Tuesday, February 6, 2018

The small winter stoneflies are filling our streams

It's the kind of day -- cold and overcast -- when I normally forego taking photos, but I changed my mind when I collected this little nymph.  A fully mature small winter stonefly, Allocapnia pygmaea, female.  The leafpacks are full of these nymphs at the moment.  Not my best photos, but nice enough to share.

Monday, February 5, 2018

Acroneuria colors: I still get surprised.

I came upon this photo the other day when reviewing my files and immediately concluded it was the common stonefly, Acroneuria abnormis.  The reason is simple.  A. abnormis nymphs, in my mind, are always this color of brown.   For example...

True, as with the nymph in this photo, they often have terga that are banded, but still the basic color is brown.  And, you may recall, on some nymphs the terga are totally brown.

Closely related to A. abnormis is A. carolinensis.  Both species have a light "M" pattern on the head, lack a row of setae at the back of the head, and A. carolinensis nymphs also have banded terga.

But A. carolinensis nymphs, as you can see are basically yellow or orange.

So it appears to be easy to tell them apart by seeing the color.   The nymph at the very top of the page is basically brown, so it must be A. abnormis -- right?  Wrong, and I should have known better.  It is morphology that we have to use in determining species; pigment is an unreliable character.  And "morphologically," abnormis and carolinensis nymphs differ in one important respect -- the banding shades are reversed.  On A. abnormis nymphs, the dark band is in front, the light band at the back, on A. carolinensis, it's just the opposite. 

Back to our nymph at the top of the page.

Yes, it's basically brown, but look at the terga.  This nymph is A. carolinesis.  And, we can find the same with A. abnormis.

Basically yellow, but the lighter bands on the terga are at the back.  It's A. abnormis.

Just a reminder, don't be too quick to jump to conclusions, and I've been guilty of this.  True, the color's a good indication, but the tergal banding is the key thing to use.

Tuesday, January 2, 2018

Some photos from my files

I've started posting pics on Instagram ("buddhabob2hanlubo"), so I've been looking through my files to find things that are post-worthy.  To my surprise, I've found a lot of nice pics that I'm not sure I've ever used in this blog.  So, here's a look at some of my favorites.

1) Above, a pair of small winter stoneflies -- Allocapnia pygmaea -- female on the right, male on the left.

2) A second small winter stonefly, female, one that was close to hatching.

3) Some small minnow mayflies.  This one is Baetis pluto.

4) Small minnow mayfly, Baetis tricaudatus.

5) Small minnow mayfly, Acentrella turbida.

6) And small minnow mayfly, Heterocloeon curiosum.


7) Spiny crawler mayfly, Ephemerella dorothea.

8) Spiny crawler mayfly, Ephemerella dorothea.

9) Spiny crawler mayfly, Ephemerella subvaria.


10) And some caddisfly larvae.  Here, some common netspinners, Diplectrona modesta.

11) Lepidostomatidae, genus Lepidostoma.

12) Weighted casemaker, Goera fuscula.


Fun.  Something to do while we wait for warmer temps -- and it would be nice if those temps come with some rain! 

Thursday, December 21, 2017

A few photos from Entry Run

I drove up to Entry Run in Greene County on Tuesday.  Didn't see anything out of the ordinary, but I got some nice photos worth posting.

Above and below, brushlegged mayfly, Isonychia sp. (probably bicolor).

I still hope to find a nymph with single forecoxal gills -- not sure it's going to happen.  All of the Isonychiidae I've found so far have a "cluster of filaments" at the forecoxae, meaning I can't ID them to the level of species.  On this nymph, those gills show up in this live photo, no need to go to the microscope.


I wasn't at all surprised to see some of our winter casemakers, a Lepidostomatidae,

and a Thremmatidae (formerly Uenoidae), Neophylax consimilis.


And, to my surprise, I also found a spiny crawler, Ephemerella subvaria, the nymph of "many colors."

There was one odd thing about this one: the pointed tubercles on terga 5, 6, and 7 were pale colored.

I'm pretty sure that on the nymphs that I've found previously, those tubercles were all black.  Strange.  I plan to look into this.  Probably just a local variation.

Sunday, December 17, 2017

Pronggilled mayfly, Neoleptophlebia assimilis: identity confirmed

On August the 7th this year, I suggested that most of the Pronggilled mayflies I've found were Neoleptophlebia assimilis (then called Paraleptophlebia assimilis).  That suggestion relied heavily on pigmentation.  On morphology, I was missing one piece of evidence: I needed to see the mandibles to be sure they weren't N. swannanoa.  I found a number of nymphs yesterday at the Doyles River (my upper site), and our identity can now be confirmed.

Let's work through our key (Larvae of the Souitheastern USA: Mayfly, Stonefly, and Caddisfly Species, pp. 140-141). 

263  Gills 2-7 forked at one-fourth or more length from base; gill trachea with distinctly pigmented branches at least in unforked region.........264

263' Gills 2-7 forked near base, usually not more than one-sixth length from base; gill trachea without distinctly pigmented lateral branches, but often with very short and faint lateral branches.......267

Here's our nymph.

(You'll recall that the former nymphs are now genus Neoleptophlebia; the latter remain Paraleptophlebia.)  We clearly move on to 264.

264  Mandibles relatively elongate, with about half length of angulate (left) mandible beyond angulate shelf.......Paraleptophlebia swannanoa

264' Mandibles not elongated as above, with less (usually much less) than half length of angulate mandible beyond angulate shelf........265

Here's what we have.

The portion above the angulate shelf is roughly 1/4 the length of the mandible.  We move on to 265.

265  Posterolateral projections present on abdominal segments 8 and 9.......Paraleptophlebia( i.e. Neoleptophlebia) assimilis  

[Note: projections on segment 8 are not well formed in young larvae.]

265' Posterolateral projections present on abdominal segment 9 only....266

Our larvae are very young.  Still you can see the projections on 8.

Species ID confirmed!  Neoleptophlebia assimilis.


Lots of Large winter stoneflies (Taeniopteryx maura/burksi) around yesterday;

Small winter stoneflies (Allocapnia pygmaea) as well.

Monday, December 11, 2017

Apatania incerta -- Little Mountain Casemaker -- at the Doyles River this morning

It's a casemaker that I don't see very often -- Apatania incerta -- but it's one of the things I was hoping to see this morning.  Beaty describes the case as "composed of mineral particles and strongly curved, cornucopia-shaped."  ("The Trichoptera of North Carolina," p. 85)  Pretty clear in the photos I've taken. 

The genus ID goes like this.

Mesonotum with two plates; metanotal sa1 sclerites absent; arrangement of sa1 associated setae in a linear transverse row...mandibles usually with uniform scraper blades (not toothed).  (Beaty, p.85)  Works for me.

On the species he adds: "larvae 6-9 mm; head dark brown to black; nota brownish-black; anterior metanotal plates replaced by row of about 20 setae; legs yellow brown."  But I'm not sure the species detail is needed.  In our new key, incerta is the only species listed for Apatania.  (Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species, p. 294)

With a Tolerance Value of 0.6, we can expect to find it only in very good streams.  And when the case is right side up, the larva is covered with a hood.  Normally, all we can see is the legs, but in this case, the part of the head also sticks out.

Saturday, December 2, 2017

Our "Green Stoneflies" (Chloroperlidae), genus Sweltsa, are Sweltsa onkos

For sometime now, based on the appearance of the adults,

my friend and I have felt strongly that our Sweltsa "green stoneflies" were Sweltsa onkos in terms of the species.  With the help of our new key -- Larvae of the Southeastern USA: Mayfly, Stonefly, and Caddisfly Species -- we can now confirm that ID.   (And yes, if the genus is Sweltsa, there is nothing "green" about either the nymphs or the adults of these Chloroperlids.)

Let me work through our key (pp. 206-208). 

72  Tibial fringe setae sparse and about half as long as median outer marginal seta......73
72' Tibial fringe setae more abundant and about as long as median outer marginal seta......77

The tibal setae is dense and long.  We move to couplet 77.

77  Longest dorsal setae on last five cercal segments about as long as 1.2- 1.5 cercal segments.......Sweltsa mediana
77' Longest dorsal setae on last five cercal segments about as long as 2 cercal segments........78

I'd go with 77'.  Certainly the longest setae on at least the last three segments are close to being the length of 2 cercal segments.

78  Abdominal terga dark brown, occiput about as dark as frons; meso- and metanota rather densely covered with long dark clothing hairs.......Sweltsa onkos
78' Abdominal terga pale brown, occiput almost entirely pale; meso- and metanota with sparse, brown clothing hairs.....Sweltsa naica

That's a no-brainer: Sweltsa onkos for sure. 

As we go through the winter, I'll keep checking Sweltsa nymphs just to be sure that onkos is the only species we have in our streams.  I can certainly say that every nymph that I have preserved keys out to onkos, and the nymphs in my photos match that description as well.