﻿402 
  ANNUAL 
  report: 
  SMITHSONIAN 
  INSTITUTION, 
  192"? 
  

  

  Therefore, 
  the 
  results 
  of 
  experiments 
  judged 
  by 
  our 
  own 
  color 
  per- 
  

   ception 
  are 
  likely 
  to 
  lead 
  to 
  erroneous 
  conclusions 
  concerning 
  the 
  

   color 
  vision 
  of 
  insects. 
  

  

  General 
  experiments 
  on 
  the 
  perception 
  of 
  light 
  or 
  other 
  stimuli 
  

   by 
  animals 
  give 
  us 
  little 
  more 
  than 
  a 
  basis 
  for 
  estimating 
  the 
  func- 
  

   tional 
  limits 
  of 
  the 
  receptive 
  and 
  sensory 
  faculties; 
  they 
  do 
  not 
  tell 
  

   us 
  in 
  most 
  cases 
  anything 
  concerning 
  the 
  nature 
  of 
  the 
  nervous 
  

   mechanism 
  that 
  produces 
  the 
  reaction. 
  By 
  a 
  more 
  circumscribed 
  type 
  

   of 
  experimentation, 
  a 
  group 
  of 
  investigators 
  interested 
  particularly 
  

   in 
  understanding 
  the 
  response 
  of 
  the 
  organism 
  have 
  sought 
  for 
  evi- 
  

   dence 
  concerning 
  the 
  nature 
  of 
  the 
  relations 
  between 
  the 
  sense 
  organs 
  

   and 
  the 
  muscles 
  that 
  control 
  the 
  reaction. 
  The 
  strictly 
  mechanical 
  

   theory 
  of 
  tropisms, 
  as 
  proposed 
  by 
  Loeb, 
  assumes 
  that 
  the 
  animal 
  

   goes 
  toward 
  or 
  away 
  from 
  the 
  source 
  of 
  a 
  stimulus 
  by 
  the 
  continuous 
  

   action 
  of 
  the 
  stimulus 
  operating 
  alike 
  on 
  both 
  sides 
  of 
  the 
  bilaterally 
  

   symmetrical 
  body. 
  The 
  behavior 
  of 
  many 
  animals, 
  of 
  insects 
  particu- 
  

   larly, 
  appears 
  to 
  be 
  closely 
  in 
  accord 
  with 
  the 
  terms 
  of 
  this 
  theory. 
  

   One 
  of 
  the 
  most 
  convincing 
  pieces 
  of 
  evidence 
  in 
  favor 
  of 
  it 
  in 
  

   entomology 
  is 
  the 
  well-known 
  fact 
  that 
  an 
  insect 
  after 
  having 
  one 
  eye 
  

   covered 
  with 
  an 
  opaque 
  substance 
  progresses 
  or 
  turns 
  in 
  circles 
  in 
  

   the 
  directions 
  of 
  the 
  open 
  eye. 
  Some 
  investigators 
  have 
  found, 
  how- 
  

   ever, 
  that 
  these 
  " 
  circus 
  movements 
  " 
  are 
  not 
  invariable 
  in 
  all 
  cases 
  

   where 
  an 
  insect's 
  sight 
  is 
  made 
  unilateral, 
  and 
  that 
  some 
  species 
  that 
  

   turn 
  in 
  circles 
  at 
  first, 
  after 
  a 
  time 
  learn 
  to 
  orient 
  themselves 
  fairly 
  

   well 
  with 
  one 
  eye 
  only. 
  If 
  the 
  light 
  entering 
  either 
  eye 
  affects 
  

   directly 
  the 
  movements 
  of 
  the 
  legs 
  on 
  that 
  side 
  of 
  the 
  body, 
  the 
  

   response 
  should 
  be 
  observable 
  if 
  the 
  insect 
  is 
  held 
  up 
  with 
  its 
  legs 
  

   free. 
  Experiments 
  made 
  by 
  Mast 
  on 
  flies 
  suspended 
  by 
  the 
  wings, 
  

   however, 
  showed 
  that 
  a 
  varying 
  light 
  stimulusi 
  produces 
  no 
  reaction 
  

   in 
  the 
  legs. 
  From 
  this 
  and 
  many 
  other 
  experiments 
  on 
  the 
  behavior 
  

   of 
  insects 
  exposed 
  to 
  controlled 
  light 
  stimuli. 
  Mast 
  concludes 
  that 
  

   any 
  hypothesis 
  "that 
  demands 
  balanced 
  action 
  in 
  the 
  receptors 
  and 
  

   locomotor 
  appendages 
  on 
  opposite 
  sides 
  does 
  not 
  fully 
  account 
  for 
  

   orientation 
  in 
  insects." 
  He 
  believes 
  that 
  there 
  is 
  a 
  differential 
  effect 
  

   of 
  the 
  stimulus 
  in 
  the 
  eyes 
  and 
  that 
  orientation 
  in 
  insects 
  is 
  de- 
  

   pendent 
  on 
  a 
  series 
  of 
  coordinated 
  reflexes 
  more 
  complex 
  than 
  that 
  

   assumed 
  by 
  the 
  theory 
  of 
  direct 
  <ropistic 
  action. 
  

  

  The 
  blowfly 
  maggot 
  has 
  been 
  used 
  by 
  several 
  investigators 
  as 
  a 
  

   subject 
  for 
  studying 
  the 
  method 
  by 
  which 
  an 
  insect 
  orients 
  itself 
  to 
  

   light. 
  When 
  the 
  maggot 
  crawls 
  it 
  proceeds 
  by 
  a 
  series 
  of 
  alternating 
  

   stretchings 
  and 
  contractions, 
  while 
  the 
  anterior 
  end 
  of 
  the 
  body 
  is 
  

   swayed 
  regularly 
  from 
  side 
  to 
  side. 
  The 
  maggot 
  has 
  no 
  eyes, 
  but 
  its 
  

   anterior 
  end 
  is 
  very 
  sensitive 
  to 
  light; 
  its 
  usual 
  responses 
  are 
  nega- 
  

   tive. 
  Herms, 
  Mast, 
  and 
  Holmes 
  have 
  argued 
  that 
  the 
  sidewise 
  move- 
  

  

  