Depends on the weather - warm and humid, lots of flies, cold and wet, very few. And it can be warm and sunny into October some years. They will eventually all disappear as the year progresses, but whilst the weather remains warm, there is a risk of flystrike. If you do get an attack on one of your sheep, ie: the eggs hatch and there are maggots in the fleece, make sure you treat the whole area with Crovect and all the maggots have completely gone. We usually cut away all the affected fleece with the dagging shears to make sure. Makes the sheep look a mess, but does the trick. ....Now someone else will correct me here if I'm wrong, but I am of the opinion that it is only the green blowfly which causes flystrike, not bluebottles or horseflies. Cheers, C.