Friday, September 13, 2013

And it's young stoneflies at the Moormans as well: Acroneuria abnormis

Still waiting for the Rivanna to drop -- though I may give it a try in the morning.  So I thought I'd have a look at the Doyles and the Moormans out by White Hall today.  As I expected, there's not a lot to see in these mountain streams at the moment.  Common netspinners, some flatheaded mayflies (including Leucrocuta), lots of young hellgrammites, and the occasional small minnow mayfly (most/all seemed to be Baetis intercalaris).   But again I saw quite a few young common stoneflies, nymphs that will most likely be hatching next year.  They were all Acroneuria abnormis.   I decided to photograph two -- one dark (in the photos above) and one light (pictured below).

Beaty describes A. abnormis -- which is the most common "common stonefly" that I see in our streams -- in the following way.  "A. abnormis -- male nymphs 15-20 mm, female nymphs 25-30 mm; dorsum of head with a well defined M-shaped head pattern, sometimes with interruptions; posterior margins of abdminal tergies light, dark tergal bands irregular...anal gills always absent." ("The Plecoptera of North Carolina," p. 14)

Our nymphs are not yet nearly that long, still the defining features are easy to see.  Note that on the darker nymph, the "M" pattern is interrupted while on the light one it isn't.


We've reached the "slow" time of year when there's not a whole lot to see in a lot of our streams.  Best to look in the Rivanna, which I ought to be able to do now that the summer rains have abated.

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