I spotted this flying red thing checking out all the branch tips of a holly bush. It flew like a wasp and looked like a wasp, so I was surprised to behold the image on my monitor later; it appears it's actually a fly. What is it? And was it looking for something to eat or lay eggs on? The holly did have aphid clusters near many branch ends, and the associated ants, but I didn't see this fly encounter any while I watched. It also wouldn't sit still, so I had a hard time getting a good image.