Looking for Bugs in the Rain: Buck Mt. Creek on Father's Day

Well, my daughter lives in Portland, Oregon, so obviously she wasn't going to call until 1:00 or 2:00 PM.  So, I decided to go to Buck Mt. Creek to look for small minnow mayflies.

It was stupid.  It was overcast -- dark sky -- but I thought it might clear.  It didn't; it rained!  But by then I had collected 20+ interesting nymphs -- so what to do?  I decided to drive back home with my bowl and take the photos back there.  Mistake.  I made a sharp turn on the way back, the bowl overturned, and out came all of my insects!  I quickly stopped at a store, bought a bottle of water, picked my bugs up from the floor of the car and made it back home with some things still intact!  Ah joy.

But, I got some good photos, including this beautiful, fully mature, Perlesta common stonefly (Perlid).  I still found some young nymphs, but I found two of these beauties in a single leaf pack.    Another look.

Actually, this is just about the only stonefly I'm finding anywhere at the moment.  The Perlodids seem to be gone -- except for some Isoperla holochloras in the high elevation tributaries to the Moormans River and up at the Rapidan.

I also saw -- but collected only a few -- a lot of flatheaded mayflies.  Three genera: Epeorus (vitreus), Maccaffertium, and Leucrocuta.  Somehow, one of the Leucrocuta nymphs I collected made it all the way home intact -- a small miracle.

The small size and large head, and the way it sped around the rock gave it away.  But remember, the key thing is that gills 1-6 have fibrilliform between the gill and the body; gill 7 does not.  I tried to get microscope photos of gills 6 and 7 this time to prove the point.  Here they are:

Gill 6:

Gill 7:

No fibrilliform.

My goal in going out today was to find some more small minnow mayflies since I want to establish the "hatch" pattern in this part of the state.  Which genus/genera do we find in the winter?  How about the summer and fall?  So far, I've found Acentrella nymphs in this stream -- all of them very small -- but I've also found, recently, a three-tailed Baetis nymph.  You may recall this recent photo.

I only found 1 nymph today -- again a three-tailed Baetis.  He did not survive the trip to my home in very good shape: still, here is a photo.

Once we see the three tails, we have to look at the "labial palps": are they "rounded" or "truncate"?  They're rounded.

And the last test -- does it have metathoracic wing pads?  Yes it does: this one is very clear.

I hope by the end of the summer I can determine the "species" as well as the genus of this "three-tailer".
I imagine these will hatch in late August or September.  But more on that later on.

Almost forgot.  I also saw a fair number of Brushlegged mayflies today, and they're already pretty big.
They're very difficult to pick up with tweezers, but I did manage to grab this one.

Flatheads, Flatheads, Flatheads: A Trip to the Mechunk

I travelled out to Mechunk Creek this morning, hoping to find some dragons and damsels, but what I found was lots and lots of flatheads.   On some of the larger rocks that I flipped over, there must have been 10-15 nymphs running around.  There were all different sizes and all different colors -- almost all were Maccaffertium in terms of the genus.  In the photo above, the nymph on the left is a Stenacron nymph, that's a Maccaffertium on the right.  Here's a good look at one of the larger Maccaffertium nymphs that I found.

You may recall that these two genera are anatomically close in terms of gill structure: in both cases the gill on segment 7 is thin and fingerlike, not at all like the gills that precede it in terms of appearance.  But, Stenacron gills (gills 1-6) are pointed; Maccaffertium gills are truncated (sort of squared off).  Here are some microscope photos that make the point clear.

Stenacron:

Maccaffertium:

The Stenacron nymph in the picture above is clearly in its "pre-hatch" colorful stage, and it's worth looking back to a photo I took on March 18th at Whippoorwill Branch of younger Stenacron and Maccaffertium nymphs that I caught swimming together.

I can't say for certain that the dramatic change in color in the nymphs that I found today is entirely because of maturing -- a difference in species might be involved.  Still, an enrichment of color and pattern is something we've witnessed all year in mayfly and stonefly nymphs as they grow and mature.

What else did I find?  Well, there were some common netspinner caddisfly larvae and some fingernet larvae as well, I also saw a fair number of Brushlegged mayflies and a couple of Perlesta common stoneflies -- and this stream is loaded with snails (mostly Pleurocerids).  But I did find one dragonfly -- another Darner dragonfly (family: Aeshnidae).  It was a big one -- a little bit over an inch.

Finally, I'm starting to find small Hellgrammites.  But the one in the picture below is sort of a "teenager" when compared to the babies we'll start to see in July and August.  If you ever find one of these and are not really sure that it's a small Hellgrammite, just look for the four hooks that are attached to prolegs at the rear of the insect: they seal the deal.

Another look at the beautiful Stenacron flatheaded mayfly found in Mechunk Creek today.

Looking for "Mr. Heptagenia" in the Moormans

We didn't find him, or her, though such distinctions hardly apply at this stage of mayfly development.

I went to the Moormans River this morning with a friend who lives on the stream -- a good entomologist and photographer in her own right.  And, yes, we were hoping to find some Heptagenia flatheaded mayflies.  No luck.  We did find this beautiful, pre-hatch, richly colored Maccaffertium flathead.  Quite a color display.  We also found a lot of these little guys --

flatheaded mayflies, genus Leucrocuta.  You may recall from my original entry on flatheaded mayflies (1/8/11) that the genera Leucrocuta and Heptagenia are, anatomically speaking, closely related, but Heptagenia nymphs have fibrilliform present on the gill on segment 7, Leucrocuta nymphs do not.
Leucrocuta nymphs also have this very big head, and you can spot them on rocks because 1) they're very little, and 2) they are very, very fast, difficult to pick up!

Our day was shortened by clouds and sprinkles, making photography pretty darn tough.  But I did manage to find a few, small Perlesta common stoneflies, one genus Acroneuria common stonefly, some common netspinners, a Polycentropodid (Trumpetnet spinner) caddisfly larva, and one lonely small minnow mafly: it turned out to be genus Acentrella.

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Describing Perlodid stoneflies:

Since my report today was a brief one, I thought I might do something that some of you are sure to enjoy (I hope all of you do).   The question is: when a specialist looks at a nymph -- a stonefly nymph -- what are some of the things that he or she looks at in terms of colors and patterns that would be relevant in determing species?    Here's our nymph: a Perlodid stonefly, genus Isoperla.

Yesterday, I sent this photo to Steven Beaty (North Carolina, Division of Water Quality) and posed the following question: "There is a prominent, white "X" behind the posterior ocelli (i.e. at the back of the head) -- does that figure into species ID."  Let me walk you through his response, using photos to point out the features that he discusses.  (As always, for best results click on the photo to enlarge it.)

"The white X is composed anteriorly of the ecdysial suture which is not typically factored into color patterns.  The posterior portion appears to be bifurcate.  Of more interest to me is the "ocellar spot" which is the large pale area within the ocellar triangle."   These photos should clarify the features he's talking about.

And for the "ocellar spot"...

He continues, "Also of note is the pale area anterior to the median ocellus which has the form of a rough "M" but with an obscure anteromedian extension (this whole pattern also appears as a transverse dark bar across the median ocellus with dark extensions back through the lateral occelli to the lateral areas of the occiput [back line of the head] -- take your pick)."     Illustration:

and

And he continues, "Also the longitudinal abdominal striping (including the somewhat interrupted medial stripe) is of note."  Illustration:

Unfortunately, after reviewing that information, he concluded "We have found very similar larvae in VA along the Blue Ridge Parkway and have labeled them as Isoperla n. sp 91... I hate to disappoint you, but I cannot make a reliable species determination on this specimen."  (This was quoted with permission.)

As I told him, I'm not disappointed at all.  I think it's pretty exciting that there are still species out there that have not yet been labeled and named!

Thank You for Your Continued Support

I am stunned -- but gratified -- by the success this blog is enjoying.    We seem to have gained more viewers in the last week or so since "page views" are starting to go over 100 a day in a regular way.
I'm SO glad that other people are finding this information -- and the photos -- useful.  I've still only heard from 3 or 4 viewers.  Don't hesitate to post comments -- or contact me at rghenricks@gmail.com -- just to let me know who you are and what you do with this information on aquatic macroinvertebrates.

One note on Perlodid stoneflies, genus Isoperla.  I've now heard from Steven Beaty at the Division of Water Quality in North Carolina.  The following Isoperla nymphs, found at two small streams that flow into the Moormans River near White Hall, VA, are apparently unidentified in terms of species.   Makes me want to explore even more of our Blue Ridge Mountain streams.

These were nymphs 5 and 6 in my posting of 5/21/11.

and

Again, many thanks.

Bob Henricks

Tolerance Values, Isoperlas, and Another Trip to the Moormans

Steven Beaty, an Environmental Biologist with the North Carolina Division of Water Quality, has contacted me about a couple of matters, providing information that I thought I would share.
First, North Carolina has recently revised the Tolerance Values it uses for benthic macroinvertebrates. That information is available on their website: http://portal.ncdenr.org/web/wq/ess/bau.  Click on the link for "Tolerance Values for Benthic Macroinvertebrates":
(http://portal.ncdenr.org/c/document_library/get_file?uuid=6cbf48c0-924f-4642-b1d3-3f39aa02185f&groupId=38364): the data is availble in Microscoft Excel format.  Some of the tolerance values I have listed for the southeast are now out of date.

Second -- and of great interest to me -- a revision is currently underway of the naming and identification of the species of the Perlodid genus "Isoperla" in the eastern part of the country.   (Thus, the information provided in my entry of 5/11, must be understood as tentative and "to be revised".)  The revision will focus on Isoperla adult identification -- not on the nymphs -- still, changes in nomenclature can be expected.  This work is being conducted by Boris Kondratieff and Stan Szczytko.

Dr. Beaty has sent me a copy of a draft version (November 16, 2010) of the Division of Water Quality's "Plecoptera In-house Taxonomy Manual," and has granted me permission to use information provided in there in my blog.   I'd like to note at least two things of interest.

1) The nymph identified in my entry of 5/11 as I. namata -- this one --

would be more properly labelled I. nr. namata.   This may be an unidentified species.  While it resembles I. namata, that species is thought to be restricted to the Ozarks and the northeast.  This is an issue that is not yet resolved.

2) The fourth nymph in my entry -- this one --

that I said might be I. holochlora, is called I. nr. holochlora in North Carolina.  It strongly "resembles" I. holochlora, but the head pattern is not exactly the same, and the abdominal banding that is very clear on I. holochlora is not clear at all on this nymph.  (I'll provide a photo of an I. holochlora nymph that I found today later on.)

(The Isoperla nymphs that were numbers 5 and 6 in my entry of 5/11, by the way, are being studied by Dr. Beaty, and I will let you know what he tells me about identification.   The photo at the top of the page is of one of those nymphs -- one that I found today.)

So, stay tuned for more on this very interesting genus.  Dr. Beaty comments that some regard North Carolina (and presumably parts of Virginia) as "the epicenter of Isoperla diversity in the world."

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Today's report.  I went back to Sugar Hollow today to a superb stream that flows into the Moormans.
I was last here on 6/2, and the insects that I found today were much the same as I found on that trip (you might want to look again at that entry):  lots of baby Roach-like stoneflies -- they were scurrying all over the place -- and lots of baby Giants.  I did find one thing that I wasn't expecting to see.

It's a Lepidostomatid case-maker!  I associate these with the winter.  But, I saw three of them today -- and it's the middle of June!

For the rest of my findings let me just provide you with pictures.  (Keep in mind that the "mystery" Isoperla at the top of the page came from today.)

1. Free-living caddisflies -- I saw at least four, three of them long (1"+) and fat!  I found three different colors, so I'll show you all three.

2. Peltoperlids (Roach-like stoneflies).  I did find a couple mature ones that still haven't hatched in addition to the hundreds (literally) of babies.

3. And finally, the genuine I. holochlora, this one pretty mature.  Note how the yellow area on the front of the head is confluent with the labial suture (the yellow line that crosses the front of the head) on I. holochlora -- not so on I. nr. holochlora (pictured above).   Also note the dark abdominal bands.

I saw very few mayflies today -- a few small flatheads, probably genus Leucrocuta.  I expected to see some Epeorus vitreus nymphs (picture of one from Buck Mt. Creek below), having seen so many Epeorus pleuralis here in the spring, but I did not see a one.

Correction: Not Controptilum -- Three-tailed Baetis

I made a mistake.  This Baetidae (small minnow) nymph that was featured in my previous entry today is not genus Centroptilum, it's genus Baetis -- the three-tailed version.

My previous photo of the labial palps was not sighted correctly.  I've just taken that photo again, and the labial palps are "rounded," not "truncate."  Take a look.

I'm not sure how I made this mistake, but I'm glad that I re-checked the head so I can post this correction.

Small minnow mayfly (Baetidae), genus Baetis, three-tailed version.  Buck Mt. Creek.

The Small Minnow Mayfly: Genus Centroptilum

I went to two streams this morning -- the Whippoorwill Branch of the Mechums and Buck Mt. Creek -- and when I came home, I thought the day had been pretty much of a bust.  My microscope work proved me wrong.  I'll note what I found at Whippoorwill Branch in a moment.  First, on the exciting find at Buck Mt. Creek.

At Buck Mt. Creek, I found a lot of small minnow mayflies on the bottoms of rocks -- and I do mean a "lot" of them.  Most were tiny, kind of yellow in color; they were genus Acentrella.  But I saw two small minnows that stood out from the crowd.  There was a tiny one with very dark wing pads.

Two tails.  And when I looked under the primary wing pads there were metathoracic wing pads: it was genus Baetis!  This is the first one I've seen here this summer; in the winter -- you may recall -- it was the only genus I found in this stream.

But it was the other "loner" that provided excitement.  It's the larger of the two small minnows in the photo at the top of the page (the other one is a small Acentrella).  Here's another look:

Note that this one has three tails.  That eliminates two genera that we've already seen here this summer: Heterocloeon and Acentrella.  So, we have to turn to the key for help with ID (Peckarsky, Freshwater Macroinvertebrates, pp. 35-36.)  When our nymph has three tails (cerci), we move to the following couplet:

41a. Third segment of labial palps truncate
41b. Third segment of labial palps rounded

The labial palps on a small minnow mayfly are not easy to see.  But my microscope was up to the challenge.  The labial palps clearly are "truncate".  (Click on the photo to enlarge.)

That sends us to the following couplet where the issue becomes: does the nymph have "metathoracic wing pads"?  It does.

Mystery solved: this is a Baetidae (small minnow mayfly), genus Centroptilum.  I've never seen one before.  What a nice find.


Now, back to the Whippoorwill, which is where I started my day.  I went there on a mission, and it's mission accomplished.  I was looking for Limnephilids, Limnephilids that make two different cases; I've seen them here before.   One of the cases is made out of pebbles and sand, the other has twigs for sides with wood chips and sand inbetween.  Neither case is especially attractive.  But the larvae construct their cases out of materials they find at hand, and I guess this is all they can find in this stream.  Here are the two cases:

I virtually "begged" the larvae to stick their heads and legs out of their cases -- they wouldn't do it!  Of course, as soon as I plopped them into vials for preservation, out they came.  Here is a microscope view of the one in the case of pebbles and sand: he looked me right in the eye.

The head has a light colored background with dark spots -- one sign of the genus Pycnopsyche.  And the other key feature -- the sclerite along the back edge of the lateral hump -- shows up very clearly in this microscope shot.

So again, our Limnephilids are genus Pycnopsyche.

The other thing I found of interest at the Whippoorwill Branch was a fingernet caddis, genus Dolophilodes, and this one posed nicely to give us a very good photo.

(Below -- the Whippoorwil Branch of the Mechums at the beginning of summer.)