Our peonies are getting close to blooming. Peonies at this stage secrete some kind of nectar or sap that is very attractive to insects. Often you will see the buds covered with ants.
They are also quite attractive to flies. Here are some that I found in the last few days.
The upper fly is a blow fly, family Calliphoridae. The one below may be Sepsis.
This is our old friend, the golden dung fly, Scathophaga.
I have no idea what this one is.
Finally, a couple of different syrphid flies:
And another one–note how this one is more slender, and the eyes are not connected.
So why do the peony buds attract insects? I have no idea. I don’t think I have seen an explanation that I believe either.
The roused bear 
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You’ve got some great macro shots here, especially ‘Sepsis’ (which is a great name for a creature!)
Yeah, but so is Scathophaga.