I am unaware of the term deer fly. The name tends to suggest that they'll bite deer; it's possible they're not interested in biting humans.
Horseflies will happily bite humans, though they are pretty well guaranteed to die in the process.
Wikipedia says that deer flies do bite humans and their bite 'may be painful'. They are a type of horsefly, suggesting that the description of their bite is understated.
I wonder if we just call the "deer fly" a "horsefly" here. We (Missouri, USA) have the little horseflies (maybe a 1/2") and then the giant horseflies (biggest I've caught was 3").
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.
Ya our jumbo horseflies can take a lot before the don't get up. I use to go out and swat them off my cattle and they'd shake it off and come right back. I now pull a wing off and leave them on the ground. Their remaining wing buzzes really loudly and the spin in circles which attracts the chickens. I can get about a hundred in a 30 minute period at the peak of their season and the hens will circle around to grab them.
In my part of the woods (Wisconsin) horseflies are quite large, between 1/2 and 1 inch but mostly around 3/4. Deer flies are much smaller with a distinctive triangular shape made by their wings when they land.
Both have a very irritating bite, but the deer fly is a small sting of pain that goes away quickly while the horsefly tends to leave a large welt that sticks around for at least a day or two.
Horseflies will happily bite humans, though they are pretty well guaranteed to die in the process.
Wikipedia says that deer flies do bite humans and their bite 'may be painful'. They are a type of horsefly, suggesting that the description of their bite is understated.