What was I seeing - Light Cahill?

[Letort]

Opening Day 2026 on Yellow Breeches, Cumberland County, healthy hatch of caddis, BWO and a yellow mayfly, which I thought looked like a light Cahill. Definitely was not a Yellow Sally. Saw one with a bright green egg sac. Air temp was about 60* at the time and it was about 9 - 10 am in the morning. Fairly prolific hatch - not cloud like, but not 1-2 either. They were largely over a run, versus broken water.

It was definitely a mayfly, two tails split, thin thorax, size 14-16. Yellow to muted yellow, segmented body.

Cahill, as I understand them, would be late May and also tend to be a late afternoon hatch. Neither of those would match up with what I was seeing.

Any one have an idea of what was going on? I had one take on a paranymph, closest thing I had in my box, as I wasn’t planning on a dry fly matching challenge on opening day.

 

[Letort]

Thinking now it could be a Light Hendrickson? I saw a pic of some that were quite light / pale yellow

 

[TimMurphy]

Dear Letort,

I've come across fishable Sulphur hatches in the Condoguinet below Letort Falls in the first week of April in years past. Where they actually Suphur's, I'm not sure of that because I never caught a fly to examine it. I will say the fish seemed to think they were Sulphur's because they ate my dry flies eagerly.

Regards,

Tim Murphy 🙂

 

[troutbert]

What did the wings look like? If they were variegated, that would indicate Light Cahill. It's very early for those.

If they were dun colored, that would indicate what I call big early sulphurs, which are usually size 14. On Spring Creek I've seen a few in late April, and heavy hatches as early as May 4.

But the Cumberland Valley is further south and lower elevation than Centre County, so the climate is noticeably warmer, so the hatches are earlier.

 

[redietz]

Thinking now it could be a Light Hendrickson? I saw a pic of some that were quite light / pale yellow

Hendricksons have three tails, as do sulfurs.

 

[Letort]

I bet it was a sulphur. Was thinking it was too early, but that would make sense. I didn't get to see the wing structure up close and I don't recall them being darker

 

[redietz]

But the Cumberland Valley is further south and lower elevation than Centre County, so the climate is noticeably warmer, so the hatches are earlier.

Earliest I've seen the early sulfurs, either in the Cumberland Valley, or on the Gunpowder here in Maryland, is the last week of April. Plus, it was a cold winter for a change and I expect hatches to be on the late side this year.

 

[Letort]

Hendricksons have three tails, as do sulfurs.

OK, clearly saw 2 tails on more than 1 insect.

 

[Bamboozle]

...It was definitely a mayfly, two tails split, thin thorax, size 14-16. Yellow to muted yellow, segmented body...,

To expand on what Redietz said:

Sulphurs & Hendricksons are genus Ephemerella

Cahills are genus Stenacron

All three have THREE tails...

 

[redietz]

To expand on what Redietz said:

Sulphurs & Hendricksons are genus Ephemerella

Cahills are genus Stenacron

Stenacron (and I believe all Hepagenids) have only two tails as duns or spinners.

 

[JG63]

Opening Day 2026 on Yellow Breeches, Cumberland County, healthy hatch of caddis, BWO and a yellow mayfly, which I thought looked like a light Cahill. Definitely was not a Yellow Sally. Saw one with a bright green egg sac. Air temp was about 60* at the time and it was about 9 - 10 am in the morning. Fairly prolific hatch - not cloud like, but not 1-2 either. They were largely over a run, versus broken water.

It was definitely a mayfly, two tails split, thin thorax, size 14-16. Yellow to muted yellow, segmented body.

Cahill, as I understand them, would be late May and also tend to be a late afternoon hatch. Neither of those would match up with what I was seeing.

Any one have an idea of what was going on? I had one take on a paranymph, closest thing I had in my box, as I wasn’t planning on a dry fly matching challenge on opening day.

Heptagenia (AKA pale evening dun) are yellow with two tails and inhabit the Susquehanna drainage - the hatch later in May but with the low water levels and high air temps the last two days, perhaps a few nymphs got confused - were any fish taking them?

 

[Letort]

Heptagenia (AKA pale evening dun) are yellow with two tails and inhabit the Susquehanna drainage - the hatch later in May but with the low water levels and high air temps the last two days, perhaps a few nymphs got confused - were any fish taking them?

There were also BWO's and caddis hatching at the same time. Fish were coming up for them and I stuck one with a paranymph. Could not tell exactly what they were feeding on. Given that they were more sipping than splashy, guessing not the caddis and probably more like an emerger

 

[JG63]

There were also BWO's and caddis hatching at the same time. Fish were coming up for them and I stuck one with a paranymph. Could not tell exactly what they were feeding on. Given that they were more sipping than splashy, guessing not the caddis and probably more like an emerger

Paranymph is always a good call

 

[Letort]

Upon further review, I am sure it was a sulphur. Two types of sulphur - one variety I about size 14 and hatches morning, mid day (what I think I saw) and the second is in the evening and size 14-`6

 

[tomgamber]

We had Cahills on Penns just before sunset.