Temporary housing or permanent shelter? Some unusual Lepidostomatidae cases

Yesterday, I was looking through some of the photos I've taken this year and was kind of struck when I saw this one.  That's a Lepidostomatid -- photo taken on 2/13 -- that is not a Lepidostomatid case.  You may recall that I ran into the very same thing three years ago (12/19/14) when I found this larva in one of our small streams in Sugar Hollow.  (See the entries of 12/19 and 12/21/14.)

At the time I pointed out that this type of case -- three-sided case made out of sections of bark or leaves -- is normally made by the Limnephilid casemaker Pycnopsyche gentilis.

Lepidostomatidae cases are normally made out of sand grains, or "they're four-sided and constructed of quadrate pieces of bark or leaf," (Glenn B. Wiggins, Larvae of the North American Caddisfly Genera, p. 156 in the 1977 edition), or a mix of the two.   For example...

Wiggins goes on to note that "Final instars in some other species assigned to Lepidostoma have cases of plant materials placed spirally or transversely."  In 2014 I thought that might explain what I had found, but there is reason to re-consider.  For one thing, the larva inside that case in 2014 was genus Theliopsyche, not Lepidostoma, and for another, the case that I found was not constructed of materials laid out spirally or transversely.   So what to make of these cases?  (I should also point out that known cases of Theliopsyche are made out of grains of sand.)

I contacted Steve Beaty.  While he didn't know the answer for certain, he suggested a number of things.  E.g., some caddisfly larvae, if they abandon their cases willingly or unwillingly, make a temporary case for protection while they make the type of case in which they're normally found.  (Interesting.  Did not know that.)  Or, it could be that the larva moved out of its own case and "borrowed" a Pycnopsyche case for awhile.  Or, this might be a case that's "typical" for one of the as yet unidentified Lepidostomatid species.   There are, by the way, 29 species of Lepidostoma in the southeast.  The larvae remain unassociated and therefore as yet undescribed.   (See Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species, p. 354.)

I decided to re-examine the larva I found in 2014 and quickly discounted the second solution.  While this cases resembles a Pycnopsyche case, it's much smaller.  It measured something like 10mm; Pycnopsyche cases are normally closer to 20.  That leaves us with the other two possibilities: either it's "temporary housing," or it's an unusual, but permanent, case of a Lepidostomatid larva that at this time is unknown.   That's about as far as we can go.

I should also be clear that while I can vouch for the identity of the 2014 larva  -- genus Theliopsyche -- I didn't keep the larva that I found this year.  Could have been Theliopsyche, could also have been Lepidostoma -- which raises even more questions.
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Theliopsyche and Lepidostoma differ in the size of the ventral apotomes and the length of the median ecdysial lines.  They look like this.

A new look at Leucrocuta

The new book on EPT of the southeast -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species (Clemson, 2017) -- provides us with a new key on the species of the flatheaded mayfly, genus Leucrocuta, so we can re-examine, with benefit, the four nymphs that we've found in local streams.  The ID's that I've arrived at to date are L. hebe, L. thetis, L. aphrodite, and L. juno, that by using three different sources: 1) the key provided in Unzicker and Carlson, "Ephemeroptera" in Aquatic Insects and Oligochaetes of North and South Carolina (pp. 3.72-3.73, 1982),  2) photos provided on the website Discover Life (http://www.discoverlife.org/mp/20q?search=Leucrocuta), and 3) Knopp and Cormier's  Mayflies: An Angler's Study of Trout Water Ephemeroptera (pp. 149-152). Let's see how those ID's hold up.

1. Leucrocuta hebe.

I just posted about this ID on 9/7,  no need to repeat what I've already said.  This keys out as L. hebe in all of my sources, including the new key.  (Also, look at the photo on Discover Life -- http://www.discoverlife.org/mp/20q?search=Leucrocuta+hebe."  The ID seems firm.

2. Leucrocuta thetis.  (pictured here and at the top of the page)

Let's begin with the key in Unzicker and Carlson (p. 3.72).  "Trachea of gills indistinct; pale markings on dorsum of abdominal segments 7 and 8 not coalesced; head without pale spots along frontal margin; lateral dark streaks present only on venter of abdominal segment 9."

All true, though I can't discount a bit of a dark streak on venters 8 and 10.  Now here's what the new key has to say.  "Gills darkened in upper half above midline of gill, with darkening sometimes extending over apex on both sides; abdominal tergum 9 brown; marginal pale areas on head present or absent." (p. 108)  Yes, tergum 9 is brown, and in this case pale areas on the head margin are not present.  Are the gills darkened in the "upper half above [the] midline of the gill"?  Yes!  But the darkening does slip over the midline near the the pointed tip.

Think we can stick with the L. thetis ID.

3. Leucrocuta aphrodite.

Unzicker and Carlson described L. aphrodite like this: "Dark areas on femora usually more extensive than light areas; dark areas of posterolateral and anterolateral angles of venter of segment 9 complete or almost complete, forming a dark margin, not divided into posterior and anterior areas."

Well, no question about the femora, but that's as far as I can go since I don't have a specimen in my collection at the moment so I could look at the venter.   Knopp and Cormier claim that "tergites 9-10 [are] paler," which I don't see.  Rather, the pale spots I normally see are on terga 1, 7, and 8 and a little on 9, as on this nymph.

Not sure where I got my ID, though I can say that other photos I've found of L. aphrodite match up with mine. (http://bugguide.net/node/view/1356607, and http://bugguide.net/node/view/1357415)  How about our new key?  Actually, this confirms our ID more than previous sources.  We get to L. aphrodite by moving from "gills without distinct tracheation" to "gills with distinct tracheation [and] "pale marginal areas present on head" (from couplet 195 to 197).  The alternative to 197 (i.e. 197') is "Head with pair of oblique dark bars between compound eyes; abdominal terga 2-9 with posterior margins with pair of purple-black transverse lines extending sublaterally...."  the description goes on, but it clearly doesn't apply.  We follow 197.  (197', by the way, leads to L. minerva, a species I haven't seen.)

Couplet 197 leads us to a long paragraph on Leucrocuta aphrodite, L. hebe, L. maculipennis, and L. juno in which we find the following note applying to L. aphrodite: "L. aphrodite and L. hebe may have a pale medial V-shaped area on abdominal terga 7, 8, and most of the medial length of 9, or on tergum 9, three connected or unconnected pale spots."  (p. 110)

Well, it's a bit of a stretch to say those markings are "V's" on terga 8 and 9, but for me that's close enough given everything else that we've seen.

I'm satisfied with L. aphrodite.  Three for three on our ID's.

4. Leucrocuta juno.

Same insect in various stages of development.   Once again, let's start with Unzicker and Carlson (pp. 3.72-3.73).  "Gills heavily shaded with purplish-black with paler areas at extreme tip, on median space next to main trachea, and near base of outer margin; dark markings at anterior margin of sternites 8 and 9, in median."

Okay on the gills, but I can't see any "dark markings at [the] anterior margin of sternites 8 and 9, in median."  So, not a whole lot to go on.  However, the nymphs in the photos above do match the L. juno nymph pictured  on Discover Life (http://www.discoverlife.org/mp/20q?search=Leucrocuta+juno).

But this time our ID is not confirmed in our new book.  Let me quote what we find there on L. juno: "Diagnostics for the L. juno larva are unknown.  It is unclear if larvae have been accurately associated with identifiable male adults, and thus the larva only is assumed to be similar to this grouping (i.e, the grouping of L. aphrodite, L. hebe, and L. maculipennis, and L. juno), and according to previous keys, to L. maculipennis in particular."   Actually, the nymphs that I've found -- those I've been calling L. juno -- key out pretty well to what our new book labels Leucrocuta sp. 1 (p. 108).   "Gills darkened along midline on both sides, then becoming infuscated, more so in the upper half of gill; abdominal terga, including 9, with extensive pale areas medially; marginal pale areas not present on head."  Yes indeed, the gills are dark on both sides of the midline this time, turning blackish toward the margins, and there are "extensive pale areas medially, on the terga" (though much smaller on segments 8 and 9.

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L. hebe, L. thetis, L. aphrodite, and possibly L. sp.1 -- that's where things stand at the moment.  One final note, I suspect that the tolerance values will differ by species if anyone gets around to working that out.  I've found L. hebe in medium streams to large rivers -- the Doyles, Buck Mt. Creek, and the Rivanna to be specific -- L. aphrodite, to date, I've only seen in Buck Mt. Creek.  L. thetis and L. sp.1 (if that's what it is), on the other hand I've only seen in the high quality small mountain streams in Sugar Hollow.

Flatheaded mayfly: Heptagenia marginalis

The Rivanna River in Charlottesville has been high and muddy most of the summer.  Some of the time that could be blamed on heavy rain -- but not all of the time.  Somebody was doing something upstream, not sure what.  In any event, it now seems to be dropping and clearing so I went to Darden Towe Park this morning to see what I could find.

There were a number of insects to photograph, but these pictures turned out the best.  Flaheaded mayfly: Heptagenia marginalis.   While I found this nymph once in the Moormans, I've seen it more often in the Rivanna at Darden Towe and always at this time of year.   Heptagenia nymphs have fibrilliform behind gill number 7 (it's absent on 7 on Leucrocuta and Nixe).   For the species ID, all we have to see are the dark sublateral streaks on the terga.

Tolerance value is 2.2 -- not all that bad for the Rivanna.  Found two.

I'm not sure what explains the bright yellow marks on one of the nymphs (terga 1, 8 and 9) but not the other.  Guess it could be a gender distinction.

A change in the pronggilled mayfly genera: new genus, Neoleptophlebia

I just learned of this change Sunday night.  Pronggilled mayflies with tracheal branching on the gills have been put into a new genus -- Neoleptophlebia -- moved from Paraleptophlebia.  Of the pronggilled nymphs that I've found, that means assimilis -- pictured above -- is now Neoleptophlebia assimilis.

Also now considered Neoleptophlebia, and additional species that we might very well find, are adoptiva, mollis, and swannanoa.

Unaffected by this are the other species I've found, those without tracheal branching, guttata, strigula, and what I think is jeanae.  They remain genus Paraleptophlebia.    These.

P. guttata

P. strigula

P. sp. (jeanae?)

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The complete list of North American Ephemeroptera (mayflies) can be found at:
https://www.entm.purdue.edu/mayfly/na-species-list.php.

Something new! An "armored mayfly" (Baetiscidae), Baetisca berneri

I just wasn't ready for this one.  In all of the years I've been out on the streams, this is the first time I've managed to find one of these nymphs.  A Baetiscidae -- armored mayfly -- which keyed out to Baetisca berneri.  I never thought I would see one.

Habitat, according to Beaty, is "Lotic, partially buried, often in shallow sandy or gravelly riffles or in edge vegetation."  ("The Ephemeroptera of North Carolina," p. 73)  And that's pretty much where I found it, by stirring up rocks and sandy gravel in a small riffle close to shore -- Rapidan River.

Genus ID: "Anterior margin of head with medial frontal projection or with anterolateral genal spines; enlarged thoracic notum fused between wing pads and forming a shield or carapace-like projection which is extended to abdominal segment 6; gills concealed beneath thoracic shield; three caudal filaments, short; body typically light brown with variable dark pigmentation."  (Beaty, p. 73)

All visible here, and this one has the genal spines.

On to the species -- it's Baetisca berneri, which is "Uncommon and very intolerant," according to Beaty.  (Would we expect anything less from the Rapidan River?!)

berneri -- nymphs 7.5-11.5 mm; genal spines present; caudal filaments prominently banded with dark brown at base; body pale with variable speckling, an interrupted dorsomedial line on abdomen; ventral surface may be speckled and brown.

There's no question about the ID, but this was a much smaller nymph than Beaty describes: it measured a mere 4.5 mm.  Sure wish it had been bigger, my photos would be much better.  As it is, I'm surprised I got any photos at all.  This little guy -- and with those big red eyes it is a "guy" -- kept darting around my petri dish making it very hard to focus.  But I still got some decent shots.

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Pretty exciting.  However, the Rapidan is very low -- it could use a whole lot of rain.

Have to post a retraction: clearly not Isonychia georgiae

The Isonychia nymphs that I found at Buck Mt. Creek, I'm afraid, were something other than I. georgiae.  I made a basic mistake.  What I thought were single filament forecoxal gills were, in fact, the labial and maxillary palps.

These are the forecoxal gills,

and as you can see they are not single filaments, what we find is a "cluster of filaments."  That eliminates the following species from consideration for the species ID: georgiae, obscura, serrata, hoffmani, and similis.  With the cluster of filments, it could be Isonychia sayi were there no "marginal spines on the distal margins" of the abdominal gills, but clearly such spines are present.

That being the case, our key -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species -- gives us the following options: 1) "Gils 6-7 (gills on abdominal segments 6-7) with row of minute robust setae along entire length of median sclerotized ridge," or 2) "Gills 6-7 without distinct row of minute setae on median sclerotized ridge." (Larvae, p. 128)  This is the ridge:

and I cannot see what is or is not on that ridge without greater magnification than I can get with my microscope.

So, back to the drawing board.   I cannot determine the species.  Were I to speculate, I'd go with Isonychia bicolor.  That is based on the fact that the unusual abdominal pattern we see on this nymph --

closely resembles Fig. 397 in our key (p. 129) which is an "I. bicolor variant,"  a species that is "widespread in the Southeast." (p. 128).  Best we can do at the moment.

Two really stunning insects today: Paraleptophlebia guttata and Leucrocuta hebe

Really gorgeous: a fully mature flatheaded mayfly, Leucrocuta hebe.  Location: Doyles River up at Blackwells Hollow Road.   Some more photos and then we'll go into the species ID.

At 4 mm, this was a very small nymph.  Still, the photos worked out just fine.  On the species ID -- in the past I've called this one Leucrocuta hebe using a number of sources.  But today I turned to our new key to see what I'd find.   This key seems to urge more caution with making this call, but all in all I think we're right with L. hebe.  New key ---

"L. aphrodite and L. hebe may have a pale medial V-shaped area on abdominal terga 7, 8, and most of the medial length of 9, or on tergum 9, three connected or unconnected pale spots (possibly even one medial spot in extreme variants).  Sternal and caudal filament markings that have been associated with either of these species vary considerably between and among populations, and other characteristics that may be of diagnostic value are not known with confidence.  For example, L. hebe might have an unmarked ventral abdomen or one with pairs of ventral spots in some populations, and also commonly a pair of posterolateral spots on sternum 9, or extensive lateral staining on 9." (Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species, p. 110)

What I see on our nymph is this.  1) There is clearly a "V" (or a "U") on tergum 7, 8 is pretty solid in color medially, and on 9, I'd say there are 3 pale unconnected spots.

This is the venter.

The ventral abdomen on our nymph is "unmarked" while on segment 9, there is, I think, lateral staining.  I think L. hebe is the right call.
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Nymph number two -- a fully mature pronggilled mayfly, Paraleptophlebia guttata.

I wasn't sure of the species ID on this little guy (also 4 mm) -- the pale terga were a little unexpected -- so I decided to key it out.  P. guttata for sure.  1) "Gills 2-7 forked near base, usually not more than one-sixth length from base; gill trachea without distinctly pigmented lateral branches."  (Larvae of the Southeastern USA, p. 140).

2) "Combined length of distal two maxillary palp segments about 1.5x or more length of proximal segment." (p. 140)  Segments 2 and 3 were 1.6 times as long as segment 1.

3) "Posterolateral projections present on abdominal segment 9 only." (p. 140)  Yes.

and 4) "Abdominal terga 2-6 laterally without blackish bands (as on P. strigula), but often with diffuse blackish spot in posterolateral corners." (p. 141) Yep, those spots are there.

 Paraleptophlebia guttata.
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Beautiful day in Virginia.  Stream level was great.  But now we're on the lookout for Hurricane Irma!