Updates from February 5, 2004
Two dear make tracks across a frozen trout stream in the deep snows of early February not far from Lake Superior. I had hoped to sample nymphs in the stream (which later turned out to be quite fertile) but it wasn't open.
This tiny spring creek is extremely fertile, and I sampled many interesting insects I didn't find anywhere else. The water was completely open even though other nearby spring creeks were frozen over and the snow was three feet deep.
Here's another of my very frigid early nymph sampling sites.
I had hoped to sample some nymphs here, but I didn't bring an ice auger.
Ephemerella aurivillii Mayfly Nymph
View 5 PicturesClose examination under a microscope showed definite small tubercles (
A few (not all) of the abdominal tubercles on this
Ephemerella needhami nymph are circled. They are especially large in this species.
Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.) on the back of this nymph. Baetidae (Blue-Winged Olives) Mayfly Nymph
View 4 PicturesThis Baetis nymph is quite a bit larger than any of the others I found in winter 2004. Abdomen segment 5 is only slightly pale while 9 and 10 are quite pale. The tail is banded at the tip. Its body measures about 9mm long. It's much larger than the other Baetis specimens I collected, and it has quite well-developed wingpads.
It's most likely a mature nymph from a very early-hatching brood. It comes from the headwaters of a very small, very spring-fed Lake Superior tributary, which wasn't at all frozen despite very frigid temperatures and 3 feet of snow on the ground. Ephemerella aurivillii Mayfly Nymph
View 3 PicturesThis specimen seems to be morphologically identical to the darker specimens of its species, but it's a very distinctly different color. I'm guessing this is a gender difference, just as I've guessed for the similar E. subvaria nymphs. Ephemerella aurivillii Mayfly Nymph
View 3 PicturesExamination of this specimen under a microscope revealed that it does have small abdominal tubercles (
A few (not all) of the abdominal tubercles on this
Ephemerella needhami nymph are circled. They are especially large in this species.
Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.), 2-banded femora (Femur: The main segment of an insect's leg close to the body, in between the tibia and the trochanter.), and banded tails.
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