cockchafer vs scarab beetle

cockchafer

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

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

scarab beetle

noun
  • Any of very many beetles, of the family Scarabaeidae, especially Scarabaeus sacer regarded as sacred by the ancient Egyptians 

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