Tuesday, March 29, 2011

Stoneflies: Pictures of How They Change, Pt. I. -- Large Winters

The development traced in this entry is that of the large winter stonefly -- family: Taeniopterygidae, genus Taeniopteryx , and the photo above shows a mature nymph -- probably 1/2" to 3/4" in length-- next to a "beginner" that was found at the end of October last year.  As with the mayflies we've viewed, we will see that as this stonefly grows and matures, it becomes darker, the wingpads lengthen, and the pattern becomes richer and more complex.  This is the large winter genus with "telescoping coxal gills," and as small as that little guy in the picture above was on October 23rd (Buck Mt. Creek), the coxal gills were very clear in a microscope view, and probably could have been seen with a loupe.

10/23: Buck Mt. Creek.

11/20: Rapidan River.  What I'd call a "teenager".  The colors are much more pronounced, the light colored stripe that runs the length of the body is very clear, and the wingpads are starting to edge off to the sides.

12/8/11: Not sure of the stream but probably Buck Mt. Creek.  The bottom nymph is fairly mature; the upper nymph is well on its way -- but note how much less the wingpads are extended in the nymph at the top.  Both nymphs were found on the same day in the same leaf pack.

2/15/11: North Fork of the Moormans.  The coxal gills are so obvious now that they can be seen with the naked eye.

2/20/11: Doyles River.  This one is almost fully mature.  All that remains is for the wingpads to darken.

For the final photo, I do not have a date or provenance, and unfortunately, it's a microscope photo.  But note how black the wingpads have become.  This one is ready to hatch.  We see very few Taeniopteryx large winter stoneflies in the streams past the end of February.

In the next entry, I will look at Strophopteryx large winter stones.

No comments:

Post a Comment