Yesterday around 6:45 pm were sitting on our back deck in Ann Arbor and there was a pleasant breeze. All of a sudden, many really tiny black bugs fell down upon us. At first we thought they were vegetation from the trees, but then they started moving. They moved very slowly, crawling, but did not fly. We had to go inside. Today, we went back outside and only saw a few on the chair cushions, that must have been left from yesterday. We thought they were all gone until around 7 pm when a few started falling again. I collected some of them in a jar, but they are too small to get a good photograph. I'm attaching a photo of one of the bugs lying on its side on a white piece of paper. They have tiny legs underneath, not off to the sides like a spider or tick. We have lots of Black Walnut trees so we think they must be falling from them. Do you have idea what they could be? Thanks, Kitty