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Photo#714945
Much smaller than R. vierecki  - Ripiphorus - female

Much smaller than R. vierecki - Ripiphorus - Female
Marana, Pima County, Arizona, USA
October 14, 2012

Images of this individual: tag all
Much smaller than R. vierecki  - Ripiphorus - female Much smaller than R. vierecki  - Ripiphorus - female Much smaller than R. vierecki  - Ripiphorus

Unusually pale-translucent elytra
From the look of the elytra, I wonder if this may have been a recently eclosed ("teneral") adult. It's a female, from the pectinate antennae (see Ripiphorus info page for details).

As far as ID goes, using the key on pg. 42 of Rivney(1), characters of the hind tarsi and abdominal coloration take this specimen to the californicus species group. The key to the californicus species group on pg. 56 of Rivney(1) leads to R. mutchleri. The description in Rivney(1) fits well (except "front legs yellow", and elytra yellow...but it looks like perhaps the elytra color hadn't "set-in" yet). The key in Linsley & MacSwain(2) likewise leads to R. mutchleri.

The size of female R. mutchleri is given as 5-7mm in Linsley & MacSwain(2), which is much smaller than that of female R. viereckl, at 9-11mm.

 
You may be right about the elytra color
did you see the male that I caught (not in copula) with the females?
his legs are all yellow and the elytra are kind of yellowish

 
Not sure about the male in thumbnail post above
I posted a more detailed comment under that image.

But the short story is: That male would seem to go to the faciatus group rather than the californicus group...where R. mutchleri lies.

So, at least going from the literature, the male in that companion post would seem to be a different species than the female here. Of course, that supposition may be more a consequence of our ignorance and/or lack of a clear understanding of the genus than of fact.