Sunday, September 21, 2014

Entry Run yields a Goerid (Weighted-case maker) with an uncommon case


I wasn't sure what to make of this case when I saw it this morning.  This kind of case is common with the Uenoids -- 4 large pebbles on either side of the case used for ballast, and a case that is tapered.  But this case was big -- 16 mm -- much too big to be a Uenoid, and in any event, it's pretty early to see a Uenoid.  Of course, it' not too early to see Goerids (Weighted-case makers): you'll recall that I found this one last week at the Rapidan River


and I found this one this morning in South River, right next to Entry Run.


But Goerids, as we can see from these photos, have "squarish/rectangular" cases with 2 stones on each side, not 4.  There was simply no doubt that this one had 4.


But when I started taking my photos, it was clear that I had found a Goerid, just one with a very unusual case.  As I was taking the photos, I could see the sharp anterolateral points on the pronotum and the mesonotal anterolateral projections, hallmarks of this genus.


When I got home, I re-examined my sources which had this to say on the cases made by Goerids.

Beaty ("The Trichoptera of North Carolina," p. 87): "Case: Similar to that of Neophylax [i.e. Uenoidae] but with a continuous row of larger ballast stones laterally, usually two."

Wiggins (Larvae of the North American Caddisfly Genera, p. 226): "Case: With a row of larger pebbles along each side of the central tube of small rock fragments, larval cases of Goera are similar only to those of Neophylax in North America.  Generally, Goera cases have fewer and larger ballast stones on each side, usually two; Neophylax cases usually have smaller ballast stones, thus more than two."

Ames (Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, p.232): Their cases have lateral ballast stones similar to those of Neophylax in Uenoidae, but they are more symmetrical and rarely have more than two stones on each side."

So, lesson learned Goera cases -- on occasion --  can have more than 2 ballast stones on the sides.
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Both of the Goerids I picked up this morning turned out to be Goera fuscula -- a "rare" species according to Beaty.  Key features: "4 pairs of sclerites on metanotum; sternal thoracic plates distinct."

Here we can see the 4 sclerites on one side of the metanotum


and the sternal thoracic plates look like this.

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Not much else to get excited about today at the stream -- which is typical for this time of year.  But I did find a young Pteronarcys biloba Giant stonefly.  Previously, I've seen nothing in Entry run but Pteronarcys proteus.



The "lateral projections" on the abdominal segments of this particular nymph were really impressive!

And as I suspected, I saw a lot of Strong-case makers, Psilotreta labida.



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Fun day.  Love it when we learn something new.  Goera fuscula.

dorsal view of case:


ventral view of case:



Tuesday, September 16, 2014

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.


Sunday, September 14, 2014

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.

Thursday, September 11, 2014

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.