Thursday, February 9, 2012

The New Kids on the Block: Nemourid Stoneflies and Small Minnow Mayflies

Just back from Buck Mt. Creek where I continue to find more and more signs of "late" winter -- on February the 9th!!  In my short visit this morning, I found a significant number of small minnow mayflies again, Heterocloeon amplum,  quite a few spiny crawlers (E. dorothea), and a fair number of Nemourid stoneflies -- genus Prostoia -- as in the picture above.  There are still winter insects around -- large winter stoneflies (but I'm only seeing Strophopteryx fasciata, no Taeniopteryx burksi), small winter stoneflies (a small  Allocapnia species), and Clioperla and Helopicus Perlodid stoneflies.  But these winter stoneflies have really diminished in number, and the new kids are taking over the streams.  The other late winter insect that is showing up in large numbers is the Perlodid stonefly, Isoperla namata (which I also found this morning in Buck Mt. Creek).

I'll just post a few photos today.

1. Some more shots of these little Nemourids (Prostoia nymphs are 5-6 mm in length, and this one was close to 6):

2. One of several small minnow mayflies that I picked up, close to 9 mm in length.

3. And one of several Ephemerella dorothea spiny crawlers.


Two comments:  1) Not only am I now finding large numbers of mayflies and stoneflies that I think of as insects that should show up later on, but some of them are already "big."  Note the length of the wing pads on the small minnow in the photo above (and in the photos I posted on Tuesday), and the length of the wing pads on this spiny crawler.  2) The small minnow mayfly in the photos above is a "female," something we can tell from the size of the head and the eyes.  The one that was featured in my last entry was clearly a male.

Adult, terrestrial males, use their large eyes to pick out the females in mating swarms.

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