Swarm

Last week I was walking along the river bank from the Urmston direction towards Stretford. Just past where the Kickety Brook path emerges on to the river bank and adjacent to Stretford Sewage Works, I suddenly became aware that the air was full of tiny black flies or gnats. Looking up, I realised that the main concentrations of these insects were around the crowns of the riverside trees (mainly poplars and sycamores). As I watched, plumes of the insects detached themselves from the main swarms and formed long, descending, smoke-like arabesques. The photograph above shows one of these plumes, just after it had formed.

I've never seen anything quite like this before - can anyone shed any light on this phenomenon?

Dave Bishop, April 2009