A pair hoverflies Eristalis nemorum [1,2] busy with a mating ritual in which the male will hover above the female, loudly buzzing. By the loud sound the male produces it can already be clear a mating ritual is in progress without before seeing it.
Literature
1 Nederlands Soortenregister2 André Schulten, februari 2014, "Fotogids ZWEEFVLIEGEN Versie 2.0"
