I don't remember the name brand, but if you go to Menard's they sell these things that are basically clear bags that get filled with stinky water that attract the flies. We had a problem with flies in our back yard that the exterminator told us was due to the neighbor's yard, so there was nothing we could do about it and recommended these bag things. They smell bad so you want to put them somewhere not by your front door, but they attract the flies, that end up in the bag and can't get out. It is totally gross, I make my husband deal with it, but I swear I haven't seen a fly in our yard since and with the amount of flies in the bags, I am guessing that we are keeping the whole block clear of flies.
D.