Wednesday, December 18, 2013

The Nemourid stonefly Soyedina: a good morning in Sugar Hollow

My friend found this one last year in a small stream at high elevation (see the entry of 3/5/13) -- but for me, this was a first.  This is the Nemourid stonefly, genus Soyedina.  I found two of them today in one of my favorite streams for looking for insects.  We have to leave this at the level of genus since only a few of these nymphs have been described to the level of species.  I can tell you that only two species are attested for the state of Virginia (Stewart and Stark, Nymphs of North American Stonefly Genera, p. 217) -- S. carolinensis and S. vallicularia.  Stewart and Stark provide illustrations of S. vallicularia (pp. 215-216), and I'd have to say I don't think that's the species we're finding.

Beaty says that Soyedina is "relatively rare," and describes it in the following way: "Nymphs 6.5-8.5 mm; pronotum with angular corners and a distinct posterolateral notch, with well developed lateral fringe; wing pads divergent; anterior thoracic gills absent." ("The Plecoptera of North Carolina," p. 5)  Stewart and Stark note the key diagnostic characters in the following way: "The short legs and fringed, notched rectangular pronotum distinguish Soyedina nymphs from the nymphs of other non gilled genera.

The nymphs that I found were young and about 6 mm in length.  It is the fore femora which are especially short, and we can see that in the photo above.  For the other features -- pronotal notch with dense lateral fringe and divergent wing pads -- the photos my friend took last year show them better than anything I managed to get.

The divergent wing pads:

The pronotal notch and lateral fringe:

The nymphs she found -- like those that I found this morning -- were a little bit "muddy," but these are nymphs that are typically "found in leaf packs in seeps and small, cold streams." (Beaty, p. 5)

Love finding new things!


But I made lot of good findings this morning.

1. The first Taenionema atlanticum large winter stonefly of the season.

In another 1-2 months they'll be looking like this.

2. A Lepidostomatid (genus Lepidostoma) in a very nice case made of sand.

3.  And three Uneoids that had also made very colorful cases.




Number one was Neophylax oligius: two and three will require more work.  They appear to be the same species that I found at the Rapidan River, i.e. N. atlanta.

Nice day at a beautiful stream.

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