Wednesday, April 30, 2014

From the Oregon trip: the spiny crawler Ephemerella infrequens and some -- as yet -- undetermined Northern case-makers

We had a lot of rain in Portland last week, but I did get in a quick trip on Sunday.  My son-in-law took me to the Washougal River in Camas, WA.  The water (run-off, snow melt) was high, but we managed to find a few insects on the rocks close to shore.

For one, the spiny crawler in the photo at the top of the page, Ephemerella infrequens.  This is also called Ephemerella dorothea infrequens, and it's almost identical to the E. dorothea nymph that we're finding right now in the East.  Here's a close match: an E. dorothea that I photographed on 5/1/12:

Dorothea infrequens is described in the following way at under "Pacific Northwest Mayflies".  "Body uniform brown color, abdomen w/weak, light markings; no abdominal tubercles...small oval gills on segs 3-7."  (

The lack of the abdominal tubercles, and the "weak, light markings," are both clear in this microscope photo.  So too are the gills.

Not too tough to ID, and as you can see, both of the nymphs we picked up had fairly long wing pads.

E. infrequens in the West hatches as the "Pale Morning Dun" (PMD), while our E. dorothea here in the East is the "Pale Evening Dun" (PED).

Another easy one, a Green stonefly -- the only stonefly we found -- genus Sweltsa, the very same Chloroperlid we're finding right now in VA.  (We found two of them.)


And now for the problem child.  We found a bunch of caddis cases that were a mix of sticks and stones.  As it turned out, the main case was a cylinder made out of pebbles to which various sticks and pieces of wood were attached.  Here are photos of two of the larvae: note that the heads are totally black and therefore not easy to see.



There is no question at all that these are "Northern case-makers" (Limnephilidae): they have very prominent lateral and dorsal humps and very visible prosternal horns.  But that's as far as I've gotten so far.  I've spent the entire morning working through the descriptions and illustrations of Limnephilid genera in Wiggins (Larvae of the North American Caddisfly Genera) but I haven't nailed it down.  Frustrating.  If we have readers from the Northwest who recognize this one, please let me know.  The cases were found on rocks in slow water next to the shore.  The heads of the larvae are dark brown/black without any markings that I can see: the gills are branched, some with three filaments, others with two.  Any thoughts?  I'm happy to provide further details on anatomical features.

We're back in Virginia, and I'm anxious to get back to the streams.  But we've just had 4-5 inches of rain so it might be awhile.  Until then, I'll continue to work on the genus and species ID of those Limnephilids I found.

Tuesday, April 22, 2014

And the answer is -- it "may" be A. internata, it may "not" be A. internata

This Acroneuria common stonefly from Sunday at Entry Run may be Acroneuria internata, but the jury is out.  That's the word from Steven Beaty.  They see this same type of Perlid in North Carolina, and they're not really sure what to call it.  At the moment they regard it as a particular form of A. abnormis, preferring to take the conservative route.   At issue, the thickness of the light colored tergal bands.  On A. internata -- you will recall -- they are "of uniform thickness"; on this nymph they are not.  The bands are thick in the middle but slightly thinner on the sides.

In the end, there is only one way to know what this is -- a uniquely patterned A. abnormis or in fact A. internata: rear one to maturity and then see what it turns into as an adult.  That's the only way we'll know the answer for certain.

I'm not sure I possess the skill set or the equipment to carry this out.  But we've now found 3 Isoperla Perlodids and this Acroneuria Perlid for which we don't know the species ID.  I might go to NC to see how the rearing is done.  Until then: this is the common stonefly (Perlid), Acroneuria sp., possibly A. abnormis, possibly A. internata.   That's where it stands.  Lots of uncertainty in the entomological world when it comes to species ID of some of our stoneflies.


Off to Oregon on Thursday -- back early next week.  If the sun shines in the West, I'll be out seeing what I can find in the streams around Portland.

Sunday, April 20, 2014

A new Perlid (common stonefly) at Entry Run? Acroneuria internata

Entry Run this morning, where the water was perfect and the insects (nymphs and larvae) were abundant.  And I may have found something new.

I took a number of photos of this Perlid: the abdomen just didn't seem right.  The genus is Acroneuria, there's no question about it, and it looks a lot like A. abnormis, the species we most commonly see.  But I'm not sure that it is: I need to run this one by Beaty.  It could be Acroneuria internata.  Here's Beaty's description: "A. internata -- male nymphs 15-18 mm, female nymphs 21-24 mm; dorsum of head with interrupted M-shaped head pattern, appearing as a transverse row of 3 light spots in front of anterior ocellus; abdomen banded, posterior margins of tergites light and of uniform thickness; anal gills absent.  Recorded from VA, WV, and GSMNP."("The Plecoptera of North Carolina," p. 14)

The size of this nymph was about 18-19 mm -- though it's not completely mature.  The "M" pattern on the head is clearly interrupted, with three pale "slashes" in front of the anterior ocellus.  And, it seems to me, that the light bands on the terga are indeed uniform in thickness.  Here's a close look.

It is that feature -- the uniform thickness of the light bands -- that distinguishes this nymph from A. abnormis.  Beaty on A. abnormis -- "posterior margins of abdominal tergites light, dark tergal bands irregular."  They look like this.

I'll get back to you when I hear back from Beaty.


There were all sorts of insects this morning on the rocks and in the leaf packs.  Here's a sample of some of the neat things I saw.

1. A beautiful Giant stonefly, Pteronarcys biloba.  Fully mature: note how the tips of the wing pads are black, not sure I've seen that before.  (Note the small minnow mayfly -- Baetis tricaudatus -- clinging to the right foreleg.)

2. There were Peltoperlids (Roach-like stoneflies) all over the place.  Those that I checked were genus Tallaperla.  On Tallaperla nymphs the "thoracic gills [are] double" and the "posterior edge of [the] prosternal plate [is] mostly straight across... [while the] metasternal plate [has] long posterior wings."  (Beaty, "The Plecoptera of North Carolina," p. 12)  Here's a good look at both of those features.

3. A gorgeous Perlodid stonefly, Diploperla duplicata.

4. A "Northern case-maker" caddisfly larva, Pycnopsyche gentilis in its case made of stones.  Very nice case, and not the only one that I saw.

A number of insects enjoyed crawling on this one.  Two Peltoperlids...

and a little spiny crawler.

5.  The most common insect today: flatheaded mayfly, Epeorus pleuralis.  Saw a lot of them ready to pop (black wing pads).

6. And another common insect today: Perlodid stonefly, Isoperla montana/kirchneri.  No surprise there.  Note that the wing pads are starting to darken.  Abdomens are kind of a butterscotch color.

7.  And a third insect that was common today: freeliving caddisfly larva, Rhyacophila fuscula.  They're getting long and fat.

But the one we need to ID for sure: common stonefly, possibly Acroneuria internata.


It's the best time of year to get to the streams -- and not just for seeing the insects.  Trillium?

Thursday, April 17, 2014

But the most common Green Stonefly we see is Sweltsa sp., and they're getting mature

Back to Sugar Hollow today, to one of my favorite streams.  And I saw a lot of these nymphs: the Green Stonefly (Chloroperlid), genus Sweltsa.  Note how these nymphs differ from the Haploperla Chloroperlid we found yesterday.


Color, -- greenish brown: tails -- medium length, slanting away from the body; size when mature --- ~7 mm; wing pads -- inner margins close to parallel to the line of the body.


Color -- golden brown; tails -- short, point straight back from body; size when mature -- 7-8.5 mm; wing pads -- inner margins diverge from the main line of the body.

Just in case you need to identify Greens to the level of genus.

"Mature" was the name of the game at this small stream today.  Beautiful insects with black wing pads that by now could be flying around.

1. Pronggilled mayfly, Paraleptophlebia sp. (mollis?)

2. Flatheaded mayfly, Epeorus pleuralis

3. And the flatheaded mayfly, Maccaffertium merririvulanum.  Not quite mature, but the wing pads are long and dark brown: size, close to 16 mm.

And the defining feature -- the pale "V's" on terga 5, 7, and 8.

Only found in pristine, headwater streams.  Like the one we went to today.


Of course not everything was mature.  Even here the spiny crawlers (E. dorothea) are taking over the stream by the hundreds, but they're still pretty small.  And I did find one real small Perlodid.

It has a long way to go before it matures into this --

one of our unknown Isoperlas.

One of my favorite sights in the spring in Virginia -- redbud trees.  Our flowering trees are in bloom wherever you look.