Cream Cahill - Maccafferitium Interpuncatatum



Staff member
Dec 13, 2021
This mayfly photograph was on the Little J at about 4:00 pm on May 20th. Pretty certain body was about 8-10mm.

Again, those just going thru the process for the first times here are some of the key indicators in identifying mayflies. Pcray1231 and sandfly have been real helpful here in this forum and are really good at this. Most of us go back to the books to verify many of the bugs we see, especially this year with hatches coing in so early. I was out with a few guys the other week, each with decades of experience and none of us called it right on the stream. Still need to look it up to get it right.

This one isn't easy, but give it a go to fill out as much data as you see and identify the mayfly.

Tails: 2 or 3
Fore wings: solid color or molted/spotted coloring
Hind wing: absent, obvious or minute (small nub behind fore wing)
Body length:
Hind wing costal bump: present or absent
Flat head: yes or no
Time of day:
Body Color:


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Female Cream Cahill - Maccaffertium mediopunctatum
haha, I think Maurice missed the point.

I'll be the first to admit I struggle to get beyond the genus. This is a maccaffertium genus. That fits all the cahills and march browns, they are closely related. I think Maurice is right on species, but am less sure of that. It wouldn't shock me if someone told me it was a March Brown, in fact, I started a thread where I misidentified a cahill and called it a March Brown. Sandfly corrected me.

2 tails, mottled wings, large/obvious hind wing.

Which kind of brings up another point. There's quite a few genus's that fit this description! Another marker to throw in there is the barred legs. I wish I had a nice list of which genus's/species have it and which ones don't. But I do know that it's pretty much on all in the maccaffertium genus, and it's also a very common genus in PA. Thus, when I see the 2 tails, mottled wings, and large hind wing, then barred legs, I usually check if it fits in maccafertium and rarely have to go beyond that.

Anyway, between march brown and light cahill, anyone have any "hard" biological markers? Generally, the cahills have more of a yellowish tint in the body, wing and tails, whereas March Browns are more brownish. But there's so much variation in color between individuals, it's not a reliable marker.
Actually I got straight to the point. I will leave the over-analyzation (pun intended) to the fast typists.

I agree though; my indicators were: two tails, Mottled wings, barred legs. Color less brown, more yellow/cream sent me to cahill (maccaffertium/old stenonema). Had to go to trout nut to get the species.

As for biological markers, meh.....March Browns are typically a week or more before the cahills and a size smaller. So it usually isn't an issue to get into that.
Yeah, but on the tiny, steep mountain freestoners timing can be all messed up! I know a few where March browns are typically June, drakes in July, and cahills in July/August.
It is a Cahill. Does anyone know why they they don't still use Stenacron? I think they are are light Cahills too.
OK then they are bigger and browner, so use the bigger and browner imitation.
dkile wrote:
It is a Cahill. Does anyone know why they they don't still use Stenacron? I think they are are light Cahills too.

Why do you say light cahill? If you check the TN site under the genus I picked it has a pic from the Little J on May 27.

My first guess without looking was light cahill or Yellow Cahill I would call it but after checking the evidence led me to my suggestion.

Whats important is its a cahill and likely the underside is cream colored like nearly all of them so a mottled winged (lemon colored) cream imitation would be the choice.
^ amen!

that was in regards to the bigger browner post
Don't put me on the defensive. I picked Stenacron, because of the body color and size...I think. But if you look at the legs it clearly is the Maccaffertium. If you match it up with a March Brown you can see how close they look. The MB is larger and has the browner coloring.

So your saying a #12 or #14 Adams then? Kidding.
Does anyone know why they they don't still use Stenacron?

Science. :)

Family/genus/species, etc. are classifications which describe how close species are related to one another evolutionarily. Species within a genus are close cousins. Within a family are distant cousins. Between families are fairly unrelated.

When we first classified them, you could consider it educated guesses based on observed traits. They did pretty good, considering the thousands of species out there and they only screwed up a few! But with more advanced methods, such as DNA analysis, we are finding our mistakes.

Stenacron still exists. It's just that some of the former members were more closely related to the species in maccafertium than they were to the species which still reside in stenacron. So they moved them. Making things clearer for entomologists, and more confusing for us fishermen!

When you compare the light/cream cahills to, say, March Browns, the close relation is obvious. All that's really different is color and timing. Which are two things that genetically can change very easily, unlike, say, growing an extra tail or a hind wing, which takes a very long time to develop.
Pink cahill(Epeorus Vitreus), however, I'm hedging my bets, because none of the suggested flies are uusually as small as 8 to 10 mm. But Pink Cahill come closest.
Epeorus don't have mottled wings. This bug clearly has mottled wings.

And I've NEVER heard Epeorus Vitreus described as a cahill of any type. I've heard them described by common names pink lady, sulpher, yellow quill, PED's, and little maryatt's, but never cahill.

I'm fairly certain you're looking at maccaffertium genus. It's just that the genus has a bunch of different species that I can't tell apart, so I have no faith that I'd get the species correct.
Chaz wrote:
Pink cahill(Epeorus Vitreus), however, I'm hedging my bets, because none of the suggested flies are uusually as small as 8 to 10 mm. But Pink Cahill come closest.

It looks like an Epeorus vitreus (Pink Lady) to me too. I didn't go through the key, I'm just going on an off the cuff, looks like that to me type of "analysis." If anyone really does take it through the key, I'd be interested in what you come up with.
E. Vitreus is a pink lady aka pink cahill. However troutnut has them as a sulphur which is the only time I've seen troutnut get something wrong. It is E Vitreus. I don't care what the common name you use for the fly pictured.
Agree with you on the naming of E. Vitreus. Pink Lady is what I've most often heard as the common name. And when people say sulfur, I usually make a point to correct it, because I think it's against better judgement to overuse the sulphur name, as there are important differences between types of yellowish bugs.

But I still struggle to call the OP's bug E. Vitreus. Wings is my holdup, I'm still calling that mottled, whereas E. Vitreus is a plain wing. Perhaps I'm overweighting the darkened cross veins. But if I saw that onstream, I'd call it a cahill every time (as in the cahills within the maccaffertium genus). If I didn't call it a cahill, I'd most likely mis-ID it as a March Brown, which is also in the maccaffertium genus. I could probably be convinced otherwise, but I'm really struggling to take it out of maccaffertium.

explain why the fly pictured above has mottled wings yet no Epeorus have mottled wings.

I've seen pink cahills on penns.....Barred legs, two tails, mottled wings and a rosey-pink cast to the body with a nearly chartreuse blotch on the underside of the thorax. I thought I must have dropped acid. I called it a pink cahill here and got chastized for making up new fly names. Nevertheless, all trilogy of indicators pointed to Stenonema (prior to the lumping into Maccaffertium with the Epeorus)

Why Epeorus is lumped into there I have no idea.....The wings are not mottled in the E-genus.

Anyway, The fly pictured cannot be Epeorus because fo the could be a pink lady (cahill) but the color is wrong IMHO. So it must be a cream or Light Cahill. I stick with cream.

TN also has the Pink Lady listed as a Epeorus albertae. But again no mottled wings and the body does not have defined segmentation with contrasting color.
Maurice, I'm agreeing with you on the ID of this critter for the same reasons. I also agree that I'd resist calling anything in epeorus genus a cahill of any sort, the name "cahill" should be reserved for the true cahills in the maccaffertium genus. I resist calling them sulfur's for the same reason, that name should be reserved for true sulfur's in the ephemerella genus.

I hate all this cross pollination of common names with different genuses, which confuses people and makes people think VERY different bugs are the same bugs. I realize you can't call any of it "wrong" as there is no accepted convention for common names. If it were up to me I'd split up the common name BWO about 4 ways too. Heck as it is, that one covers several FAMILIES, not just different genuses.

But there's a thing or two in your post that I'm not making sense of. We'll start with this.

prior to the lumping into Maccaffertium with the Epeorus

Did I miss something? To my knowledge, maccaffertium and epeorus remain very separate genus's. And as you pointed out, the easiest marker to tell between them is mottled wings of maccaffertium vs. plain wings in epeorus.
No you are right Pcray...I mis-spoke. I meant the family Heptageniidae. I actually typed that and then posted, read your post and saw you said Maccaffertium and went back and changed it. because your post mirrored mine I thought I typed the wrong word.

Anyway, I was up late, sorting through all this and I think they just don't belong together. You watch, someday they will put it all back and we can.

I think that the cahills and the March Browns do indeed belong in the same genus. What you call that genus I don't really care.