Wednesday, June 1, 2016

The spiny crawler Drunella cornutella: lots of them today at the Doyles

I noted in my last entry that I should stick to the small mountain streams for awhile: should have done that today.  The Doyles River at Blufton Road was high -- and actually a little off color.  Consequently, a lot of the insects I found were covered with silt, though it is true, Drunella nymphs are often that way when I find them.  Must be where they live.

The spiny crawler in the photo above is Drunella cornutella.  It's one of three species we have in our streams -- the other two, D. walkeri and D. tuberculata -- but it's the one we most commonly see in late May and June.  I netted four of them today in the short time that I worked in the stream, two of them already mature -- black wingpads.

Drunellas are easy to spot, those muscular fore femora give them away.  For D. cornutella, let me turn to Steve Beaty's "The Ephemeroptera of North Carolina."  "D. cornutella -- nymphs 6.4-8.5 mm; head smooth with moderately long lateral frontoclypeal projections but less than half as long as the distance between them; median ocellar tubercle blunt to moderately sharp; femora with dense row of long, fine setae on posterior margin; ratio of mesotibia to mesofemur <0.85; abdomen without paired dorsal tubercles. Collected in spring through early summer.  Common."

The nymphs that I found were 7-7.5 mm.  We can see the critical features for the cornutella ID in a single microscope picture.  Also clear in that photo,  the tubercles on the front edge of the forefemora that signal the genus ID.


Back to the small streams tomorrow.

Oh.  Also a lot of Perlesta stoneflies around.

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