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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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CaseyP's profile picture
Arlington, VA/ Mercersburg, PA

Posts: 653
CaseyP on Apr 5, 2012April 5th, 2012, 8:47 am EDT
on the Little Juniata last week we happened upon a thick hatch of large black caddis with mottled gray wings. they sure weren't the grannoms we're used to. they were about a size 10, and by the time we'd found something at the bottom of the fly boxes to try, the fish were so full they wouldn't come up any more.

sorry, no photo. any ideas?
"You can observe a lot by watching." Yogi Berra
Entoman's profile picture
Northern CA & ID

Posts: 2604
Entoman on Apr 5, 2012April 5th, 2012, 11:44 am EDT
Casey -

Hopefully, somebody with more familiarity with that stream will check in. The only thing that I can say is that there are five species of Brachycentrus (Grannom) reported in PA, so it doesn't surprise me that you may be seeing a species you haven't noticed before. You've also got a lot of rhyacophilids as well that may be possibilities. As to the black body with mottled gray wings, I'm not aware of any caddis with that combination in a size 10, though several species that have been around awhile as adults can have fairly dark bodies. Too bad you couldn't get a photo.:)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
CaseyP's profile picture
Arlington, VA/ Mercersburg, PA

Posts: 653
CaseyP on Apr 5, 2012April 5th, 2012, 6:36 pm EDT
Too bad you couldn't get a photo.:)

story of my life!! i hereby pledge to always remember that the thing really is in that pocket in the new waders...
"You can observe a lot by watching." Yogi Berra

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