﻿492 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  voi,. 
  98 
  

  

  is 
  the 
  only 
  species 
  in 
  the 
  "Biologia" 
  whose 
  generic 
  position 
  has 
  been 
  

   determined 
  by 
  this 
  method. 
  

  

  Subsequently 
  it 
  has 
  been 
  generally 
  agreed 
  that 
  the 
  characters 
  of 
  

   the 
  male 
  genitalia 
  may 
  be 
  used 
  successfully 
  to 
  distinguish 
  Ceresa 
  and 
  

   Siictocephala, 
  but 
  there 
  are 
  no 
  practical 
  applications 
  of 
  this 
  principle 
  

   in 
  any 
  published 
  works. 
  Van 
  Duzee 
  (1908, 
  pp. 
  41^2) 
  objected 
  to 
  the 
  

   use 
  of 
  the 
  characters 
  of 
  the 
  male 
  genitalia 
  for 
  distinguishing 
  the 
  genera 
  

   but 
  admitted 
  that 
  the 
  present 
  basis 
  of 
  separation 
  is 
  "purely 
  artificial" 
  

   and 
  that 
  "the 
  two 
  genera 
  run 
  into 
  one 
  another 
  by 
  insensible 
  grada- 
  

   tions," 
  while 
  Lawson 
  (1922, 
  p. 
  40) 
  has 
  suggested 
  that 
  "the 
  genus 
  

   Siictocephala 
  should 
  be 
  divided, 
  for 
  the 
  genitalia 
  of 
  S. 
  festina 
  and 
  

   S. 
  lutea 
  cannot 
  possibly 
  belong 
  to 
  members 
  of 
  the 
  same 
  genus," 
  

   Thus 
  the 
  idea 
  has 
  been 
  developed 
  that 
  the 
  division 
  between 
  Ceresa 
  

   and 
  Siictocephala 
  and 
  the 
  composition 
  of 
  Siictocephala 
  itself, 
  as 
  they 
  

   now 
  stand, 
  are 
  artificial 
  and 
  should 
  be 
  modified 
  to 
  form 
  a 
  more 
  

   natural 
  arrangement. 
  The 
  genus 
  Siiciolobus 
  Metcalf 
  (1916) 
  is 
  of 
  

   comparative 
  recent 
  erection; 
  therefore, 
  it 
  escaped 
  comment 
  in 
  the 
  

   earlier 
  publications, 
  and 
  it 
  was 
  not 
  represented 
  in 
  the 
  fauna 
  treated 
  

   by 
  Lawson. 
  

  

  In 
  extending 
  the 
  investigation 
  of 
  correlation 
  of 
  genital 
  and 
  pronotal 
  

   characters 
  to 
  include 
  all 
  the 
  Nearctic 
  Ceresini 
  it 
  has 
  been 
  found 
  that 
  

   the 
  internal 
  male 
  genitalia 
  of 
  the 
  species 
  of 
  Ceresa, 
  Siictocephala, 
  and 
  

   Stictolohus 
  form 
  natural 
  or 
  similar 
  groups 
  not 
  coincident 
  with 
  the 
  

   divisions 
  based 
  upon 
  pronotal 
  characters. 
  It 
  is 
  apparent 
  that 
  in 
  this 
  

   group 
  of 
  Ceresini 
  a 
  condition 
  has 
  been 
  developed 
  that 
  has 
  resulted 
  in 
  

   much 
  confusion 
  between 
  superficial 
  and 
  basic 
  relationships, 
  and 
  it 
  

   would 
  seem 
  that 
  our 
  present 
  interpretations 
  of 
  generic 
  and 
  specific 
  

   relationships 
  have 
  been 
  greatly 
  influenced 
  by 
  the 
  anterior 
  pronotal 
  

   characters 
  (e. 
  g., 
  the 
  metopidium 
  and 
  suprahumerals) 
  , 
  which 
  in 
  the 
  

   majority 
  of 
  cases 
  probably 
  have 
  little 
  real 
  phylogenetic 
  significance. 
  

  

  Funkhouser 
  (1917, 
  p. 
  314) 
  has 
  expressed 
  his 
  belief 
  that 
  the 
  anterior 
  

   pronotal 
  characters 
  are 
  primarily 
  specific 
  in 
  value 
  and, 
  in 
  reviewing 
  

   the 
  possibility 
  of 
  using 
  genital 
  characters 
  for 
  classification 
  of 
  the 
  

   Membracidae 
  in 
  general, 
  states 
  (p. 
  353) 
  : 
  

  

  Occasional 
  attempts 
  have 
  been 
  made 
  to 
  use 
  the 
  internal 
  male 
  genitalia 
  for 
  

   systematic 
  purposes, 
  but 
  with 
  little 
  success. 
  It 
  is 
  not 
  unreasonable 
  to 
  believe, 
  

   however, 
  that 
  these 
  structures, 
  which 
  have 
  proved 
  of 
  so 
  much 
  value 
  in 
  other 
  

   groups 
  of 
  insects, 
  should 
  be 
  equally 
  distinctive 
  in 
  the 
  Membracidae 
  if 
  the 
  charac- 
  

   ters 
  are 
  patiently 
  diagnosed 
  for 
  a 
  large 
  number 
  of 
  genera. 
  It 
  may 
  naturally 
  be 
  

   supposed 
  that 
  sexual 
  organs 
  undergo 
  less 
  change 
  when 
  insects 
  are 
  forced 
  into 
  new 
  

   conditions 
  and 
  environments 
  than 
  do 
  motor 
  or 
  protective 
  structures, 
  and, 
  being 
  

   less 
  plastic, 
  would 
  preserve 
  their 
  characters 
  and 
  readily 
  yield 
  themselves 
  to 
  generic 
  

   classifications. 
  A 
  tentative 
  study 
  has 
  seemed 
  to 
  show 
  that 
  this 
  is 
  indeed 
  the 
  case. 
  

   The 
  organs 
  have 
  become 
  modified 
  in 
  form 
  and 
  have 
  developed 
  various 
  types 
  of 
  

   claspers, 
  styles, 
  and 
  prongs, 
  but 
  the 
  necessity 
  of 
  retaining 
  the 
  function 
  of 
  the 
  

   organs 
  has 
  kept 
  these 
  modifications 
  within 
  bounds. 
  

  

  