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3. Pennsylvania Mayfly Spinner

Any ideas on this one? From NW PA. About a size 18, found around noon today in a spider web on a stream not known for either trout or bugs. I have never seen a substantial hatch of anything on this stream, but today I say these little guys along with some tricos. The stream gets pretty warm and I was fishing for smallies and chubs...yes the little bottom-feeders that everyone hates... Anyway, let me know if you have any ideas.



Mike

Hard to say for sure without a closer shot, Mike, but they look like little Leucrocuta spinners (male). Leucrocuta is a very underrated hatch at this time of year, even on legitimate trout streams.

While no bug guy like many here I'd bet a dozen flies it is a Luekon shuck. (White fly spinner)

Mike-

I believe your mayfly photo to be of two Maccaffertium pulchellum male imagos.

I appreciate everyone's input. I don't think that it is Ephoron leukon...these flies were slightly smaller, it's too early in the year and the veination on the wings is different. Also, leukon has 3 tails to my knowledge and both of these flies have only 2. Here is a closer picture of the same fly. Maybe this will help.



Mike

Wbranch,

E. leukon would be larger, the wings (even of the male spinners) retain a milky appearance and are unmarked except for a dark leading edge (no very dark cross-veins), the legs (except for the forelegs of male spinners) are atrophied and small, and the eyes are smaller and dark. (The eyes of heptageniids fluoresce in bright light.) Compare to John's photos:

http://www.wiflyfisher.com/ephoron-leukon-mayfly-hatch.asp

Roger,

It does appear to be a heptageniid, and I considered Maccaffertium and Stenacron, but they are all larger than a standard #18 (which I take to be about 6-7mm). Leucrocuta and a few Nixe or Heptagenia are in that size range. Also it seems that the darkened cluster of cross-veins are in the first space behind the costa, whereas Maccaffertium, Stenonema, and Stenacron tend to have clustered cross-veins or dark marks in the third space. I don't have examples of the other Leucrocuta (I believe that aphrodite and juno are lighter in color), but you can see the translucent abdomen on the darker hebe in Don Chandler's photo:

http://bugguide.net/node/view/203347/bgimage

Lloyd-

Oops. Didn't notice that Mike mentioned a size. Guess I need to read better and analyze less.

Lets leave it at Leucrocuta for now. The stream is right down the street and I'll be fishing it all summer. I will take more and hopefully better pictures in the future and we'll see if we can't narrow it down.

Gonzo- I was not able to find photos of L. juno or L. aphrodite. Please do let me know if anything else comes up. Thanks

Mike

Quite alright, Roger, since a heptageniid ID is about all that's fairly certain, I'll split the dozen flies with you. ;)

NOTICE- I have made a huge mistake. This fly is NOT a size 18. It is clearly 16, if not slightly larger. I just guessed earlier, but now looking at some hooks, I would put it at a size 16. I am sorry guys. Well let me know what we may be looking at now.

Well, that puts it nearer the borderline. If you can get a close-up of the wing, it should help to resolve any question about the genus in Heptageniidae.

This is a horrible photo. It may or may not be helpful.



Mike

I think it will take a clear shot of the wing (and maybe of the markings on the back) to really be able to pin it down. If it was a large #16 (say, 8-9mm), it would start to be in range for some smaller Maccaffertium or Stenacron males. If that dark blob near the leading edge of the forewing resolves into a hashmark in the third space, it would be a Stenacron something like this one:

http://bugguide.net/node/view/203191/bgimage

If it resolves into dark cross-veins in the first space, it's still probably Leucrocuta. If the cross-veins are clustered more in the second and third space, it could be Maccaffertium.

By the way, Mark, you are quite right about the three tails on Ephoron females--they never molt into spinners and mate as duns. However, the Ephoron males (the ones with the long forelegs in John's photo) do molt and have two tails.

I too didn't pay attention to the size mentioned in the initial post.

Since the size range has been revised upwards, I'm now leaning more toward a Maccaffertium ID on this one. I don't think it is pulchellum, though. Descriptions of that species mention that the mesoscutellum is entirely white. It could be modestum, mediopunctatum, or terminatum. These "cream cahills" are very difficult to separate. A clear photo and millimeter measurement might help, but given the variability (especially of modestum) it would still be difficult to be sure.

Lloyd-



Hmmm. Be cautious with such a posture. Leaning just a bit too far risks tipping over.

You're probably right about the precarious posture, Roger, but teetering on the brink is a habit of mine. :)