I found this nymph wriggling in the surface film during a hatch of related Strophopteryx adults. This nymph died in transport so it's not alive in the photos, but it's pretty close to its live colors.

This 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 aren't quite black, though, and the general color is a dark brown, though I saw nymphs with all Hendrickson color stages behaving strangely.

Here's another of the nymphs I collected behaving strangely, as described for this specimen.

Several stoneflies of this species were the first adult insects I found in 2004 when I started this site. The hatch was sparse but lasted a good part of the day, and I noted a few good rises despite the early season cold. They ended up struggling on the water's surface fairly often.

Several stoneflies of this species were the first adult insects I found in 2004 when I started this site. The hatch was sparse but lasted a good part of the day, and I noted a few good rises despite the early season cold. They ended up struggling on the water's surface fairly often.

This male died overnight before I had the chance to photograph him, so his abdomen is shorter than it should be because it shriveled a bit.