Monday, February 13, 2012

And the Stoneflies Keep Getting Bigger in Sugar Hollow

Could I start with some other photo?!  The Perlodid stonefly Malirekus hastatus, and it was a big one -- close to 1" in length.  And, note how the rear wing pads are flared out from the body; that's a sure sign that these stoneflies are getting mature.

After finding our winter small minnow mayflies (Heterocloeon amplum) last week, I thought I should return to Sugar Hollow this week to check on the stoneflies.  Lots of them, and they're all getting bigger.  Let's have a look.

1. Another, closer, look at this gorgeous Malirekus hastatus.

2. One of two Diploperla duplicatas (Perlodids) I found.

3. Two of the many, many, many Isoperla namatas.  This common Perlodid is becoming a dominant taxon in a lot of our streams as we move into spring. Monitors will be seeing a lot of them in their samples.

4. One of several large winter stoneflies -- Taenionema atlanticum -- that are still present in these small mountain streams.

5. And a "giant" Giant stonefly -- Pteronarcys scotti (I think).

There were some mayflies in the stream.  In fact, the bottoms of rocks were covered with the flatheads, Epeorus pleuralis.   I also found a few Ameletids.  But one of my favorite discoveries this morning was this beautiful aquamarine, free-living caddisfly larva, Rhyacophila nigrita.

The main thing that helps us to pin down this species is the "two-toned" pronotum -- light in the back and dark in the front -- that and the black/brown head.  Previous R. nigritas that I've found in this stream have been whitish gray, e.g. this one from 12/26.

And since I've moved our attention to the free-living caddis, I can say a little bit more about the larva I found here last month (see the entry posted on 2/2).  This one.

This is not R. nigrita; the pronotum is totally different.  And it certainly isn't the "common" Rhyacophila -- Rhyacophila fuscula -- the green one with the "topless" H pattern on a light brown head.  So, I took some microscope photos to help with ID and sent them to Steven Beaty.  Here are the photos.

1. The head -- and note the light colored dots (muscle scars).

2. The pronotum, and note the distinctive "notched" posterior edge.

I'm not really sure if these photos helped him or not, but he thought there was a good chance that this was Rhyacophila glaberrima.   However, to know that for sure, we have to know the length of segment 2 of the maxillary palpi: I wasn't able to figure that out.  If it was R. glaberrima, it's "relatively rare" (Beaty, "The Trichoptera of North Carolina").

So, we've got R. fuscula and R. nigrita in this stream for sure, and possibly R. glaberrima.  I would not be surprised to find additional species of free-living caddisflies on future trips to this gem of a stream.

Below -- and Epeorus pleuralis flatheaded mayfly stays perfectly still as a "net-winged" midge (Blephariceridae) crawls underneath.

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