There were two insects I was hoping to see at the Rapidan River this morning: I only found one -- the spiny crawler mayfly, Ephemerella subvaria. (I did not find the Perlodid stonefly, Isogenoides hansoni -- maybe next time.) Now, I could have cropped this photo for a closer view of the nymph -- but that wouldn't do justice to its actual size: 2 mm! That's small. By the time these nymphs mature in February and March -- creating the "Hendrickson" hatch -- they will be 8-12 mm, and look something like this (photo taken on 2/17 of this year).
But they really are small at the moment, and I'm pleased that my photos turned out as well as they did.
It was a morning for finding small insects -- as it should be, we're at the beginning of a new season. Here are a few more insects that will mature over the winter and hatch next year in the spring.
1. A free living caddisfly larva, Rhyacophila fuscula. This was 1/2" long at the most; at maturity the larva will be well over an inch.
A mature one in the photo below.
2. Common stonefly, Paragnetina immarginata (I think...), like the E. subvaria mayfly, a taxon I only see in this stream. I found a lot of them: here are photos of two. (The clue to a P. immarginata ID, by the way, is the dark, longitudinal bars that run about 2/3 the length of the femora.)
The largest of these was about 1/2" in length: the mature nymph is 1 1/4 -- 1/12" long -- and much more colorful.
3. Giant stonefly, Pteronarcys biloba.
This is not the first time I've seen giant stoneflies this year, but this is the first nymph that I was big enough for me to ID at sight. Still, this one was "small," a little over 1" in length. At maturity P. biloba nymphs are close to 2 inches. In one of the photos I took, you can see that little E. subvaria spiny crawler: this will give you some sense of how small it was.
4. A small Leuctrid stonefly, genus Leuctra. I don't expect to see these much before winter.
Naturally, I did find some other insects that are still "hanging on" from the season that's now ending up. These included this "humpless" case-making caddis (Brachycentrid) -- Brachycentrus appalachia:
And that little small minnow mayfly that is literally "hanging on" (!) is a still immature Baetis intercalaris. Here's a much better photo.
Finally, there was another small minnow mayfly that, as you can see, is certainly ready to hatch: Plauditus dubius, male.
It was a spectacular, early fall morning in the Rapidan valley. Lots of color -- blues, purples, oranges -- provided by the many flowering bushes.
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