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.)