Thanks.
He comes several times a day and goes to pretty much every flower on the plant. So its a matter of waiting until he hits the right flower at the right angle to catch the iridescence. Otherwise it just looks dark.
I put my chair and tripod close to the plant and waited with some coffee and a cigar. I didn't have to wait long, he buzzed over my shoulder and was nice enough to pose well!
These were taken with my D3 and a Tamron 300 f/2.8. But for some reason the exif data doesn't show that I'm also using a Tamron 2x teleconverter. So these are actually taken at 600mm.