Thursday, October 25, 2012
Did I Mention That They Grow Up in a Hurry? Clioperla Perlodids and Allocapnia Small Winter Stoneflies
I found the first Clioperla clio Perlodid stonefly of the new season just 12 days ago (see the entry posted on 10/13). It was 4 mm in length. The large Clioperla in the photo above was found in Buck Mt. Creek this afternoon: it was 8 mm long. They mature rapidly once they show up. And note that the distinctive head pattern -- the large pale area that covers the head, surrounded on all sides by a dark border -- is already quite clear on the larger of these two nymphs. On November 25th of last year, I was finding C. clio Perlodids in Buck Mt. Creek that were already fairly mature in terms of color and pattern.
I also found tons of small winter stoneflies this afternoon: the leaves in the leaf packs were covered with them. They too have grown quite a bit in two weeks time (see the entry for 10/11). The tiny nymphs that I found on 10/11 were only 3 mm long; this one was already 7 mm.
With the nymphs I was seeing today, their wing pads show up very clearly, something that was not true of those I found just two weeks ago.
Since they might be difficult to see in this photo, I decided to get a microscope view. The microscope view clearly shows that this is a genus Allocapnia Capniid: "Metathoracic [rear] wingpads usually truncate [squared off], unnotched or notched on inner margin near tip." (Peckarsky, et.al., Freshwater Macroinvertebrates, p. 66) The wing pads on this nymph were notched: the notch is very clear on the left wing pad.
Small winters are also quick to mature. The Allocapnia nymph in the photo below was also found in Buck Mt. Creek on 11/25 of last year. So in four weeks time, we may be seeing nymphs with dark wing pads that are ready to hatch.
It was not my intention to go to Buck Mt. creek when I set out this morning. My first stop was Long Island Creek which is east of Palmyra in Fluvanna county. I had high hopes; this is a very good stream. But my trip there was a big disappointment. The water was very low, and the flow has not really compacted the leaves, so I didn't find a whole lot. The only taxon I saw in big numbers was the Eccoptura common stonefly. This is their kind of water: a small, rocky, forested stream. I took a photo of the largest one that I found (well, it was the largest one that I caught!). It was unusually dark in color.
The other thing I was happy to find in this stream was a number of flatheaded mayflies, species Maccaffertium vicarium.
M. vicarium (the "March Brown" to fly fishermen) has a TV of 1.5 so I don't see it in a lot of our streams. It gets to be pretty big -- 10-18 mm -- and it's one we can ID on sight. The abdomen pattern is very distinctive. From Beaty ("The Ephemeroptera of North Carolina, p. 20): "wide dark bands on posterior margins of both dorsum and sternum of abdomen." And here they are. (The short wing pads indicate that this is a young nymph: M. vicarium usually hatches in March.)
Still searching for the first Large Winter stoneflies of the season. I might have to wait for awhile: we're expecting a visit from Hurricane Sandy!