I've been using these for 3 years since we built a compost pile and became "chicken parents".  One of these hanging over the compost keeps the flies WAY down in the yard.  Just be sure to hang it where you won't be hanging out. Peeeeuuuu, but how else to attract the flies??  It takes a few days to get "ripe" and then, boy does it fill up!  I leave the full one up while the new one gets ripe, so we're never without.  We're high in the Rocky Mountains, so our fly season is only a few months.  I top it off often & squeeze it to trap the babies that are hatched, then start flying around within the bag. Yes, you can see maggots, but it all goes tightly into a trash bag and out with the garbage on trash pick up day.  Wouldn't have chickens & compost without one of these to help!
I've been using these for 3 years since we built a compost pile and became "chicken parents". One of these hanging over the compost keeps the flies WAY down in the yard. Just be sure to hang it where you won't be hanging out. Peeeeuuuu, but how else to attract the flies?? It takes a few days to get "ripe" and then, boy does it fill up! I leave the full one up while the new one gets ripe, so we're never without. We're high in the Rocky Mountains, so our fly season is only a few months. I top it off often & squeeze it to trap the babies that are hatched, then start flying around within the bag. Yes, you can see maggots, but it all goes tightly into a trash bag and out with the garbage on trash pick up day. Wouldn't have chickens & compost without one of these to help!