﻿MIND 
  OF 
  AN 
  INSECT 
  SNODGRASS 
  403 
  

  

  merits 
  of 
  the 
  head 
  end 
  of 
  the 
  fly 
  larva 
  allow 
  the 
  creature 
  to 
  perceive 
  

   differences 
  in 
  the 
  intensity 
  of 
  light 
  at 
  different 
  angles; 
  by 
  avoiding 
  

   the 
  stronger 
  sensations 
  as 
  much 
  as 
  possible, 
  therefore, 
  the 
  maggot, 
  

   when 
  once 
  set 
  in 
  motion 
  by 
  the 
  light 
  stimulus, 
  crawls 
  automatically 
  

   away 
  from 
  the 
  light 
  source. 
  This 
  conception 
  of 
  the 
  mechanism 
  of 
  

   orientation 
  substitutes 
  for 
  the 
  idea 
  of 
  the 
  mechanical 
  effect 
  of 
  a 
  

   continuous 
  action 
  of 
  the 
  stimulus 
  the 
  idea 
  of 
  the 
  perception 
  of 
  a 
  

   change 
  of 
  intensity 
  in 
  the 
  stimulus 
  and 
  a 
  regulation 
  of 
  movements 
  

   accordingly. 
  As 
  Holmes 
  states 
  it, 
  "of 
  a 
  number 
  of 
  random 
  move- 
  

   ments 
  in 
  all 
  directions, 
  only 
  those 
  are 
  followed 
  up 
  which 
  bring 
  the 
  

   animal 
  out 
  of 
  the 
  undesirable 
  situation." 
  

  

  It 
  is 
  difficult 
  to 
  avoid 
  injecting 
  the 
  idea 
  of 
  conscious 
  perception 
  into 
  

   the 
  interpretation 
  of 
  experiments 
  on 
  differential 
  perception, 
  but, 
  as 
  

   Bouvier 
  points 
  out, 
  this 
  less 
  direct 
  form 
  of 
  orientation 
  toward 
  or 
  

   away 
  from 
  a 
  stimulus 
  may 
  be 
  seen 
  as 
  but 
  an 
  automatic 
  response 
  

   resulting 
  from 
  a 
  combination 
  of 
  tropisms 
  and 
  differential 
  sensitivity. 
  

   The 
  facts 
  observed 
  in 
  such 
  cases 
  are 
  characteristic 
  of 
  all 
  members 
  of 
  

   a 
  species; 
  there 
  is 
  no 
  individuality 
  of 
  response, 
  no 
  alteration 
  of 
  it 
  

   from 
  experience. 
  

  

  REACTION 
  TO 
  HEAT 
  (THERMOTROPISM) 
  

  

  Insects 
  are 
  definitely 
  responsive 
  to 
  changes 
  in 
  temperature, 
  but 
  

   their 
  thermic 
  reactions 
  are 
  probably 
  caused 
  by 
  the 
  physiological 
  effect 
  

   of 
  heat 
  in 
  their 
  tissues, 
  since 
  insects 
  are 
  not 
  known 
  to 
  have 
  specifia 
  

   temperature 
  receptive 
  organs. 
  Because 
  insects 
  have 
  no 
  means 
  of 
  con- 
  

   serving 
  the 
  heat 
  produced 
  in 
  their 
  bodies, 
  the 
  continuance 
  of 
  their 
  

   metabolic 
  processes 
  depends 
  upon 
  heat 
  received 
  from 
  the 
  outside, 
  

   and 
  therefore 
  insects 
  in 
  general 
  are 
  most 
  active 
  in 
  warm 
  weather 
  or 
  

   where 
  they 
  find 
  artificial 
  heat. 
  The 
  small 
  size 
  of 
  their 
  bodies 
  makes 
  

   insects 
  particularly 
  subject 
  to 
  loss 
  of 
  heat 
  by 
  radiation, 
  for 
  the 
  smaller 
  

   the 
  animal 
  the 
  greater 
  in 
  proportion 
  is 
  the 
  extent 
  of 
  its 
  exposed 
  

   surface. 
  If 
  an 
  insect 
  had 
  to 
  keep 
  warm 
  all 
  the 
  time 
  it 
  would 
  exhaust 
  

   itself 
  by 
  eating, 
  for 
  Kennedy 
  has 
  calculated 
  that 
  if 
  an 
  insect 
  con- 
  

   sumed 
  a 
  quantity 
  of 
  energy-forming 
  food 
  the 
  same 
  in 
  proportion 
  to 
  

   its 
  surface 
  exposure 
  as 
  that 
  consumed 
  by 
  a 
  mouse 
  or 
  a 
  man 
  it 
  would 
  

   have 
  to 
  eat 
  six 
  and 
  one-fourth 
  times 
  its 
  weight 
  in 
  food 
  every 
  day. 
  

   This 
  law 
  of 
  inverse 
  relation 
  between 
  size 
  and 
  heat 
  radiation, 
  how- 
  

   ever, 
  is 
  modified 
  by 
  many 
  other 
  factors 
  ; 
  otherwise 
  we 
  should 
  find 
  the 
  

   larger 
  insects 
  active 
  at 
  lower 
  temperatures 
  than 
  the 
  smaller 
  ones. 
  

   The 
  activity 
  of 
  different 
  species, 
  in 
  fact, 
  shows 
  a 
  considerable 
  range 
  

   of 
  tolerance 
  to 
  low 
  temperatures, 
  irrespective 
  of 
  size; 
  many 
  very 
  

   small 
  flies 
  appear 
  early 
  in 
  spring 
  before 
  the 
  end 
  of 
  cold 
  weather, 
  

   and 
  the 
  moths 
  of 
  the 
  fall 
  cankerworms 
  emerge 
  from 
  the 
  ground 
  to 
  

   lay 
  their 
  eggs 
  late 
  in 
  the 
  fall 
  or 
  early 
  in 
  winter 
  at 
  northern 
  latitudes. 
  

  

  