Gleason,

The answer to your questions are yes and yes. Normand and OkFlyfisher have given you good info on Isonychia patterns. More generally to answer your first question, though, there are a lot of resources here on FAOL like the ?Not Quite Entomology? section already mentioned that will give patterns and helpful info on fishing specific hatches, like time of day (morning afternoon, evening) that hatches typically occur and water type (fast, riffles, slow etc.) where they?re most likely to be found, as well as the more general info on time of year they emerge. (For example, Isonychia are often found in or below riffles and typically hatch in late afternoon to early evening.)

There are also other sites on the web like www.troutnut.com if you want to go really crazy with the details and biology of different hatches. Some excellent books to check out are Hatches II by Caucci (for mayflies) and Caddisflies by Lafontaine, with hatch specific fly patterns covering different stages of the life cycles of specific hatches. Good winter reading, but now it?s time to fish!.

Hatch Charts are another resource too. You can google them for areas you plan to fish, or better, get them from local fly shops since hatches may vary somewhat from river to river.

Here?s one for Southern Ontario as an example:

http://www.grindstoneangling.com/hatch.html

When trying to match a specific hatch, remember that there are different stages to think about (nymphs, emergers, duns, and spinners for mayflies and larvae, pupae, and adults for caddis) though the duns and adult caddis get most of the press. So feel free to tie patterns for Isonychia that match the large size, usually 10, and some 12. (A few earlier season mid summer Iso hatches can even be 8s.) Just match the body and wing color of the natural at your tying desk. Iso nymphs are dark, often with a white stripe down each side. And the duns have dark reddish brown or chocolate bodies, cream colored tails and dark gray wings.

There are also many ?styles? of fly patterns, especially for dry flies. Don?t feel you need all of them, but here are some dun Iso patterns as examples:

Catskill style with hackle (like the Adams). I like Dun Variants, but other good ones for the Iso hatch are Slate Drakes, Chocolate Duns, and dry versions of a Lead Wing Coachman. I mostly fish Dun Variants in size 10 and carry a few in size 12 and a couple in 8. It?s a good pattern to skitter around on the surface during a hatch too. I use a Dun Variant at least 80% of the time for Isonychia.

Wulff style hair wing Mahogany Duns are great for fast water and riffles in 10 and 12 and better visibility in lower light than the Dun Variants, but not as a close an imitation as a Dun Variant INHO.

Deer hair dries like Comparaduns, SparkleDuns and Haystacks in sizes 10 and 12 with dark gray wings, cream tails (or amber shuck) and dark reddish brown bodies. The Haystack is a great rough water pattern, the others are better for slower water.

Parachute style would work too I bet, though I haven?t tried them for Iso.

To imitate other stages of Isonychia:

Spinner White-Gloved Howdy is an Iso spinner pattern (so called because the adult Iso has white tips on its front legs) in 10 and 12 or you could make your own Iso spinner version with cream hackle tails, dark reddish brown body with poly wings tied spent wing. Or you could clip the hackle off the bottom and top of a Dun Wing Variant if they?re only taking spinners like I do when I?m lazy. Iso spinner falls can be very good. Tend to be heaviest in early evening.

A wet fly like the Lead Wing Coachman size 10, 12 is worth having too for the Iso hatch to fish on the swing down and across current.

Nymphs large dark ones are good in 10 and 12 for Iso. Since you probably already have them in your box, try Bead Head Prince and unweighted Prince nymphs in 10 and 12. You can fish the BH deep, and fish the unweighted prince higher in the water column to imitate an emerger. (You can even hang the unweighted version off a high floater like a Haystack or Mahogany dun as a dropper by tying it on 6? of tippet to the bend of the dry.) Other good ones for Iso nymphs you may already have in your box are Zug Bugs and black, brown or peacock wooly buggers (you may need to clip the tails shorter if you aren?t getting any hits on the buggers). The Isonychia Compara-nymph. is a more ?exact? imitation. Try a nymph if nothing is happening on top to your dries. Iso nymphs are fast swimmers and can be quite active throughout the day even though nothing is happening on top, so give a nymph a shot dead drifting and with quick strips to up your odds if nothing is happening on top, and to extend your fishing time since the Iso hatch doesn?t usually get going until late afternoon.

To just limit things to a few patterns, I go with a lot of Dun Variants in 10, some in 12. A few Mahogany Duns in 10, a couple wet Lead Wing Coachman in 12, some 10 White Gloved Howdys (or poly winged Iso spinners or clipped hackle Dun Variants) and some BH and unweighted Prince Nymphs in 10 and 12 and feel very well covered for Isonychia.

Hope this helps. Good luck!

peregrines