Thursday, October 9, 2014

Goera (Weighted-case maker) day in Sugar Hollow: in twos and threes and fours!

I knew that the water was low -- but I decided to have a look anyway -- so off to one of my favorite streams.  I didn't see much -- too early for the stoneflies and mayflies to fill up the leafpacks -- though I did see quite a few small Giant stones.  But there were Goeras all over the place.  How did I miss them in previous years?  Simple enough.  Their cases look exactly like little pebbles that are scattered on rocks.  But they no longer fool me.

I noted in the entry of 9/21 that Goeras are normally found in cases with two stones on each side.  But on 9/21 I found that nice case with four stones on each side.  Found another today (photo above), and I also found two that had three stones to a side.  Photos.  Two stones, three stones, and four stones.



and Four -- of which I got some very good photos.

Big case: 17 mm.

What about species?  They all seemed to be G. calcarata -- though I have reservations.  I'd base the ID -- of G. calcarata -- on two things: 1) the larva has no sternal plates (see photos in the 9/21 entry), and 2) the central ridge of the pronotum is raised.

So why do I have reservations?  I'm not sure about the metanotal sclerites.  Do these larvae have 3 pairs of sclerites (G. calcarata) or 4 pairs of sclerites (G. fuscula)?   (This is the larva from the four-stone case.)

Beaty has assured me that the larva from the Rapidan River (previous entry) was indeed G. calcarata.

And the larva from Entry Run -- on which the sternal plates were very distinct -- I am sure was G. fuscula.

But I have trouble deciding about the larvae that I found today.  I'll let you know if I figure it out.

We had an inch of rain two nights ago -- but we need a lot more to fill up our streams.  This is where I was looking today.

Here's a spot slightly lower last spring.

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