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Updates from March 17, 2004

Closeup insects by Troutnut from the Namekagon River and Miscellaneous Wisconsin in Wisconsin

Ephemerella subvaria (Hendrickson) Mayfly NymphEphemerella subvaria (Hendrickson) Mayfly Nymph View 3 PicturesThis is one of the nymphs I collected doing something very, very strange on March 17th 2004. In the middle of the day, around 2 pm, in the water right around my feet I watched lots of Ephemerella nymphs clumsily swimming up all the way to the surface and then just kind of drifting and wiggling around in the water column. None hatched. They seemed to do it more intensely when the sun was out. It wasn't the time of day for the normal invertebrate drift phenomenon, and as far as I know invertebrate drift doesn't involve this kind of clear effort to swim all the way to the surface. I didn't need a net to catch them, I just reached down into the water and grabbed them with my fingers just below the surface.

The prominent abdominal tubercles (
A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled.  They are especially large in this species.
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.
)
aren't quite black, though, and the general color is a dark brown, though I saw nymphs with all Hendrickson color stages behaving strangely.
Collected March 17, 2004 from the Namekagon River in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006
Ephemerella subvaria (Hendrickson) Mayfly NymphEphemerella subvaria (Hendrickson) Mayfly Nymph View 2 PicturesHere's another of the nymphs I collected behaving strangely, as described for this specimen.
Collected March 17, 2004 from unknown in Wisconsin
Added to Troutnut.com by Troutnut on January 25, 2006

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