Ran into a solid hatch of what I believe were two different kinds of light-colored mayflies last night on Hammer. I am not sure what the first one is. White fly?

2a and 2b are the same bug. Appears to be some sort of drake. I am only really familiar with Green drakes and this one looked a little different and slightly smaller. Although when I was there two weeks ago, I captured one mayfly that was definitely a green drake so I guess it could be one.

Sorry I couldn't get better pics with my cell phone.

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Neither are "whiteflies." Hazarding guesses is something close to a grey fox and some form of cahill. Not enough identifiers for even pcray to be 100% sure.

Definitely not a white fly in the first. (Their legs are practically non-existent.)

Other than that, kinda hard to tell from the pictures. The "arm bands" on the upper forelegs suggests that they might both be from clinger type nymphs; the lower one might be a light cahill. ( would certainly use a light cahill to imitate it).

cream cahill spinner and a light cahill spinner

They are all cahills of some sort.

Look like Cahills. I've seen a few on our local brookie streams lately.

Cahills. Hammer has a good cahill hatch (not as good as the sulphurs)

Thanks all. I Did not know Cahills got that large. They were impressive.

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How big were they?

If they were really big, they might have been Yellow Drakes.

You can check out pictures of those (and Cahills) on Troutnut.com.

Yeah those last two are big...I'd say some sort of drake. Even the wings are a coarsly mottled like a drake. and the top of the abdomen is contrasting too much for Cahills.

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They're not drakes. The dead give away is the "arm bands" on upper segment of the front legs -- generally, only heptagenids (clinger nymph mayflies) have them. (None of the drakes do.)

There's probably a dozen or more species within that family that are called "Cahills". They vary in color with exact species, gender, dun vs spinner, location where they're found, and time of season. You can't go by color.

Some of them are quite large. Here's a picture from troutnut that shows one that's somewhere between a size 10 and a size 8:

Troutnut light cahill

Yeah, really, and MB's can be fit into the same group of bugs. They are very closely related to cahills.

The photo is a little out of focus but I'm pretty sure the two bottom pictures are Ephemera varia. yellow drake spinner. The head is not that of a heptageniid. The banding on the front legs is at the joint between the femur and tibia.The abdominal markings look to be E. varia

I looked up The yellow drake pictures mentioned by troutbert. I'm not convinced they are a match, but there were only three pics on troutnut. The mottling on the wings definitely does not match any Cahill pic that I can find. The one i posted here was on the larger side of what I saw. I'm not great at guessing hook size but I would say easily a #10. Possibly #8.

I am leaning drake now but I really don't know what kind it would be. My first thought on the stream was a small green drake. I have seen GDs/coffin flies that size on streams here in centre county- not in the same league size wise as the ones you see on Penns.

For those who said yellow drake. What identifiers do you use to tell the difference between those and green drakes?

They are too small to be drakes, look at the size of the bug compared to the guys hand and fingers. Not even big enough to be a MB.