Thursday, August 9, 2012

A Netspinner That I'll Have to ID When I Return From Vacation

I wasn't really counting on finding a new one this morning when I went to Buck Mt. Creek, but so much for expectations.  Unfortunately, I've not yet figured out the ID, and since I'm busily packing for two weeks in the Northwest, I'll have to work on that when I return.  This is a species that seems to have no markings/pattern on the top of the head.  Here are some additional photos.

The head is dark brown, the nota are dark brown, and so too is the abdomen.  It is, for sure, Hydropsyche in genus -- not Ceratopsyche -- which we can tell by the presence of "scale hairs" on the abdominal terga: Ceratopsyche don't have them.  In the photo below, the "scale hairs" are the short, wide, black hairs that look something like seeds.

I thought that this might be Hydropsyche betteni since H. betteni "mature larvae usually have a uniformly dark head" (Beaty, "The Trichoptera of North Carolina," p. 75).   But H. betteni also "has a low rounded tubercle (bump) on [the] back dorsum of [the] head" (Beaty, p. 75).  I looked hard for a bump, but it just isn't there.   There is also the fact that H. betteni usually have a "black" head and black nota.  I suspect that the netspinner in the photo below, which I found in Powells Creek in the spring of last year, was indeed H. betteni.


I didn't find a whole lot at Buck Mt. Creek -- netspinners, fingernets, and flatheaded mayflies -- so I decided to stop at the Moormans on my way back to town (where the Moormans flows under Free Union Road).  Here the taxa was varied.  Lots of netspinners, lots of fingernet larvae, small minnow mayflies (H. curiosum), a few spiny crawlers (S. serratoides), and all sorts of flatheaded mayflies (e.g. Epeorus vitreus, Heptagenia marginalis, Maccaffertium ithaca).  Oh, and lots of small hellgrammites, something I also saw at Buck Mt. Creek.

There was no question about the ID of the common netspinners here: they were clearly Hydropsyche venularis, the same species I found in the Rivanna last weekend (tolerance value, 5.1).   The head pattern clearly gave them away.

Remember that the two pale spots on the frontoclypeus (top of the head) often merge to form a single stripe.  I looked at three different larvae -- all three were the same.

In this last photo, the head pattern looks a little bit different, but it's just the camera angle.  In any event, the yellow "rectangular" marks at the back of the head are easy to see.

One other photo.  This is a beautiful flatheaded mayfly, Heptagenia marginalis.  It's still a young one -- note the short wing pads -- but the colors are fully developed.  Love the way they spread those tails!


I'm off to Montana early Saturday morning -- the annual fly fishing trip -- and them I'll move on to Portland where my daughter gets married on 8/25.  Somewhere in there I'll probably squeeze in some time for getting some photos of some of those different EPT species that we see in that part of the country.
Back to posting entries at the end of August or the start of September.

1 comment:

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