
  them 
  

   all 
  into 
  one 
  genus 
  under 
  the 
  name 
  of 
  Cerostoma, 
  Latreille. 
  If 
  we 
  

   do 
  this 
  we 
  must 
  also 
  include 
  in 
  the 
  genus 
  the 
  species 
  known 
  as 
  

   Theristis 
  mucronella, 
  as 
  it 
  only 
  differs 
  from 
  the 
  rest 
  in 
  degree. 
  This 
  

   arrangement 
  we 
  find 
  in 
  Meyrick's 
  " 
  Handbook." 
  If 
  we 
  prefer 
  to 
  

   make 
  use 
  of 
  separate 
  genera, 
  we 
  may 
  break 
  up 
  the 
  British 
  species 
  

   in 
  the 
  following 
  manner. 
  I 
  am 
  indebted 
  to 
  Mr. 
  Durraut's 
  kindness 
  

   for 
  the 
  generic 
  names 
  here 
  employed. 
  

   '•' 
  Hypsilnphus, 
  Fab. 
  

   rittella, 
  L. 
  

   sequella_ 
  CI. 
  

   radiatella, 
  Don. 
  

   parenthe 
  sella, 
  L. 
  

   Ahebaea, 
  Hb. 
  

  

  sijlcella, 
  L. 
  

   alpella, 
  Schift*. 
  

   lucella, 
  F. 
  

   Trachoma, 
  Wallgn. 
  

   asperella, 
  L. 
  

   scahrella, 
  L. 
  

   horridella, 
  Tr. 
  

   Harpipteryx, 
  Hb. 
  

  

  viemorella, 
  L. 
  

   xylostella, 
  L. 
  

   Theristis, 
  Hb. 
  

  

  »)ucronella, 
  Sc. 
  

   The 
  species 
  which 
  exhibit 
  great 
  variation 
  are 
  H. 
  vittella, 
  

   H. 
  radiatella, 
  H. 
  parenthesella 
  and 
  T. 
  viucronella. 
  

  

  Hypsilophus 
  vittella, 
  L. 
  " 
  Sys. 
  Nat." 
  ed. 
  X., 
  264. 
  

  

  Usually 
  this 
  species 
  is 
  grey 
  or 
  brown 
  grey, 
  much 
  mixed 
  with 
  

   white 
  and 
  spotted 
  with 
  dark 
  grey. 
  A 
  black 
  or 
  very 
  dark 
  brown 
  

   irregular 
  streak 
  runs 
  along 
  the 
  basal 
  half 
  of 
  the 
  dorsum. 
  This 
  

  

  *For 
  the 
  genus 
  containing 
  the 
  species, 
  marginellus, 
  juniperellus, 
  etc., 
  the 
  

   name 
  Dichomerus 
  should 
  be 
  employed 
  instead 
  of 
  I'lysoloplius 
  {Hypsilophus). 
  

  

  