Ritualized acoustic signals in caterpillars

Some caterpillars can communicate by scraping their bottoms on a leaf to make a sound indicating that the leaf is occupied.

...the evolution of the scraping display had allowed the caterpillars to resolve their conflicts without fighting.  "So our idea is that these ritualised signals actually prevent damage to both contestants - they resolve conflicts in a more 'civilised' way." 

Too bad humans can't do the same.