Sunday, May 6, 2012

They Do Make Some Very Strange Cases: Finding an Interesting Limnephilid (Northern Case-maker Caddis)

Now, I have better photos than this, but let's start with the overall view.  Limnephilid (Northern Case-maker caddisfly larva) -- probably genus Pycnopsyche (but I still have to check) -- the case measured 2 1/4" from stem to stern!  (Yes: it was Pycnopsyche.  Larva was 24 mm long.)

I returned to one of our small streams in Sugar Hollow today -- after heavy rain last night there was not much choice about where to go.   I'm not surprised that I found this case-maker today: if you've been reading along over the winter and spring, you'll know that I've been finding lots of Limnephilids in Sugar Hollow all season.  In the winter, the cases I saw were the three-sided cases made out of sections of leaves.  Cases like this.

More recently, the cases I've seen have all been made out of small pebbles: I've seen dozens of these in the last couple of weeks, and I saw two today.  (Remember that Pycnopsyche Limnephilids often use the three-sided leave cases when they're still small but switch to firmer building materials as they mature.)

But we can't be surprised to find a new type of case.  Limnephilids make all sorts of cases, and I found two really neat ones last year at the Rapidan River.  This one:

And this one -- which resembles the one found today.  It's worth noting, on the question of genus, that Thomas Ames (Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, p. 253) states that "A patchwork of small woody piece sandwiched between larger sticks is...typical of Pycnopsyche."

Time to get up to the Rapidan River and see what the Limnephilids are up to in that stream this year!

I had hoped to make a morning of stream work today -- but I got caught in the rain and had to head home.  And, we've had overcast skies all day long, so the photos I got aren't the best -- but they'll do.

1. A flatheaded mayfly, Epeorus pleuralis, a small one, but one that's mature.

2. Spiny crawler mayfly, E. dorothea, and again one with black wing pads that's ready to hatch.

3. And in my tray, I found a tiny, tiny, small minnow mayfly that must have been clinging to our Northern case-maker's case.  It was too small (2 mm)  to photograph even using my macro lens.  So, I decided to see what I could do with a live insect using my microscope.  What a challenge!  I'd get ready to hit the shutter and that mayfly would scoot!  This is the best I could do.

And a side view:

The genus is Acentrella, of that I'm pretty sure, but that's as far as I'd go at this point.  I think from now on I'll stick to "macroinvertebrates" and leave the "microinvertebrates" alone!

Another view of our Limnephilid.  Remember that the larva itself is less than half the length of the case: it's 1/2 -- 3/4" long.  (Live photo is from a larva found last year.)

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