For the last two weeks we have had several swarms of flying bugs. They stay together, so you just see a cloud of insects approaching. They are at different stages too, some tiny bug clouds, and a couple of large ones including one that hangs out by the back door for about 3-4 hours every day from afternoon to early evening. Nothing seems to affect them - water, waving something at them, they immediately regroup and carry on flying around each other.
Does anyone know what they are and if they're likely to die off soon?