Friday, November 29, 2013

Fairly certain I'd see the case-maker Apatania incerta at the Doyles River this morning

No, that isn't Apatania -- but it's a very nice look at the Perlodid stonefly, Diploperla duplicata.  I saw a number of them this morning -- by far, the largest Diploperlas I've seen this season.


But I found, for the first time this season, several "little mountain casemakers" -- family, Apataniide.

This was a very small larva.  The case was less than 4 mm in length; the larva went about 3.  Still, the distinguishing features were clear: case of small pebbles and sand grains, tapered, cornucopia shaped with a hood; larval body yellow; no sclerites at the sa1 position on the metanotum.  And as I noted in the last entry, the hooded case covers the head of the larva when it's crawling around, but you can often see the legs sticking out to the side.

Also clear in this sample, the larvae sometimes add larger pebbles/crystals to the hood of the case.

I think it's safe to call the larvae I find Apatania incerta.  But I should note that Beaty cautions to leave our ID at the level of genus -- Apatania -- which, notes Thomas Ames, is "the most common eastern species, with a range as far south as the southern highlands.  (Thomas Ames, Caddisflies, p. 229.)  A. incerta is described by Beaty, in fact it's the only larva that he describes, and that description matches our larva.  Also, he notes that two other secies -- A. pravaelens and A. rossi -- have been synonymized with A. incerta (Flint, 2007).  But that synonymy has not yet been accepted in with the World Trichoptera Checklist.  (Beaty, "The Trichoptera of North Carolina," p. 85)  So, it's genus Apatania if we want to be cautious; species Apatania incerta if we add these qualifications.

In any event, I found them in the Doyles last year, and at the Rapidan, and in some smaller streams as I recall.  The tolerance value is only 0.6.

Other photos:

1. A large winter stonefly, Taeniopteryx burksi/maura.  Note the "coxal gills" in the second photo.

2. And a Clioperla clio Perlodid.  Only one, I expected to see a lot more.

Stonefly nymphs like to crawl on the sides of the petri dishes.

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