﻿270 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  arisen 
  from 
  lateral 
  continuations 
  of 
  the 
  dorsal 
  plates 
  of 
  the 
  body-seg- 
  

   ments 
  with 
  which 
  they 
  are 
  connected." 
  

  

  Now, 
  speculating 
  on 
  the 
  primary 
  origin 
  of 
  wings, 
  we 
  need 
  not 
  sup- 
  

   pose 
  that 
  they 
  originated 
  in 
  any 
  aquatic 
  form, 
  but 
  in 
  some 
  ancestral 
  

   land 
  insect 
  related 
  to 
  existing 
  cockroaches 
  and 
  Termes. 
  We 
  may 
  imag- 
  

   ine 
  that 
  the 
  tergites 
  (or 
  notum) 
  of 
  the 
  two 
  hinder 
  segments 
  of 
  the 
  

   thorax 
  grew 
  out 
  laterally 
  in 
  some 
  leaping 
  and 
  running 
  insect; 
  that 
  the 
  

   expansion 
  became 
  of 
  use 
  in 
  aiding 
  to 
  support 
  the 
  body 
  in 
  its 
  longer 
  

   leaps, 
  somewhat 
  as 
  the 
  lateral 
  expansions 
  of 
  the 
  body 
  aid 
  the 
  flying 
  

   squirrel 
  or 
  certain 
  lizards 
  in 
  supporting 
  the 
  body 
  during 
  their 
  leaps. 
  

   By 
  natural 
  selection 
  these 
  structures 
  would 
  be 
  transmitted 
  in 
  an 
  im- 
  

   proved 
  condition 
  until 
  they 
  became 
  flexible, 
  i. 
  e., 
  attached 
  by 
  a 
  rude 
  hinge- 
  

   joint 
  to 
  the 
  tergal 
  plates 
  of 
  the 
  meso- 
  and 
  metathorax. 
  Then 
  by 
  contin- 
  

   ued 
  use 
  and 
  attempts 
  at 
  flight 
  they 
  would 
  grow 
  larger, 
  until 
  they 
  would 
  

   become 
  permanent 
  organs, 
  though 
  still 
  rudimentary, 
  as 
  in 
  many 
  existing 
  

   Orthoptera, 
  such 
  as 
  certain 
  Blattarise 
  and 
  Pezotettix. 
  By 
  this 
  time 
  a 
  

   fold 
  or 
  hinge 
  having 
  been 
  established, 
  small 
  chitinous 
  pieces 
  inclosed 
  

   in 
  membrane 
  would 
  appear, 
  until 
  we 
  should 
  have 
  a 
  hinge 
  flexible 
  enough 
  

   to 
  allow 
  the 
  wing 
  to 
  be 
  folded 
  on 
  the 
  back, 
  and 
  also 
  to 
  have 
  a 
  flap- 
  

   ping 
  motion. 
  A 
  stray 
  tracheal 
  twig 
  would 
  naturally 
  press 
  or 
  grow 
  into 
  

   the 
  base 
  of 
  the 
  new 
  structure. 
  After 
  the 
  trachea 
  running 
  towards 
  the 
  

   base 
  of 
  the 
  wing 
  had 
  begun 
  to 
  send 
  off 
  branches 
  into 
  the 
  rudiment- 
  

   ary 
  structure, 
  the 
  number 
  and 
  direction 
  of 
  the 
  future 
  veins 
  would 
  be- 
  

   come 
  determined 
  on 
  simple 
  mechanical 
  principles. 
  The 
  rudimentary 
  

   structures 
  beating 
  the 
  air 
  would 
  need 
  to 
  be 
  strengthened 
  on 
  the 
  front 
  

   or 
  costal 
  edge. 
  Here, 
  then, 
  would 
  be 
  developed 
  the 
  larger 
  number 
  of 
  

   main 
  veins, 
  two 
  or 
  three 
  close 
  together, 
  and 
  parallel. 
  These 
  would 
  be 
  

   the 
  costal, 
  subcostal, 
  and 
  median 
  veins. 
  They 
  would 
  throw 
  out 
  branches 
  

   to 
  strengthen 
  the 
  costal 
  edge, 
  while 
  the 
  branches 
  sent 
  out 
  to 
  the 
  outer 
  

   and 
  hinder 
  edges 
  of 
  the 
  wings 
  might 
  be 
  less 
  numerous 
  and 
  farther 
  

   apart. 
  The 
  net-veined 
  wings 
  of 
  Orthoptera 
  and 
  Pseudoneuroptera, 
  as. 
  

   compared 
  with 
  the 
  wings 
  of 
  Hymenoptera, 
  show 
  that 
  the 
  wings 
  of 
  net- 
  

   veined 
  insects 
  were 
  largely 
  used 
  for 
  respiration 
  as 
  well 
  as 
  for 
  flight, 
  

   while 
  in 
  beetles 
  and 
  bees 
  the 
  leading 
  function 
  is 
  flight, 
  that 
  of 
  respi- 
  

   ration 
  being 
  quite 
  subordinate. 
  The 
  blood 
  would 
  then 
  supply 
  the 
  parts,, 
  

   and 
  thus 
  respiration 
  or 
  aeration 
  of 
  the 
  blood 
  would 
  be 
  demanded. 
  As 
  

   soon 
  as 
  such 
  expansions 
  would 
  be 
  of 
  even 
  slight 
  use 
  to 
  the 
  insect 
  as 
  

   breathing 
  organs, 
  the 
  question 
  as 
  to 
  their 
  permanency 
  would 
  be 
  settled. 
  

   Organs 
  so 
  useful 
  both 
  for 
  flight 
  and 
  aeration 
  of 
  the 
  blood 
  would 
  be 
  still 
  

   further 
  developed, 
  until 
  they 
  would 
  become 
  permanent 
  structures, 
  genu- 
  

   ine 
  wings. 
  Thej 
  would 
  thus 
  be 
  readil^^ 
  transmitted, 
  and 
  being 
  of 
  more 
  

   use 
  in 
  adult 
  life 
  during 
  the 
  season 
  of 
  reproduction, 
  they 
  would 
  be 
  still 
  

   further 
  developed, 
  and 
  thus 
  those 
  insects 
  which 
  could 
  fly 
  the 
  best, 
  i. 
  e.,. 
  

   which 
  had 
  the 
  largest 
  wings, 
  would 
  be 
  most 
  successful 
  in 
  the 
  struggle 
  

   for 
  existence. 
  Thus 
  also, 
  not 
  being 
  so 
  much 
  needed 
  in 
  larval 
  life 
  before 
  

   the 
  reproductive 
  organs 
  are 
  developed, 
  they 
  would 
  not 
  be 
  transmitted 
  

  

  