Owls are famously capable of swivelling their heads so that they can look directly behind them, but hoverflies have even more flexible necks. This one landed in front of me and began to clean its tongue with one of its feet, then........
..... swivelled its head through 180 degrees to clean the top of its head. That's its tongue pointing upwards.
Consider for a moment what goes on in a hoverfly's brain during this contortion.
Those large compound eyes given it almost 360 degree vision, above, below, to both sides and also, to a considerable extent, behind. So when it rotates its head like this its image of the world must invert in a fraction of a second. Often they'll rotate their heads clockwise through 180 degrees, and then do the same anticlockwise.
I'm struggling to imaging what the sensation must feel like .... maybe something like one of those big dipper rides .....?