Insects from pine trees

This afternoon (13/1/2015) we were looking out of our sunroom and noticed a strange bit of mist.  On getting my binoculars on the case I found it to be a cloud of tens of thousand of insects.  They appeared with naked eye to be flying away, but with binoculars I thought they were circling.

Here are some images

In the second one it may be possible to see there are two streams coming from the top of each tree.

There was a loud buzzing noise but that could just be several thousand wings.

Earlier in the day Frances had been to some nearby willows and they were infested with many little black soft bodied insects.  Perhaps they shifted to the pines and were swarming?

Help!! Any information welcome.

A colleague, from Wamboin, had noticed a similat phenomenon, but involvng eucalypts rather than pines!  Here are the photos he took with his phone.

I have consulted some expert friends.   Their responses were:

• I would have gone for chironomids. I recall years ago driving along the Coorong and passing many great columns of 'smoke' that comprised millions of such insects, and somewhere at the time I read that midges form mating swarms like that. 
• My first guess would be midges (Chironomidae) of some sort, but other families of flies can also produce big swarms. If you do get a more definitive answer I would love to know. 
• There are several possibilities but mating swarms of chironomid midges are the most likely.  With all the water in the dams at the moment large numbers could be produced.  There are pictures similar to yours photographed in the UK.  There is the yellow swarming fly which is abundant at the moment but the swarms occur on vegetation.  If you see any more swarms check underneath them for stragglers on the ground. Aphids do fly in huge numbers but do not form coherent interactive swarms of the kind shown in your images. 
• A fourth correspondent who is a midge specialist has confirmed the identification  and also advised "The 'two' streams are not 'coming from' - but the swarm(s) are using the tops of the trees as a marker to maintain coherence of the swarm. Swarms are of males - its a display to which the females fly and select their mate - then pair in the air and they leave.  There are true reports of firies being called by residents seeing truly immense swarms in Germany and USA. There is a wood cut somewhere of a german church spire with 'smoke' billowing from the steeple."

A week later (20/1/2015) - on a much clearer evening the swarm was back: I hadn't seen it in the intervening period.  Here are a couple more images.

This first one gives an indication of the density of the swarm, and the number of animals in it - it is a clip from the second image.

It is now clear they aren't midges, but are in fact another type of fly.