Friday, December 26, 2014
Large winter stones and Uenoids: reporting on two different streams
I've just returned from one of my small streams in Sugar Hollow where I found that winter is now in full swing. Lots of small winter stoneflies, some Leuctrids (Needleflies), a few small Perlodids, oodles of Epeorus pleuralis flatheaded mayflies on the bottoms of rocks, and Giant stones (Pteronarcys proteus) that are getting fairly mature (they'll hatch in March and April). And I found a large number of the large winter stonefly that we find in these small mountain streams -- Taenionema atlanticum (photo at the top of the page). Beaty says they are "rarely collected" ("The Plecoptera of North Carolina," p. 7) -- a statement I've always found strange. They abound in these small streams, and I find them as well in the Rapidan River.
In the photo at the top of the page, you can make out one of the key features for identification, the "ninth sternal plate [is] broad apically" (Beaty, p. 7).
This can be used to distinguish T. atlanticum from a similar large winter stonefly, Strophopteryx limata. (Beaty, pp. 6 and 7)
And the Uenoids (Little northern case-makers) are starting to show up on the rocks. Picked up two this morning, both were Neophylax consimilis.
(That young Free-living caddisfly larva that shows up in these photos is either R. glaberrima or R. invaria (Banksi complex). Can't be sure which it was since I decided not to preserve it. Both are fairly rare.)
Neophylax consimilis, you may recall is a Uenoid that has "ventral clavate gills" on abdominal segment 1, these...
but it does not have a tubercle on its head. In some cases, the head/face is completely brown -- true of the nymphs that I found this morning -- in others there's an orange/red spot in the center.
That orange/red spot was very clear on this N. consimilis that I found last weekend in a trip to the upper reaches of Buck Mt. Creek. (Click on the photo to enlarge.)
And there was another Uenoid up there, Neophylax oligius.
N. oligius, like N. consimilis, lacks a tubercle on its head, and it has ventral clavate gills. But note the different marks on the face. N. oligius has a long orange stripe on its face that extends from the top to the bottom.
And to end up where we began, Buck Mt. Creek was loaded with a quite different large winter stonefly: the large winter that we see in a lot of our streams, Taeniopteryx burksi/maura.
Pretty easy to recognize this one by the colors and that long, medial yellow stripe that runs the length of the body. But if you want confirmation, flip it over. There are long, telescoping gills at the base of each of the legs (coxal gills).
This is a fairly tolerant nymph with a tolerance value of 6.6. (T. atlanticum has not been assigned a TV: too uncommon.)