Saturday, November 21, 2015

It's the "rapid" Rapidan at the moment -- but I got some nice photos

Actually, it was pretty scary up there this morning.  The water was very high and very fast (see the photo below), and I had to stay close to the shore to look through the leaf packs.  Lots of pronggilled mayflies now, and a smattering of small winter stoneflies.  But I did find some insects that made for very nice photos.

The first, a Lepidostomatid.  I didn't keep it, so I can't be sure of the genus ID -- but it's probably Lepidostoma.  In any event, I couldn't resist taking some shots of that beautiful case.

Excellent photos of the adults in Ames' Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, pp. 186-189.  I take it these hatch as the "scaly brown sedge" in March and April.  But at time of year, anglers at the Rapidan will be focussing on prolific hatches of "yellow sallies."

And the other treasure this morning -- the "golden stones," Agnetina capitata.   Since I reviewed the species identification of A. capitata in my entry of 9/7, I'll just point out the 1) setal row on the occiput, and 2) the presence of anal gills.

I found three nymphs in the leaf packs, and since I seem to find this species in a regular way at the Rapidan River, I'm starting to wonder just how "rare" it is.  Beaty's comment: "Listed by NC Natural Heritage Program as Significantly Rare (2010)."  ("The Plecoptera of North Carolina," p. 15).


The sunlight was great, but the water...roaring!

Sunday, November 15, 2015

Surpise, surprise! Paragnetina fumosa at Buck Mt. Creek

And a very pleasant suprise.

I went to Buck Mt. Creek this morning with low expectations.  I was pretty sure that I'd see small winter stoneflies -- and I did.  I was hoping to see the common stonefly Acroneuria lycorias since this is the only place that I've seen it.  No luck with that species, but I still made out very well.

It's the common stonefly, Paragnetina fumosa.  This is only the second nymph that I've found.  The other was also at Buck Mt. Creek, on April 17, 2013 (see the entry posted that day).  That nymph was a bit more mature, but not a heck of a lot.  Still, the diagnostic features -- see below -- are more readily seen.

For the identification, I turn to Steven Beaty's "The Plecoptera of North Carolina," p. 18.  "P. fumosa -- nymphs ?? mm; frons with a pair of yellow spots lateral to the median ocellar spot, median ocellar spot often congruous with pale yellow transverse band near labrum; thoracic nota with complex and extensive pattern of yellow markings; yellow femora with one sometimes two distinctive dark brown transverse bands; abdominal terga 3-4, 5 with a pair of pale markings and 8 and 9 mostly pale; anal gills present or absent.  Common and widespread."

Let's have a look.  On this close up of the head, we can see 1) the "yellow spots lateral to the median ocellar spot," 2) how the median ocellar spot is nearly congruous with the yellow band near the labrum, 3) and the row of spinules on the occiput, typical of the genus.

For the abdomen --

easy to see the paired pale markings on terga 3-5.  We can almost see that the anal gills are absent (were it not for the silt on the nymph!), and we can see the transverse band (bands?) on the femora.

Paragnetina fumosa.  Sweet!


The small winter stoneflies were numerous -- 3-4 in every leaf pack that I picked up.  Still immature, but the wing pads are fully developed.  Most likely, Allocapnia pygmaea which is the most common species we see.


Our streams are finally dropping, but as you can see, the leaf packs are still pretty muddy from the high, fast conditions we've had of late.  Still, we should be able to start looking again.

Note:  On reflection, I think I misidentified the "transverse bands" on the femora.  On this nymph, I see one "full" and one "partial" transverse band on the femora.