Monday, November 17, 2014
We appear to have found a third stong-case maker species: Psilotreta rufa. (Well, there's no "we" involved: the larva was found by my friend in Sugar Hollow, the one who lives next to this superb little stream.)
We've collaborated on the ID, but all of the photos of rufa were taken by her.
Almost all of the Odontocerids I see are Psilotreta labida, a larva with a broad dark stripe extending from the head through the mesonotum and long, pointed anterolateral pronotal projections.
You'll recall that I found hundreds of them just a few weeks ago in the Rapidan River. The only other species I've seen -- and I've only found it in one little stream -- is Psilotreta frontalis.
We see that same dark band on P. frontalis -- but the pronotal projections are short.
Clearly, the larva my friend found last week is something entirely different. There is no dark band on the head and the nota: rather, the head and pronotum are a dark, reddish brown while the mesonotum is almost entirely yellow.
Our new larva keys out to Psilotreta rufa which Beaty describes in the following way.
(P. rufa) -- larvae up to 11 mm; head and pronotum uniformly reddish brown without stripes but may have darker pigmentation along frontoclypeal and coronal sutures...head longer than wide and relatively flat between carinae; seta 17 about half the length of seta 15; pronotum darker laterally; anterolateral pronotal projections short. ("The Trichoptera of North Carolina, p. 97)
The color of the head and pronotum, the shape of the head (longer than wide), and the short pronotal projections all show up very well in the following photo.
We might see darker pigmentation along the frontoclypeal suture in the following photo -- but the color distinction is admittedly slight.
But this very nice lateral photo clearly shows that the pronotum is dark laterally, and, I think, that the head between the carinae is "relatively flat." (The carinae are the raised ridges that run from front to back on either side of the head.)
That leaves us with the question of the relative lengths of seta 17 and 15. I confess that I had no idea where to look for these setae until we found the following article, one that is referenced by Beaty: C.R. Parker and G.B. Wiggins, "Revision of the caddisfly Genus Psilotreta (Tichoptera: Odontoceridae)," ROM (Royal Ontario Museum): Life Sciences Contributions, No. 144 (1987). In that article, on p. 29, the head and nota of P. rufa are illustrated in detail, and setae 17 and 15 are clearly marked: 17 is behind the frontoclypeal suture, and 15 is along the carina, the ridge. Unfortunaely, despite the very fine photos my friend has provided, I can't be sure I can pick out those hairs!
Nonetheless, Parker and Wiggins describe P. rufa in a way that supports our identification.
p. 10 "head uniformly reddish brown or with pale areas laterally; thoracic nota uniformly reddish brown to pale yellowish." Yes.
p. 21 "Head longer than wide, and in lateral aspect posterodorsal angle more or less squared; dorsum relatively flat between carinae; seta 17 thinner than, and usually about one-half as long as, seta 15. Pronotum with projection of anterolateral corner short, about 0.2X middorsal length of pronotumn. Mesonotum with black marking along posterior ridge extending laterad to posterior inflection."
The point of inflection is where the thin band we can see above the thicker black band rises up at the side. If you look closely you can see it in the following photo.
I'm not sure we really need to see the head setae to make this identification given the preponderance of evidence that we have. Psilotreta rufa.
Two final points of interest. 1) The habitat for P. rufa (Parker and Wiggins, p. 21) is a perfect match for our stream: "P. rufa larvae occur in small spring seeps and spring-fed streams." And 2) Parker and Wiggins include the following site among the locations where rufa is found: Albemarle County in Virginia, south fork of the Moormans River above the Charlottesville Reservoir. (p. 22) Bingo! Not at all far from the small stream in which this larva is living.
Friday, November 14, 2014
I'm going on record: in the future when it's 34º and windy, I am not going out to the streams! Wow -- that was cold.
I went to one of our good, headwater streams in Sugar Hollow this morning hoping to find -- what else? -- Molanna, since I've not yet seen one myself. So I focussed on silt-covered rocks in still water pools. No luck. I did continue to see "weighted-case makers" (Goera fuscula) and decided to take some photos of this larva since it had made this colorful, kind of lopsided case.
Other pix of the same larva.
Note the pronotal and mesonotal anterolateral projections, key features on the Goerids.
What a beauty.
In the leaf packs I saw a number of insects, including a lot of Giant stoneflies, some of which were getting quite large. This one was 35 mm. Pteronarcys proteus. (Good lighting makes for good photos.)
A couple of oddities. Number one, this small common stonefly.
Strange colors -- but it may be a nymph that just recently molted. No anal gills, and no setal row on the occipital ridge. That normally means Acroneuria abnormis, and there is an A. abnormis population that inhabits this stream. However, if it is A. abnormis, it appears to the "brown" one, the one that lacks a clear yellow "M" on the head and has an abdomen that's uniformly brown. But -- "early times," as the British would say.
Number 2 is this little case that I found.
I couldn't see a larva inside, so I brought it home for a microscope look. It was abandoned. But it appears to be the case of a young Uenoid, the case-maker that will soon be showing up in large numbers in all of these streams.
No warm up for most of a week. Hope to get out next Thursday.
Tuesday, November 11, 2014
A significant find in Sugar Hollow: new taxon -- the "hooded-case maker" (Molannidae), Molanna blenda
While I was taking advantage of our beautiful weather to play some golf yesterday, my friend in Sugar Hollow was adding a new caddsifly to our EPT list for central Virginia: the "hooded-case maker" Molanna blenda.
Molannidae is often found in still water -- "lakes or the slower currents of rivers and streams" (Wiggins, p. 290), where they are not often easy to find since they "inhabit the sand and mud substrates of these sites." (Wiggins, Larvae of the North American Caddisfly Genera, 1st ed., p. 290)
But they can be found in "cool spring-fed streams" (Beaty, "The Trichoptera of North Carolina," p. 96) which is where this one was found. It was on a rock, covered with silt, but gave itself away when it moved. The stream is that special 1st order stream that flows close to my friend's home. This one.
Hooded-case makers get their name from their cases -- which indeed have a hood, or "cowl," at the anterior end, and the case is "flanged" on the sides. Ames notes that the cases also have "a ragged posterior opening on the dorsal side" (Thomas Ames, Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, p. 206). E. g.
As you can see, the hood almost completely covers the head of the larva. For the genus ID -- and there's only one genus in our part of the country, Molanna -- we need a close look at the claws on the hind (metathoracic) legs. Beaty, "Claw of metathoracic leg shorter and more stout than claws of other legs and setose." (p. 96) I think we can see that in this live picture (my friend prefers not to preserve any insects).
Beaty's description of M. blenda reads as follows: "larvae 10-12 mm; apex of base of tibial spine extends well past tibiotarsal joint; membranous area at constriction of frons capitate; moderately wide black banding along frontoclypeal and coronal suture." ("Capitate" means "abruptly enlarged and globular.") I can't make a call on the tibial spine, but the "enlarged globular" membranous area at the front of the head is very clear in our photos as are the wide black bands that border the frontoclypeal suture. Another view.
Very cool. Obviously it's time for me to get my priorities straight and get back to the streams! Still, it's so nice to play golf at this time of year :) (Behind the 9th green at Meadow Creek golf course in Charlottesville.)
(Please note that all photos of the Molanna were taken by my friend and posted with her permission.)
Friday, November 7, 2014
First of the season: Perlodid stonefly, Helopicus subvarians. It's one of the few stonefly nymphs that we see that's colorful from the very beginning. It's also one of the biggest -- longest -- Perlodid stoneflies we see -- 17-20 mm when it's mature. And they're quite striking when they're mature.
2/27/14 -- not yet mature.
3/14/12 -- fairly mature
2/6/12 -- very mature.
According to Stewart and Stark (p. 400), subvarians is the only Helopicus species we find in VA, and the distinguishing feature of this particular species is the fairly straight anterior edge of the dark transverse band on the head (Beaty, "The Plecoptera of North Carolina," p. 21). While that straight edge is very clear in the 2/6 photo above, that is not the case with the immature nymphs from this morning.
With a tolerance value of 1.2, it's a species we find in fairly clean streams. I always see lots of them in the Doyles and at Buck Mt. Creek.
Another day when taking photos was tricking: breezy with fast moving clouds. Still, awfully nice out there at the moment.
Sunday, November 2, 2014
A challenging day for photography. It was cold -- 46º -- and extremely windy (= watering eyes). But the real challenge was the sun -- which kept popping in and out of fast moving clouds. But I still did alright.
I continued to see strong-case makers (Odontoceridae) and humpless case-makers (Brachycentridae) -- but not nearly as many as I saw here last month (10/5). Rather, the small mayflies and stoneflies that will mature in the spring are suddenly here in big numbers. I left the pronggilled mayflies alone, choosing to focus instead on...
1. The spiny crawler mayfly, Ephemerella subvaria (in the picture at the top of the page). Dozens and dozens of them in the leaf packs, and you can see them at once because of their colors. The tibial banding, by the way is a key for identification.
They'll be hatching in March and April, and when mature they look more like this.
2. Perlodid stonefly, Isoperla montana/kirchneri. First of the season.
Very, very small: I'm pleased that this turned out as well as it did. Given the size -- about 3 mm -- I should hesitate on the ID, but I feel pretty confident. Look at one that's fairly mature.
There are commonly two dark bars at the back of the head, and the abdomen's striped with the middle stripe formed by a series of crosses (or a line with dots on either side). That middle stripe was already clear in a microscope view, and you can actually see the dark bars at the back of the head on this tiny nymph.
3. Another small Isoperla -- about 7 mm -- which turned out to be I. similis.
These mature rather quickly. I found this one in February last year.
The head pattern is distinctive: "head brown with a pair of pale spots near labral suture, a pale M-shaped mark anterior to median ocellus and pale marks anterolateral to the lateral ocelli." (Beaty, "The Plecoptera of North Carolina," p. 24) Difficult to see the "pale spots near the labral suture" on this young nymph. But you can see them if you look closely.
3. Common stonefly, Paragnetina immarginata.
So much nicer when we find them in July. Spectacular, really.
Still, we can already see a lot of key features. "M-pattern with medial pale line extended anteriorly, often connected to pale frontoclypeal margin; yellow femora distinctively patterned with dark brown longitudinal bar extending about 2/3 the length; abdominal terga banded, anterior half dark; anal gills absent." (Beaty, p. 18) All Paragnetina nymphs have a complete setal row on the occipital ridge (back of the head).
4. And I saw a number of, not so small, flatheaded mayflies, Maccaffertium pudicum.
When mature, this is one of the biggest Maccaffertiums that we see: 11-14 mm.
Such a pleasure to go to a stream where there are so many insects to see.