I have been reading, again, about Vince Marinaro and his contributions to fly tying/fishing. I read his books many years ago and forgot a lot of what I had read.
One of his big contributions is the Thorax Style fly. Now, he tied his with huge wings. I don't see folks tying thorax flies that way anymore. But, his idea of the short hackle being wrapped in an "X" fashion sure does produce a footprint similar to the real insect on the water surface, as seen from below.
Anyway, I tied a "not so good" version of a thorax fly when thinking of him. If I can, I will also post a pic of one tied by Vince Marinaro himself......
From a photo in Mike Valla's book "Founding Flies".