Monday, December 16, 2013

The Uenoids (little northern casemakers) at the Rapidan River: best bet is Neophylax atlanta

Now back to the species ID of the Uenoids I found yesterday.    Everything points to Neophylax atlanta, a species that is "apparently rare" according to Beaty ("The Trichoptera of North Carolina, p. 86).  This is confirmed by the source on all things Neophylax -- The Caddisfly Genus Neophylax (Trichoptera: Uenoidae), a book that was jointly authored by R.N. Vineyard, G.B. Wiggins, H.E. Frania, and P.W. Schefter (Royal Ontario Museum, 2005).  "N. atlanta remains one of the rarest species of the genus in eastern North America." (Vineyard, p. 45)  For "Distribution" they note, "Neophylax adults have been collected near small streams in the foothills of the Appalachian Mountains in the southeastern United States from Virginia to Alabama."

I'll approach this ID first in a negative then in a positive way.  First, have a look at this microscope shot of one of the larvae, noting the clavate ventral gills and the dark head and legs.

1. Process of Elimination.  Of the 9 species of Neophylax described by Steven Beaty (pp. 86-87), only 5 -- N. atlanta, N. oligius, N. consimilis, N. mitchelli, and N. ornatus -- have clavate ventral gills, so we know where to begin.  We can eliminate oligius and consimilis since our larva has no markings at all on its head/face.  N. oligius, you'll recall, has a well defined yellow-orange stripe...

and N. consimilis has one or two pale spots which sometimes merge to form a short stripe.

The head/face of our larva is uniformly dark brown/black.  We can also rule out mitchelli.  Mitchelli has a very distinct tubercle on top of its head --

nothing like that on our larva.   There may be a low rounded frontoclypeal tubercle on our larva, but Beaty assures me that such a "bump" is common on Neophylax.

So our larva is N. atlanta or N. ornatus.  Vineyard, note that "the larva of N. ornatus is similar to that of N. atlanta," (p. 62) but they describe the head as "yellow to yellowish brown" (p. 10) which is not at all true of our larva.  Also, they note that Neophylax ornatus is restricted to springs and small first-order streams." (p. 63)  The Rapidan is no longer a first-order stream where these larvae were found.  So, the "process of elimination" seems to point to Neophylax atlanta.

2. Larval Description.  But what is the larval description of N. atlanta?  Can we see the anatomical features we need to see for that ID?  Two of those features are easy to see: our larva has ventral gills and it does not have a "frontoclypeal tubercle" (Vineyard, p. 45).  But there are five other features that require some microscope work.    (For the detailed larval description, see Vineyard,, p. 45).

1. There is "a relatively large number of long pronotal setae."  Yes.

2. There are "relatively short spines along the anterior margin of the pronotum."  Yes.

3. We should see "about 4 setae" at the sa3 position of abdominal segment 1.  I think I can see 5 on this larva -- probably close enough.

4. There are "lateral gills" at 2p and 3a -- i.e. on the posterior (p) edge of abdominal segment 2 and the anterior (a) edge of segment 3.  They're difficult to see...but they're there.  Look closely; the tips overlap.

5.  And now for the toughy, which apparently is a critical feature.  Ugh!  There is a "spiculate microsculpture on the pronotum," (p. 45), i.e. it looks "grainy" or "cobbled."  I can see it with my microscope.  This is the best I could do with my photos.  A really good look would probably require an electron microscope.

When all of this evidence is taken together, I think Neophylax atlanta is a pretty safe bet for our ID.  I've added this taxon to our EPT list.

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