Where I live, deer and horse fly are sorta interchangeable terms. Quebec. We do have different breeds of them too. Early in summer, the head biting one. Lat

Where I live, deer and horse fly are sorta interchangeable terms. Quebec. We do have different breeds of them too. Early in summer, the head biting one. Later, near August, there is one with a yellow back, and it goes for ankles! That's pants in sock season time. There are loads of bot flies too. They supposedly go for cattle, but I've caught mice with their larvae, so I worry about napping outside, during their season. From upstream: Horseflies will happily bite humans, though they are pretty well guaranteed to die in the process. Not sure this is a deer fly. The ones I hit, often just fall off, then fly away. You usually have to crush them with your foot to kill them. They are tough.