Tuesday, October 29, 2013
This morning, my friend with all sorts of connections -- ahem! -- got us invited to look at a new stream at Montfair Resort Farm (http://www.montfairresortfarm.com/) a beautiful place to vacation and hike in the hills above the Doyles River. We had a number of streams from which we could choose, so we hiked down to a small one -- remote -- that empties into a pond.
This turned out to be a very small stream, low water at the moment, and there were not a whole lot of riffles. Still, we saw plenty of insects including what for me would be a new Stong-case maker species, Psilotreta frontalis. I'm not 100% sure of this ID, but let me lay out the evidence, such as it is, using Beaty's "The Trichoptera of North Carolina," p. 97.
P. frontalis -- larvae up to 14 mm; coloration variable, generally a broad black stripe extending dorsally over head, sometimes wider than frontoclypeus; two light areas anteromedial to eyes extending to anterolateral corners of frontoclypeus in all but darkest specimens; dark on pro- and mesonotum confined to middle stripes and lateral edge; pronotum with anterior edge slightly darker than ground color; anterolateral pronotal projections relatively short. Spring fed streams in Sandhills and Mountains.
We need a close-up of the head, pronotum, and mesonotum which I've tried to produce in the following photo.
1. There clearly is a broad black stripe extending over the head, and it is indeed wider than the frontoclypeus in places.
2. I really don't know about the pale areas anteromedial to the eyes. That's where I need to do further work.
3. We can see that there are black stripes on the pro- and mesonotum in the middle and on the sides.
4. No question that the anterior edge of the pronotum is darker than the ground color.
5. And, I think the anterolateral projections on the pronotum are shorter than those that I normally see.
a. today's larva
b. what I normally see, which I think is Psilotreta labida
So a tentative conclusion on this: the Strong-case makers that I saw today might be Psilotreta frontalis. Whatever they were, there were a lot of them!
As for the rest...
1. Flatheaded mayfly, Maccaffertium merririvulanum, one of the two species we normally see in small head-water streams. Note the pale "V" marks on segments 7-9.
2. And the other flathead that we commonly see with M. merririvulanum -- Maccaffertium pudicum.
3. A tiny pronggilled mayfly, genus Paraleptophlebia
4. And a Saddle-case maker -- Glossosoma nigrior.
Saddle-case makers, because their cases are open at both ends, can reverse direction inside of their cases, with their heads sticking out at the top and then at the bottom. Right after I took this photo, this larva ducked back into the case -- and then it popped its head out the bottom.
And then it went back to the top!
5. Oh, there were also quite a few Roach-like stoneflies around -- clearly genus Tallaperla.
Looking forward to returning to Montfair soon to get into more of their streams.
They're are a lot of people sampling streams at the moment as the fall sampling season comes to its close. If you're out there, and you live in our part of the country, there's a good chance you'll be seeing tiny, large winter stoneflies (genus, Taeniopteryx) and small winter stoneflies (genus Allocapnia). Your monitors will probably urge you to keep them for identification back at the lab.
But, it's actually fairly easy to ID them right in the field for those of you urged to do family level ID.
That's a large winter stonefly in the photo at the top of the page. The photo was taken on 10/27 last year. Clearly, it looks nothing like the large winter stonefly pictured in Voshell's Freshwater Invertebrates, p. 134. He's showing you what they will look like when they're mature. More like this.
But you can probably ID these large winters right in the field with a loupe, even at this time of year.
Look for 4 things. 1) These nymphs are "freckled," "spotted," the colors range from gray (very small) to reddish brown (somewhat larger); 2) The bases of the antennae are unusually thick; 3) There's a pale , medial stripe running from the head to the tails; And 4) to really be sure that this is a Taeniopteryx large winter stonefly, flip it over and look for "coxal gills."
They look like bean sprouts, and they're very large on the very smallest of nymphs.
Small winter stoneflies. They always show up towards the end of October.
And there are two ways to recognize them. 1) When they're small, they're virtually transparent. When I put them into my petri dish to take a picture, I sometimes have trouble making out where they are. And 2) they're "floaters." Maybe they're just too light to sink! They always seem stay on top of the water when put into a tray.
This feature is commonly seen even with larger nymphs -- even when they're mature.
Sunday, October 27, 2013
When I was at the point of posting yesterday's entry I had second thoughts and almost hit "delete" instead of "publish." I should have. After closer study this morning, I've determined that the Goerids I found yesterday were, species, Goera fuscula, not Goera calcarata.
The thing that bothered me yesterday -- that drove me to look at these insects again -- was the size. The larva that I examined was 11 mm: Beaty has "8-9 mm" for G. calcarata, but "9-11mm" for G. fuscula. So let's have a look at Beaty's description of G. fuscula.
G. fuscula -- larvae 9-11 mm; 4 pairs of sclerites on metanotum; sternal thoracic plates distinct; face with central area smooth; posterior carina sharp and high. Mountains only. Rare with less that 15 BAU records. (Beaty, "The Trichoptera of North Carolina," p. 87)
1. As I've already noted, the larva that I pulled from its case and measured was 11 mm; the case was 12 mm.
2. There are indeed 4 pairs of sclerites on the metanotum, not 3! If you look directly down on the dorsum of the metanotum you'll only see three, but if you turn the larva on its side, you'll then see the 4th. (Sclerites are bounded, dark spots on the fleshy body, normally containing setae.)
3. And yes, the sternal thoracic plates are distinct. That's the first thing I noted this morning. That on its own eliminates G. calcarata for the ID.
4. Head/face -- it's flat, almost depressed, surrounded by a quite clear carina.
Another look at the carina and head/face in a photo from my friend in Sugar Hollow.
Goera fuscula. The tolerance value remains undetermined since it's an uncommon species.
One other point of interest on Goera in general. On Friday, when my friend and I went to that small stream in Sugar Hollow, she saw some cases that looked like Goera. They appeared to be sealed off for pupation, but she took them home for a look. After a time, the larvae emerged -- the cases weren't sealed off at all!
The same thing happened to me yesterday. Here's what I saw.
I was initially disappointed since I knew by the cases that these were Goerids: but then they emerged.
When I was reading Glenn Wiggins (Larvae of the North American Caddisfly Genera, 2nd edition, 1996) on the Goerids, I discovered that this is characteristic of the Goerids. Look at this photo from my friend's collection, then I'll quote from his book.
"Larvae of the Goeridae are characterized by major modifications to the thoracic nota. The pronotum is enlarged and thickened laterally; sclerotized plates of the mesonotum are subdivided into two or three pairs of smaller sclerites, and the mesepisternum is extended anterad as a prominent process. These modifications are integrated to form a set of close-fitting sclerites forming an operculum that closes off the anterior opening of the case when the larva withdraws."(Wiggins, p. 226)
So, if you find one of these cases and it appears to be sealed -- don't be too sure!
Saturday, October 26, 2013
(Please read the next entry. This ID was wrong. The larvae I found were G. fuscula.)
I've been waiting a long time to see this one -- but it's not really that photogenic! This is the first Goerid (Weighted-case maker) I've seen, and I had to go to the South River (Greene County) to find it, that despite the fact that my friend has found them in a regular way in the small streams in Sugar Hollow.
But what really sets the Goerid apart is the pronotum: "pronotum produced anterolaterally into wide, sharply pointed processes." (Beaty, p. 87) This is the best I could do in a live view.
They're easier to see in this microscope view as is the pointed nature of the head.
Another view -- live view -- of the pronotal and mesonotal projections taken by my friend in Sugar Hollow.
According to Ames (Caddisflies, p. 232) the most common Weighted-case maker we see is Goera calcarata, and that's the species I found. Beaty describes G. calcarata in the following way:
G. calcarata -- larvae 8-9 mm; 3 pairs of sclerites on metanotum; pronotum with central raised area the anterior margin with conspicuous spicules; sternal thoracic plates indistinct. Common in the Mountains and Sandhills. In North Carolina, G. calcarata is given a TV of 1.0.
Of the features noted by Beaty, the "3 pairs of sclerites on the metanotum" were very clear.
I could not see any plates on the thorax. But in the end, the metanotal sclerites will do to establish the identification since the other species that are found in NC (G. fuscula and G. stylata) both have 4 pairs of sclerites, not 3. This larva was 11 mm.
Goera is known to fly fishermen as the "Little gray sedge," and according to Ames (p. 232) "They appear through June in the mid-South and into August in the Adirondacks and New England."
Nice to finally add this to my list.
1. Odontocerids (Strong-case makers) -- Psilotreta labida. They were easy to spot on the rocks.
2. A pretty, small minnow mayfly -- Acentrella turbida. Fully mature.
3. And -- finally -- the first small winter stoneflies of the new season.
Not much to look at at this stage of the game.
All Goerids were found in Entry Run, a tributary of South River.
Thursday, October 24, 2013
My friend and I went to a small stream in Sugar Hollow this morning where I was hoping to find some freeliving caddisfly larvae and more Perlodid stones -- but it's still a little too early. We did see some small Chloroperlids, lots of small flatheaded mayflies, and a good number of common stoneflies: they all looked to be Acroneuria abnormis, but I didn't keep any to check. But the insect of the day was the Giant stonefly, Pteronarcys proteus. The leafpacks were loaded with them. And while most were on the small side, we did find some -- like the one in the picture above -- that clearly will be hatching by the end of the winter. This one was a beauty!
Note one of the key feature for species ID -- the lateral projections on abdominal segment 7 are closer in shape/size to those on segment 6 than to those on segment 8.
2. Malirekus hastatus. I wasn't completely shutout in my search for Perlodids: I did find this Malirekus hastatus (you'll recall that I found one on 10/8 as well).
These are great streams for Perlodids, and we'll be seeing more and more species as we move through the winter and spring.
3. Baetis tricaudatus. This one surprised me: the small minnow mayfly Baetis tricaudatus. I've come to think of this as a species that we start to see in the winter -- my thinking is in need of revision!
A very handsome male (large, red eyes). Note the diagnostic features of the pale, medial line on the abdominal terga and the very short middle tail (caudal filament).