My pony and horse had them on them and as quick as I killed them there were more.
Even on the yard I bathed them and horse flys apeared again some quite big so I was squashin them so thay fell off and thay ended up as spider fodder then I found 4 of them in his groin.
1 landed on his sheif and the next thing I saw was blood.
I have kept mine in at the moment as its been hot and with the flys my barn owners pony was bitten to pieaces so we washed her down and applyed savalon to the fly bites.
Even with fly sheets thay are a pain.