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  BKITISH 
  LEPIDOPTERA. 
  

  

  AmblypUlia) 
  we 
  may 
  consider 
  the 
  normal 
  arrangement 
  of 
  dorsal 
  spines, 
  viz., 
  a 
  

   double 
  spine 
  (one 
  being 
  the 
  base 
  of 
  tubercle 
  i, 
  the 
  other 
  of 
  tubercle 
  ii). 
  It 
  has 
  a 
  

   small 
  mediodorsal 
  spine 
  on 
  the 
  4th 
  or 
  5th 
  abdominal 
  segment. 
  It 
  has 
  no 
  extra 
  

   hairs 
  on 
  appendages 
  or 
  elsewhere. 
  

  

  Oxyptilus 
  (parvidactyla) 
  : 
  Specially 
  modified 
  for 
  existence 
  in 
  a 
  cocoon, 
  and 
  

   with 
  means 
  for 
  travelling 
  to 
  and 
  fro 
  therein. 
  It 
  has 
  no 
  mediodorsal 
  spines, 
  and 
  

   the 
  dorsal 
  spines 
  exist 
  only 
  on 
  the 
  4th 
  to 
  8th 
  abdominal 
  segments, 
  are 
  single, 
  and 
  

   modified 
  into 
  a 
  hook 
  suitable 
  for 
  assisting 
  retrograde, 
  and 
  preventing 
  forward, 
  

   movement. 
  The 
  genital 
  bosses 
  on 
  the 
  9th 
  abdominal 
  segment 
  are 
  developed 
  into 
  

   great 
  hooks, 
  arranged 
  with 
  concavity 
  forwards. 
  There 
  is 
  no 
  forward 
  cremaster, 
  

   and, 
  though 
  there 
  are 
  many 
  long 
  hairs 
  of 
  the 
  posterior 
  cremaster, 
  their 
  ends 
  are 
  

   insufficiently 
  hooked 
  to 
  be 
  functional. 
  They 
  would 
  form 
  an 
  excellent 
  buffer 
  on 
  

   rapid 
  retrograde 
  movement. 
  The 
  other 
  hairs 
  are 
  fairly 
  developed, 
  but 
  there 
  are 
  no 
  

   extra 
  ones 
  on 
  appendages 
  or 
  elsewhere. 
  

  

  The 
  two 
  species, 
  distans 
  and 
  laetus, 
  are 
  possibly 
  the 
  most 
  difficult 
  in 
  

   the 
  European 
  " 
  plume 
  " 
  fauna 
  to 
  separate 
  in 
  the 
  imaginal- 
  stage 
  by 
  

   means 
  of 
  wing 
  structure 
  and 
  markings, 
  yet, 
  in 
  their 
  early 
  stages, 
  they 
  

   are 
  most 
  widely 
  divergent, 
  and 
  this 
  divergence 
  is 
  supported 
  by 
  an 
  

   exceedingly 
  well 
  marked 
  structural 
  difference 
  in 
  the 
  <? 
  genitalia 
  of 
  the 
  

   two 
  insects. 
  Before 
  entering 
  into 
  a 
  detailed 
  account 
  of 
  the 
  differences 
  

   existing 
  between 
  the 
  genitalia 
  of 
  these 
  two 
  species, 
  so 
  similar 
  in 
  

   appearance, 
  we 
  may 
  quote 
  Chapman's 
  general 
  remarks 
  on 
  the 
  genitalia 
  

   of 
  the 
  group. 
  He 
  writes 
  (in 
  litt.) 
  : 
  "The 
  $ 
  appendages 
  in 
  the 
  

   Oxyptilids 
  bear 
  some 
  resemblance 
  to 
  those 
  of 
  the 
  Agdistids, 
  but 
  differ 
  

   very 
  much 
  from 
  those 
  of 
  all 
  other 
  plumes. 
  In 
  the 
  Platyptiliids 
  we 
  

   have, 
  roughly 
  speaking, 
  a 
  form 
  of 
  appendages 
  not 
  widely 
  different 
  from 
  

   those 
  of, 
  say, 
  the 
  Noctuids 
  or 
  butterflies, 
  i.e., 
  a 
  chitinous 
  ring 
  with 
  a 
  

   dorsal 
  process 
  more 
  or 
  less 
  produced 
  in 
  the 
  median 
  line, 
  and 
  one 
  pair 
  

   of 
  hinged 
  processes, 
  'the 
  clasps,' 
  with 
  other 
  smaller 
  interior 
  processes, 
  

   and, 
  centrally, 
  the 
  oedeagus. 
  In 
  the 
  Oxyptilids, 
  however, 
  no 
  chitinous 
  

   ring 
  is 
  very 
  obvious, 
  nor 
  is 
  there 
  a 
  marked 
  central 
  dorsal 
  process 
  (it 
  is 
  

   small, 
  pale, 
  and 
  hidden 
  between 
  the 
  other 
  parts, 
  and 
  is 
  difficult 
  to 
  

   see), 
  but 
  besides 
  the 
  oedeagus, 
  there 
  seem 
  to 
  be 
  not 
  one, 
  but 
  three 
  

   pairs 
  of 
  lateral-hinged 
  appendages, 
  and 
  which 
  of 
  these 
  is 
  the 
  homologue 
  

   of 
  the 
  clasp 
  in 
  the 
  Platyptiliids 
  is 
  not 
  quite 
  easy 
  to 
  pronounce. 
  The 
  

   dorsal 
  pair 
  presents 
  a 
  very 
  clasp-like 
  form, 
  but 
  the 
  articulation 
  is 
  

   dorso-lateral, 
  whilst 
  that 
  of 
  the 
  second 
  pair 
  is 
  ventro-lateral, 
  which 
  

   suggests 
  that 
  these 
  are 
  the 
  clasps 
  as 
  seen 
  in 
  most 
  of 
  the 
  other 
  groups 
  

   of 
  plumes 
  ; 
  their 
  somewhat 
  less 
  simple 
  structure 
  points 
  in 
  the 
  same 
  

   direction. 
  The 
  third 
  pair 
  is 
  hardly 
  visible 
  in 
  any 
  other 
  plumes, 
  but 
  

   is, 
  I 
  think, 
  "seen 
  (along 
  with 
  the 
  clasps) 
  in 
  some 
  other 
  families 
  ; 
  they 
  are 
  

   comparatively 
  small 
  and 
  quite 
  ventral. 
  The 
  structure 
  of 
  the 
  $ 
  appen- 
  

   dages 
  shows 
  that 
  the 
  Buckleriids 
  (pallidum 
  and 
  siceliota) 
  belong 
  to 
  the 
  

   Oxyptilid 
  group. 
  The 
  different 
  Oxyptilid 
  species 
  differ 
  especially 
  in 
  

   the 
  relative 
  proportions, 
  forms, 
  and 
  directions 
  of 
  these 
  lateral 
  apophyses 
  

   To 
  compare 
  distans 
  and 
  laetus 
  in 
  illustration 
  : 
  

  

  (1) 
  The 
  dorsal 
  pair 
  of 
  apophyses 
  are 
  wider 
  and 
  heavier 
  in 
  distans, 
  the 
  dorsal 
  

   margin 
  nearly 
  straight, 
  but 
  bent 
  dorsad 
  near 
  the 
  extremity, 
  beyond 
  the 
  bend 
  the 
  

   texture 
  of 
  the 
  appendage 
  is 
  a 
  little 
  different. 
  There 
  is 
  a 
  wide 
  basal 
  attachment, 
  

   but 
  the 
  lower 
  margin 
  rapidly 
  approaches 
  the 
  dorsal, 
  and 
  then, 
  bending 
  forwards, 
  

   makes 
  the 
  basal 
  half 
  somewhat 
  triangular, 
  the 
  terminal 
  half 
  somewhat 
  baton-like. 
  

   In 
  laetus 
  the 
  general 
  structure 
  is 
  the 
  same, 
  but 
  the 
  terminal 
  half 
  is 
  much 
  more 
  

   slender, 
  and, 
  instead 
  of 
  bending 
  dorsad 
  and 
  terminating 
  in 
  a 
  rounded 
  end 
  as 
  in 
  

   distans, 
  it 
  curves 
  ventrad, 
  becomes 
  rather 
  thinner, 
  and 
  ends 
  in 
  a 
  slight 
  terminal 
  

   enlargement 
  with 
  a 
  ventral 
  projection 
  or 
  point. 
  There 
  is 
  little 
  difference 
  in 
  length 
  

   (about 
  0'34mm. 
  from 
  dorsal 
  angle 
  of 
  base 
  to 
  end), 
  but 
  the 
  more 
  slender 
  and 
  curved 
  

   process 
  in 
  laetus 
  makes 
  it 
  look 
  longer. 
  

  

  