Thursday, May 30, 2013

Another surprise at Buck Mt. Creek: the spiny crawler Drunella cornutella

This is the Drunella species I was hoping to find at the upper Doyles river two weeks ago, since, until this morning, that's the only place where I had seen it.  Drunella cornutella is "slim and trim" compared to the other Drunellas we see in this stream: Drunella walkeri and Drunella tuberculata.
The striking feature -- the "long conical, semilunar lateral frontoclypeal projections" (Beaty, "The Ephemeroptera of North Carolina," p. 25).  These.

This is another taxon -- along with things like roll-winged stoneflies, net-winged midges, and green stoneflies (genus Alloperla) -- that I just don't expect to see in this stream, at least not this far down from its source.  The tolerance value is 0.0.  For a full run-down of the diagnostic features of D. cornutella, look back at my posting of 5/27/12.   Here are more photos.


I saw a lot of Drunellas today, most were in the moss and grass on the tops of rocks out in the stream.  All of these were the common species I see at Buck Mt. Creek -- D. tuberculata.  I took photos of two of them.  The first corresponds to the colors that I normally see; the second is one that's fully mature -- deep rich colors and black wing pads.  The thorax and legs were the color of wine.



But without any question, the nymph of the day in terms of big numbers was the flatheaded mayfly Epeorus vitreus (TV, 1.2).   All over the place at the moment -- just turn over any big rock and you'll see them.  But, you've got to be quick if you want to get one -- they don't wait around to be stared at!

The vein pattern on the gills is much more pronounced than that of Epeorus pleuralis.  But the key feature to see for ID is the "four irregular pale spots on the anterior margin of the head, two submedial and two sublateral."  (Beaty, "Ephemeroptera," p. 17)  These.

Keeping the legs and gills intact on these nymphs -- what I always want for my pictures -- is a real challenge.

The only stoneflies I'm seeing in a lot of our streams at the moment are Isoperla holochlora (Perlodid) and the genus Perlesta common stone.

And the only mayfly I saw today was a tiny, tiny, male Plauditus dubius (two tails with medial banding).  Also a tough subject for the guy holding the camera.


But I was so happy to see D. cornutella.  Beaty says that it's "common," but that does not seem to be true in the streams that I visit.  Size: 7 mm.

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