﻿HOW 
  INSECTS 
  FLY 
  SNODGRASS 
  409 
  

  

  and 
  the 
  honeybee 
  440 
  when 
  at 
  its 
  best, 
  though 
  when 
  tired 
  its 
  hum 
  indi- 
  

   cates 
  a 
  wing 
  speed 
  of 
  only 
  330 
  beats 
  a 
  second. 
  By 
  the 
  same 
  test, 
  the 
  

   mosquito, 
  it 
  is 
  said, 
  must 
  make 
  as 
  high 
  as 
  600 
  wing 
  beats 
  a 
  second. 
  

   The 
  wing 
  movements 
  have 
  been 
  studied 
  also 
  with 
  mechanical 
  appa- 
  

   ratus 
  and 
  from 
  serial 
  photographs. 
  The 
  records 
  of 
  different 
  investi- 
  

   gators 
  differ 
  considerably, 
  but 
  it 
  must 
  be 
  recognized 
  that 
  experimental 
  

   results 
  give 
  at 
  best 
  only 
  the 
  rate 
  at 
  which 
  the 
  insect 
  moved 
  its 
  wings 
  

   under 
  the 
  conditions 
  of 
  the 
  experiment; 
  it 
  is 
  well 
  known 
  that 
  most 
  

   insects 
  can 
  vary 
  the 
  speed 
  of 
  their 
  normal 
  flight 
  within 
  wide 
  limits. 
  

   Marey 
  (1869a) 
  obtained 
  graphic 
  records 
  of 
  the 
  wing 
  beats 
  on 
  a 
  revolv- 
  

   ing 
  cylinder, 
  and 
  he 
  gives 
  330 
  wing 
  strokes 
  a 
  second 
  for 
  the 
  house 
  fly, 
  

   240 
  for 
  a 
  bumblebee, 
  190 
  for 
  the 
  honeybee, 
  110 
  for 
  a 
  wasp, 
  28 
  for 
  a 
  

   dragon 
  fly, 
  and 
  9 
  for 
  the 
  cabbage 
  butterfly. 
  Voss 
  (1914), 
  however, 
  

   calculating 
  the 
  rate 
  of 
  the 
  wing 
  mo'tion 
  from 
  series 
  of 
  moving-picture 
  

   photographs, 
  obtained 
  in 
  most 
  cases 
  lower 
  figures; 
  the 
  honeybee, 
  by 
  

   his 
  test, 
  making 
  180 
  to 
  203 
  wing 
  strokes 
  a 
  second, 
  the 
  house 
  fly 
  from 
  

   180 
  to 
  197, 
  the 
  mosquito 
  from 
  278 
  to 
  307, 
  while 
  various 
  other 
  insects 
  

   have 
  mostly 
  a 
  slower 
  rate. 
  In 
  general, 
  it 
  may 
  be 
  said, 
  the 
  flies 
  and 
  

   bees 
  have 
  the 
  highest 
  rate 
  of 
  wing 
  movement; 
  most 
  other 
  insects, 
  by 
  

   comparison, 
  being 
  slow 
  of 
  flight 
  and 
  correspondingly 
  slow 
  in 
  wing 
  

   motion. 
  The 
  lowest 
  records 
  of 
  %ving 
  speed 
  are 
  found 
  among 
  the 
  

   butterflies 
  and 
  moths, 
  the 
  cabbage 
  butterfly 
  making 
  at 
  best 
  about 
  9 
  

   strokes 
  a 
  second, 
  and 
  some 
  of 
  the 
  noctuid 
  moths 
  about 
  40 
  ; 
  the 
  sphinx 
  

   moths, 
  on 
  the 
  other 
  hand, 
  are 
  swift 
  flyers 
  and 
  move 
  the 
  wings 
  at 
  a 
  

   high 
  rate 
  of 
  speed. 
  The 
  reader 
  may 
  find 
  summarized 
  statements 
  on 
  

   the 
  recorded 
  rates 
  of 
  the 
  wing 
  strokes 
  in 
  insects 
  given 
  by 
  Voss 
  (1914) 
  

   and 
  by 
  Prochnow 
  (1921-1924). 
  

  

  The 
  movements 
  of 
  flexion 
  and 
  extension. 
  — 
  The 
  movements 
  by 
  which 
  

   the 
  wings 
  are 
  folded 
  after 
  flight, 
  or 
  extended 
  preliminary 
  to 
  flight, 
  are 
  

   executed 
  too 
  rapidly 
  to 
  be 
  observed 
  closely 
  in 
  a 
  living 
  insect 
  ; 
  but 
  the 
  

   action 
  of 
  a 
  wing 
  and 
  the 
  operation 
  of 
  the 
  flexor 
  mechanism 
  can 
  be 
  well 
  

   studied 
  in 
  freshly 
  killed 
  specimens. 
  A 
  grasshopper, 
  a 
  bee, 
  a 
  fly, 
  or 
  

   most 
  any 
  insect 
  sufficient!}^ 
  large 
  will 
  answer 
  the 
  purpose, 
  but 
  the 
  

   grasshopper, 
  or 
  particularly 
  the 
  scorpion 
  fly, 
  Panorpa, 
  will 
  be 
  found 
  to 
  

   be 
  a 
  very 
  suitable 
  subject. 
  If 
  the 
  wing 
  of 
  a 
  fresh 
  specimen 
  is 
  slowly 
  

   folded 
  posteriorly 
  over 
  the 
  back 
  and 
  then 
  brought 
  forward 
  into 
  the 
  

   position 
  of 
  flight, 
  the 
  accompanying 
  movements 
  of 
  the 
  articular 
  

   sclerites 
  on 
  one 
  another 
  can 
  be 
  observed, 
  and 
  from 
  their 
  action 
  the 
  

   probable 
  working 
  of 
  the 
  flexor 
  mechanism 
  in 
  the 
  living 
  insect 
  can 
  be 
  

   deduced. 
  

  

  First 
  we 
  must 
  look 
  again 
  at 
  the 
  plan 
  of 
  the 
  general 
  wing 
  structure. 
  

   (Figs. 
  14, 
  22 
  A.) 
  The 
  region 
  of 
  the 
  articular 
  sclerites, 
  or 
  axillaries, 
  

   forms 
  a. 
  triangle 
  at 
  the 
  base 
  of 
  the 
  wing 
  (Ax) 
  with 
  its 
  apex 
  (c) 
  sup- 
  

   porting 
  the 
  base 
  of 
  the 
  vannal 
  region 
  (V). 
  When 
  the 
  distal 
  parts 
  of 
  

   the 
  wing 
  are 
  well 
  differentiated, 
  the 
  vannus 
  is 
  usually 
  separated 
  from 
  

  

  