potato bug vs rolly polly

potato bug

noun
  • The woodlouse, various terrestrial crustaceans of suborder Oniscidea. 

  • Any of various insects that feed on or harm potato plants. 

  • The Colorado beetle or Colorado potato bug (Leptinotarsa decemlineata). 

  • The Jerusalem cricket, various insects of the genus Stenopelmatus. 

  • The striped blister beetle or old-fashioned potato bug (Epicauta vittata). 

rolly polly

noun
  • A woodlouse. 

  • A forward roll or a backwards roll. 

How often have the words potato bug and rolly polly occurred in a corpus of books? (source: Google Ngram Viewer )