﻿408 
  

  

  ANNUAL 
  KEPOET 
  SMITHSONIAN 
  INSTITUTION, 
  1929 
  

  

  would 
  record 
  its 
  motions 
  on 
  the 
  paper. 
  Figure 
  21 
  shows 
  two 
  of 
  the 
  

   curves 
  obtained 
  by 
  Ritter 
  with 
  this 
  apparatus 
  when 
  the 
  head 
  of 
  the 
  

   fly 
  was 
  directed 
  opposite 
  the 
  movement 
  of 
  the 
  sliding 
  board. 
  The 
  

   lines 
  of 
  these 
  tracings, 
  therefore, 
  may 
  be 
  taken 
  to 
  show 
  the 
  track 
  

   described 
  by 
  the 
  wing 
  tips 
  in 
  normal 
  forward 
  flight. 
  Instead 
  of 
  

   making 
  a 
  figure 
  8, 
  the 
  wings 
  of 
  a 
  fly 
  in 
  motion 
  describe 
  a 
  series 
  of 
  

   open 
  loops 
  in 
  which 
  the 
  downstroke 
  takes 
  the 
  form 
  of 
  an 
  italic 
  curve 
  

   inclined 
  from 
  above 
  downward 
  and 
  forward, 
  while 
  the 
  reverse 
  stroke 
  

   goes 
  from 
  below 
  upward 
  and 
  posteriorly. 
  The 
  distance 
  between 
  

   the 
  loops 
  will 
  depend 
  on 
  the 
  speed 
  at 
  which 
  the 
  insect 
  flies. 
  The 
  

   rotary 
  movement 
  of 
  the 
  wings 
  is 
  most 
  accentuated 
  in 
  swift-flying 
  

   insects, 
  such 
  as 
  the 
  dragon 
  flies, 
  bees, 
  and 
  flies, 
  which 
  have 
  relatively 
  

  

  Figure 
  21.— 
  Curves 
  described 
  by 
  the 
  tip 
  of 
  a 
  blowfly's 
  wing 
  in 
  flight. 
  Tracings 
  

   made 
  by 
  the 
  tip 
  of 
  the 
  wing 
  of 
  a 
  fly 
  held 
  stationary 
  with 
  the 
  head 
  directed 
  toward 
  

   the 
  movement 
  of 
  the 
  recording 
  surface. 
  (From 
  Ritter, 
  1911) 
  

  

  narrow 
  wings; 
  in 
  slower-flying 
  insects 
  with 
  broad 
  wings, 
  such 
  as 
  the 
  

   grasshoppers 
  and 
  butterflies, 
  the 
  up-and-down 
  movement 
  is 
  the 
  

   principal 
  one. 
  

  

  That 
  the 
  movements 
  of 
  animals, 
  including 
  the 
  flight 
  of 
  insects, 
  

   could 
  be 
  studied 
  from 
  series 
  of 
  moving-picture 
  photographs 
  was 
  

   first 
  demonstrated 
  by 
  Marey 
  (1901). 
  With 
  more 
  improved 
  methods, 
  

   von 
  Lendenfeld 
  (1903), 
  Bull 
  (1904), 
  and 
  Voss 
  (1914) 
  have 
  obtained 
  

   cinematographic 
  records 
  giving 
  a 
  convincing 
  demonstration 
  of 
  the 
  

   nature 
  of 
  the 
  insect 
  wing 
  movements 
  in 
  flight. 
  Voss 
  made 
  calula- 
  

   tions 
  from 
  his 
  serial 
  pictures 
  of 
  the 
  number 
  of 
  wing 
  strokes 
  a 
  second 
  in 
  

   many 
  species 
  of 
  insects. 
  However, 
  much 
  of 
  interest 
  might 
  yet 
  be 
  

   done 
  by 
  this 
  method 
  of 
  research. 
  

  

  The 
  rapidity 
  of 
  the 
  wing 
  movements 
  varies 
  greatly 
  in 
  different 
  

   insects. 
  The 
  first 
  statements 
  concerning 
  the 
  rate 
  of 
  vibration 
  of 
  insect 
  

   wings 
  are 
  those 
  of 
  Landois 
  (1867) 
  deduced 
  from 
  observations 
  on 
  the 
  

   pitch 
  of 
  the 
  sound 
  made 
  by 
  insects 
  in 
  flight. 
  Landois 
  thus 
  estimated 
  

   that 
  the 
  house 
  fly 
  makes 
  352 
  wing 
  strokes 
  a 
  second, 
  a 
  bumblebee 
  220, 
  

  

  