Is it possible now to identify Perlesta nymphs to the level of species?

I was pleased to see that in our new key -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species -- six species of Perlesta (Perlidae, common stoneflies) have been described: shubuta, cinctipes, decipiens, teaysia, frisoni, and adena.   At last, I can see which species we have in our streams in May and June.

Let's work on that nymph in the photo at the top of the page, one that I found in Buck Mt. Creek.  The key begins in this way (p. 224).

120  Abdominal terga with dark, freckle-like spots around bases of intercalary setae (fig. 3.245)......121
120'  Abdominal terga without freckled appearance.....123

Lots of dark freckles on this one.  We proceed to 121.

121 Dark transverse pigment band through ocellar area bearing scattered dark spots (Fig. 3.246) .... Perlesta shubuta
121' Dark transverse pigment band on head uniformly colored, without darker spots (Fig. 3.247) .....122

No question that there are scattered dark spots in that band on our nymph.

Pretty darn easy.  However, to date, this species has only been found in AR, IA, IL, KY, MI, MO, MS, and OK -- i.e. not in the state of Virginia.  Still, it's shubuta that our key yields, and I've found nymphs that key out the same in the Rivanna,

and in the Doyles.

Great!  But what about those Perlesta that I've found in the small streams in Sugar Hollow?  Can we ID them as well?   Here's a pic of one of those nymphs.

If you look closely you'll see that there are some freckles on the abdominal terga, but nothing like our nymphs from Buck Mt Creek, the Rivanna, and the Doyles -- i.e. it doesn't have a "freckled appearance."  So, I think we should go from couplet 120 to couplet 123.

123  Pronotum with a pair of dark parenthesis-shaped bars (Fig. 3.249); head without pale M-line .... Perlesta teaysia
123' Pronotum without dark parenthesis-shaped bars (Fig. 3.251); head with pale M-line, but sometimes incomplete ....124

The dark band on our nymph goes completely around the pronotum, it's not limited to the "parenthesis" marks on the lateral edges, and, the M-line on this nymph is clearly present and well-defined.  On to 124

124 Most of dark pigment on head restricted to area of frons anterior to lateral ocelli (Fig. 3.251); known from the Appalachians and areas east of the mountains ... NC, SC, TN, VA, WV .....Perlesta frisoni
124' Dark pigment on head coverng most of frons anterior to ecdysial suture; known from the Cumberland Plateau and areas to the north and west ... IN, KY, OH, TN .....Perlesta adena

The dark pigment is clearly restricted to the "area of [the] frons anterior to [the] lateral ocelli".  We've got Perlesta frisoni.

Same ID for another nymph from the same stream.

So our new key allows us to identify at least some of the Perlesta we find in our streams.  Very exciting news.  But when I asked Steve Beaty about this this morning, he said it's not safe to use this key.

That sent me back to his descriptions in "The Plecoptera of North Carolina,"  (pp. 48-49)  where I found the following statement.

Notes: North Carolina has very high diversity of Perlesta, most of which are currently undescribed in the immature stage.  While many nymphs appear highly freckled, some nymphs have few or inconspicuous freckles.  It is inadvisable to use a new Perlesta key (Stark, 2016 in press) [that's the key we've been citing] as it contains only 6 of the 17 regional species (two of which are not known from NC).  Preliminary use of the key has led to immediate failure for most NC specimens.  It is not uncommon to get 2-3 nymphal habitus forms at one site.

So that's that. Have to follow his advice and leave our Perlesta ID at the level of genus.  Probably stuck at that level for a long time to come.

But was it really Drunella tuberculata?

I've been working my way through this new book on species ID of mayflies, caddisflies, and stoneflies -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species (Clemson University Press) -- excited to see that we might be able to ID a number of things to the level of species, things that we've been stuck at genus ID up until now.  But when I came to the section on Drunella spiny crawlers (pp. 86-87) I was taken back by the illustrations I saw.  Specifically, the illustrations of the heads of D. tuberculata and D. allegheniensis.  Here they are, tuberculata on the left, allegheniensis on the right.

Problem.  The heads of the nymphs that I've been calling D. tuberculata -- including the nymph at the top of the page --look nothing like that illustration.  Rather, they seem to match D. allegheniensis. The heads on my nymphs have long tubercles like those on allegheniensis (not the tiny bumps of tuberculata), a dark, longitudinal band behind the lateral ocelli, and what appear to be two rows of setae at the front of the head, not simply one.

Better post a new entry, I thought, showing the error I made and correctly keying this out to D. allegheniensis.  And, I decided I'd use both the key in the new book and Steve Beaty's description in "The Ephemeroptera of North Carolina," p. 47-48.   To my surprise I found out that I had been right all along!

Let's start with our new key (Larvae of the Southeastern USA, p. 86).

139 Pair of submedian spines present on abdominal terga and well developed on at least terga 5-7; head roughened with pair of spines or tubercles between eyes above ocelli.....140
139' Pair of submedian spines absent on abdominal terga; head relatively smooth between eyes and above ocelli, not roughened as above...142

We've already seen that our nymph has tubercles on the head, it also has submedian spines on terga 5-7.

So on to 140.

140  Moderately long, somewhat coarse setae densely rowed at distal margin of clypeus....141
140' Clypeus not as above.... Drunella walkeri

Well, our nymph appears to have two rows of setae a the clypeal margin, but it clearly isn't D. walkeri.  Walkeri looks like this.

On to 141.

141  Posterior margins of abdominal terga 8 and 9 with long hairlike setae protruding dorsally...claws with few denticles situated basally....Drunella tuberculata
141' Posterior margins of abdominal terga 8 and 9 without long hairlike setae protruding dorsally...claws with denticles along most of length....Drunella allegheniensis

The moment of truth.  As it turns out there are long hairlike setae on the posterior margins of abdominal terga 8 and 9 -- very long on 8.

And the denticles on the tarsal claws are just at the base, not along the full length of the claw.

I'll be damned.  If we ignore that illustration and rely on the key, we have to conclude that our nymph is D. tuberculata.  But does our ID hold up when we move on to Beaty's description?  Let's take a look.

tuberculata -- nymphs 7-9 mm; head with long occipital tubercles not divergent apically; frons with dark transverse band interrupted medially, if present; small, blunt posteromedial tubercle on mesothorax; abdomen with long paired dorsal tubercles on segments 5-7; ... segments 8-9 with long hair absent medially; dorsal surface brown to dark brown, segments 8 or 8-9 with extensive pale areas; ventral surface pale. ... Uncommon.

1. Our nymph was 8 mm long.

2. We've already seen that the tubercles on the head are very long, and they seem to converge apically, not diverge.  (Note: on allegheniensis they do diverge, as in the illustration at the top of the page.)

3.  There is a dark tranverse band on the frons, but it seems to be interrupted.

4. The mesothoracic tubercle is both small and blunt.

5. We've already seen the long tubercles on terga 5-7, and the long hair on 8 and 9 is indeed absent medially.

6. Dorsal surface "brown to dark brown" -- not so much on this nymph.  But certainly true of previous tuberculatas I've found, especially those that were fully mature (which is what counts in making ID's).

7. And the ventral surface is pale.  (The dark dots are unmentioned by Beaty, but they also show up in Don Chandler's photo [http://www.discoverlife.org/mp/20p?see=I_DSC94&res=640].)

Drunella tuberculata for sure.
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All in all a very instructive exercise.  Lesson learned?  As always, rely on the keys and descriptions: illustrations can be helpful, they can also mislead.

Montana Part II., Mayflies: Two new ones and two we've seen before

The two new mayflies I found were both flatheaded mayflies.  Both were in the lower Clark Fork River at Petty Creek.  This one, genus Epeorus, species longimanus.

The genus ID was easy -- note the two tails -- and it looks just like the Epeorus nymphs we find in our own streams: pleuralis and vitreus.  But what species?  According to the Montana Field Guide (http://fieldguide.mt.gov/displaySpecies.aspx?family=Heptageniidae), there are four species of Epeorus that occur in Montana: albertae, deceptivus, grandis, and longimanus.   As it turns out, longimanus has one very distinctive mark of identification: there are dark dots in the middle of the femora.  (http://www.flyfishingentomology.com/PNW%20Mayflies.htm)

In addition, "the first and last gills meet under [the] body to form suction discs."  Yes -- though one of the last gills is missing on our specimen.

You may recall that I had previously found another Epeorus -- 9/3/12 -- in a much smaller stream, Grant Creek.

At the time, I identified this one as Epeorus deceptivus.   Just to be sure, I once again consulted Rohrbeck's species descriptions, and I'm pretty sure that I identified that one correctly.    In any event, our ID this time was pretty easy to make: Epeorus longimanus.

The other flatheaded mayfly I found that I've not seen before was very small -- 4-5 mm -- and it was also in the Clark Fork.

Looking at the size and the shape, my guess was Leucrocuta for the genus, and I was right.  The key -- no fibrilliform behind the 7th gill.

Species ID?  Can't do it.  Leucrocuta nymphs are very difficult to identify to the level of species.  In the new book on Larvae of the southeastern USA (see the entry of 7/10) the editors key out L. thetis and L. minerva, but leave untouched, the nymphs of aphrodite, hebe, maculipennis, and juno.   The Montana Field Guide (same page as noted above) notes two species of Leucrocuta that occur in Montana: maculipennis and petersi.    That's as far as we can go.

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Found two other nymphs that I've seen previously in my trips out in August: the small minnow mayfly Baetis tricaudatus -- female and male --  and the spiny crawler Drunella coloradensis.

I'm intrigued by D. coloradensis: it seems to come in all sorts of colors.  Here are just a few that I've found in previous trips.

Pretty remarkable nymph.

New caddis casemakers from my trip to Montana

It was a very good trip.  Fishing was great -- so too was the insect collecting.  In this entry, two caddisfly casemakers that I've not seen before: next entry, two new flatheaded mayflies.

Number one, this neat larva with a prominent dorsal hump and long stringy gills.  Found this one in a backwater eddy of the Bitterroot River, kind of like this one.

The water was still, relatively shallow (1-2'), with a sandy bottom.  There were about a dozen of these crawling along on the sand.

This identification has given me fits.  I got it into my mind -- given that prominent hump and the long, single gills -- that it had to be Phryganeidae (Giant Casemaker).  That led me astray for most of yesterday.  That just didn't work, so I keyed it out and came out to Limnephilidae, Northern Casemaker.   One of the things that led me in that direction was the fact that the mesonotum has sclerotized plates while the metanotum is largely membranous with sclerites at sa1, sa2, and sa3.

That led me to Wiggins (Larvae of the North American Caddisfly Genera, 1977), where I worked through the descriptions and illustrations of the various genera of Limnephilidae.  Even then, the genus ID wasn't real clear.  But in the end, I've decided that the probable genus ID is Psychoglypha (Wiggins, p. 280-281).  Here's Wiggins' description:

Larvae of Psychoglypha spp. are sufficiently divergent morphologically that it is difficult to find characters diagnostic for the genus.  The two sclerites lying close to the dorsal edge of the lateral hump of abdominal segment I provide the only consistent character discovered thus far for all the larvae we have collected.

I can see such sclerites on the larva I found, and, they are the same shape and size that we see in Wiggins' illustration (p. 281).

A few other features.

...in a few species stout spines and setae occur along the pronotum and on the sclerite of segment IX and the lateral sclerites of the anal prolegs.

The spines and the setae on the pronotum seem to me to be present on this particular larva, and the stout setae on the sclerites on segment IX and the anal prolegs clearly have "stout spines and setae."

Head markings usually consist of dark brown spots and blotches on a yellowish brown background, except in P. bella where the head and legs are uniform dark brown.  Abdominal gills are single.  Length of larva up to 26 mm.  

The gills are single for sure (not branched).  The head color -- I see a dark brown head and legs, but P. bella is a species that has not yet been found in MT.  (But it is listed in Rohrbeck in his record of Psychoglypha species. ???)  The Psychoglypha species that have been found in Montana are alascensis, prita, and subborealis.  (See Natureserve Explorer, explorer.natureserve.org).  This larva was only 16 mm, and the case was 29mm.   But I think this larva was still immature.   For the habitat, Wiggins says this: "Psychoglypha larvae occur in a wide range of cool-water habitats, ranging from springs runs to larger streams and their marginal pools."  I can live with a "marginal pool" for this one.  In any event, at this point, Psychoglypha is my best guess for the genus ID.   I might know more if I can get Steve Beaty to have a look at this larva.

More photos.

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Number two, a Uenoid.

I found these Uenoids in a small mountain stream that's across the street from the motel we use: Grant Creek.   There were a bunch of them attached to the rocks near the shoreline.

All Uenoids are genus Neophylax, but what about the species ID?  For a number of reasons, I think it's N. splendens.  Let's go over the data.   To begin with, the source I use to work on genus and species ID for the insects I find in Montana is Roger Rohrbeck's Fly Fishing Entomology, here using the descriptions found in the section "Pacific Northwest Caddisflies" (http://www.flyfishingentomology.com/PNW%20Caddisflies.htm).   There are three species of Neophylax described at this site: occidentis, rickeri, and splendens.  I think we can eliminate N. occidentis.  The pronotum of the species is described as "front 1/3 light, rear 2/3 dark," and "evenly spaced spines at front edge with only a few scattered hairs on rest of pronotum."  Don't see that at all on our larva.  There are quite a few, very small, hairs on the surface of the pronotum, and the front 1/3 is actually darker than the rear.

That brings us to rickeri and splendens.  There are a couple of things that lead me to an N. splendens ID.  First of all, on rickeri, there are "short stout black setae scattered evenly across entire surface of [the] pronotum," while on splendens there are "fewer dark thick setae concentrated towards back."  Have a look.

I'd say there are thick dark setae at the back of the pronotum, with smaller setae mainly along the inner edges of the pronotal plates.

Secondly, Rohrbeck notes that "there are prominent gill-like filaments on the underside of ab1."  That means clavate gills on the venter.

And there they are.  But there is more.  The key source to use on Neophylax species ID is the book The Caddisfly Genus Neophylax (Royal Ontario Museum, 2005), edited by R.N. Vineyard, G.B. Wiggins, H.E. Frania, and P.W. Schefter.  There it is clear that rickeri and splendens are similar in many ways (e.g., dark heads and legs).  But on rickeri they note that the spines on the leading edge of the pronotum are "moderate in size" while those on splendens are "small".  I'd go with small.

Also a critical factor, rickeri is said to inhabit "medium to large streams" while splendens "occurs in small first-to third- order streams.  Grant Creek is, without question, one of the latter.  You might recall the photo I posted in April.

So I'd lean towards N. splendens for the ID.  But as always, I could be wrong, and rickeri can't be ruled out without closer inspection than I can do.
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Good fun as always, and going to Montana in July instead of August -- when we normally do -- means finding a new set of insects.  In the next entry, a look at a new Epeorus and a new Leucrocuta.