Green Drakes on the Loyalhanna?

Sounds like a green drake. If you get a nice cool drizzly day in the next few days, you could have decent early or all day fishing.
It usually takes more than a few drakes to get the fish keyed on them.
I'd also carry the brown drake and sulphurs & spinner patterns.
 YOu should get a hold of Green Weenie. He knows the hatches there.

No. Drakes are very big.
2 tails??  That may be a typical yellow quill/ light cahill species. 

Yessir 
They live in the silt and come out awhile before hatching.
try a green drake wiggle nymph.
Hope you get a good hatch. Brown Drakes,too. 

Yes, the Loyalhanna has a Green Drake hatch.  Not a big hatch but it is a hatch. They are currently on the upper end of the stream and should be around the delayed harvest area this week.  I have seen them as far down as Legion Keener Park in Latrobe.  You are also going to see a lot of sulphers and dortheas in the next few days.

The Green Drake nymph inhabit silty pools where they burrow and form U-shaped tunnels. They swim up to the surface to emerge. They use a strong wiggling motion to swim upward and that usually gets the trouts attention. If they happen to drift into the riffles, they kinda freeze up and stop wiggling until they hit slower water again where they again attempt to emerge.
 Coffins fly upstream and lay eggs in the fast water.
Once in awhile, we get a decent drake hatch here in NW PA.
The better local hatches I've seen have been on cool and rainy late afternoons. Those type of days keep the bugs floating on the surface for a longer period of time before they take flight. On some of the streams I fish, the drakes are much darker than what you usually see on PA water, such as Penns Creek.
 

Don't get over enthralled with Green Drakes.  Typically they don't live up to the hype.

LA1,

I'm sure we'll meet at some point. I normally fish portions of Mill where I dont see another soul until I get back to a road, or, as was the case a few days ago, until I follow the stream right into a few backyards. On that note...I've gotten very leery about fishing an area like that after a bad experience on Elk where I got chased off land that wasn't really marked as private. Basically, I'd rather just not fish it than take a chance at making hard feelings. This time, however, I saw a guy in a yard who smiled and waved, so I stuck around till dark, then left the way I came.

I primarily fish no farther downstream than the causeway, with 90% of my fishing at or above the DHALO. Hatch wise, I hit a pretty decent hatch of sulphurs up there a few weeks ago, and slate drakes have been consistent on Mill, and to a lesser extent, Loyalhanna, until just this week. Did okay during the hatch (but even better during the spinnerfall at dusk) with a #14 parachute adams (which I tie with a moose mane tail, slightly longer than the pattern calls for, at first because it was easier to tie, then, because it outproduced the ones I tied with hackle tails).

Finally, funny you should mention crappie in riffles...I did the same thing in the Conemaugh a month or so back. Nice fish at about 13-14".

My money's on Brown Drake spinner.  The super long front legs and three tails is what makes me think that.
 
Not very common, but when you find them, it's usually good fishing.
 
http://www.troutnut.com/fullsize/picture-im_regspec/248

No problem.
 
Now you have to tell me which stream that was on.