The sunshine over the past few days has brought out the insects. Here are a couple of hoverflies mimicking bumblebees
This is a female Volucella bombylans – note the featherlike antennae
And this is Merodon equestris – it is mimicking the Common Carder Bumblebee
A Dartmoor blog 
I’ve seen and photographed V.bombylans a couple of weeks ago in one of my favourite local hoverfly haunts. Nice to see the narcissi form of M.equestris you’ve captured here and I will keep my eyes open as I had them in my garden last year along with the bulborum form.
A very interesting blog Adrian.
I enjoyed reading your informative, beautifully illustrated post.
A friend and I have been finding large black hoverflies in Kelly Bray and on Kit Hill in South-east Cornwall, near the Devon border. Not sure if I can include a photo here in this comment, but they have black round shiny spiky-haired bodies and ginger furry heads with large eyes. They look like bumblebees, but in a Dennis the Menace and Gnasher sort of way. Perhaps I can send you a photo via Twitter or Facebook, as you might know what they are. Thank you.
Thank you adrian.colston@gmail.com