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.

Haploperla:


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.


Sweltsa:


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.


Wednesday, April 16, 2014

The Green Stonefly Haploperla brevis -- and other treasures at the Whippoorwill Branch


After two inches of rain yesterday I didn't hold out much hope for finding good insects this morning -- but I was surprised.

In the photo at the top of the page, the Green Stonefly (Chloroperlid), Haploperla brevis.  Though Beaty says this genus and species is "relatively common" ("The Plecoptera of North Carolina," p. 9), this is only the second one that I've found.


Beaty describes Haploperla in the following way.  "Nymphs ~ 7 mm; cerci without dorsal or ventral intercalary hairs, setae at apex of cercal segments only; pronotum with sparse setae, longest and most numerous at anterior corners; long pronotal fringe hairs are at least 0.3 - 0.4 times the pronotal width; inner margin of hind wing pads subparallel to body axis; pronotum and tergites lightly setose; fore leg with sparse fringe of long setae on tibia; body light brown, nearly concolorous."  "H. brevis -- fits genus description."  Elsewhere, the NC tolerance value is given as 1.4.

1. Our nymph measured about 6 mm.

2. The lack of intercalary hairs on the cerci can be seen in the following photo.



3. And here is a view of the long setae on the corners of the pronotum.  I'd agree that the longest hair that we see is .3 - .4 times as long as the pronotal nymph.


4. The hind wing pads -- and the primary wing pads for that matter -- are indeed subparallel to the body, but we can only see that in a microscope view.   (Note: in many keys, this feature is the defining feature of this genus.)


5. And here we can see the "sparse fringe of long setae" on the fore tibia.


Haploperla brevis.  Made the whole trip worthwhile.

_______________

But I also found the freeliving caddisfly larva Rhyacophila carolina for the first time this season at the Whippoorwill Branch.



R. carolina is distinguished by its golden brown head, the lack of ventral teeth on the anal claw,


and the fact that the head is very wide at the rear -- in fact at that point it's almost as wide as it is long.


R. carolina is part of a group (the R. carolina group) that is found predominantly in the southeast.  The group includes R. fenestra/ledra, a species we also see in the summer.  This one.


TV for R. carolina is 0.4.
________________

Another beauty this morning, a fairly mature common stonefly, Eccoptura xanthenses.  Note how the wing pads are long, and curved at the rear.  This one measured about 17 mm.


________________

But the most common insect today -- the spiny crawler, E. dorothea.  Get ready to be overwhelmed if you're out there taking your samples.



For the species ID, you need a close view of the terga.  There are no tubercles (projections) on the rear edges of the terga on the nymphs of this species.

_________________

But this one was special -- Haploperla brevis.


Sunday, April 13, 2014

Spiny Crawlers: The move from E. invaria to E. dorothea


I went to Buck Mt. Creek this morning hoping the water had dropped.  It hadn't -- still high and a little off color.  Nevertheless, I found a number of interesting things, and I wasn't sure what my focus should be.  But let's start here.

The spiny crawler "explosion" that we see every spring has already begun.   I saw large numbers of them this morning, and the leaves and grasses and root balls in the water will soon be absolutely crawling with spinys.  The species we see in the spring is Ephemerella dorothea, but preceding them in a lot of our streams are the E. invaria nymphs -- which is what you see in the photo at the top of the page.  The E. invarias are on the way out; the one in that photo is fully mature (black wing pads).  It measured 9-10 mm.  I photographed two of the E. dorotheas I found: they were only 5 mm.



If you monitor streams, your samples will soon be dominated by these spiny crawlers -- E. dorothea.  E. dorothea, by the way, hatches as the "Eastern Pale Evening Dun (PED)"; E. invaria hatches as the "Eastern Sulphur Dun."  (On mayfly hatches, see Knopp and Cormier's Mayflies: An Angler's Study of Trout Water Ephemeroptera.)
________________

Feature story number two: two more Isoperlas showed up for the spring.  The first, a very tiny (3.5 mm) Isoperla holochlora.



Note how the pale yellow spot anterior to the median ocellus is fully open to the labrum at the front of the head (vs. what we saw with I. nr. holochlora).  In a normal year, these nymphs would be much bigger by now.  I found this one on 4/24/12.  So we're pretty far behind.


And the other small Isoperla I found was the one I've been calling Isoperla nr. orata on which see the posting of 4/7/14.  This measured ~ 5mm.



I knew what it was when I focussed in with my camera.  Initially, again, I thought it was Isoperla montana/kirchneri of which I saw dozens this morning.  This is I. montana/kirchneri, one that I found on 4/12/13 -- one year ago today.


Compare the patterns on the heads.

I. montana/kirchneri.  Note how the gray bars behind the lateral ocelli extend fully to the back of the head.  Also, the projections on the front on the dark transverse bar are relatively short.


I. nr. orata has a quite different look.  Those projections are long, and the gray bars -- more like spots -- do not reach to the back of the head.


They differ in one other way.  The paired black spots on the abdominal terga on I. montana/kirchneri -- these...


are missing from I. nr. orata.  Just have to know what to look at.
________________

One other insect showed up for the first time.  A small (4 mm) Nemourid, genus Amphinemura, the one with the frilly gills at its neck.   I could see the gills clearly when the nymph turned on its side.  This is the genus I'd like to get down to species.


_______________

And for beautiful insects, hard to beat this fairly mature Perlodid stonefly, Helopicus subvarians.  Saw 4 or 5.


This nymph was probably ~ 20 mm.  Note how H. subvarians dwarfs a typical I. montana/kirchneri Perlodid.

________________________

And farewell to Ephemerella invaria, at least in Buck Mt. Creek, for another year.