Saturday, August 18, 2012

A Montana Sampler

I did a whole lot of fishing last week -- but I did find time to collect, and photograph, a few insects.  I'd like to say I can identify everything right down to the level of species, but alas, my microscope is back home in Virginia.  So, in this entry I'll just post some of the photos I've taken.   Full species ID will have to await future study.

Before I begin, let me note the sources I'll use to determine genus and species ID, though I am sure of the genus ID of all of most of the insects I've found.

A. For genus ID, we must use Merritt, Cummins and Berg, An Introduction to the Aquatic Insects of North America (2008 edition).   The EPT genera we find in the West often differ from those we find in the East.

B. For species ID of the EPT we find in the Northwest, go to, a wonderful site maintained by Roger Rohrbeck.  There you can find the following keys:

1. Fly Fishing Entomology: Pacific Northwest Mayflies (Ephemeroptera):
2. Fly Fishing Entomology: Pacific Northwest Stonelfies (Plecoptera):
3. Fly Fishing Entomology: Pacifici Northwest Caddisflies (Trichoptera):

1. The spiny crawler mayfly in the photo at the top of the page is genus Drunella (note the tubercles/bumps on the leading edges of the femora).  This is a genus we have in the East, but I don't think that we have this particular species (that's something that I have to check).  From the descriptions we find at the Fly Fishing Entomology website, I would guess that this is a Drunella coloradensis, or a Drunella flavilinea -- apparently the two are difficult to tell apart.  Neither has tubercles on the head; both have banded tails.  The banded tails are very clear on this photo:

As you can tell from the wing pads, this nymph is fairly mature.  The adults of this species go by a number of names: the Dark Olive Dun, Lesser Green Drake, Western Green Drake, Slate-winged Olive, and Autumn Green Drake --just to mention a few.

2. Another spiny crawler mayfly -- and in this case I know the species ID -- Timpanoga hecuba.

This is another spiny that will be hatching in the near future: Montana fly fishing guides refer to this as the "Hecuba" hatch -- it's a big, red mayfly.  T. hecuba is very distinct because of the shape of its head: this is known as having a "complete frontal shelf".  I've pointed that out, as well as the large operculate gills on segment 4 that cover the rest of the gills, in the following photo:

It's a strange one!

3. A Giant stonefly which is either Pteronarcys californica or Pteronarcys dorsata.  In either case, it will hatch as a "Salmonfly."  Since the salmonfly hatch is essentially over in western Montana, this is either a "late bloomer" or a nymph that will hatch sometime next year.

Were we back East, I'd say for sure that this is P. dorsata because of the sharp points on the corners of the pronotum.  But this seems to be part of the genus description of Pteronarcys nymphs in the West.  I hope further work will help me to pin this one down.  I found this nymph in the Blackfoot River, by the way, a river famous for its salmonfly hatches.


4. A small minnow mayfly (Baetidae).

This is the only small minnow species I saw, and I'm not even sure of the genus.  Again, were we back East, I'd say it's a Baetis -- it has three tails.  But there more small minnow genera out West, and I need to work on this one in some detail when I get home.  Here's a small minnow that was already mature.  I think this is the same species as the nymph in the previous photo, but I don't want to say that for sure.


5. A common netspinner larva, family Hydropsychidae.

I found the light stripes on the head and pronotum quite striking.  Again, I can't be sure of the genus, to say nothing of species: all of that requires microscope work.


6. On final photo, this one of a Perlid -- common stonefly.  This photo was taken with my little Canon PowerShot camera -- we were floating a river, and I didn't have my good camera along.

From the "Flyfishing entomology" descriptions, I would guess that this is a Claassenia sabulosa nymph.  The key features to look for are the complete setal row at the back of the head and the "M" shape in the middle of the head.

Lots to work on when I get home.  But, I'm in Oregon now and plan to go fishing -- and look for more insects -- in a local stream tomorrow.

And then there was the Osprey that perched high up on a pine and watched us have lunch on the banks of the Blackfoot.  (Had to use the telephoto lens for this one, of course, the macro lens wouldn't have done me much good!)

Oh yes -- and we did catch some fish, all of which were released.

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