May bug vs doodlebug

May bug

noun
  • cockchafer 

doodlebug

noun
  • An automobile converted into a cheap tractor for a small farm during the Second World War. 

  • Someone who draws constantly. 

  • An idiot. 

  • A slackard or time-waster. 

  • The V-1 flying bomb. 

  • A woodlouse. 

  • An antlion larva (Myrmeleontidae). 

  • A divining rod or similarly intended device. 

  • A term of endearment. 

  • A cockchafer (genus Melolontha). 

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