What has happened to the flies?

We have had 3 picnic lunches and 2 BBQ dinners in Central Western NSW over the last few days and have not been bothered by flies. Our day at the zoo was also 'fly free' despite the amount of dung evident in the enclosures. I am not complaining, but am certainly intrigued about the lack of flies. It might be worth a query to the CSRIO.