Sunday, September 10, 2017

Something new! An "armored mayfly" (Baetiscidae), Baetisca berneri

I just wasn't ready for this one.  In all of the years I've been out on the streams, this is the first time I've managed to find one of these nymphs.  A Baetiscidae -- armored mayfly -- which keyed out to Baetisca berneri.  I never thought I would see one.

Habitat, according to Beaty, is "Lotic, partially buried, often in shallow sandy or gravelly riffles or in edge vegetation."  ("The Ephemeroptera of North Carolina," p. 73)  And that's pretty much where I found it, by stirring up rocks and sandy gravel in a small riffle close to shore -- Rapidan River.

Genus ID: "Anterior margin of head with medial frontal projection or with anterolateral genal spines; enlarged thoracic notum fused between wing pads and forming a shield or carapace-like projection which is extended to abdominal segment 6; gills concealed beneath thoracic shield; three caudal filaments, short; body typically light brown with variable dark pigmentation."  (Beaty, p. 73)

All visible here, and this one has the genal spines.

On to the species -- it's Baetisca berneri, which is "Uncommon and very intolerant," according to Beaty.  (Would we expect anything less from the Rapidan River?!)

berneri -- nymphs 7.5-11.5 mm; genal spines present; caudal filaments prominently banded with dark brown at base; body pale with variable speckling, an interrupted dorsomedial line on abdomen; ventral surface may be speckled and brown.

There's no question about the ID, but this was a much smaller nymph than Beaty describes: it measured a mere 4.5 mm.  Sure wish it had been bigger, my photos would be much better.  As it is, I'm surprised I got any photos at all.  This little guy -- and with those big red eyes it is a "guy" -- kept darting around my petri dish making it very hard to focus.  But I still got some decent shots.


Pretty exciting.  However, the Rapidan is very low -- it could use a whole lot of rain.

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