﻿392 
  

  

  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  The 
  general 
  wing 
  mechanism, 
  including 
  the 
  muscles 
  that 
  generate 
  

   and 
  regulate 
  the 
  wing 
  movements, 
  will 
  be 
  described 
  in 
  following 
  sec- 
  

   tions. 
  To 
  understand 
  how 
  the 
  motor 
  elements 
  give 
  the 
  essential 
  

   movements 
  of 
  flight 
  to 
  the 
  wings, 
  it 
  will 
  be 
  necessary 
  first 
  to 
  know 
  

   something 
  of 
  the 
  structure 
  of 
  the 
  wings 
  themselves 
  and 
  the 
  details 
  of 
  

   their 
  connections 
  with 
  the 
  body. 
  The 
  principal 
  features 
  of 
  the 
  wings 
  

   are 
  the 
  veins, 
  the 
  articulation 
  to 
  the 
  body, 
  the 
  flexor 
  apparatus, 
  and 
  

   the 
  differentiation 
  of 
  the 
  wing 
  area 
  into 
  special 
  regions 
  in 
  insects 
  that 
  

   flex 
  the 
  wings. 
  

  

  The 
  iving 
  veins. 
  — 
  The 
  wings 
  of 
  adult 
  insects 
  are 
  thin, 
  membranous 
  

   extensions 
  of 
  the 
  body 
  wall 
  strengthened 
  by 
  the 
  riblike 
  thickenings 
  

   known 
  as 
  veins. 
  (Fig. 
  10.) 
  The 
  principal 
  veins 
  of 
  each 
  wing 
  spring 
  

   from 
  the 
  wing 
  base 
  and 
  branch 
  in 
  varying 
  degrees 
  in 
  the 
  distal 
  parts 
  

   of 
  the 
  wing. 
  The 
  work 
  of 
  many 
  entomologists 
  has 
  shown 
  that, 
  under- 
  

   lying 
  the 
  great 
  diversity 
  of 
  vein 
  pattern 
  in 
  the 
  numerous 
  groups 
  of 
  

   insects, 
  there 
  is 
  evidently 
  one 
  fundamental 
  plan 
  of 
  wing 
  venation. 
  

   All 
  winged 
  insects, 
  therefore, 
  would 
  appear 
  to 
  be 
  derived 
  from 
  one 
  

  

  primitive 
  stock 
  

   that 
  evolved 
  the 
  

   paranotal 
  lobes 
  in- 
  

   to 
  movable 
  organs 
  

   of 
  flight. 
  

  

  The 
  system 
  of 
  

   naming 
  the 
  prin- 
  

   cipal 
  veins 
  now 
  

   commonly 
  adopted, 
  

   with 
  a 
  few 
  altera- 
  

   tions, 
  by 
  nearly 
  all 
  

   entomologists 
  is 
  

   that 
  worked 
  out 
  

   by 
  Comstock 
  and 
  Needham, 
  shown 
  diagrammatically 
  in 
  Figure 
  10 
  A. 
  

   The 
  first 
  vein 
  is 
  the 
  costa 
  (C) 
  ; 
  it 
  usually 
  forms 
  the 
  anterior 
  margin 
  of 
  

   the 
  wing, 
  but 
  sometimes 
  it 
  is 
  submarginal. 
  The 
  second 
  vein 
  is 
  the 
  

   subcosta 
  (Sc), 
  typically 
  forked 
  into 
  two 
  short 
  branches. 
  The 
  third 
  

   vein 
  is 
  the 
  radius 
  (R), 
  usuall}^ 
  the 
  strongest 
  vein 
  of 
  the 
  wing; 
  distally 
  

   it 
  forks 
  near 
  the 
  middle 
  of 
  the 
  wing, 
  and 
  the 
  posterior 
  prong 
  (Rs) 
  

   breaks 
  up 
  into 
  four 
  branches. 
  The 
  fo\irth 
  vein 
  is 
  the 
  media 
  (M), 
  

   forked 
  dichotomously 
  into 
  four 
  principal 
  branches. 
  The 
  fifth 
  vein 
  is 
  

   the 
  cubitus 
  (Cu), 
  with 
  two 
  branches. 
  The 
  rest 
  of 
  the 
  wing 
  veins, 
  

   according 
  to 
  the 
  Comstock-Needham 
  system 
  of 
  vein 
  nomenclature, 
  

   are 
  the 
  anal 
  veins, 
  distinguished 
  as 
  the 
  jfirst 
  anal 
  (lA), 
  second 
  anal 
  

   (2A), 
  etc. 
  

  

  There 
  are 
  certain 
  objections 
  to 
  including 
  all 
  the 
  veins 
  posterior 
  to 
  

   the 
  cubitus 
  under 
  the 
  one 
  term 
  "anal." 
  In 
  the 
  first 
  place, 
  the 
  so- 
  

   called 
  first 
  anal 
  is 
  foimd 
  to 
  be 
  in 
  some 
  cases 
  a 
  basal 
  branch 
  of 
  the 
  cub- 
  

  

  FiGURE 
  9. 
  — 
  A 
  May 
  fly, 
  a 
  member 
  of 
  the 
  order 
  Ephemerida 
  

   rest 
  the 
  wings 
  are 
  folded 
  vertically 
  over 
  the 
  back 
  

  

  When 
  at 
  

  

  