Updates from February 6, 2004

I know most people know what a worm looks like, but when trying to tie an imitation, the memory is often a poor source of accurate color information, and a picture helps to get the right shade. One thing that surprised me in my sampling is that quite a few worms did turn up. Before I was a fly fisherman, when I used worms for bait, I always thought they were merely a tantalizing morsel and not a regular trout food, but I've since realized that there are quite a few worms that live in the sediment on a stream bottom.

Longnose Dace Rhinichthys cataractae

Longnose Dace Rhinichthys cataractae

This is another unusual brown Ephemerella nymph. The "fan-tail" which defines the Ephemerella genus is particularly evident on this specimen.

This is another peculiar brownish Ephemerella. It has double-banded tibiae and prominent black-fringed tubercles.

This pretty Ephemerella nymph has really weird markings. It has one band on the tibiae and a thin but distinct dorsal stripe faded in the center which looks very different from the stripes on Ephemerella needhami and Ephemerella aurivillii. It definitely has the fan tail characteristic of the Ephemerella genus.

I looked at this nymph closely under a microscope to ascertain some key features I was wondering about in previous photographs of similar specimens. It definitely does have the fan-tail characteristic of the Ephemerella genus. It also has strongly 2-banded tibiae and definite tiny abdominal tubercles.

Here's another nymph with strange markings subvaria. I suspect it's the same species and it's just wide individual variation.

Here's another nymph with the strange brownish coloring rather than the olive I usually see for subvaria. I suspect it's the same species and it's just wide individual variation.

Here's one of the darkest E. subvaria nymphs I've seen.

I saw under a microscope that the gills on this specimen aren't tracheated.

This nymph is an extremely early instar.

This nymph is an extremely early instar.

This nymph is an extremely early instar.

This nymph is an extremely early instar.

Looking at this one under the microscope, I noted that is has untracheated gills which fork 1/3 of the way from the base and postero-lateral spines on abdominal segment 9

This is a very early instar.

Here are the 4 main color variations I've found that I'm considering to be E. subvaria.

I looked at this small Ephemerella nymph very carefully under a microscope. It as no abdominal tubercles and 1-banded tibiae. I think just a very early instar invaria nymph.

Looking at this specimen under a microscope revealed prominent sharp abdominal tubercles. Also, abdominal segment 9 is distinctly longer than abdominal segment 8, meaning this is definitely a Eurylophella nymph.

Key features I discerned with a microscope include that the femoral flange is blunt (again, given the other features and location, I probably misread this one), postero-lateral spines with the anterior longer, and the first gill is not extended.

Key features I discerned with a microscope include that the femoral flange is sharp, and the first gill is not extended.

Key features I discerned with a microscope include that the femoral flange is blunt (later note: on nymphs of this size, it's somewhat ambiguous and the femora can be damaged in the collection process), the postero-lateral spines have a longer anterior, the first gill is not extended, all gills are tracheated, and the femora have a distinctive brown spot on the center while all the other spots are gray.

This specimen has indistinct gill veinlets, a rounded seventh gill, and no bands on the tails.

This nymph has only two real tails. The third is present, but too short to see in these pictures. It has particularly small gills and indistinct gill veinlets.

This nymph has gills with indistinct veinlets, segments 5, 9, and 10 pale, a rounded 7th gill, and a very short middle tail.

Close examination under a microscope revealed that this Baetid nymph has segment 5 pale, segments 8, 9, and 10 pale but less so, a middle tail almost as long as the outer tails, conspicuous gill veinlets, no bands on its tails, and pointed, slender 7th gills.