Monday, August 22, 2016

Back from Montana -- and we've got some new taxa

But I'll start with one that I first saw last year.  This is the spiny crawler, Ephemerella aurivilli.   You may recall that I found these nymphs in Rock Creek last year (posting of 8/10/15), but because the nymphs are dark brown to black, and because the weather was bad that day, I was unable to get any good photos .  But this year, I hit it just right.

Two features distinguish this nymph.  First, the "top hind edge of (at least) segments 3-7 [have] small to medium tubercles."  (You can see them as well in last year's entry.)  (For the key features on E. aurivilli, go to

And second, the "hind corners of abdominal segment 3 [has] points similar to [the] following segments."

I suspect the adult of this species is identified as a Pale Morning Dun since that is a major hatch on Rock Creek -- and other streams -- at this time of year, but I can't find a source that confirms that. Ephemerella dorothea infrequens is confirmed as a PMD, so too is Ephemerella excrucians (see  So I can't confirm this ID.  Still....


Now on to new things.  Two new caddis case-makers.

Number one, The Brachycentrid (humpless case-maker), Brachycentrus americanus.

(I may have messed up last year when I called the humpless case-maker I found on that trip, Brachycentrus occidentalis.)

Like the Brachycentrus larvae that I commonly see at the Rapidan River -- Brachycentrus appalachia -- this larva makes a 4-sided case out of strips of vegetation, which we can see in both of these pictures.   But for the ID of the species we find in the pacific northwest, we have to look at the descriptions provided at the website "Flyfishing Entomology" (  B. americanus is described in the following way:  "Small ridge above the eyes; 1st abdominal segment w/2 (not 4) long, dark hairs in the middle; cases typically 4-sided and made of plant pieces, but may incorporate sand and other kinds of debris."  Both of the anatomical features noted can be seen in my microscope photos.

ridge above the eyes

and the 2 setae in the middle of abdominal segment 1 (venter)

I'd say we're good with that ID.


For the other case-maker I found, I did not get very good photos -- the larva refused to stick its head out of the case.  But it did take a peek!

And I did get another photo that helped with the ID.

The case has a "hood" that covers the head of the larva when its face down.  To me that indicates the family Apataniidae, genus Apatania.  Remember that this is a taxa that we also find in the southeast (Apatania incerta) so we have Steven Beaty's description.  "Mesonotum with two plates; metanotal sa1 sclerites absent; arrangement of sa1 associated setae in a linear transverse row."  ("Trichoptera," p. 85)  We find those features for sure.

How about the species ID?  We apparently have two choices, A. sorex or A. tavala (  But neither species is fully described.  Rather, we find this: for A. sorex -- "Emergence: Jan thru Jun," and for A. tavala -- "Lives in high, cold streams of the Cascade Mountains, and is considered a species of concern."  Not enough to go on, so we'll have to leave this one at the level of genus.


These are the streams where I was finding my insects.

Rock Creek

the Upper Clark Fork

and Norman Maclean's Big Blackfoot River

Oh, and yes I was fishing for big, beautiful trout!

A 17" Cutthroat -- which was released back into the river.

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