flyA few pictures to illustrate the problem...
 
stable fly compared to house fly
  
Stable fly (top) house/bush fly (bottom)
 Note the piercing proboscis of the stable fly.
     
cow running to dislodge flies   flies on cows legs

Beast running – endeavouring to dislodge flies, to no avail.

Stable fly inside and outside front legs where stock find it difficult to stop flies settling and biting.
horse
  
horse
Photos depicting a horse’s reaction to stable fly bites. The bites come up in welts, which are extremely itchy. The horse then rubs welts until his skin is red raw. Owners have tried steroid injections to help alleviate the horses’ allergic reaction to the stable fly bites and have tried all known sprays.....which have VERY limited effect.
     
Stable fly larvae in crop waste
Stable fly larvae in crop waste
Stable fly larvae in crop waste
Stable fly larvae in crop waste
   
Typical fly larvae in crop waste
Stable fly larvae in crop waste