These black ants were emerging for their nuptial flight last week when the weather was hotter, drier and less windy. Winged males and females (queens) fly in order to mate, the queens going on to form new colonies and can live several years,while the males die off in a few days. These were all males, as the queens are larger. Usually they fly a bit later in the summer, but these were in the entrance to the greenhouse, so got an early start thanks to being in a warmer environment.