﻿384 
  AJSTNUAL 
  REPORT 
  SMITHSONIAN 
  IIS^STITUTION, 
  1929 
  

  

  The 
  wings 
  of 
  insects 
  are 
  organs 
  sui 
  generis, 
  which 
  is 
  to 
  say, 
  there 
  is 
  

   nothing 
  else 
  exactly 
  like 
  them. 
  In 
  fact, 
  it 
  may 
  be 
  claimed 
  that 
  insects 
  

   are 
  the 
  only 
  animals 
  that 
  possess 
  true 
  wings. 
  The 
  wings 
  of 
  a 
  bird, 
  

   or 
  the 
  wings 
  of 
  a 
  bat 
  are 
  merely 
  the 
  fore 
  legs 
  of 
  the 
  animal 
  made 
  over 
  

   for 
  purposes 
  of 
  flying; 
  the 
  flying 
  fishes 
  ghde 
  through 
  the 
  air 
  on 
  their 
  

   pectoral 
  fins, 
  but 
  these 
  organs 
  also 
  are 
  the 
  fore 
  hmbs, 
  which 
  were 
  

   modified 
  primarily 
  for 
  swimming; 
  the 
  flying 
  mammals 
  are 
  equipped 
  

   with 
  folds 
  of 
  skin 
  along 
  the 
  sides 
  of 
  the 
  body, 
  which 
  enable 
  them 
  to 
  

   extend 
  their 
  leaps 
  from 
  one 
  tree 
  to 
  another, 
  but 
  such 
  dermal 
  expan- 
  

   sions 
  are 
  parachutes 
  rather 
  than 
  organs 
  of 
  true 
  flight. 
  

  

  I. 
  THE 
  ORIGIN 
  OF 
  INSECT 
  WINGS 
  

  

  Insects 
  are 
  among 
  the 
  oldest 
  of 
  all 
  animals 
  that 
  have 
  living 
  repre- 
  

   sentatives 
  on 
  the 
  earth 
  to-day. 
  Their 
  earliest 
  fossil 
  remains 
  that 
  have 
  

   been 
  found 
  occur 
  in 
  the 
  rocks 
  of 
  the 
  geologic 
  period 
  commonly 
  known 
  

   as 
  the 
  Carboniferous, 
  which, 
  according 
  to 
  present 
  methods 
  of 
  calcu- 
  

   lating 
  past 
  time, 
  may 
  have 
  been 
  laid 
  down 
  as 
  long 
  ago 
  as 
  300,000,000 
  

   years. 
  Mammals, 
  birds, 
  and 
  flowering 
  plants 
  did 
  not 
  then 
  exist, 
  and 
  

   such 
  reptiles 
  and 
  amphibians 
  as 
  were 
  contemporaneous 
  with 
  the 
  

   Carboniferous 
  insects 
  were 
  quite 
  different 
  creatures 
  from 
  their 
  

   modern 
  relatives. 
  Vegetation, 
  however, 
  was 
  abundant, 
  and 
  there 
  

   were 
  forests 
  of 
  tall 
  trees, 
  though 
  both 
  the 
  trees 
  and 
  the 
  plants 
  of 
  the 
  

   undergrowth 
  had 
  more 
  the 
  appearance 
  of 
  ferns 
  than 
  of 
  any 
  of 
  our 
  

   modern 
  kinds 
  of 
  plants, 
  except 
  the 
  few 
  species 
  directly 
  descended 
  from 
  

   Carboniferous 
  ancestors. 
  The 
  Carboniferous 
  forests 
  flourished 
  prin- 
  

   cipally 
  in 
  swampy 
  districts 
  and 
  around 
  the 
  edges 
  of 
  lagoons, 
  where, 
  as 
  

   a 
  result 
  of 
  the 
  subsidence 
  of 
  the 
  land, 
  masses 
  of 
  sodden 
  debris 
  and 
  

   fallen 
  tree 
  trunks 
  accumulated 
  through 
  long 
  ages, 
  and 
  have 
  produced 
  

   most 
  of 
  our 
  present 
  deposits 
  of 
  coal. 
  

  

  The 
  conditions 
  of 
  the 
  Carboniferous 
  swamp 
  forests 
  were 
  favorable 
  

   to 
  two 
  classes 
  of 
  insects, 
  namely, 
  insects 
  adapted 
  to 
  living 
  in 
  the 
  forests 
  

   themselves, 
  and 
  others 
  adapted 
  to 
  unhindered 
  flight 
  over 
  open 
  

   stretches 
  of 
  water. 
  A 
  review 
  of 
  the 
  known 
  Carboniferous 
  insects 
  

   shows 
  that 
  these 
  two 
  types 
  actually 
  predominated, 
  or 
  almost 
  exclu- 
  

   sively 
  made 
  up 
  the 
  insect 
  fauna 
  of 
  the 
  forests 
  and 
  swamps 
  of 
  that 
  

   time. 
  The 
  insects 
  of 
  the 
  first 
  class 
  consisted 
  principally 
  of 
  roaches 
  

   (fig. 
  1); 
  those 
  of 
  the 
  second 
  class 
  comprise 
  dragon 
  flies. 
  May 
  fly 
  like 
  

   insects, 
  and 
  insects 
  of 
  an 
  extinct 
  group 
  kno\vn 
  as 
  the 
  Paleodicty- 
  

   optera 
  (fig. 
  2 
  A). 
  It 
  is 
  very 
  doubtful, 
  however, 
  that 
  the 
  insects 
  

   known 
  from 
  the 
  Carboniferous 
  rocks 
  represent 
  anything 
  like 
  the 
  

   variety 
  of 
  insect 
  forms 
  that 
  existed 
  at 
  the 
  time 
  these 
  rocks 
  were 
  laid 
  

   down, 
  for 
  there 
  were 
  large 
  areas 
  of 
  open 
  country 
  on 
  both 
  continents 
  

   where 
  many 
  species 
  may 
  have 
  flourished 
  whose 
  remains 
  have 
  not 
  been 
  

   preserved. 
  

  

  