Friday, July 21, 2017

New caddis casemakers from my trip to Montana


It was a very good trip.  Fishing was great -- so too was the insect collecting.  In this entry, two caddisfly casemakers that I've not seen before: next entry, two new flatheaded mayflies.

Number one, this neat larva with a prominent dorsal hump and long stringy gills.  Found this one in a backwater eddy of the Bitterroot River, kind of like this one.


The water was still, relatively shallow (1-2'), with a sandy bottom.  There were about a dozen of these crawling along on the sand.

This identification has given me fits.  I got it into my mind -- given that prominent hump and the long, single gills -- that it had to be Phryganeidae (Giant Casemaker).  That led me astray for most of yesterday.  That just didn't work, so I keyed it out and came out to Limnephilidae, Northern Casemaker.   One of the things that led me in that direction was the fact that the mesonotum has sclerotized plates while the metanotum is largely membranous with sclerites at sa1, sa2, and sa3.


That led me to Wiggins (Larvae of the North American Caddisfly Genera, 1977), where I worked through the descriptions and illustrations of the various genera of Limnephilidae.  Even then, the genus ID wasn't real clear.  But in the end, I've decided that the probable genus ID is Psychoglypha (Wiggins, p. 280-281).  Here's Wiggins' description:

Larvae of Psychoglypha spp. are sufficiently divergent morphologically that it is difficult to find characters diagnostic for the genus.  The two sclerites lying close to the dorsal edge of the lateral hump of abdominal segment I provide the only consistent character discovered thus far for all the larvae we have collected.

I can see such sclerites on the larva I found, and, they are the same shape and size that we see in Wiggins' illustration (p. 281).


A few other features.

...in a few species stout spines and setae occur along the pronotum and on the sclerite of segment IX and the lateral sclerites of the anal prolegs.

The spines and the setae on the pronotum seem to me to be present on this particular larva, and the stout setae on the sclerites on segment IX and the anal prolegs clearly have "stout spines and setae."





Head markings usually consist of dark brown spots and blotches on a yellowish brown background, except in P. bella where the head and legs are uniform dark brown.  Abdominal gills are single.  Length of larva up to 26 mm.  

The gills are single for sure (not branched).  The head color -- I see a dark brown head and legs, but P. bella is a species that has not yet been found in MT.  (But it is listed in Rohrbeck in his record of Psychoglypha species. ???)  The Psychoglypha species that have been found in Montana are alascensis, prita, and subborealis.  (See Natureserve Explorer, explorer.natureserve.org).  This larva was only 16 mm, and the case was 29mm.   But I think this larva was still immature.   For the habitat, Wiggins says this: "Psychoglypha larvae occur in a wide range of cool-water habitats, ranging from springs runs to larger streams and their marginal pools."  I can live with a "marginal pool" for this one.  In any event, at this point, Psychoglypha is my best guess for the genus ID.   I might know more if I can get Steve Beaty to have a look at this larva.

More photos.




_________________

Number two, a Uenoid.




I found these Uenoids in a small mountain stream that's across the street from the motel we use: Grant Creek.   There were a bunch of them attached to the rocks near the shoreline.

All Uenoids are genus Neophylax, but what about the species ID?  For a number of reasons, I think it's N. splendens.  Let's go over the data.   To begin with, the source I use to work on genus and species ID for the insects I find in Montana is Roger Rohrbeck's Fly Fishing Entomology, here using the descriptions found in the section "Pacific Northwest Caddisflies" (http://www.flyfishingentomology.com/PNW%20Caddisflies.htm).   There are three species of Neophylax described at this site: occidentis, rickeri, and splendens.  I think we can eliminate N. occidentis.  The pronotum of the species is described as "front 1/3 light, rear 2/3 dark," and "evenly spaced spines at front edge with only a few scattered hairs on rest of pronotum."  Don't see that at all on our larva.  There are quite a few, very small, hairs on the surface of the pronotum, and the front 1/3 is actually darker than the rear.


That brings us to rickeri and splendens.  There are a couple of things that lead me to an N. splendens ID.  First of all, on rickeri, there are "short stout black setae scattered evenly across entire surface of [the] pronotum," while on splendens there are "fewer dark thick setae concentrated towards back."  Have a look.



I'd say there are thick dark setae at the back of the pronotum, with smaller setae mainly along the inner edges of the pronotal plates.

Secondly, Rohrbeck notes that "there are prominent gill-like filaments on the underside of ab1."  That means clavate gills on the venter.


And there they are.  But there is more.  The key source to use on Neophylax species ID is the book The Caddisfly Genus Neophylax (Royal Ontario Museum, 2005), edited by R.N. Vineyard, G.B. Wiggins, H.E. Frania, and P.W. Schefter.  There it is clear that rickeri and splendens are similar in many ways (e.g., dark heads and legs).  But on rickeri they note that the spines on the leading edge of the pronotum are "moderate in size" while those on splendens are "small".  I'd go with small.


Also a critical factor, rickeri is said to inhabit "medium to large streams" while splendens "occurs in small first-to third- order streams.  Grant Creek is, without question, one of the latter.  You might recall the photo I posted in April.


So I'd lean towards N. splendens for the ID.  But as always, I could be wrong, and rickeri can't be ruled out without closer inspection than I can do.
_________________

Good fun as always, and going to Montana in July instead of August -- when we normally do -- means finding a new set of insects.  In the next entry, a look at a new Epeorus and a new Leucrocuta.

No comments:

Post a Comment