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black and orange beetle - Ectopria nervosa - female

black and orange beetle - Ectopria nervosa - Female
Groton, Middlesex County, Massachusetts, USA
July 17, 2009
Size: ~4mm

Moved from Beetles.

Psephenidae: Ectopria nervosa
it is.

hmm... isn't bicolored pronotum diagnostic for E. thoracica?
must be a girl

I was
surprised by the appearance of E. thoracica, as it has been in synonymy of nervosa for ca. 100 years. I finally got around to tracking down the basis upon which it had reappeared. Warren Brigham alluded to these being different in the Carolinas Aquatic Manual (1981), and in his description of E. leechi (also 1981) separated thoracica from nervosa based on color pattern of the pronotum and features of the genitalia, without formally removing thoracica from synonymy and without providing any illustrated comparative features. The only other direct reference to these two as separate species was by Hilsenhoff & Schmude in their treatment certain aquatic beetles families of Wisconsin.
Anyone who has many specimens of nervosa/thoracic should be a bit squeamish in using the pronotal color patterns, as they seem to blend seamlessly with enough material - it is NOT black and white (or black and orange) feature. With this in mind I dissected the male genitalia out of a series of specimens from NH, ME, and PA ranging from completely black to strongly bicolored pronota. The genitalia appeared to me to be identical, and the length/width rations were all similar - centered on 0.4X times as wide as long (interestingly higher than the highest value that Brigham gave, .32X, which was for E. nervosa, and much much higher than for "thoracica" (0.26X). The subapical callosities of the parameres seemed to be strongest for two bicolored individuals, and not for the all-dark "nervosa" form as stated in Brigham's key.
Perhaps there is another species with very narrow genitalia present, but with the devaluation of the pronotal color pattern and the uniform proportions of the genitalia of our material in the Northeast, I will still go with Ectopria nervosa as the correct name for our area until much better supported statements are developed.

sounds convincing -- thanks for the exposé, Don.
i moved all the northeastern thoracica-like images to this page

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