This rhipiphorid was found on a hot afternoon in high-desert sagebrush scrub habitat. It's clearly a female, from the mono-flabellate antennae...and the behavior. It was ovipositing into flower heads of rabbitbrush, Ericameria nauseosa (= Chrysothamnus nauseosus). Looking closely, one can discern that the sharply-tapered posterior portion of the abdomen is bent nearly 160° forward, and is being thrust into the interior of a flower bud. This is typical behavior for female rhipiphorids, whose hatched larvae then wait for a visiting bee to "board" and ride with back to the bee's nest...where they parasitize the brood.

This female, though engrossed in her task, was nevertheless quite alert...and unfortunately she darted off too soon (i.e. before I could get better pictures from more angles, and call out to my field companions so they could see her). However, I had a pleasant surprise when I pulled up the literature to ID this one...because it turned out to be one of the relatively few Rhipiphorus that are straightforward and unambiguous to key to species! From Linsley & MacSwain(1)(1951), diagnostic characters for the female are:

1) First segment of posterior tarsus obliquely truncate at apex, usually elevated and shorter than following segments combined.2) Head and thorax dark, abdomen wholly or partially reddish or yellow.3) Antennae ten-segmented; pronotum, except smooth areas, very densely punctate; posterior tarsal claw with seven inner teeth. 5-8 mn.
The truncate hind-basitarsus is clearly visible in my 1st and 3rd images...and of course the black head & thorax vs. the yellowish-red abdomen are strikingly evident in all the photos. But (again, satisfyingly unequivocal for a Rhipiphorus ID!) the antennal character is a clincher: you can clearly count 8 antennal flagellomeres (each with a single conspicuous flag-like "ramus") in most these images, and together with the (less conspicuous) pedicel and scape...that gives 10 antennal segments.

For additional supporting characters, I consulted the original description of Rhipiphorus epinominae in Linsley & MacSwain(1950) [available online...scroll down the column at right on this web page to select the 3rd-to-last paper]. Therein the authors indicate: "elytra uniformly straw-yellow, apices broadly rounded; wings lightly infuscated from middle to apex, more heavily so along subapical fourth of anterior margin". The only obvious discrepancy with the description I notice here is "Legs brown to yellow-brown"...which I'm guessing may be attributable to the the author's use of non-fresh specimens as the basis for their diagnosis (rather than live material, as in the photos, where the legs are more vibrantly black). I'm guessing the legs may age to look more brownish (or leg color may be variable?).

While most the R. epinomiae material listed in Linsley & MacSwain(1950/1951) in from farther south in California (i.e. eastern Riverside and Imperial Counties), it's reassuring that one record is given for a female from Hot Creek, Mono County on August 1, 1936. That locality and date (modulo the year!) are nearby in space and time.