This fly was on the yard waste bin, and carries a mite. When under light, the fly runs around with short flights (in the vial), and is hard to catch at a still moment. Sometimes it rubs its hind legs quickly as though to knock the mite off. It was going to be spider food, but the spider didn't eat it, so the spider went free and I took a close look. It's interesting that it has short hairs on the front edges of the wings, not unlike those of an owl.