Hey those flies can bite Hard!!!!! (at least the girl flies do..they need the blood to make the eggs) maybe your dog knows this instinctively..i hate fly bites. I was in court with my daughter once (sigh) and we are all sitting there with our hands in our laps..in dresses like we should be and this one fly bites first my leg..then someone elses..you could see one person jump after another. Speaking of which one just came in here and it is time for it to die! Victor found a Junebug (talk about early) the other day and he thought he had something grand..