Abington, Montgomery County, Pennsylvania, USA July 15, 2007 Size: About 3 mm.
I finally found a caterpillar with parasitic wasps emerging from the cocoons on a caterpillar of Manduca sexta. I even managed to video one of them in action, plus a very angry caterpillar trying to get rid of its parasites. See the video.
For more on this kind of caterpillar.
Southeastern PA.