Black flies are not usually regarded as important trout fare, but scientific studies of some rivers have shown them to make up the majority of the trout's diet. Such places are few and far between, but anglers should be aware of the possibility and keep a lookout for high concentrations of the larvae.
Jpsully on Sep 15, 2006September 15th, 2006, 1:13 pm EDT
Very nice site, indeed!
Just wanted to acknowledge your assistance and say thanks for your help in identifying a bug I happened to seine out of the Upper Delaware this week - on a drizzly afternoon, there were tiny BWO's coming off in small numbers; but also present (in greater numbers) was a size 24/26 down-winged light-olive insect, with black mottling, that I had not seen before. They rode the current for quite a while, and the trout were quietly sipping them. After describing the fly (as best I could), you were able to provide photos, along with the suggestion that these were "blackflies" (Simulidae). I had no idea that these flies were present in the Delaware system, but will certainly carry a few imitations from now on (just in case).