The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
As usual, I reserve the right to be completely wrong.:)
There were enough of these flitting around in the evening to keep the fish looking up. Anglers can easily confuse these with Dicosmoecus species (October Caddis) at this time of year, but their wings are quite different and they like gentler flows.