I was beginning to think that the pupa was dead but it emerged today, 11/29/09. I am not including the date in the data field because it has been indoors for the last week. I was afraid that it would overwinter as a pupa and that I would never get the adult if I waited for months.
It looks rather similar to the Syrphus I raised last year, but not quite. The larva and pupa also looked somewhat different. I am hoping that it is a different species and even genus. After all it was feeding on aphids that feed on milkweed; the one I raised last year fed on aphids that ate trumpet honeysuckle (it also accepted aphids from my rose bush).
I am always amazed how big they look when they unfold and come out of their tight package, the pupal skin.

Update. Dr. Chris Thompson says: "The species is Eupeodes (Metasyrphus) americanus (Wiedemann)".

Higher res. image