Sunday, July 29, 2012

Our "Fall" Odontocerids -- Stong Case-maker Caddisflies -- Are Already Here: The Rapidan River

It's July 29th, but when I stepped into the Rapidan River this morning, there they were: six Odontocerid cases on a single large rock.  But everything else has been early this year -- so why not?  I didn't see them last year until September 18th.  The nice thing about this case-making caddis is that you don't have to hunt to find them: you'll see their tube-like cases made of pebbles and sand on the tops of rocks where the larvae are grazing.  And you can pick them up firmly with tweezers: the cases really are "strong," you're not going to crush them.

The genus is Psilotreta: for species ID, we have to wait until they're fully mature -- these clearly were not.
(For the five species of Psilotreta found in the southeast, look at Steven Beaty's "The Trichoptera of North Carolina.")

But the case-maker that still covers the rocks in the Rapidan River is the "Humpless case-maker" -- family, Brachycentridae.  The species we find here is Brachycentrus appalachia, on which see the entry of 7/10.
I got some nice photos of a fair-sized one today, sticking its head out of its 4-sided case.

And yes, the larval body really is green!

There were lots of common netspinners present this morning -- as we're seeing at the moment in all of our streams -- fingernet netspinners as well (genus Dolophilodes).  And I saw a good number of flatheaded mayflies: Epeorus vitreus and a few Maccaffertium ithaca.  But the mayfly I was hoping to see was the small minnow mayfly, and I was not disappointed.  I found a few A. nadineae nymphs and a couple of Plauditus dubius females.  The latter surprised me -- I thought this species had hatched by this time of the year.

A. nadineae and P. dubius in the same photo:

Acentrella nadineae (male):

Plauditus dubius (female):  (Note the medial band on the tails.)


Stoneflies?  I'm starting to see a lot of small to mid-sized Perlids, as we should at this time of the year, and I also continue to see some genus Perlesta Perlids in the Rapidan -- elsewhere, this genus has hatched.  But the prize stonefly of the day was another BIG (1 1/4"?  1 1/2"?) Paragnetina immarginata.

Magnificent!  These are hatching right now as "Golden Stones" -- in fly fishing terms -- and I saw a lot of "shucks" on rocks to prove it.  This one will surely be joining them soon.

(Below: two of the Odontocerids that I picked up when I walked into the stream.)

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