﻿398 
  

  

  LNNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  19 
  29 
  

  

  Since 
  the 
  wing 
  is 
  a 
  double-walled 
  fold 
  projecting 
  from 
  the 
  body, 
  its 
  

   basal 
  part 
  (fig. 
  12) 
  is 
  two-layered, 
  one 
  layer 
  being 
  continuous 
  with 
  the 
  

   tergal 
  wall 
  of 
  the 
  segment, 
  the 
  other 
  with 
  the 
  pleural 
  wall. 
  The 
  axil- 
  

   lary 
  scierites 
  are 
  contained 
  in 
  this 
  articular 
  region. 
  On 
  the 
  humeral 
  

   angle 
  of 
  the 
  latter 
  is 
  a 
  small 
  lobe 
  (tg), 
  in 
  some 
  insects 
  developed 
  into 
  a 
  

   scale 
  overlapping 
  the 
  wing 
  base, 
  and 
  known 
  as 
  the 
  tegula. 
  The 
  pos- 
  

   terior 
  part 
  of 
  the 
  wing 
  base 
  is 
  membranous, 
  and 
  its 
  posterior 
  border 
  is 
  

   thickened 
  and 
  corrugated, 
  giving 
  the 
  appearance 
  of 
  a 
  marginal 
  liga- 
  

   ment, 
  or 
  axillary 
  cord 
  

  

  W- 
  n 
  I 
  \nmr~7/''^''y^^ 
  {AxC), 
  continued 
  

  

  from 
  the 
  posterior 
  

   angle 
  of 
  the 
  tergum 
  

   a 
  varying 
  distance 
  

   into 
  the 
  posterior 
  

   margin 
  of 
  the 
  wing. 
  

   The 
  ventral 
  sup- 
  

   port 
  of 
  the 
  wing 
  is 
  the 
  

   same 
  in 
  all 
  insects, 
  

   consisting 
  of 
  the 
  

   pleural 
  wing 
  process 
  

   (fig. 
  13, 
  WP) 
  which 
  

   rises 
  from 
  the 
  pleural 
  

   wall 
  of 
  the 
  segment 
  

   and 
  forms 
  a 
  fulcrum 
  

   for 
  the 
  wing 
  base. 
  

   In 
  insects 
  that 
  have 
  

   axillary 
  scierites, 
  the 
  

   second 
  axillary 
  {2 
  Ax) 
  

   rests 
  directly 
  upon 
  

   the 
  wing 
  process. 
  

   Lying 
  in 
  the 
  mem- 
  

   brane 
  beneath 
  the 
  

   wing 
  base, 
  anterior 
  

   and 
  posterior 
  to 
  the 
  

   fulcrum, 
  are 
  usually 
  

   two 
  scierites 
  {Ba, 
  Sa) 
  

   intimately 
  associated 
  

   with 
  the 
  wing. 
  The 
  

   first 
  is 
  ih.Q 
  hasalare 
  {Ba), 
  the 
  second 
  the 
  subalare 
  (Sa). 
  Both 
  scierites 
  

   are 
  derived, 
  not 
  from 
  the 
  wing, 
  but 
  from 
  the 
  upper 
  edge 
  of 
  the 
  pleural 
  

   wall, 
  and 
  in 
  some 
  adult 
  insects 
  the 
  basal 
  are 
  remains 
  as 
  a 
  partly 
  detached 
  

   lobe 
  of 
  the 
  latter. 
  These 
  two 
  epipleural 
  plates 
  are 
  important 
  elements 
  

   of 
  the 
  wing 
  mechanism, 
  for, 
  as 
  we 
  shall 
  see, 
  they 
  form 
  insertion 
  points 
  

   for 
  two 
  large 
  wing 
  muscles. 
  The 
  basalare 
  is 
  connected 
  by 
  a 
  ligamentous 
  

  

  Figure 
  13. 
  — 
  Diagram 
  of 
  the 
  pleural 
  elements 
  of 
  the 
  wing 
  mechanism, 
  

   left 
  side 
  of 
  a 
  segment, 
  o, 
  Membranous 
  connection 
  of 
  basalar 
  sclerite 
  

   (Ba) 
  with 
  anterior 
  angle 
  of 
  wing 
  base; 
  Aph, 
  anterior 
  phragma; 
  3 
  Ax, 
  

   ventral 
  plate 
  of 
  second 
  axillary; 
  b, 
  membranous 
  connection 
  of 
  subalar 
  

   sclerite 
  (i>a) 
  with 
  second 
  axillary 
  (2 
  Ax); 
  Ba, 
  basalare; 
  Cx, 
  coxa; 
  E, 
  

   pleural 
  muscle 
  of 
  basalare; 
  M', 
  coxai 
  muscle 
  of 
  basalare; 
  M", 
  coxal 
  

   muscle 
  of 
  subalare; 
  PIS, 
  pleural 
  suture; 
  PN, 
  postnotum; 
  Pph, 
  pos- 
  

   terior 
  phragma; 
  Sa, 
  subalare; 
  W, 
  base 
  of 
  wing, 
  elevated; 
  WP, 
  pleura 
  

   wing 
  process 
  

  

  