﻿116 
  BRITISH 
  LEPIDOPTERA. 
  

  

  plumules 
  being 
  much 
  narrower, 
  and 
  the 
  fissures 
  rather 
  more 
  deeply 
  

   cut, 
  the 
  neuration, 
  however, 
  is 
  of 
  the 
  same 
  type 
  except 
  that 
  the 
  

   modification 
  of 
  the 
  wing 
  has 
  thrown 
  the 
  points 
  at 
  which 
  some 
  of 
  the 
  

   nervures 
  reach 
  the 
  margin 
  into 
  rather 
  different 
  positions. 
  In 
  the 
  

   Trichoptilids, 
  apparently, 
  the 
  most 
  extreme 
  modification 
  on 
  this 
  branch 
  

   occurs, 
  the 
  plumules 
  being 
  so 
  slender 
  as 
  to 
  be 
  almost 
  filiform. 
  Side 
  by 
  

   side 
  with 
  this 
  development 
  in 
  the 
  character 
  of 
  the 
  hindwing 
  plumules 
  in 
  

   the 
  Platyptiliids 
  and 
  Oxyptilids 
  is 
  the 
  peculiar 
  and 
  characteristic 
  appear- 
  

   ance 
  of 
  the 
  bunch 
  or 
  bunches 
  of 
  black 
  scales 
  on 
  the 
  third 
  plumule. 
  

   They 
  are 
  restricted 
  to 
  this 
  side 
  of 
  the 
  phylum, 
  and 
  little 
  is 
  known 
  of 
  

   their 
  character 
  and 
  function. 
  They 
  do 
  not 
  appear 
  so 
  low 
  down 
  as 
  the 
  

   Stenoptiliids, 
  and 
  they 
  are 
  lost 
  again 
  by 
  the 
  time 
  they 
  reach 
  the 
  most 
  

   specialised 
  Trichoptilids, 
  e.g., 
  Buckleria 
  (pallidum). 
  In 
  the 
  Oida?mato- 
  

   phorids 
  on 
  the 
  Alucitine 
  side 
  of 
  the 
  phylum, 
  the 
  first 
  fissure 
  of 
  the 
  hind- 
  

   wings 
  is 
  more 
  deeply 
  cleft 
  and 
  the 
  plumules 
  more 
  linear 
  than 
  in 
  the 
  

   Stenoptiliid 
  and 
  Platyptiliid 
  genera, 
  showing 
  a 
  less 
  generalised 
  form 
  than 
  

   the 
  latter, 
  whilst 
  in 
  the 
  Leioptilids 
  they 
  are 
  still 
  more 
  lineated. 
  In 
  the 
  

   Alucitines 
  (e.g., 
  Alucita 
  pentad 
  actyla) 
  the 
  plumules 
  are 
  of 
  the 
  same 
  linear 
  

   form, 
  and 
  the 
  neuration 
  is 
  modified 
  accordingly; 
  the 
  Alucitid 
  branch 
  

   carries 
  two 
  nervures 
  into 
  the 
  third 
  plumule, 
  the 
  Platyptiliid 
  branch 
  only 
  

   one. 
  Walsingham 
  observes 
  (Ent. 
  Mo. 
  Mag., 
  xxi., 
  pp. 
  175-176) 
  that 
  the 
  

   hindwings 
  of 
  Reptaloba 
  (argyriodactyla) 
  , 
  the 
  forewings 
  of 
  which 
  have 
  

   already 
  been 
  noted 
  (antea) 
  as 
  possessing 
  four 
  lobes, 
  have 
  the 
  normal 
  

   three 
  lobes, 
  ;: 
  the 
  upper 
  cleft 
  extending 
  very 
  slightly 
  beyond 
  the 
  middle, 
  

   the 
  lower 
  cleft 
  reaching 
  nearly 
  to 
  the 
  base, 
  the 
  posterior 
  lobe 
  being 
  

   toothed 
  with 
  projecting 
  tufts 
  of 
  scales 
  on 
  the 
  inner 
  margin. 
  

  

  One 
  of 
  the 
  most 
  important 
  structural 
  features 
  of 
  the 
  Alucitid 
  imago 
  is 
  

   the 
  frenulum. 
  We 
  are 
  indebted 
  for 
  our 
  detailed 
  knowledge 
  of 
  this 
  organ 
  

   in 
  the 
  Alucitids 
  to 
  Griffiths, 
  who 
  has 
  discovered 
  that 
  the 
  whole 
  of 
  the 
  

   plumes 
  divide 
  up 
  sharply 
  into 
  two 
  sections, 
  viz., 
  (1) 
  The 
  ? 
  with 
  one 
  

   spina 
  or 
  " 
  the 
  one-spina 
  group," 
  (2) 
  The 
  $ 
  with 
  two 
  spinas 
  or 
  "the 
  

   double-spina 
  group." 
  The 
  former 
  contains 
  the 
  Agdistids, 
  Stenoptiliids, 
  

   Oxyptilids, 
  Amblyptiliids 
  and 
  Platyptiliids 
  ; 
  the 
  latter 
  the 
  Merrifieldiids, 
  

   Oidaematophorids, 
  Leioptilids 
  and 
  Alucitids. 
  On 
  this 
  point, 
  Griffiths 
  

   writes 
  (in 
  litt.): 
  " 
  The 
  normal 
  development 
  of 
  the 
  frenulum 
  in 
  lepidoptera 
  

   consists 
  of 
  a 
  spina, 
  single 
  in 
  the 
  j 
  , 
  but 
  double, 
  at 
  least, 
  in 
  the 
  ? 
  , 
  

   many 
  species 
  having 
  in 
  the 
  latter 
  sex 
  a 
  number 
  of 
  small 
  and 
  weak 
  

   spina?. 
  In 
  the 
  Alucitids 
  w 
  r 
  e 
  find 
  that, 
  in 
  numerous 
  species, 
  the 
  $ 
  has 
  

   a 
  single 
  spina, 
  as 
  in 
  the 
  $ 
  , 
  whilst 
  in 
  other 
  species 
  the 
  spina 
  is 
  double. 
  

   It, 
  therefore, 
  becomes 
  possible 
  to 
  divide 
  these 
  interesting 
  insects 
  into 
  

   two 
  groups 
  ; 
  those 
  in 
  which 
  the 
  spina 
  of 
  the 
  $ 
  is 
  single, 
  and 
  those 
  in 
  

   which 
  it 
  is 
  double. 
  The 
  measurements 
  of 
  the 
  spina, 
  given 
  below, 
  have 
  

   been 
  made 
  with 
  a 
  micrometer 
  ruled 
  to 
  hundredths 
  and 
  thousandths 
  of 
  

   an 
  inch, 
  and 
  those 
  for 
  the 
  length 
  have 
  been 
  made 
  under 
  a 
  Zeiss 
  A.A. 
  

   object 
  glass, 
  whilst 
  those 
  for 
  diameter 
  have 
  been 
  carefully 
  made 
  under 
  

   a 
  Zeiss 
  C 
  objective. 
  It 
  may 
  be, 
  however, 
  that 
  differences 
  may 
  occur 
  

   both 
  in 
  length 
  and 
  thickness 
  of 
  the 
  spina 
  in 
  individual 
  specimens, 
  there- 
  

   fore 
  the 
  comparison 
  of 
  these 
  details 
  might 
  not 
  in 
  all 
  cases 
  be 
  sustained 
  

   if 
  a 
  large 
  number 
  of 
  examples 
  were 
  examined. 
  Where 
  the 
  spina 
  of 
  the 
  

  

  * 
  Walsingham 
  also 
  observes 
  (op. 
  cit.) 
  that 
  " 
  the 
  first 
  plumule 
  of 
  the 
  hindwings 
  

   does 
  not 
  'become 
  wider 
  from 
  the 
  base 
  to 
  the 
  tip,' 
  as 
  asserted 
  by 
  Walker, 
  and 
  there 
  

   is 
  more 
  than 
  one 
  small 
  squamous 
  tuft 
  on 
  the 
  posterior 
  lobes 
  of 
  the 
  hindwings." 
  

  

  