Found on fern leaves underneath a sapling where ants were farming aphids. It had rained the night before, and everything was still heavy with water. However several wasps and a couple types of flies were visiting the area underneath this "aphid"-infested sapling:


A second very similar fly was found on an adjacent leaf within inches of the one pictures above, which lead me to suspect that, judging from the size and spacing of the eyes, that the one above is a female and the other one (pictured below) is a male of the same species, but I'm not entirely sure.