My post of two days ago was premature. I had forgotten all about the article I read just two weeks ago(!), written by R.P Randolph and W.P. McCafferty: "First Larval Descriptions of Two Species of Paraleptophlebia (Ephemeroptera: Leptophlebiidae)", Entomological News 107 (4) 225-229, 1996. The two species described are Paraleptophlebia assimilis and Paraleptophlebia jeanae. In the article, the authors note: "In present keys to the larvae of Paraleptophlebia, P. jeanae will key with P. debilis (Walker) at couplet 9 of Traver (1935: 515) and couplet 7 of Burks (1953: 90). This is because of the similarity of gill structure, posterolateral projections on abdominal segments 8 and 9, and brown banding on the legs of P. jeanae and P. debilis."
Their description of P. jeanae goes into detail on 1) the parts of the head (head capsule, eyes and antennae, labrum, mandibles, maxillary palps, hypopharnyx, etc.); 2) the markings on the thorax and legs; and 3) abdominal coloration. Of all of these features, most important of all is the mouthpart structure. ("Although abdominal coloration may prove to be unreliable to differentiate the larvae of these two species [i.e. debilis and jeanae], mouthpart structure will consistently distinguish them.") Of course, that's the one thing I cannot examine without a specimen or two, something I won't collect until next winter or spring. Bummer.
What I can see is the abdominal coloration, and that is very interesting. Let me review what they say.
Abdominal coloration variable: abdominal tergum 1 brown; terga 2-9 often with paired crescent-shaped pale markings submedially on each tergum; submedial tergal markings less often coalescing, forming larger pale area in posterior area of terga: submedial tergal markings also less often appearing as pair of submedial streaks along entire dorsum of abdomen; lateral margins of abdominal terga 2-9 pale; tergum 10 brown, pale medially. Posterolateral corners of segments 8 and 9 extended into sharp projections.
Take a look at the abdomens of the two nymphs my friend has found in her small stream in Sugar Hollow (which correspond to my nymph at the top of the page).
(Should be "on posterior edge of tergites.")
On the second nymph, we can very clearly see that the submedial tergal markings (the crescent-shaped marks) coalesce "forming [a] larger pale area in [the] posterior area of [the] terga."
Hmm... Very intriguing. Still, remember that they insist that we must see the mouthparts to be certain of our ID.
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Have to leave it there until sometime next spring. In the meantime, the safe ID is "Paraleptophlebia debilis/jeanae."
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