You see a few up on Kinder and on Howden regularly, I think they are as you say common, they are just quick at getting away. on a summer morning with good eyesight you should detect some on south facing slopes warming up.(Not in a running sense)
Plenty of those huge black flies on Kinder this morning, I could hardly see or breath for them, huge swarms of the blighters, ended up cutting the run short because of it.