deer fly vs gadfly

deer fly

noun
  • A Eurasian species of louse fly in the family Hippoboscidae, Lipoptena cervi; parasites of elk, deer and other bovine animals, sucking blood and laying eggs in the fur of the host animals. 

  • A gold- or green-eyed horsefly of the genus Chrysops in the family Tabanidae; pests to cattle, horses and humans, feeding on their blood. 

gadfly

noun
  • Any dipterous (“two-winged”) insect or fly of the family Oestridae (commonly known as a botfly) or Tabanidae (horsefly), noted for irritating animals by buzzing about them, and biting them to suck their blood; a gadbee. 

  • Synonym of gadabout (“a person who restlessly moves from place to place, seeking amusement or the companionship of others”) 

  • A person or thing that irritates or instigates. 

  • A person who takes without giving back; a bloodsucker. 

  • A person who upsets the status quo by posing novel or upsetting questions, or attempts to stimulate innovation by being an irritant. 

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