blackfly vs gnat

blackfly

noun
  • Any of various small black bloodsucking flies of the family Simuliidae. 

  • A black or dark green aphid (Aphis fabae) that is a common pest of agricultural crops. 

gnat

noun
  • Any small insect of the order Diptera, specifically within the suborder Nematocera. 

  • An annoying person. 

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