Sunday, August 24, 2014

A new one in Montana: the Perlodid stonefly, Kogotus

This is one that we don't get to see in the East: the Perlodid stonefly, genus Kogotus (K. modestus and K. nonus are both found in Montana).  I was totally stumped by the ID, so I did what we should always do with a new stonefly -- I keyed it out, using Stewart and Stark's Nymphs of North American Stonefly Genera (pp. 361-364).  The lack of thoracic gills, the unidentate lacinia, the lack of dark longitudinal bands on the abdominal segments, and the absence of a "transverse anterior suture" on the mesosternal Y-ridge, led me to Kogotus (pp. 413-416).

Let's note certain key features.  1) "Head with light M pattern anterior to darker M between antennae; light spot in ocellar triangle and 2 small light spots outside lateral ocelli."  Check.

2) Lacinia unidentate.  Yes.

3) "Pronotum light, encircled with brown band except light lateral margins; a few tiny marginal spinules, but mostly glabrous."  All easy to see in this photo.

4) "Y-arms of mesosternum meet posterior corners of furcal pits; no transverse anterior suture connecting furcal pits."  Yes.

And one more thing.  5) "Male and female 8th abdominal sterna with mesoposterior interruption of posterior setal row."

The Northwestern Perlodid stonefly, genus Kogotus.  I'll let you know if I'm successful in getting this down to the level of species -- but there are only two choices: nonus and modestus.


The other stonefly I found -- and photographed -- is one that I've found once before: Oregon, August, 2012 (entry posted on 8/22).  The common stonefly, Calineuria californica.

This Perlid is attested in Alberta, British Columbia, California, Idaho, Montana, Oregon, and Washington.  (See Stewart and Stark, p. 329)

A quick review of critical features.  (All quotes from Stewart and Stark.)  1) "Body 17-25 mm, dark brown patterned with yellow."  This immature nymph was just 17 mm.  2) "SL gills (subanal gills) absent."  We can see that in the photos.  3) "Lacinia bidentate, terminal tooth strongly curved."  Yes.

4) "Dorsum of body covered with fine, dark clothing hairs and scattered short, thick bristles."  Yes.

5) "Occipital setae scattered near postocular fringe but arranged in a close set row behind ocelli."  Also, "Head with pale, oval spot surrounding lateral ocelli."  Both features are clear in this photo.

Common stonefly, Calineuria californica.


And one more insect -- sort of.  I was hoping to get a live photo of an "October Caddis" -- the Northern case-maker, genus Dicosmoecus.   Every case that I found, save one, was sealed up with the larva in pupation.  (In Montana, the "October" caddis tends to hatch in November.)  But in the Blackfoot River, I did find one that was open.

This is a large caddis: the case was 25 mm.  But, I could not get the larva to come out of its case!  Maddening.  And I waited a very long time.  To see it, I had to preserve it.  And here it is.

Wiggins' description reads as follow.  "These larvae are large and stout-bodied; sclerotized parts of the head and thorax are mostly uniform dark brown to black."  For sure.  "The tibiae of all legs have several pairs of stout spurs

and there are metanotal setate on the membrane between the primary sclerites."

Finally, "On segment IX a band of 20-40 setae extends ventrad from each side of the dorsal sclerite."  I didn't count them, but 20-40 seems right.

On the case, Wiggins notes, "Final-instar larvae have a case of fine gravel, regular in outline, slightly curved, and often somewahat flattened."  Like the case in the photo above.  "In the early instars cases are largely of plant materials."  You might recall that I found one of those immature larvae in such a case in Oregon in May.  (See post of 5/1/14.)

All quotes from Glenn B. Wiggins, Larvae of the North American Caddisfly Genera, University of Toronto Press, 1977.)

I wish I could have found time to get some more photos of insects: the streams that we fish are healthy with good populations.  Unfortunately, the trout fishing just got in the way!  Below, an 18" "cutbow" (Cutthroat and Rainbow hybrid) from the Upper Clark Fork.  What a beauty!

Friday, August 15, 2014

Case-maker day at the Rapidan River

(Obviously "not" a case-maker caddisfly larva -- but still one of the prettiest common stoneflies we find: Paragnetina immarginata.  It's a small one.  Even so, it measured -- I'd guess -- about 20 mm.  The Rapidan is one of the few places I see them.)

It was another day when I expected to find lots of small minnow mayflies, and I did find a couple.  But of much greater interest, I found 5 different case-maker families: Goeridae (Goera calcarata), Limnephilidae (Pycnopsyche scabripennis), Brachycentridae (Brachycentrus appalachia), Odontoceridae (Psilotreta labida), and Glossosomatidae (Glossosoma nigrior).

1. Weighted-case maker, Goera calcarata

The Goerid was the first thing I found, not something I ever expected to see.

I thought it was a Glossosomatid (Saddle-case maker) until I dropped the case into my bowl.  The two large pebbles on either side of the case immediately gave it away: Goeridae, the "weighted-case maker."   I thought these showed up in late fall and winter -- thinking I have to revise.

A defining trait of Goera -- in addition to the conspicuous case -- the "pronotum [is] produced anterolaterally into wide, sharply pointed processes." (Beaty, "The Trichoptera of North Carolina," p. 87)  Easy to see in the first photo.

This appeared to be Goera calcarata.  It was about 8 mm long with 3 pairs of sclerites on the metanotum.  Also, I did not see any sternal thoracic plates (which are distinct on Goera fuscula -- see the entries posted on 10/27/13 and 11/27/13), and there were "conspicuous spicules" on the anterior edge of the pronotum.  (For all of these traits see Beaty.)

By the way, if you find one of these cases but don't see the larva, turn the case on its back.  This larva only emerged when its case was flipped over.


2. Northern case-maker, Pycnopsyche scabripennis

I usually see these in the spring, so this too appeared to me to be out of season.  But there it was.  This is a large larva: the case was 25 mm, the larva about 22.  Nothing special I thought -- until I got home and downloaded my photos.  Then I spotted what looked to me like a tiny case on the side of the case.

And it was!  Under the microscope, I peeled this little case off and pulled it apart, finding this inside.

It's a midge!  How about that.  Actually, there's a whole world of "micro" midges, and my friend in Sugar Hollow has found them before.  Chironomids of any size, are difficult to ID to the level of genus, let alone species (over 20,000 species world-wide), so this is as far as I go.  Still, a very cool find.

(Is that the midge head and proleg I see sticking out?)


3. Humpless case-maker Brachycentrus appalachia

This was not a surprise.  This is a caddis that is plentiful in this stream, especially at this time of year -- and I saw a lot of cases today.

But do you notice what's on the side of this case as well?  It was another midge case.

When I peeled this one off it measured about 2 mm.  This one, however, was not occupied.

4. Strong-case maker , Psilotreta labida

Not a good photo, but it was a very small larva.  It's the start of the season for these larva: more common in the next 2-3 months.

5. Saddle-case-maker, Glossosoma nigrior

And by the time I got around to photos of the Glossosomatids, they had all climbed out of their cases!

A fun day -- and oh yes, I did photograph one of the small minnow mayflies.  It was a male Plauditus dubius.  Tiny: 3-4 mm.

Thursday, August 14, 2014

And it's another, unidentified, summer Lepidostomatid: Doyles River this time

I wasn't sure where to go to this morning, and I'm not terribly thrilled with my choice.  Still, I haven't looked in the Doyles for a long time, and I was expecting to see lots of small minnow mayflies.  I didn't.  I saw one, small, Baetis intercalaris.  Mostly, I saw tiny flatheaded mayflies and common netspinner larvae.

Just this one item of interest.  I spotted what looked to me like a case on the side of a rock and put it into my bowl hoping to see a caddis larva stick its head out.  Nothing.  It took about 20 minutes before I saw a little head and some legs.

Off to the car to get my camera and set up my gear.  Then I waited and waited and waited -- nothing ever came out of the case.  Still I took some photos, and as you can see in the photo at the top of the page, the larva did at least peek outside of its case.  A few more views.  (Look closely at the opening at the top.)

Of course when I put it into a vial for preservation it immediately emerged.


It was a very small larva -- about 6.5 mm.  But like the larva I found last week at the Rivanna, it was genus Lepidostoma.  Whatever the species, it clearly differs from those that we find in the winter.  I'd venture a guess that this larva was also distinct from the one I found at the Rivanna.

Remember that Beaty lists over 20 species of Lepidostoma in North Carolina, most of which remain undescribed.  A very distinctive feature of this particular larva -- dark head, pronotum, and mesonotum with very pronounced light colored muscle scars throughout.  I wish I could show that  to you with photos, but I dropped the tray in my lab, and there was no way to find such a small larva on a light colored speckled rug.  Oh joy.  Still, you can see the muscle scars on the head in the one photo I managed to take.

Very unusual.  I hope to do the Rapidan River tomorrow.  Sunday, it's off to Montana!

Saturday, August 9, 2014

They're so hard to find: the "long-horned case-maker" (Leptoceridae), Nectopsyche exquisita

(Note: Entries from now on will normally focus on unusual, or new, insects and -- when I can get them -- good photos.)

I was so happy to see this this morning.  The Rivanna River at Darden Towe Park: a long-horned caddisfly (Leptoceridae), genus -- Nectopsyche; species -- exquisita; tolerance value, 4.3.  They make thin cases of sand which are attached to plant stems, the tough, green, vegetation that covers a lot of the rocks in the Rivanna in summer.  Finding one among all of the stems sticking up from those rocks is a matter of luck: I think I've compared it before to "looking for a needle in a haystack."

The "long-horned caddisfly" gets its name from the size of its antennae: they're exceptionally long.  That's true for the adult as well as the larva.  On most case-makers, the antennae are tough to see, even with a microscope view.  Not so with this one.

On the genus ID, Beaty has this to say: "Hind tibia not secondarily divided; middle leg with slender, slightly curved claw; circularly roughened lateral hump with posteriorly directed sclerotized bar which is apically curved towards the venter." ("The Trichoptera of North Carolina," p. 92)

For the "curved claw" and the "lateral hump" we need microscope shots.

But the lack of division in the hind tibia shows up very well in this live shot from this morning.

Also visible in this photo are two of the features used to establish the species ID: the mottled head and the dark bands at the joints on the legs.  Beaty: "N. exquisita - larvae up to 13 mm; metasternum with 8 setae; dorsum of head mottled with combination of light spots surrounded by dark pigmentation and dark spots on a light background; middle and hind legs completely dark or with dark banding at joints (but varies in some populations).  Case tubular and tapered, made mostly of sand with plant stems extending from anterior end.  Common and widespread." (p. 92)

The dorsum of the head also shows up very well in this photo.  That's the small minnow mayfly Heterocloeon curiosum (female), going along for the ride!

A wonderful find.  It's one of the insects I hope to see every summer.

I was also able to get some good shots of a fully intact flatheaded mayfly, Heptagenia marginalis.

This is the largest nymph that I saw -- but I saw a lot of them on the rocks.  The lime-colored spots on terga 1, 8, and 9 -- and the tapered shape of the body -- give them away.  A beautiful insect.


But this was the catch of the day.