I'm amazed that this photo turned out so well. This large winter stonefly nymph was 1.5 mm long, and it was -- still is -- a dark, cloudy morning! I'm really pleased. (I did add some light with a small LED flashlight.)
In addition, I had to wait a long time for this nymph to get into position. For the first 20 minutes, it stayed curled up in a ball -- which is the large winter's favorite pose. This.
But, success. By January, of course, I'll be thoroughly sick of seeing these things, but finding the first one is always a thrill.
The species? Taeniopteryx burksi, one of three large winter species that I've found in our streams (we'll see the other two before very long: Strophopteryx fasciata and Taenionema atlanticum). Like the small winter stoneflies (Capniidae), large winter stoneflies (family name, Taeniopterygidae) grow up in a hurry. Here is a sequence of stages from photos that I took last year.
11/2/11: Still very small but colors and patterns are more developed.
11/17/11:
11/25/11: Note that the wing pads have started to curl (back edge).
12/13/11: Fairly mature. Wing pads are fully developed.
1/5/12: Fully mature. Wing pads are black.
2/6/12: Another one that's ready to hatch.
Most of these nymphs -- this species -- mature and hatch in January and February. It would be unusual to see one in March. Groups that don't monitor their streams in the winter never get to see them.
_______________
Taeniopteryx burksi, from p. 8 in Steven Beaty's "The Plecoptera of North Carolina," p.8.
Genus Diagnosis: Nymphs have a single telescopic gill (sometimes retracted) on the coxa of each leg; complete dorsal cercal fringe; some species have a median dorsal stripe.
T. burksi -- male nymphs 8.7-9.5 mm, female nymphs 10-12 mm; femora almost entirely light; light dorsal abdominal stripe bordered by dark stripes; light stripe continues onto head to the epicranial suture; terga with slender bristles and posterior margin with short blunt setae and the occasional long hair; cerci half as long as body with proximal third dark and the remainder yellow.
We can't see all of these features on the tiny nymph that I found this morning -- but we can see some.
Two pairs of the coxal gills are actually visible in one of my photos. They're creamy white, finger-like projections, and note that they're fairly long. (Actually, if you look closely at the photo at the top of the page you can see gills sticking out between the second and third pair of legs.)
Also, while we cannot yet see the light stripe on the abdomen of this nymph, the part that extends to the head is clear, as is the epicranial suture.
But for a good look at the critical T. burksi features, let's have a closer look at more mature nymphs from last year.
ventral view: coxal gills
dorsal view: femora, abdominal stripes, epicranial suture, long cerci that are dark at the base and yellow at the tips.
T. burksi is a large winter stonefly that we see in a lot of our streams. With a TV of 6.6, it's fairly tolerant for a stonefly. Still, it's a beautiful insect, and I'm so glad that the large winter season has finally started.
(For stream monitors -- three features to look for to help with ID on these very small nymphs: 1) they tend to be short: head is wider than the abdomen; 2) the antennae are long and very thick at the bases (pedicels); 3) the body is "freckled," "spotted".)
No comments:
Post a Comment