Thursday, December 22, 2016
The "Appalachian Springfly" -- Isogenoides hansoni
Of the many "rare" and "uncommon" taxa that I find at the Rapidan River, this may be the one I like best. It was one of the things I was hoping to see this morning and I lucked out.
The features noted as critical of the genus ID by Steven Beaty are these: "...mesosternum with median longitudinal suture joining fork of mesosternal grooves to transverse anterior suture; prominent submental gills, projecting about three times their basal width." ("The Plecoptera of North Carolina," p. 57) Here you go.
(Look closely, the median line is hard to see.)
On the species ID he says this: "nymphs 16-24 mm. Head with conspicuous, sharply delineated pale M-pattern anterior to median ocellus; ocellar triangle bordered by dark brown but with pale, ovalized central spot; occiput brown anteriorly with light brown reticulated areas enclosed by spinule row...; pronotum widely margined with brown."
Isogenoides hansoni, the "Appalachian Springfly".
The Rapidan water levels are great at the moment, and there are lots of good leafpacks around, all loaded with Pronggilled mayfly nymphs. But there were other things that provided good photos.
1. Giant stonefly, Pteronarcys biloba (the "Knobbed salmonfly")
This beauty measured 34 mm! I had to get up on my knees to get a photo of the whole nymph.
2. And again one of those "ho-hum" -- gorgeous! -- spiny crawlers. Ephemerella subvaria.
3. A very small common stonefly, Agnetina capitata. I saw a number of A. capitatas that were quite a bit larger than this.
3. A couple of shy Lepidostomatids, one young one with a "mixed media" case.
4. And a "humpless casemaker" -- Brachycentrus appalachia -- with a young Isoperla montana nymph hitching a ride. (First I. montana nymph of the season.)
The Rapidan River in winter