Tuesday, October 28, 2014

Small winter stones and the Perlodids: the new season begins at Buck Mt. Creek

I would have bet money that I'd find them today -- and I did: Clioperla clio Perlodids and Allocapnia small winter stones (Capniidae).    C. clio in the photo above, and here's one of 3-4 of the small winters that I found in the leaves.

The small winter stoneflies are very small at the moment: this one was 4 mm.  The C. clio Perlodid, at 7 mm, was a little bit bigger.

To me, the appearance of these particular stoneflies marks the start of the new season.  While we can see common stoneflies (Perlidae) -- especially Acroneurias -- just about anytime of the year (most Perlids have a 2 year life cycle), small winter stoneflies are univoltine (1 year life cycle) with rapid growth: they show up sometime in October (usually late), and they're pretty well gone by the beginning of March.  Here are some Allocapnia nymphs from previous years.

November 2012

December 2012

Perlodid stoneflies are also univoltine, but we can see them right into June, though the latest I've found C. clio was April.  Pretty spectacular when they're fully mature.

Pretty nice in February as well.  (Last year, Buck Mt. Creek)


Acroneuria carolinensis/Acroneuria lycorias

But I found another stonefly this morning in Buck Mt. Creek.  This.

Having just reviewed the ID of Acroneuria carolinensis (see the entry of 10/23), I knew right away what it was: A. carolinensis, right?  Still, given the problem of confusion with A. lycorias nymphs, I thought I'd best look for anal gills.  And look what I found!

I'll be damned: it could be A. lycorias.  You'll recall that Frison had argued that A. carolinensis and A. lycorias look much alike, but carolinensis lacks anal gills, lycorias has them.  But then, Beaty muddies the waters by saying that on carolinensis "anal gills usually absent," while on lycorias nymphs "anal gills [are] usually present, sometimes small."  ("The Plecoptera of North Carolina, p. 14 -- I've italicized the usually for emphasis).   So we can't be certain of the ID, but A. lycorias may be found in some of our streams.

(By the way, the nymphs that I found at the Doyles River last week did not have anal gills -- double checked.  I would not be surprised to find A. carolinensis (TV of 1.2) at the upper Doyles, and A. lycorias (TV of 2.1) in Buck Mt. Creek.)

Other pix from this morning.

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