May bug vs cockchafer

May bug

noun
  • cockchafer 

cockchafer

noun
  • Any of the large European beetles from the genus Melolontha that are destructive to vegetation. 

  • Any of various other similar beetles, such as of the genera Acrossidius, Cyphochilus, Rhopaea, etc. 

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