Summer insects at the Rivanna: Heterocloeon curiosum (small minnow mayfly) and Hydropsyche venularis (common netspinner)

The Rivanna is still running high and fast -- but it's clear.  So I was able to turn over some rocks -- and sort through vegetation -- close to the shore in Darden Towe Park.

The small minnow mayfly at the top of the page -- Heterocloeon curiosum -- is the most common Baetid we see in this stream in the summer, and this morning there were a lot of them on the rocks.  I now know them by sight, but with a loupe you can pick out a distinguishing feature: the gray pigmentation at the center of each of the gills.

But to be sure of your ID, you have to see the "forecoxal gills," finger-like projections at the base of the front legs.  These:

No need for a microscope if you can get a photo like that!  Like many small minnow mayflies, H. curiosum nymphs are sexually dimorphic -- males and females have different colors and patterns.  That's a male at the top of the page, and this is a female:

Note the pale colored "U" on the thorax of the male.  And here's a photo of male and female together.  (I almost always find them together.)

By the way, don't be mislead by this photo, in which the male is the larger of the two: female nymphs, when mature, are always larger than males.  H. curiosum is an insect I look forward to seeing here in the summer.  I've only seen them in one other stream: the Moormans River, especially at Free Union Bridge.
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And of course there were lots of common netspinners around: it's the most common insect we see in the Rivanna in summer.  They love the gnarly vegetation that grows on the rocks in the river, though today I couldn't get out to those rocks.  The netspinner I most commonly see in the Rivanna is Hydropsyche venularis, and that's the one I ran into this morning.

This one we ID by noting two features: 1) the pale, anterolateral dots on the head -- which often merge into a stripe:

And the muscle scars on the side of the head that curve dorsad (upward) at the rear of the head:

H. venularis is a very tolerant caddisfly larva with a TV of 5.1.  But then, it has to be to survive the Rivanna in summer where the water can get very warm (it already is).   That it needs to draw oxygen from water that has little in it might explain why the abdominal gills seem to be so dense and thick on this species.

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Sure hope the water keeps dropping so I can get back here more often.   You don't have to struggle to find things in here in the summer.

Paraleptophlebia guttata and Paraleptophlebia mollis: Pronggilled mayflies in local streams

Based on photos by Donald Chandler -- a reliable specialist -- posted on "Discover Life," I suspect that the pronggilled mayfly that I found today is Paraleptophlebia guttata.  Please look at the following page: http://www.discoverlife.org/mp/20p?see=I_DSC155&res=640.

And based on photos by Tom Murray posted on "Bugguide.net,"  I would have to conclude that the pronggilled nymphs I most commonly find are Paraleptophlebia mollis. (See: http://bugguide.net/node/view/263140/bgimage.)

Both species are found in North Carolina.  (Beaty, "The Ephemeroptera of North Carolina," p. 40)

The only safe way to establish species ID, however, is to key out specific anatomical features. These identifications should be seen as tentative until I can find some way to do that.   In the meantime I have noted these names in our EPT list.

Stumped by a pronggilled mayfly at the Rapidan River

As I was collecting insects this morning at the Rapidan River, I was very excited to see this little (5mm) nymph.  It's a pronggilled mayfly, and as I was taking my photos I was quite sure it was another Habrophlebia vibrans, a species I've seen only one time before -- two years ago at the Rapidan River in spring.    This is Habrophlebia vibrans.

When I got home and downloaded my photos, I quickly saw that I was mistaken.  Note how the gills are in "clusters" on the H. vibrans nymph, not so on the nymph that I found this morning.  The gills on that nymph are "forked, bilamellate," which is the form that gills take on the genus we most commonly see in our streams -- Paraleptophlebia.  However, the Paraleptophlebias that I normally see look like this.

Not only does the color and pattern differ significantly from this morning's nymph, note the difference in gills.  Those on the nymph in this photo, fork at the middle of the gill, and in the portion in front of the fork, there are well defined tracheal branches.  These.

The gills on the nymph that I found this morning are forked from the base of the gills, and they lack tracheation.

More photos:

I'm not sure what I found.  At the moment, I think this nymph is also Paraleptophlebia, it's just a different species than the Paraleptophlebias that I normally see.  Beaty notes that North Carolina has at least 8 species of Paraleptophlebia, but he tells us to leave ID at the level of genus ("The Ephemeroptera of North Carolina," p. 40).   Still, apparently there is a key one can use to narrow this down, so I plan to look into this further.

(By the way, I have seen photos of Paraleptophlebias with gills that lack tracheation like the one that I found this morning.  See, for example, the photo of Paralpetophlebia bicornuta at http://bugguide.net/node/view/796600.)
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Other discoveries this morning.

1) A beautiful flatheaded mayfly, Epeorus vitreus.  There seemed to very few of them around.  (Note how transparent the leading edge of the head has become.)

2. I saw a lot of the "summer batch" of Brachycentrids (humpless casemakers), Brachycentrus appalachia.

3. Small minnow mayfly, Baetis intercalaris.  (Also saw Acentrella turbida nymphs.)

4. A quite mature Perlodid stonefly, Isoperla holochlora.  These are long gone from most of the streams that I visit, but the Rapidan is up in the mountains where things take longer to mature.

5. And then there was this wonderful butterfly which stopped by to see what on earth I was doing!

Feel free to help me out with identification.

Is it a new species of Saddle-case maker? Glossosoma intermedium?

I didn't expect to see a whole lot this morning -- and I didn't.  Still, this one may be of interest.  It's a Saddle-case maker (Glossosomatid) that I found in one of the small mountain streams in Sugar Hollow.  I don't really expect to see Glossosomatids during the summer -- but I guess that I should.
Beaty notes -- on Glossosoma nigrior, the species that we normally see: "Relatively common during spring and late summer."  ("The Trichoptera of North Carolina," p. 66)

This larva, too, is a Glossosoma in terms of the genus -- but is it G. nigrior?  Beaty describes G. nigrior in the following way: "pronotum with small black spot above forecoxae; small sclerite in intersegmental fold between thorax and first abdominal segment laterally (separates out from G. intermedium).  Only confirmed species in NC."

I can easily see the G. nigrior markings on the Glossosomatids that I find in the spring.  Here's the spot on the pronotum.

And the sclerite in the intersegmental fold looks like this.

The problem is that I can't see that sclerite on the larva that I found this morning.

And I take it that that is the very thing that separates G. nigrior from G. intermedium.

More to come on this one.  Obviously, I've sent my photos to Beaty for confirmation since G. intermedium isn't found in his state.  But maybe there's something there that I'm missing.

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Three other photos.

1. In the Moormans itself, I found this "Rolled-winged stonefly" (Leuctridae), genus Leuctra.  This is another taxon that I expect to see in the winter and spring.  Still, Beaty notes, "Widespread and very common during the spring and summer." (The Plecoptera of North Carolina," p. 2)  And I do recall finding mature nymphs in the autumn.  This is a small one: the wing pads are very hard to see.

2.  Also in the Moormans below the first bridge, and also unexpected, a small "Roach-like" stonefly (Peltoperlid).   I do expect to see little nymphs during the summer, I just don't expect to see them in a river the size of the Moormans, I normally find them in the small mountain streams.  Explanation?  Well, Beaty does say of Tallaperla (this genus), that it's "common in clean Mountain and Northern Inner Piedmont streams," ("Plecoptera," p. 12) so the distribution might be greater than I had concluded.  The other possibility is that these nymphs have been washed down into the Moormans by the flash floods of recent weeks.

3.  And -- hooray, hooray -- one we do expect to see -- the flatheaded mayfly, Epeorus vitreus.  They're still pretty common.

EPT List: Summer insects in the Rivanna

It's mid-July, and I've still not made it to the Rivanna: it remains high, fast, and muddy.  Maybe next week or the week after.

I mainly look in the Rivanna during the summer since the water is too high or too cold during the rest of the year.  I'd really like to see what I would find there in late winter and spring.  But for the moment, this accounting will only list summer insects.  I've seen 7 species in the Rivanna that I've not seen anywhere else -- as best as I can remember: the small minnow mayflies Heterocloeon petersi (pictured above) and Iswaeon anoka; the little stout crawlers (Tricorythodes); the common stonefly Agnetina annulipes (though I may have seen this one at Buck Mt. Creek as well); the tiny micro caddisflies, family Hydroptilidae; Long-horned caddisflies, Nectopsyche exquisita; and the Emerald dragonflies, Neurocordulia obsoleta.

Dragonflies and damselfies are common in the Rivanna during the summer, as are common netspinners (Hydropsyche venularis and Hydropsyche rossi).   Surprisingly, there are Giant stoneflies in this big river, but in the summer, they're too small to identify to the level of species.

          EPT Species List for the Rivanna River in Summer

I. Ephemeroptera (Mayflies)

1. Baetidae (Small minnow mayflies)

1. Acentrella turbida

2. Baetis intercalaris

3. Baetis pluto

4. Heterocloeon curiosum

5. Heterocloeon petersi

6. Iswaeon anoka
7. Labiobaetis propinquus

2. Heptageniidae (Flatheaded mayflies)

1. Heptagenia marginalis

2. Maccaffertium modestum

3. Stenacron interpunctatum

3.  Ephemerellidae (Spiny crawler mayflies)

1. Serratella serratoides

4. Leptohyphidae (Little stout crawler mayflies)

1. Tricorythodes

II. Plecoptera (Stoneflies)

1. Taeniopterygidae (Large winter stoneflies)

2. Taeniopteryx burksi/maura (in the fall)

 3. Perlidae (Common stoneflies)

1. Acroneuria abnormis

2. Agnetina annulipes
3. Agnetina flavescens

4. Pteronarcys (Giant stoneflies)

1. Pteronarcys dorsata

III. Trichoptera (Caddisflies)

*1. Hydroptilidae (Micro caddisflies)

1. Hydroptila (?)

2. Philopotamidae (Fingernet caddisflies)

1. Chimarra

3. Hydropsychdae (Common Netspinners)

1. Hydropsyche rossi

2. Hydropsyche venularis

4. Brachycentridae (Humpless case-makers)

1. Brachycentrus appalachia

5. Lepidostomatidae

1. Lepidostoma

6. Leptoceridae (Long-horned case-makers)

1. Nectopsyche exquisita

2. Oecetis

IV.  Odonata (Dragonflies and Damselflies)

1. Narrow-winged damselflies (Coenagrionidae) -- genus Argia

2. Broad-winged damselflies (Calopterygidae)  - Haeterina americana

3. Clubtail dragonflies (Gomphidae) -- Hagenius brevistylus

4. Emerald dragonflies (Corduliidae) -- Neurocordulia obsoleta

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Photos of some of the common -- and some of the uncommon -- summer insects in the Rivanna.

1. Small minnow mayfly, Iswaeon anoka.  (Uncommon species)

2. Small minnow mayfly, Heterocloeon petersi.  (Also uncommon)

3. Small minnow mayfly, Heterocloeon curiosum.  (Common)

4. Little stout crawler, genus Tricorythodes

5. Long-horned caddisfly, Nectopsyche exquisita

Odonata

1. Broad-winged damselfly, Haeterina americana

2. Narrow-winged damselfly, genus Argia

3. Club-tailed dragonfly, Hagenius brevistylus

4. Emerald dragonfly, Neurocordulia obsoleta

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The Rivanna River at Crofton.