Hoverfly male (Eupeodes possibly americanus) Bombay Hook NWR (Nov. 27, 2006) (Eupeodes because of thin black margin) - On Wild R

Hoverfly male (Eupeodes possibly americanus) Bombay Hook NWR (Nov. 27, 2006) (Eupeodes because of thin black margin) - On Wild Radish, in the company of a Spotted Cucumber Beetle. (see description) On Wild Radish - Raphanus raphanistrum

See comments in re margined abdomen:
Eupeodes because of the thin black line separating the top and bottom of the abdomen.
http://bugguide.net/node/view/400095/bgimage

male because the eyes are set close together - see:

http://www.microscopy-uk.org.uk/mag/artmay07/cd-hoverflies.html

There's a Spotted Cucumber Beetle hiding beneath another Wild Radish flower, just to the right of the Hoverfly.

EOL says:
http://eol.org/pages/750834/overview
"The species of Eupeodes show an unusual amount of intraspecific variation in color of head, legs, abdomen, and body pile; in some and perhaps in all species, these variations seem to result from differences in temperature during the pupal stage (Dusek and Laska 1974). (...)"

If that's so, then perhaps this is Eupeodes americanus.