﻿POLLINATION 
  AND 
  FERTILIZATION 
  151 
  

  

  An 
  idea 
  of 
  the 
  number 
  of 
  insect 
  visits 
  made 
  to 
  some 
  flowers 
  

   may 
  be 
  gathered 
  from 
  the 
  fact 
  that 
  in. 
  a 
  single 
  locality 
  one 
  

   hundred 
  kinds 
  of 
  insects 
  have 
  been 
  seen 
  to 
  frequent 
  dandelion 
  

   flowers. 
  The 
  statistics 
  in 
  regard 
  to 
  visitors 
  to 
  the 
  flowers 
  of 
  

   yarrow, 
  Canada 
  thistle, 
  and 
  the 
  willows 
  are 
  fully 
  as 
  remarkable. 
  

  

  142. 
  Odors 
  of 
  flowers 
  as 
  attractions 
  to 
  insects. 
  It 
  is 
  evident 
  

   from 
  familiar 
  facts 
  that 
  many 
  insects 
  have 
  an 
  acute 
  sense 
  of 
  

   smell. 
  The 
  way 
  in 
  which 
  flies 
  are 
  attracted 
  by 
  decaying 
  meat 
  

   or 
  fish, 
  and 
  bees 
  and 
  wasps 
  by 
  a 
  cider 
  press 
  at 
  work 
  or 
  by 
  

   fruit-preserving 
  operations, 
  is 
  a 
  matter 
  of 
  common 
  observation. 
  

   A 
  single 
  cluster 
  of 
  carrion-scented 
  flowers 
  has 
  been 
  known 
  to 
  

   attract 
  carrion 
  flies 
  and 
  dung 
  beetles 
  from 
  a 
  distance 
  of 
  hun- 
  

   dreds 
  of 
  yards. 
  Some 
  flowers, 
  such 
  as 
  those 
  of 
  the 
  Virginia 
  

   creeper 
  (Psedera), 
  the 
  Dutchman's-pipe, 
  the 
  blueberries, 
  and 
  

   many 
  others, 
  are 
  so 
  inconspicuous 
  that 
  apparently 
  their 
  numer- 
  

   ous 
  insect 
  visitors 
  must 
  be 
  attracted 
  by 
  an 
  odor 
  which 
  is 
  almost 
  

   or 
  quite 
  imperceptible 
  to 
  us. 
  

  

  It 
  seems 
  certain 
  that 
  the 
  odors 
  of 
  flowers 
  have 
  been 
  devel- 
  

   oped 
  with 
  reference 
  to 
  the 
  sense 
  of 
  smell 
  in 
  animals 
  (usually 
  

   insects), 
  and 
  that 
  these 
  odors 
  serve 
  as 
  a 
  most 
  efficient 
  means 
  

   of 
  securing 
  insect 
  visits. 
  

  

  It 
  is 
  a 
  most 
  interesting 
  fact 
  that 
  many 
  flowers 
  give 
  off 
  their 
  

   scent 
  mainly 
  at 
  the 
  time 
  of 
  day 
  when 
  the 
  insects 
  which 
  polli- 
  

   nate 
  them 
  are 
  most 
  active. 
  Thus, 
  some 
  catchflies, 
  the 
  petunias, 
  

   some 
  kinds 
  of 
  tobacco, 
  and 
  several 
  honeysuckles 
  have 
  little 
  

   odor 
  by 
  day 
  but 
  are 
  very 
  fragrant 
  at 
  night, 
  when 
  the 
  moths 
  

   which 
  pollinate 
  them 
  are 
  on 
  the 
  wing. 
  On 
  the 
  other 
  hand, 
  

   many 
  plants 
  of 
  the 
  Pea 
  family, 
  which 
  are 
  pollinated 
  by 
  day- 
  

   flying 
  bees 
  and 
  butterflies, 
  give 
  off 
  their 
  scent 
  mostly 
  by 
  day, 
  

   and 
  especially 
  in 
  strong 
  sunshine. 
  

  

  143. 
  Colors 
  of 
  flowers 
  as 
  attractions 
  to 
  insects. 
  There 
  has 
  

   been 
  much 
  discussion 
  among 
  botanists 
  as 
  to 
  how 
  far 
  insects 
  are 
  

   led 
  to 
  visit 
  flowers 
  by 
  displays 
  of 
  color. 
  It 
  appears 
  to 
  be 
  fairly 
  

   certain 
  that 
  no 
  insects 
  can 
  make 
  out 
  the 
  forms 
  and 
  sizes 
  of 
  

   objects 
  at 
  a 
  distance 
  of 
  more 
  than 
  six 
  feet, 
  and 
  that 
  many 
  are 
  

   unable 
  to 
  see 
  clearly 
  even 
  two 
  feet. 
  In 
  spite 
  of 
  this, 
  however, 
  

  

  