Hey Jay.
edit-- I see Fyshstryker beat me to it What he says.---
Ultra hair probably won't work so well. You want something stiff to support the back of the fly if you're tying dries. Depending on what you're tying, and the size you have a lot of options:
For big fast water flies (Wulffs, Humpies etc)
Deer body hair (not bucktail), same stuff you use to spin heads. If you don't have a patch, the crappy hair at the base of a bucktail- the hollow stuff that flares when you tie deceivers, is probably great for tails- it's hollow and floats well which is why it flares and is similar/identical to deer body hair.
Moose Body hair
Slower water, using split tails
microfibbettes (on larger flies size 12 and up you can use bristles from a Nylon paint brush)
Elk or Moose Mane (used in SW sometimes for shrimp antennae)
mink tail fibers
natural bristles from a paintbrush (artist or house paint brush)
and dry fly hackle barbs
Depending on how long a tail you need (shank length) you can use
fibers from a dry fly neck or saddle feather (about 6-12 more for bigger flies, less for smaller)
Spade hackle- these are spade or "pear" shaped with a dramatic taper feathers on the lower outside edge of capes and the top of saddles. They tend to have longer barbs than other feathers on a neck or saddle. Depending on how the birds were trimmed you sometimes get a bunch.
Coq de Leon hackle fibers. These feathers are sold in tailing packs by Whiting for around 16 bucks. Superb for tails. If you're going to do a lot of tying, a saddle for 22 bucks is a better buy than a pack for a few bucks more. Get a "Medium Pardo" (a medium gray shade with mottling)
Wet Flies
pheasant tail fibers, hen feather fibers, goose or turkey biots (from leading edge of a primary flight feather), etc.
Another alternative that you might have if you tie a lot of SW crab stuff is Sparkle Yarn (or Antron, Z-lon etc). You can use a sparse sprig of that (like 12 fibers or so the length of the shank or hook gap width) in place of a "regular" tail. This imitates the "shuck" or nymphal case as the dun mayfly emergers, and there are several dry fly patterns that use this. Most shucks are amber, tan, or brown.
If you're looking to get into this, some good patterns are Sparkle Duns and X Caddis. They use short fine deer hair sold as "Comparadun" or "Coastal" deer hair in place of expensive dry fly hackle. A patch 2"x2" will set you back 3 bucks and is good for about 100 flies. If you get a couple of patches- bleached, natural medium gray-brown and natural dark gray-brown and a 12 pack assortment of dry fly dubbing (like SuperFine or Fly Rite) and some amber or light brown sparkle yarn (you can buy cards with short lengths from a fly shop for 2-3 bucks, or get a whole skein of "Rug Yarn for a buck at a crafts/sewing store). With those 2 patterns in different sizes and colors, you can imitate just about any caddis (X Caddis) or mayfly (Sparkle Dun) you might run into. You can google those patterns for step by steps.
Hope this helps. Tell us what you're tying or if you're looking for ideas maybe we could give you some suggestions.
mark
) I have some ultrahair (aka supreme hair) for tying surfcandies and other SW patterns. Would a few of those fibers work for mayfly tails or would I need something with floatant applied to it (aka microfibbets)?
