I'll second Afish's and WildTigerTrout's posts above.
Mid to late fall is a very under appreciated time to use terrestrials IMO. Moreover, they work especially well on selective risers that, in the springtime, might have required a close imitation. In my experience, this time of year, you can often catch trout that are sipping some small aquatic insect by offering them a beetle or ant. After the summer, they just seem to have terrestrials imprinted in their mind and, although they might be feeding on midges or BWO emergers, they can't resist an ant or small cricket. If you find a selective fish sipping some little mystery stuff and he ignores your efforts to match the hatch.....show him a small terrestrial (I really like a small hornet this time of year). It doesn't always work of course, but often that terrestrial will get eaten.