deer fly vs horsefly

deer fly

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

  • 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. 

horsefly

noun
  • Any of several medium to large flies, of the family Tabanidae, that suck the blood of mammals (not to be confused with Stomoxys calcitrans, the stable fly, or dog fly). 

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