Wednesday, March 20, 2013

Rhyacophila carolina at a small stream in Sugar Hollow

The plan was to go to Buck Mt. Creek where I'm sure the winter insects -- H. amplum small minnow mayflies, Clioperla clio Perlodids, etc. -- are fairly mature.   But BMC is still high, fast, and off-color.  I'm still restricted to the small, first order streams in Sugar Hollow: I'm not even sure that the Rapidan is doable yet.

My choice today was a small stream that spills into the Moormans not far from the first bridge.  This is only the second time that I've stopped there.  I sure didn't have to look very hard to find lots of interesting insects.  While here, too, the E. dorothea spiny crawlers dominated my findings, I was most excited about this free-living caddisfly larva, Rhyacophila carolina, one that I've only seen in a few of our streams.  Tolerance value: 0.4.

There are three features that distinguish this species, one is the color of the head and pronotum: golden brown (Beaty, "The Trichoptera of North Carolina," 60).   That's very clear in all of my pictures.

Number two -- there are no ventral teeth (denticles) on the anal claws.

And number three -- the sides of the head are "rounded," not "parallel."  Compare R. carolina with R. nigrita.

R. carolina, according to Beaty, is the "second most common Rhyacophila in NC."

For the rest, pretty much what we'd expect to find in a small mountain stream at this time of year.

1. Spiny crawler mayflies, E. dorothea.  As I did at the Whippoorwill last week, I found both the large nymphs that are dark brown with a pale dorsal stripe,  nymphs that are already fairly mature,

and some much smaller nymphs that still have a long way to go.  However, these E. dorotheas were not so much "speckled" -- as those at the Whippoorwill were -- as highly patterned, and one was a very odd color, very orange.

2. A Limnephilid (Northern case-maker), genus Pycnopsyche -- the one with the three-sided case made out of segments of leaves.

3. Common stonefly, Eccoptura xanthenses.  I saw quite a few -- this was their kind of stream.

4. And as you can see in that photo, I found some Uenoids, including two very small Neophylax aniqua.  Here is a close-up of the one in the photo above.  The blunt tubercle on the head is visible even though the larva was only 2.5 mm.

Here's a second N. aniqua: this one was 3 mm long.

I also found two N. concinnus Uenoids: the photos of this one were the best.

N. concinnus larvae have a small, rounded tubercle on the head which you can see if you enlarge this photo.   They also have a "spiculate" pattern on the frontoclypeus and fairly large spines on the anterior of the pronotum.

And no clavate gills.


Note the difference in size of two of the E. dorotheas.

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