It's funny the things that stick with you from childhood. Certain events, places and people seem to take on an almost mythical status. Flying Ant Day was one of those.
Now, I am not an entomologist, so hopefully one will explain the exact biology behind this, but this is how we saw it as kids. On one day of the year, usually in July, normally the hottest day of the year, the city would be filled with thousands of large winged ants. They weren't very good at flying and spent most of their time crawling on the pavements and cars. For this one day, the city was ruled by the ants. We'd excitedly rush out of school, and, walking home, watch the antics of the ants with their seemingly unrealistic wings. We found it even more fascinating than our other hot-summer afternoons watching the "ant motorways".
I've never worked out how they all knew when to emerge, but it seemed to make sense as it would have improved their chances of mating. Whatever the true significance of this day, it was there in our childhood calendar. A day to be anticiptaed almost as much as Halloween would, for example.
One question that we had at the time was answered for me: is it the same day all over the country? This mystery was solved by the fountain of knowledge that is Big Brother. This year they had flying ant day on Big Brother UK, and it was a week after Bristol's. So there we go.