I've been thinking that I would like to know about Aquatic Insects more in detail. Last week I met this book casually at bookstore next to my parents' house. It was much better than I expected! If you are interested in such a kind of stuff, let me recommend it for you.
My rough guess says this should be Akamadara mayfly' dun. It was on the post box yesterday. His huge turban eyes told me he was male.
And I found its spinner and shuck also on the our apartments' wall. He must have molted on the wall! Perhaps it is a good place to observe their life, because it locates just by the Kise river.