Tuesday, May 31, 2011

The Genus Remenus: Yet Another Perlodid Stonefly

Back from vacation -- time to get back to...well, it's not really work: too much fun!

I went to Buck Mt. Creek this morning to look for bugs in the heat (92 degrees!), and I found a real assortment.  I wasn't sure what to call this entry, but I felt that a new genus deserved its own headline.
Perlodid stonefly; genus, Remenus.  I've never seen this one before.  The distinguishing features are: 1) no submental gills; 2) the "mesosternal" ridge is shaped like a "Y"; and 3) the lacinia terminates in a single tooth (this sets it apart from the genera Diploperla, Isoperla, and Clioperla).  Here's what that looks like:

This is not the only Perlodid genus I found today.  I continue to find Isoperla holochloras.  This one -- rather light in color:

and this one -- much darker.  Note that although the Isoperla "abdominal banding" seems to be missing in the photo below, it was clearly visible when I looked at this nymph with the scope.

On the genus Remenus, I might add that it strikes me as very unique in appearance.  It is uniformly orange in color and lacking in pattern (save for a few marks on the head), and the head seems out of proportion to the rest of the body.  Look at this picture where the Remenus nymph is right next to an Isoperla in my tray.

The insects I found, for which I will not provide photos include: water penny beetles, Dryopid beetles, riffle beetles (adults), flatheaded mayflies (Epeorus, Maccaffertium, and Leucrocuta), and small minnow mayflies (genus Acentrella).   What I did not find -- spiny crawler mayflies, genus Ephemerella!!!  Not a one.  And just a few weeks ago that was the dominant taxon in all of the sampling that I was doing.  Pretty amazing.  Of course that does not mean they have all hatched in other streams (or in this one, for that matter).

I did find three other insects which deserve to be pictured.  First, I did find one lonely spiny crawler mayfly, but it was genus Drunella, and it was HUGE (1/2 -- 3/4" long).  It was clearly close to hatching.  Note the black wing pads; also note the prominent "tubercles" on the leading edge of the fore femoras, a defining trait for this genus.

Second, I found a Ceratopogonidae ("biting midge," "no-see-um"), and I was actually able to get a pretty good picture (they're very small).   Cerats differ from the common midges we see (Chironomids) in a number of ways.  They are longer and thinner than "normal" midges; they are "zebra-like" in color pattern; they have pointed heads; and they do not have prolegs in the front or the back.  (For a good picture of a "Chironomid" midge, see the entry for 3/2/11.)  Click on the photo below for a better view.

Finally, I finally found a dragonfly: it was a Darner (family Aeshnidae).  I've been expecting to see dragonfly nymphs, and there were a number of adult terrestrials flitting around in the tall grasses that border the stream.  Darner dragonflies are normally dark brown to black in color, with long tapered bodies.  Also, you will often find them -- as I did with this one today -- in leaf packs close to the shore.

Not very pretty -- but then, not everything can look like a Perlodid stonefly!  It's good to be back, and readers can expect a steady supply of new entries now that the summer's begun.

Saturday, May 21, 2011

The Perlodid stonefly, genus Isoperla: Can we pin down some of the species?

In the entries I've posted throughout the winter and spring, I've focussed a lot on Perlodid stoneflies, in part because I've found large numbers of them, and in part because they're beautiful insects.  My intention in writing this blog was to focus on identification of family and genus, and I've been able to identify five different Perlodid genera: Clioperla, Diploperla, Isoperla, Helopicus, and Yugus.  At the outset of my work, I had only seen one Perlodid genus when sampling our streams -- Isoperla -- and in particular the type of Isoperla that's pictured at the top of this page.

However, I now know that we have, in Virginia, at least 12 species of Isoperla Perlodids -- this based on the species distribution list published by Stewart and Stark (Nymphs of North American Stonefly Genera (Plecoptera), pp. 412-13).   They are: I. bilineata, I. dicala, I. holochlora, I. lata, I. major, I. marlynia, I. namata, I. orata, I. signata, I. similis, I. slossonae, and I. transmarina.

To date, I have found at least 5 -- and possibly 6 -- of these species.  Using photos in Bugguide.net, and with the help of comments from some of the experts at Bugguide.net, I think I can identify to the level of species 3 out of the 6.  I hope that eventually I'll be able to identify the rest -- but that will clearly require assistance from qualified specialists.

In the meantime, I thought I'd pull together all of my data so readers can see the species that I've found so far.  Let me begin with a review of the key features that identify the genus Isoperla, illustrating those traits with microscope photos.  (All quotes are from Barbara Peckarsky, et.al., Freshwater Macroinvertebrates of Northeastern North America, pp. 71-73.)

1) "Anterior ends of arms of Y ridge of mesosternum meet posterior corners of furcal pits" (i.e., the forked points of the "Y" point up.)

2) Submental gills are absent.

3) "Lacinia with a shorter spine mesal to major spine and commonly with additional spinules or hairs."

and 4) "Dorsal abdominal segments with alternating transverse or longitudinal light and dark stripes or bands."   This trait is clearly visible in the photo at the top of the page.  However, Stewart and Stark (Nymphs of North American Stonefly Genera, pp. 410-11) qualify this.  They caution that "several Isoperla species lack the typical abdominal pigment pattern."  This is worth keeping in mind.

I will now show you photos of the nymphs I have found -- two for each of the species -- followed by a microscope shot of the head, since the head pattern seems to be a relevant factor in determining species.

1. Isoperla namata (I think -- using photos in Bugguide.net.  I originally thought this was I. montana, but that species is not attested in the state of Virginia.)

2. Isoperla similis (I think -- using photos in Bugguide.net.)

3. Isoperla holochlora (identified by experts at Bugguide.net.)

4. Isoperla sp. (Note: This may also be Isoperla holochlora: some experts say "yes"; others say "no".  It does not have alternating light and dark abdominal stripes.  But, this speciment is still immature, and the head pattern is certainly similar to I. holochlora.)

5. Isoperla sp.

6. Isoperla sp.

Any help from professional entomologists with species identification of the Isoperla nymphs pictured above will be greatly appreciated.

One final note on "tolerance values" for at least some of the Isoperla genera supposedly found in Virginia (the values given are those used in North Carolina).

I. bilineata          5.5
I. dicala              2.2
I. holochlora       0.0
I. namata            1.8
I. orata                0.0
I. similis               0.7
I. slossonae         2.6
I. transmarina     5.6

Friday, May 20, 2011

Getting Ready to Leave the Nest: Mature Insects Everywhere You Look

Not a benthic macroinvertebrate!  This big snapping turtle was lazily crossing the road as I made my way back from Sugar Hollow this morning.  He didn't seem to mind my taking this picture -- but I decided not to get any closer!

With almost all of our streams still running muddy and high, I headed back to Sugar Hollow today to see what I could find in another small stream that flows into the Moormons.  This stream is almost directly across the valley from the one I visited yesterday.  But it's smaller, and if anything it drops even more steeply downhill.

"Mature" is the word for the day.  Lots of nymphs with black wing pads, including this Ameletid mayfly.

This is a treat.  You may recall that I saw quite a few Ameletids in a number of streams -- all small streams -- in February and March.  I've seen very few since, and I thought they had all hatched.  So it was really nice to see this one.  All insects mature and hatch later in these high mountain, 1st level streams.  As fly fishermen know -- "the hatch moves upstream".  The insects of a particular family or genus will hatch first in the lower parts of a river or stream, and the hatch progresses upstream as the weather warms and the colder waters upstream along with it.

Another insect I'm finding less often downstream -- the Epeorus flatheaded mayfly.  Again, I found a mature one up here.

Beautiful, light coloration.  Not sure if that's a matter of habitat and location or having just molted to a new instar.

Finally -- a nice mature Perlodid stonefly: Isoperla, what else?!   This does not seem to be any of the three species I found yesterday -- judging by the head pattern.

(Sorry for the quality of this particular photo.  We had low light conditions at the time.)   The Isoperla picture below, on the other hand, does match up with one of the species we saw yesterday.

I need to send my Isoperla shots from yesterday and today to the folks at Bugguide.net to see if they can help me out with species ID.

The final picture I'm posting today is a Freeliving caddisfly larva.  It's a very unusual color, kind of an aqua blue or green.  As I've noted in previous entries, "color" cannot be used as a key trait for family identification when it comes to this caddis family.


VACATION.  Please note that I'll be in Italy all of next week.  So please look for a new post around the 1st of June.

Thursday, May 19, 2011

So many species -- so little time! Perlodid Isoperlas

It was a frustating day on the stream: in one sense, a disaster!   But more on that in a moment.

We had 3.5 inches of rain on Tuesday -- another 1/2 inch yesterday.    Where on earth did I find any clean water to search for some bugs?  I decided to look at one of the tribs to the Moormans I sample -- one that goes unnamed.  The water was high and roaring -- but clear -- so I assembled my gear and started to look.

Nothing under the rocks (well, one lonely Epeorus flatheaded mayfly): the water was simply too swift.
So I started sorting through leaf packs.  That proved to be very productive.  They were loaded with spiny crawlers -- no surprise there -- and I picked up all sorts of stoneflies.  I even found a Dytiscid (a Predaceous Diving Beetle: photos to follow below).  But the "prize" was a BIG common burrower mayfly -- over an inch in length -- that I think was genus Hexagenia.  I have to say "I think" because I never got a picture (= disaster)!   When I went to put it into my dish for a photo, I dropped it, and although I looked myself silly, I never found it.  What a loss!  I hope this isn't a "once in a lifetime".  Common burrowers (Ephemeridae) live in the substrate, but this one had clearly been washed into the leaves by the scouring of the stream.

The other problem I had -- well, it's not really a problem -- was that I found all sorts of Perlodid stoneflies that I knew were Isoperlas (confirmed at home with the microscope) -- but they're species that I don't recognize, with the exception of one holochlora.  Pictures.

1) Another shot of the one in the photo above.  First time I've seen this species.

2) Isoperla type two

and 3) a pair of Isoperlas -- the one on the left is Isoperla holochlora.

So many species -- so little time.  (Stewart and Stark -- Nymphs of North American Stonefly Genera, pp. 412-13 -- list a total of 57 species of Isoperla in North America, but only 11 are attested for Virginia.)

Just a couple of other photos to show.  One is a beautiful spiny crawler (genus Ephemerella): they're really starting to mature.

Another: an adult Perlodid stonefly.  I suspect it's genus Isoperla.

And finally, a couple of pix of the Dytiscid (predaceous diving beetle).  The first is a live shot: the second, one done at home with my microscope.  Anyway you look at it, this is one mean looking critter!  In the microscope photo, it's easy to see the "breathing tube" this insect uses as a "snorkel" to get its air.  (Click on the photo to enlarge.

Sunday, May 15, 2011

A Quick Look at Some Streams: the Lynch River and Ballinger Creek

Those of you who live in cenrtral Virginia know what a gray, dismal, drizzly weekend it's been.  So, I could sit around and twiddle my thumbs, or go out to some streams, even though, because of the dark skies, I despaired of getting any good photos.  Yesterday, I took a quick trip to the Lynch River, and this morning I headed down to Ballinger Creek (Fluvanna County).  My main goal was to look for some small minnow mayflies.

I found none at the Lynch River -- not one.   They were here in the winter (genus Baetis: see my entry for 3/16), and I know from sampling with StreamWatch that they're here in large numbers again in the fall (genus Acentrella), but there were none to be found yesterday.

So, what did I find?  At first, nothing special.  Lifting rocks, I saw lots of flatheaded mayflies -- mostly Epeorus in terms of the genus -- and lots of spiny crawlers (Ephemerella, and a couple Drunella).   But I fared better when I spread out a leaf pack, one of the few I could find (this stream was "scoured" by the flooding rains we had in this part of the county at the end of last month).  Tons of spiny crawlers, of course, but also some beautiful stoneflies -- especially the one at the top of the page.  That's a Perlodid stonefly, genus Diploperla, and with those black-tipped wing pads, it will be hatching real soon.  Here's another look at this beautiful creature.

I also found, in terms of stoneflies, two other types of Perlodid: Isoperla montana, (I think that's the species) the most common Perlodid we see, and Isoperla holochlora (on which, see my recent entries on the Rapidan River and Powells Creek).   But a neat thing happened when I set up my gear to take pictures.  Look what showed up to supervise what I was doing!

Ain't that a beauty!  Perlodid stonefly, Isoperla montana, but an "adult" that had recently hatched.  And I got some really nice photos since it was in no hurry to leave!

On to today and Ballinger Creek (Fluvanna County).  Here I did find a small minnow mayfly, but it was a small one, and my pictures are not very good.

I preserved it so I could check out the genus.  It appears to be Acentrella -- the same genus of small minnow mayfly that I found last week at Buck Mt. Creek.   How do we know?  Well, it has two tails, and it has normal gills (that eliminates Heterocloeon) -- which brings us to Baetis or Acentrella.  If "metathoracic wing pads" are present, it's Baetis; if they are not, it's Acentrella.  Have a look for yourself (obviously, a microscope photo).

I've pointed to the posterior edge of the metathorax, where the wing pad should be: nothing there.  So, in the winter I found nothing by "two tailer" Baetis small minnow mayflies: so far I've found Heterocloeon and Acentrella at Buck Mt. Creek, "three tailer" Baetis at Powells Creek, and Acentrella again in Ballinger Creek.    We'll keep an eye on this as the summer develops.

I found a number of interesting insects this morning, including a grayish colored Freeliving caddisfly larva, a number of small Perlid stoneflies,  and a Hydrophilidae (water scavenger beetle, order Coleoptera).  This is a strange looking critter that we don't get to see all that often (the head's pointing right).

But the find that pleased me the most was this beautiful flatheaded mayfly, genus Stenacron, that had just recently "molted" (hence the very light color).  When I first saw such a light colored mayfly, I e-mailed Rose Brown, excited that I had found an "albino".  She quickly corrected my error!  Beautiful -- the way the dark gills stand out against the very light-colored body.  It won't take long for the pigment to turn this mayfly it's normal brownish gray.

The Lynch River in springtime.