I noticed this Greater Bee Fly (Bombylius major) hovering and darting about in the garden this week, it kept returning to the same spot after chasing off intruders to its airspace. I had my bird lens on so had a go at a few action shots…
This is my favourite one because it looks like the air narwhal is attempting to hit the bullseye with that impressive proboscis 
If you love solitary bees, you might not like the idea of kleptoparasites but for me, a healthy population of solitary bees should attract parasites - it’s nature’s way of maintaining balance 
Here’s a video I shot of the less common Dotted Bee Fly (Bombylius discolor) when I was based in the Cotswolds:
Female Bee Flies are fascinating to watch, they hover over the nest holes of mining bees and flick their eggs into the entrance from a great distance. If you’re really observant, you might notice them collecting sand via their backend! The jury is out on why they do this but a couple of the most plausible theories are that they are collecting sand to use as weights to assist with the egg flicking or that they are using sand to help keep the eggs separate or to stop them drying out in some way. I actually managed to shakily film a different species of Bee Fly, the even less common Downland Villa Bee Fly (Villa cingulata), doing this a few years ago in Stroud Cemetery:
