Saturday, May 4, 2013
Isoperla day at Buck Mt. Creek -- plus a "long-horned case-maker"
For the first half hour this morning I thought this entry would be entitled "The day of the Drunella (spiny crawler) at Buck Mt. Creek." Then I pulled a big root ball out of the water -- and it was loaded with insects, including three different species of Isoperla Perlodids: Isoperla davisi (in the photo above), Isoperla dicala, and Isoperla, species unknown (still waiting to hear from Steven Beaty).
If you've been reading along, you'll remember that I found my first I. davisi Perlodid last month at Buck Mt. Creek on the 14th. I was delighted to find another, and especially one that was fully mature.
Very unusual -- at least in my experience -- to see the primary wing pads spread out in that fashion.
Isoperla dicala -- I found two, and one was quite large with wing pads well spread. Unfortunately, the antennae got broken, so I'm not real pleased with my photos.
Alas! The pictures of the smaller one turned out a bit better.
And then there's this unknown Isoperla that keeps showing up in our streams. I sent one to Steven Beaty and will post his reply once he has time to determine what the species might be.
It's a beautiful insect. It looks a lot like Isoperla montana (or I. n. sp.), but the abdominal stripes aren't the same, neither is the lacinia (more on that when I can say more about the species ID.)
And then there was this little case-making caddisfly larva -- which took me by surprise.
Actually, I found two of them, and look at the shape of the other case.
"Cornucopia-like" -- I thought I had found Apataniids. But then the one little larva started to crawl out of its case, and I could tell by the color and the looks of the larva that these had to be something else.
The length of the back legs ought to give you a clue. They were Leptocerids (Long-horned case-makers), genus Oecetis. The Leptocerid that I'm used to seeing is Nectopsyche, the one I find in the summer in the Rivanna.
We recognize Leptocerids from two distinct anatomical features: 1) the hind pair of legs is longer than those in the front, and 2) the antennae are very long (hence "long-horned"). For the genus ID, let me turn to Barbara Peckarsky (Freshwater Macroinvertebrates, p. 114): "Mandibles long, sharp at apex, with medial teeth well below apex; maxillary palps extending far beyond anterior edge of labrum; case robust, often shaped like horn of plenty." The mandibles, maxillary palps, and the antennae are pointed out in this photo.
That was a shocker. This is only the second time that I've seen this type of Leptocerid. When I have time I'll attempt a species ID.
Oh yes, and there were a lot of Drunellas today at the stream. I think they were all D. tuberculata, but I'll check that for sure later on. Drunella is a genus of spiny crawler that I've only seen in a few of our streams: Buck Mt. Creek, the Moormans at Free Union bridge, and the Doyles just north of White Hall.