﻿HOW 
  INSECTS 
  FLY 
  SNODGRASS 
  417 
  

  

  The 
  hawk 
  moths 
  made 
  a 
  speed 
  up 
  to 
  15 
  meters 
  a 
  second, 
  followed 
  

   closely 
  by 
  Tabanus 
  hovinus 
  going 
  at 
  a 
  rate 
  of 
  14 
  meters. 
  A 
  dragon 
  

   fly 
  {Lihellula 
  depressa), 
  doing 
  ordinarily 
  4 
  meters 
  n 
  second, 
  can 
  

   make 
  6 
  to 
  10 
  meters 
  in 
  the 
  same 
  time 
  when 
  flying 
  rapidly. 
  A 
  house 
  

   fly 
  travels 
  from 
  2 
  to 
  2.3 
  meters 
  a 
  second; 
  a 
  bumblebee 
  (Bombus) 
  

   from 
  3 
  to 
  5. 
  The 
  honeybee, 
  Demoll 
  says, 
  when 
  flying 
  unladen 
  from 
  

   the 
  hive, 
  has 
  a 
  speed 
  of 
  3.7 
  meters 
  a 
  second, 
  but 
  on 
  the 
  return, 
  if 
  

   loaded 
  with 
  pollen, 
  its 
  speed 
  is 
  cut 
  down 
  to 
  2.5 
  meters 
  for 
  the 
  same 
  

   unit 
  of 
  time. 
  Tlie 
  pollen 
  load 
  of 
  the 
  bee, 
  according 
  to 
  Demoll, 
  weighs 
  

   about 
  20 
  milligrams, 
  wliich 
  is 
  approximately 
  30 
  per 
  cent 
  of 
  the 
  body 
  

   weight 
  of 
  the 
  bee. 
  

  

  The 
  ability 
  merely 
  to 
  progress 
  through 
  the 
  a,ir 
  is 
  not 
  efficient 
  

   flight. 
  The 
  smaller 
  grasshoppers 
  leap 
  into 
  the 
  air 
  and 
  sustain 
  them- 
  

   selves 
  for 
  some 
  distance 
  by 
  movements 
  of 
  the 
  wings, 
  but 
  they 
  have 
  

   small 
  power 
  of 
  dii-ecting 
  their 
  course 
  after 
  they 
  leave 
  the 
  ground. 
  

   Some 
  of 
  the 
  migratory 
  locusts 
  ascend 
  to 
  great 
  heights 
  and 
  go 
  long 
  

   distances 
  on 
  the 
  wing, 
  but 
  they 
  are 
  probably 
  dependent 
  largely 
  on 
  

   the 
  wind 
  for 
  transportation. 
  The 
  Carolina 
  locust 
  is 
  a 
  better 
  flyer, 
  

   but 
  its 
  course 
  on 
  the 
  wing, 
  though 
  more 
  or 
  less 
  directive, 
  appears 
  

   to 
  be 
  rather 
  haphazard. 
  Real 
  flight 
  involves 
  the 
  ability 
  to 
  steer 
  a 
  

   definite 
  course, 
  and 
  to 
  turn 
  this 
  way 
  or 
  that 
  as 
  exigencies 
  demand. 
  

   By 
  this 
  test 
  the 
  majority 
  of 
  insects 
  are 
  expert 
  flyers, 
  and 
  we 
  need 
  

   only 
  observe 
  a 
  dragon 
  fly 
  foraging 
  for 
  smaller 
  insects 
  over 
  the 
  water, 
  

   one 
  of 
  the 
  smaller 
  horseflies 
  dodging 
  rhe 
  ineffectual 
  counter 
  strokes 
  

   of 
  its 
  intended 
  victim, 
  or 
  a 
  hawk 
  moth 
  poised 
  in 
  the 
  air 
  as 
  it 
  extracts 
  

   the 
  nectar 
  from 
  the 
  depths 
  of 
  a 
  corolla, 
  to 
  realize 
  how 
  adroitly 
  insects 
  

   can 
  make 
  use 
  of 
  their 
  wings 
  in 
  controlling 
  their 
  flight. 
  

  

  Insects 
  are 
  not 
  provided 
  with 
  rudders. 
  There 
  is 
  little 
  evidence 
  

   that 
  they 
  use 
  their 
  bodies 
  or 
  their 
  legs 
  to 
  direct 
  or 
  alter 
  their 
  course 
  

   while 
  in 
  the 
  aii\ 
  Stellwaag 
  (1916), 
  who 
  has 
  made 
  a 
  special 
  study 
  of 
  

   the 
  steering 
  powers 
  of 
  insects, 
  points 
  out 
  that 
  if 
  directive 
  flight 
  were 
  

   accomplished 
  by 
  movements 
  of 
  the 
  legs 
  or 
  the 
  abdomen, 
  these 
  m-ove- 
  

   ments 
  could 
  be 
  detected 
  in 
  the 
  more 
  slowly 
  flj'^ing 
  species, 
  whereas, 
  

   in 
  fact, 
  no 
  such 
  movements 
  are 
  either 
  visible 
  by 
  close 
  inspection 
  or 
  

   can 
  be 
  detected 
  by 
  mechanical 
  devices. 
  Shadowgraphs 
  of 
  flying 
  

   insects, 
  he 
  says, 
  record 
  no 
  alteration 
  in 
  the 
  position 
  of 
  the 
  body 
  or 
  of 
  

   the 
  legs 
  during 
  a 
  change 
  in 
  the 
  direction 
  of 
  flight. 
  Observations 
  on 
  

   insects 
  held 
  in 
  a 
  pair 
  of 
  tweezers 
  and 
  tm'ned 
  at 
  various 
  angles 
  also 
  

   failed 
  to 
  show 
  compensatory 
  movements 
  in 
  the 
  body 
  or 
  appendages. 
  

   Finafly, 
  Stellwaag 
  resorted 
  to 
  experimentation 
  on 
  living 
  insects 
  

   impaled 
  on 
  slender 
  pins 
  thrust 
  vertically 
  through 
  the 
  thorax. 
  Insects 
  

   thus 
  secured 
  vibrate 
  the 
  wings 
  as 
  in 
  flight 
  and 
  revolve 
  to 
  the 
  right 
  or 
  

   the 
  left 
  on 
  the 
  axis 
  of 
  the 
  pin, 
  w^hether 
  the 
  latter 
  is 
  held 
  vertical 
  or 
  

   inclined, 
  but 
  the 
  turning 
  is 
  never 
  accompanied 
  by 
  movements 
  of 
  the 
  

  

  