In modern "match the hatch" dry fly fishing, this style of fly has gone the way of greenheart and the gut leader.
In a couple of old books I have recently read, the author not only assumed the reader used bivisables, but fished them more often than the winged flys we use today.
I have always carried a few and I remember days when they were just the thing.
As recently as this past weekend I caught a few trout on a bivisable.
I was wondering if anyone else still fished this very productive style of fly.