coprophagan vs dung beetle

coprophagan

noun
  • Any of a number of beetles that feeds on dung. 

dung beetle

noun
  • Any of the true dung beetles of subfamily Scarabaeinae. 

  • Any of the beetle of the family Scarabaeidae (scarab beetles), especially of the subfamilies Scarabaeinae and Aphodiinae, noted for rolling dung into balls for use as food or as brooding chambers. 

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