Monday, September 7, 2015

The beginning of fall at the Rapidan River


It still doesn't feel a whole like fall in Virginia, but the leaves are coming down in the mountains.  Lots of insects moving around in the leaf packs -- both stoneflies and flatheaded mayflies.

In the photo above, one of the stoneflies I'm always happy to see -- I've only seen it four times -- the Perlid (common stonefly), Agnetina capitata.  It's too uncommon to be assigned a tolerance value in North Carolina.  In fact, in 2010 it was listed as "significantly rare" by the NC Natural Heritage Program.  (Beaty, "The Plecoptera of North Carolina," p. 15)  But the Rapidan River is a high quality stream.


A. capitata -- lateral arms of M-pattern on head directed laterally; dark area between lateral ocelli sometimes lighter to median ocellus; dorsum of abdomen banded, posterior margins dark and with a triangular mesal area anteriorly projecting forming an apparent mid-dorsal longitudinal stripe; apex of tergum 10 light with dark pigmentation faintly continuous mesally, sometimes with a small median projection directed distally.  (Beaty, p. 15)  And remember, Agnetina nymphs have anal gills, and they have a thin setal row at the back of the head.


It's a young one.  We find mature nymphs in the spring.  Got a very cool photo when that nymph turned on its side.

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There are still some Epeorus vitreus flatheaded mayflies around and also some mature, Maccaffertium ithacas.  I got a nice picture of one that was fully intact.


It kindly turned over so we could see the transverse bands on the sterna with the characteristic "anterolateral projections."

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Also present in significant numbers, the "fall" caddisfly case-makers: the "humpless case-maker," Brachycentrus appalachia


and the "strong case-maker," Psilotreta labida.

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