﻿HOW 
  INSECTS 
  FLY 
  SNODGRASS 
  

  

  397 
  

  

  articulated 
  by 
  a 
  longitudinal 
  hinge 
  to 
  the 
  edge 
  of 
  the 
  terguni 
  (T). 
  Its 
  

   anterior 
  end 
  is 
  curved 
  outward 
  and 
  usually 
  is 
  connected 
  with 
  the 
  base 
  

   of 
  the 
  subcostal 
  vein 
  {Sc). 
  The 
  second 
  axillary 
  {2 
  Ax) 
  lies 
  distal 
  to 
  the 
  

   first, 
  and 
  is 
  obliquely" 
  hinged 
  to 
  the 
  outer 
  edge 
  of 
  the 
  latter. 
  This 
  scle- 
  

   rite 
  is 
  the 
  pivotal 
  plate 
  of 
  the 
  wing 
  base 
  since 
  its 
  ventral 
  surface 
  rests 
  

   upon 
  the 
  pleural 
  wing 
  process. 
  (Fig. 
  13, 
  WP.) 
  The 
  radial 
  vein 
  

   (fig. 
  12, 
  R) 
  is 
  flexibly 
  attached 
  to 
  its 
  outer 
  end, 
  and 
  the 
  point 
  of 
  union 
  

   (d) 
  constitutes 
  the 
  principal 
  hinge 
  of 
  the 
  anterior 
  part 
  of 
  the 
  wing 
  with 
  

   the 
  axillar}" 
  elements. 
  The 
  third 
  axillary 
  (3 
  Ax) 
  lies 
  posterior 
  to 
  the 
  

   other 
  two 
  with 
  its 
  long 
  axis 
  transverse. 
  Its 
  proximal 
  end 
  articulates 
  

  

  t^ 
  HP 
  2 
  Ax 
  bf 
  

  

  Rm 
  

  

  / 
  / 
  \ 
  \ 
  

  

  PNP 
  AxC 
  3Ax 
  jf 
  

  

  Figure 
  12. 
  — 
  Diagram 
  of 
  basnl 
  structure 
  of 
  wing 
  in 
  wing-flexing 
  insects. 
  ANP, 
  Anterior 
  notal 
  

   wing 
  process; 
  I 
  Ax, 
  SAi, 
  SAx, 
  first, 
  second, 
  and 
  third 
  axillaries; 
  AxC, 
  axillary 
  cord; 
  6, 
  articula- 
  

   tion 
  of 
  third 
  axillary 
  with 
  terguni; 
  bf, 
  basal 
  fold 
  of 
  wing, 
  plica 
  basalis; 
  C, 
  costa; 
  c, 
  distal 
  end 
  

   of 
  third 
  axillary; 
  ICxi, 
  first 
  cubitus; 
  2Cu, 
  second 
  cubitus; 
  D, 
  flexor 
  muscle; 
  d, 
  articulation 
  of 
  

   radius 
  with 
  second 
  axillary; 
  e, 
  articulation 
  of 
  subcosta 
  with 
  first 
  axillary;/, 
  articulation 
  of 
  third 
  

   axillary 
  with 
  second 
  axillary; 
  HP, 
  humeral 
  plate; 
  ;/, 
  jugal 
  fold 
  of 
  wing, 
  plica 
  jugalis; 
  Ju, 
  jugal 
  

   region; 
  M, 
  media; 
  to, 
  proximal 
  median 
  plate; 
  to', 
  distal 
  median 
  plate; 
  n 
  V, 
  last 
  vannal 
  vein; 
  

   PNP, 
  posterior 
  notal 
  wing 
  process; 
  R, 
  radius; 
  Rm, 
  remigial 
  part 
  of 
  wing; 
  Sc, 
  subcosta; 
  T, 
  

   tergum; 
  tg, 
  rudiment 
  of 
  tegula; 
  V, 
  vaiuial 
  part 
  of 
  wing; 
  IV, 
  2 
  V-n 
  V, 
  first 
  to 
  last 
  vannal 
  veins; 
  

   vf, 
  vannal 
  fold 
  of 
  wing, 
  plica 
  vannalis 
  

  

  with 
  the 
  tergum, 
  and 
  its 
  distal 
  extremity 
  supports 
  the 
  bases^of 
  the 
  

   posterior 
  group 
  of 
  wing 
  veins 
  {V). 
  A 
  process 
  on 
  the 
  basal 
  part 
  of 
  the 
  

   third 
  axillary 
  gives 
  insertion 
  to 
  a 
  muscle 
  (D) 
  which 
  arises 
  on 
  the 
  lateral 
  

   wall 
  of 
  the 
  segment. 
  The 
  third 
  axillary 
  and 
  its 
  muscle 
  constitute 
  

   the 
  motor 
  elements 
  in 
  the 
  flexor 
  mechanism 
  of 
  the 
  ^\dng. 
  When 
  a 
  

   iourth 
  axillary 
  is 
  present 
  it 
  intervenes 
  between 
  the 
  base 
  of 
  the 
  third 
  

   and 
  the 
  tergum. 
  In 
  the 
  distal 
  part 
  of 
  the 
  axillary 
  region 
  there 
  are 
  

   usually 
  on'e 
  or 
  more 
  accessory 
  median 
  "plates 
  (m, 
  m') 
  associated 
  with 
  

   the 
  bases 
  of 
  the 
  median 
  and 
  cubital 
  veins. 
  The 
  median 
  plates 
  are 
  

   more 
  variable 
  than 
  the 
  well-defined 
  axillaries; 
  the 
  proximal 
  one 
  (m) 
  

   is 
  usually 
  attached 
  to 
  the 
  distal 
  part 
  of 
  the 
  third 
  axillary. 
  

  

  