﻿MIND 
  OF 
  AN^ 
  INSECT 
  SNODGRASS 
  409 
  

  

  organs. 
  The 
  idea 
  of 
  radio 
  or 
  X-ray 
  communication 
  between 
  animals 
  

   is 
  absurd, 
  because 
  the 
  energy 
  waves 
  involved 
  are 
  produced 
  artificially 
  

   only 
  by 
  high-power 
  electrical 
  apparatus. 
  

  

  III. 
  INSTINCT 
  OF 
  INSECTS 
  

  

  That 
  the 
  complicated 
  instincts 
  of 
  insects 
  are 
  to 
  be 
  analyzed 
  into 
  

   series 
  of 
  coordinated 
  reflexes 
  has 
  been 
  shown 
  in 
  a 
  most 
  interesting 
  

   set 
  of 
  experiments 
  made 
  by 
  Miss 
  Isabel 
  McCracken 
  on 
  the 
  mating 
  and 
  

   egg-laying 
  habits 
  of 
  the 
  silkworm 
  moth 
  and 
  by 
  the 
  studies 
  of 
  S. 
  

   Kopec 
  on 
  the 
  gypsy 
  moth. 
  

  

  The 
  normal 
  habits 
  of 
  the 
  silkworm 
  moths 
  are 
  so 
  simple 
  that 
  the 
  

   insects 
  make 
  excellent 
  subjects 
  for 
  experimentation. 
  The 
  moths 
  live 
  

   for 
  about 
  two 
  weeks, 
  they 
  take 
  no 
  food, 
  and 
  their 
  only 
  important 
  

   instincts 
  are 
  those 
  of 
  mating 
  and 
  egg 
  laying. 
  They 
  do 
  not 
  fly, 
  they 
  

   do 
  not 
  object 
  to 
  being 
  handled, 
  and 
  they 
  make 
  no 
  effort 
  to 
  escape. 
  

   As 
  soon 
  as 
  the 
  adults 
  issue 
  from 
  the 
  cocoons 
  mating 
  takes 
  place 
  

   between 
  the 
  males 
  and 
  the 
  females, 
  and 
  the 
  latter 
  then 
  proceed 
  with 
  

   their 
  egg 
  laying, 
  depositing 
  during 
  the 
  next 
  12 
  to 
  72 
  hours, 
  accord- 
  

   ing 
  to 
  Miss 
  McCracken, 
  their 
  total 
  content 
  of 
  from 
  300 
  to 
  500 
  eggs. 
  

   The 
  eggs 
  are 
  not 
  all 
  laid 
  at 
  once, 
  but 
  in 
  several 
  sets 
  of 
  different 
  num- 
  

   bers 
  deposited 
  at 
  varying 
  intervals. 
  The 
  egg-laying 
  female 
  moves 
  

   the 
  end 
  of 
  her 
  bod}^, 
  or 
  " 
  ovipostor," 
  from 
  side 
  to 
  side, 
  and 
  the 
  

   eggs 
  are 
  placed 
  in 
  regular 
  transverse 
  rows, 
  being 
  stuck 
  to 
  the 
  sup- 
  

   porting 
  surface 
  by 
  a 
  liquid 
  cement 
  discharged 
  from 
  glands 
  opening 
  

   near 
  the 
  orifice 
  of 
  the 
  oviduct. 
  Unmated 
  females 
  lay 
  their 
  eggs 
  in 
  

   the 
  same 
  manner 
  as 
  do 
  the 
  mated 
  females, 
  but 
  they 
  prolong 
  the 
  

   laying 
  period 
  from 
  6 
  to 
  10 
  days. 
  

  

  After 
  learning 
  the 
  normal 
  behavior 
  of 
  the 
  silkwonn 
  moths, 
  Miss 
  

   McCracken 
  made 
  experiments 
  on 
  the 
  insects 
  to 
  determine 
  the 
  rela- 
  

   tion 
  between 
  their 
  reflexes 
  and 
  the 
  individual 
  centers 
  of 
  the 
  nervous 
  

   system. 
  By 
  cutting 
  off 
  the 
  heads 
  of 
  both 
  mated 
  and 
  unmated 
  

   females, 
  which 
  could 
  be 
  done 
  without 
  apparent 
  distress 
  to 
  the 
  insects, 
  

   it 
  was 
  found 
  that 
  the 
  bodies 
  alone 
  made 
  no 
  spontaneous 
  efforts 
  at 
  

   egg 
  laying, 
  but 
  that 
  they 
  could 
  be 
  induced 
  to 
  oviposit 
  by 
  gentle 
  

   pressure 
  on 
  the 
  abdomen. 
  When 
  thus 
  artificially 
  stimulated, 
  the 
  

   headless 
  females 
  deposited 
  their 
  eggs 
  in 
  exactly 
  the 
  same 
  way 
  as 
  do 
  

   the 
  complete 
  insects, 
  and 
  by 
  the 
  influence 
  of 
  this 
  stimulation, 
  repeated 
  

   from 
  day 
  to 
  day, 
  they 
  were 
  induced 
  to 
  lay 
  the 
  full 
  number 
  of 
  eggs, 
  

   after 
  which 
  they 
  lived 
  about 
  as 
  long 
  as 
  the 
  normal 
  moths. 
  Headless 
  

   females, 
  moreover, 
  could 
  be 
  mated 
  with 
  normal 
  males, 
  and 
  thus 
  made 
  

   to 
  produce 
  fertile 
  eggs. 
  

  

  Since 
  insects 
  have 
  two 
  important 
  nerve 
  masses 
  in 
  the 
  head, 
  the 
  

   brain 
  and 
  the 
  suboesophageal 
  ganglion 
  (figs. 
  2, 
  4, 
  6, 
  ^?% 
  SceGnff), 
  

   Miss 
  McCracken's 
  experiments 
  do 
  not 
  show 
  from 
  which 
  head 
  center 
  

  

  