﻿ANIMAL 
  BEHAVIOUR 
  199 
  

  

  of 
  ganglia 
  which 
  are 
  able 
  to 
  control 
  many 
  actions 
  by 
  them- 
  

   selves. 
  We 
  must 
  remember 
  that 
  a 
  wasp 
  or 
  a 
  bee 
  may 
  go 
  

   on 
  feeding 
  after 
  its 
  tail 
  has 
  been 
  cut 
  off, 
  as 
  Baron 
  Mun- 
  

   chausen's 
  horse 
  went 
  on 
  drinking 
  after 
  most 
  of 
  its 
  body 
  had 
  

   been 
  shot 
  away. 
  Even 
  a 
  decapitated 
  insect 
  can 
  do 
  a 
  good 
  

   deal, 
  like 
  St. 
  Denis 
  who 
  walked 
  round 
  the 
  town 
  with 
  his 
  

   head 
  in 
  his 
  hands. 
  But 
  whatever 
  may 
  have 
  been 
  the 
  saint's 
  

   reflections, 
  we 
  may 
  be 
  sure 
  the 
  insect 
  has 
  none. 
  

  

  Before 
  going 
  further 
  let 
  us 
  take 
  a 
  thoroughly 
  typical 
  

   instance 
  of 
  instinctive 
  behaviour, 
  and 
  there 
  is 
  no 
  better 
  

   than 
  that 
  of 
  the 
  Yucca 
  Moth 
  (Pronuba 
  yuccasella) 
  , 
  which 
  

   has 
  been 
  often 
  cited. 
  When 
  the 
  large 
  yellow 
  bells 
  of 
  the 
  

   Yucca 
  open, 
  each 
  for 
  a 
  single 
  night, 
  the 
  silvery 
  moth, 
  just 
  

   emerged 
  from 
  her 
  chrysalis, 
  sets 
  forth 
  to 
  visit 
  them. 
  From 
  

   the 
  anthers 
  of 
  one 
  she 
  collects 
  pollen, 
  which 
  she 
  kneads 
  into 
  

   a 
  ball, 
  and 
  holds 
  beneath 
  her 
  head. 
  She 
  flies 
  to 
  another 
  

   flower, 
  pierces 
  the 
  pistil 
  with 
  her 
  ovipositor, 
  lays 
  her 
  eggs 
  

   among 
  the 
  ovules, 
  and 
  then 
  places 
  the 
  fertilising 
  pollen- 
  

   pellet 
  in 
  the 
  funnel-shaped 
  opening 
  of 
  the 
  stigma. 
  Without 
  

   the 
  pollen 
  thus 
  brought 
  by 
  the 
  moth 
  the 
  ovules 
  would 
  not 
  

   develop. 
  The 
  larva? 
  of 
  the 
  moth 
  eat 
  a 
  share 
  of 
  the 
  developing 
  

   ovules, 
  but 
  not 
  more 
  than 
  about 
  half 
  are 
  required. 
  So 
  that 
  

   both 
  plant 
  and 
  insect 
  are 
  served. 
  In 
  referring 
  to 
  this 
  ex- 
  

   traordinary 
  case 
  Prof. 
  Lloyd 
  Morgan 
  writes 
  : 
  " 
  These 
  mar- 
  

   vellously 
  adaptive 
  instinctive 
  activities 
  of 
  the 
  Yucca 
  moth 
  

   are 
  performed 
  but 
  once 
  in 
  her 
  life, 
  and 
  that 
  without 
  in- 
  

   struction, 
  with 
  no 
  opportunities 
  of 
  learning 
  by 
  imitation, 
  

   and, 
  apparently, 
  without 
  prevision 
  of 
  what 
  will 
  be 
  the 
  out- 
  

   come 
  of 
  her 
  behaviour; 
  for 
  she 
  has 
  no 
  experience 
  of 
  the 
  

   subsequent 
  fate 
  of 
  the 
  eggs 
  she 
  lays, 
  and 
  cannot 
  be 
  credited 
  

   with 
  any 
  knowledge 
  of 
  the 
  effect 
  of 
  the 
  pollen 
  upon 
  the 
  

   ovules. 
  The 
  activities 
  also 
  illustrate 
  what 
  is 
  by 
  no 
  means 
  

  

  