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  V. 
  Notes 
  on 
  the 
  Ancestry 
  of 
  the 
  Diptera, 
  Hemiptera 
  and 
  

   other 
  Insects 
  related 
  to 
  the 
  Neuroptera.* 
  By 
  G. 
  

   Chester 
  Crampton, 
  Ph.D. 
  Communicated 
  by 
  

   G. 
  T. 
  Bethune-Baker, 
  F.L.S., 
  F.Z.S. 
  

  

  [Read 
  March 
  5th, 
  1919.] 
  

  

  The 
  greater 
  part 
  of 
  winged 
  insects 
  now 
  living 
  may 
  be 
  

   grouped 
  into 
  two 
  principal 
  sections, 
  one 
  of 
  which, 
  the 
  

   so-called 
  Plecopteradelphia, 
  or 
  Plecopteron 
  " 
  brother- 
  

   hood," 
  contains 
  the 
  lower 
  insects 
  more 
  closely 
  related 
  to 
  

   the 
  Plecoptera 
  — 
  such 
  as 
  the 
  Blattoid 
  superorder 
  (Blaltidae, 
  

   Mantidae, 
  Isoptera, 
  Zoraptera, 
  etc.), 
  the 
  Orthopteroid 
  

   superorder 
  (saltatorial 
  Orthoptera, 
  Phasmidae, 
  Grylloblat- 
  

   tidae, 
  etc.), 
  and 
  the 
  Plecopteroid 
  superorder 
  (Plecoptera, 
  

   Embiidae, 
  Dermaptera, 
  Coleoptera, 
  etc.), 
  together 
  with 
  their 
  

   fossil 
  relatives 
  ; 
  while 
  the 
  second 
  section, 
  the 
  so-called 
  

   Neuropteradelphia, 
  or 
  Neuropteron 
  " 
  brotherhood," 
  

   contains 
  the 
  higher 
  insects, 
  more 
  closely 
  related 
  to 
  the 
  

   Neuroptera 
  — 
  such 
  as 
  the 
  Psocidse, 
  Mallophaga, 
  Pedicu- 
  

   lidae, 
  Hemiptera, 
  Hymenoptera, 
  Diptera, 
  Mecoptera, 
  

   Trichoptera, 
  Lepidoptera, 
  Neuroptera, 
  etc., 
  with 
  their 
  

   fossil 
  relatives. 
  In 
  the 
  following 
  discussion 
  the 
  two 
  

   sections 
  described 
  above 
  may 
  be 
  referred 
  to 
  simply 
  as 
  the 
  

   Plecopteron 
  section 
  (or 
  group) 
  and 
  the 
  Neuropteron 
  section 
  

   (or 
  group). 
  

  

  It 
  would 
  be 
  extremely 
  difficult 
  to 
  find 
  any 
  features 
  

   peculiar 
  to 
  all 
  of 
  the 
  members 
  of 
  one 
  section, 
  and 
  not 
  

   occurring 
  in 
  any 
  members 
  of 
  the 
  other 
  section; 
  but 
  it 
  

   may 
  be 
  said 
  of 
  most 
  of 
  the 
  insects 
  belonging 
  to 
  the 
  Pleco- 
  

   pteron 
  section, 
  that 
  their 
  mouthparts 
  are 
  usually 
  strongly 
  

   mandibulate 
  and 
  well 
  developed; 
  while 
  in 
  the 
  insects 
  

   belonging 
  to 
  the 
  Neuropteron 
  section, 
  the 
  mouthparts 
  of 
  

   many 
  are 
  slender 
  and 
  greatly 
  modified. 
  In 
  many 
  of 
  the 
  

   insects 
  of 
  the 
  Plecopteron 
  group 
  there 
  is 
  a 
  marked 
  tendency 
  

   toward 
  the 
  reduction 
  (and, 
  in 
  some 
  cases, 
  of 
  a 
  thickening) 
  

   of 
  the 
  fore-wings 
  ; 
  while 
  in 
  the 
  insects 
  of 
  the 
  Neuropteron 
  

  

  * 
  Contribution 
  from 
  the 
  Entomological 
  Laboratory 
  of 
  the 
  

   Massachusetts 
  Agricultural 
  College, 
  Amherst, 
  Mass. 
  

  

  TRANS. 
  ENT. 
  SOC. 
  LOND. 
  1919. 
  — 
  PARTS 
  I, 
  II. 
  (JULY) 
  

  

  