Thursday, April 26, 2012

The Spiny Crawler "Eurylophella verisimilis"

I noted on Tuesday that I was hoping to ID the Eurylophella spiny crawlers that I've been finding to the level of species: it turned out to be pretty straight forward.  All of the Eurylophellas that I've found so far are Eurylophella verisimilis, which, it turns out, is "the most common Eurylophella in the Piedmont and Mountains" (Beaty, "The Ephemeroptera of North Carolina," p. 29).

E. verisimilis belongs to the E. bicolor group (Beaty, p. 28) on which the "submedian tubercles on terga 1-4 [are] relatively short, stout and blunt."  (I couldn't get a good photo of that.)  On the species ID, Beaty says the following:

E. verisimilis -- nymphs 6.8-9.2 mm; this is the only species in the bicolor group with well-developed occipital tubercles; the dorsal tubercles are dark on segments 5-7 (between gills).

Both of those features are easy to see.  (My largest nymphs were 7-8 mm.)

Occipital tubercles:

Dark tubercles on segments 5-7:

The large gills on segment 4 -- operculate gills -- cover and protect the delicate gills on segments 5-7.
This is a nymph that is somewhat tolerant of siltation (TV = 3.9), so the gills must be protected.   Three of the four E. verisimilis nymphs that I've found have been pretty well covered with sand and mud.

This nymph was the one that I found at Powells Creek on Tuesday (4/24).

And I found this one in a small stream in Sugar Hollow on 3/21/11.  (Note the dirt!)

And the most mature specimen that I've seen is this one: Buck Mt. Creek, 6/3/11 (also pictured in the photo at the top of the page.)

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