ooo blimey … I see what you mean!
no I hadn’t considered anything like that, probably because all my detailed wildlife watching is on an area of woodland/heath with just one little pond that only fills during the winter. So I encounter very little that could be described as aquatic, certainly no caddis flies.
but it certainly looks like such a mass of eggs even though there is no hint of water anywhere near those trees.
so as they say “every day is a school day”!
thanks very much Mike
Alan