﻿PEOCEEDINGS 
  OF 
  THE 
  I'OUIITH 
  ENTOMOLOGICAL 
  MEETING 
  371 
  

  

  acts 
  previously 
  suggested 
  to 
  him 
  by 
  the 
  operator 
  as 
  being 
  appropriate 
  

   under 
  the 
  circumstances. 
  

  

  In 
  dealing 
  with 
  the 
  application 
  of 
  this 
  analogy 
  to 
  the 
  case 
  of 
  insects, 
  

   we 
  may 
  leave 
  on 
  one 
  side 
  the 
  problem 
  of 
  defining 
  precisely 
  what 
  corres- 
  

   ponds 
  to 
  the 
  " 
  operator." 
  Though 
  naturally 
  essential 
  to 
  a 
  proper 
  

   understanding 
  of 
  insect 
  psychology, 
  the 
  answer 
  to 
  this 
  question 
  need 
  

   not 
  necessarily 
  afEect 
  the 
  matter 
  as 
  viewed 
  from 
  the 
  practical 
  stand- 
  

   point. 
  " 
  Analogy," 
  as 
  has 
  been 
  safely 
  remarked, 
  " 
  is 
  not 
  the 
  same 
  

   thing 
  as 
  homology," 
  but 
  taking 
  the 
  hypnotic 
  idea 
  as 
  a 
  working 
  basis, 
  

   the 
  cardinal 
  point 
  is 
  the 
  limitation 
  or 
  specialization 
  of 
  the 
  insect's 
  

   receptivity 
  to 
  a 
  few 
  particular 
  stimuli 
  which 
  will 
  in 
  very 
  many 
  cases 
  

   be 
  found 
  to 
  be 
  quite 
  narrowly 
  defined. 
  It 
  is 
  this 
  limitation 
  or 
  narrowly 
  

   defined 
  specialization, 
  still 
  partly 
  hypothetical 
  but 
  already 
  ascertained 
  

   definitely 
  in 
  a 
  few 
  instances, 
  and 
  indicated 
  to 
  my 
  mind 
  in 
  very 
  many 
  

   others, 
  which 
  promise 
  most 
  from 
  the 
  practical 
  point 
  of 
  view. 
  The 
  

   more 
  narrowly 
  defined 
  the 
  stimulus 
  which 
  regulates 
  any 
  particular 
  

   activity 
  of 
  an 
  insect, 
  the 
  less 
  difiicult 
  it 
  will 
  be 
  to 
  take 
  advantage 
  of 
  it 
  

   or 
  to 
  neutralize 
  its 
  action. 
  In 
  this 
  connection 
  the 
  experiment 
  of 
  Vers- 
  

   chaffelt, 
  who 
  found 
  that 
  the 
  larva3 
  of 
  the 
  common 
  white 
  butterfly, 
  Pieris 
  

   brassiccB, 
  which 
  ordinarily 
  feed 
  upon 
  leaves 
  of 
  Cruciferce, 
  are 
  swayed 
  

   in 
  their 
  choice 
  of 
  food 
  not 
  by 
  the 
  fact 
  of 
  whether 
  the 
  food 
  offered 
  them 
  

   is 
  or 
  is 
  not 
  a 
  portion 
  of 
  a 
  cruciferous 
  plant, 
  but 
  simply 
  by 
  the 
  presence 
  

   or 
  absence 
  of 
  a 
  group 
  of 
  chemical 
  compounds 
  (the 
  mustard 
  oils), 
  is 
  

   of 
  extreme 
  interest, 
  and 
  is 
  in 
  a 
  direct 
  line 
  of 
  research 
  likely 
  to 
  afford 
  

   results 
  of 
  the 
  highest 
  economic 
  importance. 
  

  

  Observations 
  of 
  my 
  own 
  on 
  the 
  influence 
  of 
  certain 
  smells 
  on 
  male 
  

   fruit 
  flies 
  have 
  shown 
  that 
  ChcBtodacus 
  diversus 
  is 
  most 
  strongly 
  attracted 
  

   by 
  any 
  substance 
  which 
  contains 
  iso-eugenol, 
  while 
  Ch. 
  zonatus 
  and 
  

   Ch. 
  fernigineus 
  can 
  in 
  the 
  same 
  way 
  be 
  controlled 
  in 
  their 
  movements 
  

   to 
  a 
  remarkable 
  extent 
  by 
  the 
  use 
  of 
  the 
  allied 
  substance 
  methyl- 
  

   eugenol. 
  Whether 
  these 
  smells 
  characterize 
  the 
  females 
  of 
  these 
  

   species, 
  or 
  whether 
  they 
  are 
  sign-posts 
  leading 
  to 
  a 
  particular 
  plant 
  

   or 
  fruit, 
  has 
  not 
  yet 
  been 
  definitely 
  ascertained 
  ; 
  the 
  value 
  of 
  the 
  

   ■ 
  observation 
  lies 
  in 
  the 
  specific 
  character 
  of 
  the 
  reaction 
  to 
  particular 
  

   compounds. 
  An 
  interesting 
  sequence 
  to 
  the 
  identification 
  of 
  these 
  

   attractive 
  compounds 
  was 
  the 
  fact 
  that 
  by 
  exposing 
  eugenol, 
  a 
  

   substance 
  closely 
  allied 
  to 
  the 
  two 
  already 
  mentioned, 
  I 
  discovered 
  

   an 
  entirely 
  new 
  species 
  of 
  fruit 
  fly, 
  which 
  was 
  thus 
  enticed 
  from 
  out 
  of 
  

   the 
  unknown 
  by 
  a 
  calculated 
  appeal 
  to 
  a 
  hypothetical 
  olfactory 
  sus- 
  

   ceptibility. 
  

  

  Other 
  flies 
  have 
  been 
  found 
  to 
  respond 
  in 
  a 
  more 
  or 
  less 
  similar 
  way 
  

   to 
  the 
  smells 
  of 
  acetic, 
  butyric 
  and 
  valeric 
  acids. 
  As 
  these 
  acids 
  aye 
  

  

  