﻿94 
  Dr. 
  G. 
  C. 
  Crampton's 
  Notes 
  on 
  the 
  Ancestry 
  of 
  the 
  

  

  section 
  the 
  fore-wings 
  are 
  frequently 
  better 
  developed 
  

   than 
  the 
  hind 
  ones. 
  Long 
  cerci 
  (and 
  in 
  the 
  males 
  of 
  some, 
  

   styli 
  also) 
  are 
  present 
  in 
  many 
  of 
  the 
  insects 
  belonging 
  to 
  

   the 
  Plecopteron 
  section 
  ; 
  while 
  in 
  the 
  insects 
  belonging 
  to 
  

   the 
  Neuropteron 
  section 
  they 
  are 
  wanting 
  or 
  vestigial 
  as 
  

   a 
  rule, 
  and 
  in 
  the 
  latter 
  insects 
  the 
  plates 
  bearing 
  the 
  cerci 
  

   (" 
  paraprocts 
  " 
  or 
  parapodial 
  plates) 
  are 
  usually 
  greatly 
  

   modified 
  or 
  united 
  with 
  the 
  terminal 
  segments 
  of 
  the 
  

   abdomen 
  ; 
  while 
  in 
  the 
  insects 
  of 
  the 
  Plecopteron 
  group 
  

   they 
  are 
  usually 
  distinct 
  and 
  well 
  developed. 
  Gonopod- 
  

   like 
  {i. 
  e. 
  forceps-hke) 
  genitalia 
  are 
  never 
  found 
  in 
  the 
  

   males 
  of 
  the 
  Plecopteron 
  section 
  thus 
  far 
  examined, 
  while 
  

   this 
  type 
  of 
  genitalia 
  does 
  occur 
  in 
  the 
  males 
  of 
  some 
  of 
  

   the 
  Neuropteron 
  section. 
  The 
  type 
  of 
  metamorphosis 
  

   (or 
  lack 
  thereof) 
  exhibited 
  by 
  a 
  group 
  of 
  insects 
  is 
  a 
  matter 
  

   of 
  minor 
  importance 
  in 
  the 
  study 
  of 
  relationships, 
  since 
  in 
  

   some 
  famihes 
  of 
  insects 
  such, 
  for 
  example, 
  as 
  the 
  Coccidae, 
  

   the 
  males 
  undergo 
  a 
  metamorphosis 
  while 
  the 
  females 
  of 
  

   the 
  same 
  species 
  do 
  not. 
  It 
  may 
  be 
  stated, 
  however, 
  that 
  

   with 
  the 
  exception 
  of 
  the 
  Coleoptera, 
  etc., 
  the 
  insects 
  

   belonging 
  to 
  the 
  Plecopteron 
  section 
  do 
  not 
  exhibit 
  a 
  

   marked 
  metamorphosis 
  ; 
  while 
  many 
  of 
  the 
  insects 
  of 
  the 
  

   Neuropteron 
  section 
  (excepting 
  the 
  Psocidae, 
  Hemiptera, 
  

   etc.) 
  exhibit 
  a 
  marked 
  tendency 
  in 
  this 
  direction. 
  

  

  So 
  httle 
  is 
  known 
  of 
  the 
  anatomical 
  details 
  of 
  the 
  extinct 
  

   fossil 
  insects 
  called 
  Palaeodictyoptera 
  (which 
  have 
  departed 
  

   but 
  httle 
  from 
  the 
  ancestral 
  condition 
  of 
  winged 
  insects 
  in 
  

   general) 
  that 
  it 
  is 
  impossible 
  to 
  determine 
  their 
  closest 
  

   affinities. 
  I 
  beheve, 
  however, 
  that 
  the 
  very 
  ancient 
  

   though 
  somewhat 
  aberrant 
  orders 
  Plectoptera 
  (Ephemerida) 
  

   and 
  Odonata, 
  among 
  recent 
  insects, 
  are 
  more 
  closely 
  related 
  

   to 
  certain 
  Palaeodictyoptera 
  than 
  they 
  are 
  to 
  either 
  the 
  

   Neuropteron 
  section 
  or 
  the 
  Plecopteron 
  section, 
  and 
  I 
  would 
  

   therefore 
  provisionally 
  include 
  the 
  Plectoptera 
  (Epheme- 
  

   rida) 
  and 
  the 
  Odonata 
  with 
  the 
  Palaeodictyoptera 
  (and 
  

   related 
  fossil 
  forms) 
  in 
  a 
  third 
  section 
  of 
  winged 
  insects 
  

   called 
  the 
  Plectopteradelphia 
  or 
  Ephemerid 
  " 
  brother- 
  

   hood," 
  which 
  will 
  be 
  referred 
  to 
  as 
  the 
  Ephemerid 
  section, 
  

   or 
  group, 
  in 
  the 
  following 
  discussion. 
  

  

  In 
  most 
  (if 
  not 
  all) 
  of 
  the 
  members 
  of 
  the 
  Ephemerid 
  

   section 
  the 
  wings 
  cannot 
  be 
  folded 
  along 
  the 
  abdomen 
  (a 
  

   very 
  primitive 
  condition), 
  and 
  the 
  wing 
  venation 
  has 
  

   departed 
  but 
  httle 
  from 
  the 
  original 
  condition 
  in 
  many 
  

   members 
  of 
  this 
  group. 
  Indications 
  of 
  a 
  shifting 
  of 
  the 
  

  

  