Cox Arboretum, Dayton, Montgomery County, Ohio, USA May 8, 2011 Size: 1/3" - 1/2"
I've come up with one similar photo:
http://bugguide.net/node/view/19582/bgimage
But looking at the geographic distribution, Dayton would be at the northern end of its range. Even that image looks like it was a tough id so I'm not real sure about this one.