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  XI. 
  Scent-organs 
  in 
  the 
  genus 
  Hydroptila 
  (Trichoptera). 
  

   By 
  Maktin 
  E. 
  Mosely, 
  F.E.S. 
  

  

  [Read 
  October 
  15th, 
  1919.] 
  

  

  Plates 
  XVIII 
  and 
  XIX. 
  

  

  Scent-organs 
  in 
  the 
  Trichoptera 
  have 
  so 
  far 
  attracted 
  

   but 
  httle 
  attention, 
  and 
  there 
  are 
  few 
  references 
  to 
  them 
  

   in 
  the 
  writings 
  of 
  entomologists. 
  

  

  Packard 
  in 
  his 
  " 
  Textbook 
  of 
  Entomology," 
  p. 
  198, 
  

   refers 
  to 
  the 
  presence 
  of 
  scent-scales 
  on 
  the 
  wing 
  of 
  Mysta- 
  

   cides 
  punctata. 
  Scales, 
  or 
  thickened 
  hairs, 
  are 
  found 
  

   abundantly 
  in 
  the 
  male 
  sex 
  on 
  the 
  maxillary 
  palpi 
  and 
  in 
  

   certain 
  areas 
  of 
  the 
  wings 
  in 
  some 
  genera 
  of 
  the 
  Serico- 
  

   stomatidae, 
  notably 
  Lepidostoma, 
  Silo, 
  and 
  Goera, 
  and 
  

   they 
  are 
  also 
  to 
  be 
  found 
  on 
  the 
  wings 
  of 
  certain 
  species 
  

   of 
  Setodes, 
  Bercea, 
  Glossosoma 
  and 
  others. 
  

  

  In 
  Sericostoma 
  the 
  inner 
  surfaces 
  of 
  the 
  maxillary 
  palpi 
  

   of 
  the 
  (^ 
  are 
  densely 
  clothed 
  with 
  masses 
  of 
  yellowish 
  hairs 
  

   or 
  " 
  fluff." 
  It 
  is 
  suggested 
  that 
  these 
  hairs 
  form 
  part 
  of 
  

   a 
  system 
  for 
  the 
  distribution 
  of 
  scent. 
  A 
  full 
  description 
  

   of 
  the 
  palpi 
  is 
  given 
  by 
  Bruce 
  F. 
  Cummings 
  in 
  the 
  

   Proceedings 
  of 
  the 
  Zoological 
  Society 
  of, 
  London, 
  1914, 
  

   pp. 
  459-474, 
  and 
  reference 
  made 
  to 
  them 
  by 
  W. 
  Mliller, 
  

   " 
  Archiv. 
  f. 
  Naturgesch." 
  1887, 
  pp. 
  95-97. 
  "l 
  have 
  failed 
  

   to 
  find 
  further 
  references 
  to 
  scent-organs 
  in 
  the 
  Trichoptera. 
  

  

  In 
  Hydroptila 
  the 
  patterns 
  of 
  scent-organ 
  are 
  varied. 
  

   In 
  some 
  species 
  there 
  are 
  two 
  eversible, 
  tubular 
  filaments, 
  

   clothed 
  with 
  golden 
  yellow 
  or 
  else 
  black 
  scent-hairs 
  

   (PL 
  XVIII, 
  figs. 
  5 
  and 
  6; 
  PI. 
  XIX, 
  fig. 
  9); 
  in 
  another 
  

   species 
  there 
  are 
  four, 
  without 
  any 
  hairs 
  at 
  all 
  (PL 
  XVIII, 
  

   figs. 
  1, 
  2, 
  and 
  3). 
  The 
  tubular 
  filaments 
  are 
  probably 
  

   everted 
  by 
  the 
  action 
  of 
  fluid 
  pressure. 
  In 
  some 
  species 
  

   scent-scales 
  are 
  present 
  ; 
  in 
  others, 
  they 
  have 
  not 
  as 
  yet 
  

   been 
  made 
  out. 
  The 
  scent-organ 
  may 
  consist 
  of 
  a 
  mem- 
  

   brane 
  at 
  the 
  back 
  of 
  the 
  lobes, 
  which 
  form 
  so 
  distinctive 
  

   a 
  feature 
  of 
  the 
  genus. 
  The 
  membrane 
  is 
  capable 
  of 
  consid- 
  

   erable 
  dilatation 
  and 
  carries 
  a 
  few 
  battledore 
  scent-scales 
  on 
  

  

  TRANS. 
  ENT. 
  SOC. 
  LOND. 
  1919. 
  — 
  PARTS 
  HI, 
  IV. 
  (DEC.) 
  

  

  