Presumably ovipositing, otherwise I don't understand the curious dance this colourful fly was doing. Quite the display given its wing and body colours and patterns.
An unusual fly: red-belted hoverfly, Brachypalpoides lentus – a sawfly mimic. The larva is yet to be described. About 20 observations in the whole UK; 172 globally.
From Hyde Park, London (June 2023). Standing right next to Peter Pan's statue.
Apologies for the poor pictures, but here's a little bee-mimicking robber fly, after and before catching a tiny bee for dinner. I followed this wily hunter around for quite a while, and he wasn't pleased with my interference so he didn't let me get very close.
Why are flies so fast? (www.infoterkiniviral.com)
Flies have many adaptations that enable them to increase speed and have maneuver and perception abilities