As much as anything, the anglers will clue you in to the midge hatch. You will see them hunched over in concentration like herons. The better ones will be in as close as they can get to the dimpling trout. What you'll notice is the rythmic flicking of casts toward a porpoising trout and the lack of any other motions. The only exception will be the gentle tug that sets a very small hook attached to the leader by a very delicate tippet. The playing of the trout, if it is a good one, will be a cat-and-mouse sort of ecstacy.