The "transformation": An Acentrella nadineae small minnow mayfly hatches right in front of my eyes

It was bound to happen.  If you go to streams as often as I do, putting mayfly nymphs and stonefly nymphs -- some fully mature -- into your bowl, someday, something is going to hatch.  And it happened today, and I got to see it step-by-step.

Here's the nymph I had collected.

The colors looked a little bit off -- A. nadineae nymphs are very distinct with splotches of red and orange.  E.g. here's a a real beauty that I photographed on 8/30/12.

Still, there was no doubt about the ID.  Look at the gills.  From Beaty, "gills elongate, asymmetrical, and with basomedial pigmentation splotches." ("The Ephemeroptera of North Carolina," p. 4)  No doubt about it.

Before very long, I had two signs that this nymph was in the process of hatching.  In this photo -- in which the nymph is "hitching a ride" on a "Weighted case-maker" (Goeridae) -- note how the tails are curling up.  That's what they look like on the adults.  In fact, this looks like an adult sans the wings.

Second sign.  Note the "bubble" that has appeared on the thorax of the nymph.  The thorax is cracking as the wings start to emerge.

In a flash, the wings came out and the adult popped out of my dish.  (Shoot!  Forgot to look in my dish for the "shuck.")

But before it flew away -- and it did -- it perched on my petri dish long enough for me to get a couple of photos.

That was a treat.  If I use some of the photos I have in my files, we can see the whole process of maturation.

1) tiny nymph

2) a nymph that's fairly mature

3) fully mature -- black wing pads

and then from today ---

And for the fly fishermen in the group -- time to get out the BWO's (Blue-winged Olives).  The fall hatch has begun.
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A few other photos from this morning -- though not nearly so exciting.

1. Small minnow mayfly, Baetis intercalaris.  Also fairly mature.

2. A pair of Goera calcarata "Weighted case-makers."

3. And the smallest of the small: spiny crawler mayfly, Ephemerella subvaria.  Recognized it by the colors.  We see the large, mature nymphs in March and April.

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For a complete description of the hatching/emerging process, see Knopp and Cormier, Mayflies: An Angler's Study of Trout Water Ephemeroptera, pp. 10-16.

Hitchin' a ride: fun photos from the past

I'll be off to the Rapidan River on Tuesday, but every so often I check through my photos to see what I'm most likely to see at a certain time of year.  And here was this very cool photo of a small minnow mayfly, Acentrella nadineae, that I found last year at the Rapidan on 9/16.   It decided to ride out its time in my petri dish on the back of the case of this humpless case-maker, Brachycentrus appalachia.

When I returned to the Rapidan in October (10/15/13), this move was repeated by a very young spiny crawler mayfly nymph, Ephemerella subvaria.

When I have more than one insect in my petri dish when I take photos, it isn't uncommon for a small insect -- especially a mayfly nymph -- to cling  to something else, especially to the case of a case-maker caddis.  It's good to remember that this happens in real life in the streams as well.  Why waste energy swimming or crawling about on your own when there's a free ride to be had?

So I decided to look through my files to see if there were other times in the past when this has resulted in my getting some pretty nice photos.  Here we go.  I'll use a chronological order.

1. A "baby" Giant stonefly clings to the tail of a more mature nymph.  Both nymphs are Pteronarcys proteus.  6/1/11.

2. A very small stonefly, Isogenoides hansoni,  "peeks" inside the case of a humpless case-maker.
9/12/11.

3. A small minnow mayfly, Acentrella turbida, rides the back of a Giant stonefly.  10/9/11.

4.  Mayfly nymphs and caddisfly larvae also enjoy riding atop the cases of other caddis case-makers.
Here's an Ameletid mayfly nymph (Ameletus lineatus) and a Lepidostomatid caddis riding on the three-sided leaf case of a Pycnopsyche gentilis (Northern case-maker).  2/29/12.

5.  A small minnow mayfly, Baetis intercalaris, holding on to the tail end of a humpless case-maker case.  9/22/12.

6.  Not really a case of "hitching a ride," but a nice photo of two caddisfly case-makers lying side-by-side in my dish: humpless case-maker, Brachycentrus appalachia, and a "little mountain case-maker," Apatania incerta.  Rapidan River, 1/4/13.

7.  And I totally missed my first sighting of an Isoperala orata Perlodid stonefly nymph.  It was clinging to the case of a Northern case-maker, Pycnopsyche scabripennis.  Rapidan River, 5/13/13.

8.  Another mayfly holding on to the pebble case of a Pycnopsyche gentilis (Northern case-make): this time a small spiny crawler.  4/20/14.

9. And quite recently -- 8/15/14 -- at the Rapidan River, I found this midge larva, inside of a case, attached to another Pycnopsyche scabripennis Northern case-maker larva.  8/15/14.

10.  One more.  I don't have the date, but it was sometime early this year.  A Uenoid caddisfly larva in its little case made of pebbles and sand, crawling around on a Pycnopsyche gentilis Northern case-maker in a case that's part leaves and part pebbles.

More "oddities" to come in future entries -- but first, let's see what we can find in that clean mountain stream.

The autumn stoneflies in the Rivanna

I went to the Rivanna at Crofton this morning, where I found pretty much what I expected to see: the common stonefly, Agnetina annulipes; the giant stonefly, Pteronarcys dorsata; and the same common stonefly that I found at Darden Towe Park, Acroneuria arenosa (or possibly A. evoluta).

In the photo above, a fairly immature A. annulipes (measured about 9 mm), and here's one even smaller (only 5 mm).

Agnetina Perlids have a complete setal row at the back of the head (occiput), and anal gills are present.  While neither feature is crystal clear in my photos, if you look closely, they can be seen in this one.

Other key features: "head pattern roughly M-shaped with arms directed posterolaterally," "dorsum of abdomen banded, with dark bands on anterior half of segment," and "tergum 10 mostly dark including apex."  (Beaty, "The Plecoptera of North Carolina," p. 15)  The banding shows up the best on the small nymph in the photo above: we can see the arms on the M, and dark color of tergum 10, in just about all of the photos.  Actually, in this photo we can see all of the features.

I saw a lot of these Perlids today, and I'll continue to see them well into the fall.  They're fairly common in the Rivanna at this time of year.
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Giant stonefly, Pteronarcys dorsata

And I saw a lot of these "giants" -- Pteronarcys dorsata.   This is a fairly tolerant species -- 2.4 -- and it's the only species of giant I've seen in the Rivanna.   Characteristics: "Lateral angles of pronotum produced, anterolateral ones almost hook-like;  no lateral projections on abdominal segments; each tergite with anterior and posterior abdominal spots sometimes confluent to give the abdomen a longitudinally striped appearance (3-5 stripes possible)."  (Beaty, "Plecoptera," p. 28)  Very striped it is.

Two interesting shots.  The first, a ventral view of the thoracic gills of the giants:

the second, a side view of one of my nymphs as it climbed on top of another.

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Common stonefly, Acroneuria arenosa/evoluta

Since I've already covered the problem we have with the ID of this particular Perlid,  I'll just post some of my photos.  The anal gills (black/gray) are clearly visible on both of the nymphs that I photographed: on one, the M pattern is clearly there but faint -- which points to A. arenosa.   But, both nymphs are still immature.  What I need to see is what the head will look like on these nymphs when they're mature.

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Common netspinner, Hydropsyche venularis

Though I found very few -- not sure I saw any -- common netspinners last week at Darden Towe Park, at Crofton, there were still some crawling in the vegetation on rocks.  I got some fairly good photos of this one, and it turned out to be Hydropsyche venularis, one of two species that I commonly see in this river.

The yellow marks on the head are key to identification.  On H. venularis, there are two pair of yellow dots on the top of the head, but the two often merge into one.

Still, to distinguish venularis from rossi, we must look at the muscle scars on the side of the head.  On H. venularis the rows of muscle scars "curve dorsad posteriorly." (Beaty, "The Trichoptera of North Carolina," p. 76)  You can see that with the top row in this microscope photo.

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The weather is changing at last: cooler temps on the way.  So I should start to get out more often and start looking at smaller streams.