Saturday, June 3, 2017

Teloganopsis deficiens, Micrasema wataga and other good finds at the Rapidan River

Good morning at the Rapidan River, though the water was high, and I had to stick close to shore.

1. Teloganopsis deficiens.  This is only the second time that I've seen this little mayfly.  The first was back on June 10, 2012, so it's been awhile.  It has a tolerance value of 2.6: as Beaty notes -- "This species in intolerant."  (Beaty, "The Ephemeroptera of North Carolina," p. 63)

He also notes that "the double pale dorsal stripe" makes field ID fairly easy, but to be sure we have to check the cerci.  On this species, there are no intersegmental setae, just "whorls of spines at [the] apex of each segment."

But for that feature, it could be confused with a Serratella nymph, which it clearly resembles.  Very cool.


2. Micrasema wataga.

This is the first time I've found this caddisfly larva (Brachycentridae: "humpless casemaker"), and I'm so bummed that my photos didn't turn out all that well.

Alas.  When I first saw this case in my bowl, I was sure that I knew what it was: had to be Micrasema bennetti since I had found that before, back in April 2013.

Note that the case is the same: a round cylinder made of strips of vegetative matter.  But, the heads are entirely different.


Beaty describes wataga this way: "head rounded; head pattern mottled brown on lighter background, usually with a pale spot encompassing frontoclypeal angle and surrounding area.  Case vegetable and mostly straight." ("The Trichoptera of North Carolina," p. 80)  That's a match.

Some other comments of interest.  "Micrasema is almost always associated with living vascular plants (moss, Podostemum, etc.) in fast water."  This one was attached to a piece of grass that I inadvertently put into my bowl.  And on the genus he adds, "Very intolerant.  Larvae are generally small in summer...and more abundant and diverse in larger streams, often 2-3 species."  And we've got M. wataga and M. bennetti both in the Rapidan River.

3. Perlodid stonefly, Remenus sp. (bilobatus?)

Obviously the best photos I got today.   While this nymph keys out to Remenus bilobatus, Beaty cautions to leave ID at the level of genus.  There are at least two other known species of Remenus: their larvae have not been described.

The key to the ID?  Among other things, the lacinia is unidentate -- no submental teeth.


A good day -- though I'd like to have better photos of that Micrasema wataga.  Fortunately, we do have some good pics of the species that my friend took of two larvae she found in the Moormans in June 2012.  So much better.  She was using a more powerful lens.

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