Flitting around rather vigorously on the lily leaves and duckweed in our pond are lots of small flies. They are seen around the pond every summer and are distinguished by white tips to the wings. They have iridescent bodies and cannot stay still for more than a fraction of a second.
I have always assumed that the males of the species have the white tips to their wings and the females do not. The males dance around the females opening their wings and flashing the white tips. This seems like a courtship ritual or some form of pair bonding behaviour. Interestingly, I only observed this dance between two flies at a time, even though there were dozens of them about.
Having taken a little time to look them up, these little flies are of a species called Poecilobothrus nobilitatus. They are predatory animals, feeding on miniscule grubs and larvae of small species. I could not find much information about them, but similar species have soil dwelling larvae. The frogs in the pond are always alert when these flies are active.