This ripiphorid was found by Emily Coin during the 2nd day of the AZ BugGuide Gathering. It was nestled amidst the foliage of a clump of mule-fat (
Baccharis salicifolia) in the Santa Cruz River wash. It's the same individual as in Alice's post below:
The monopectinate antennae clearly indicate it's a female. Alice, in her post, noted the mass of eggs within the curled leaf just below the ripiphorid...also visible here as a white blur. I don't know for sure whether those eggs were laid by this beetle, but my photo was taken shortly after Alice's, and I think I can see more eggs in my image than I can see in Alice's...though that may just be a result of the different angle. It's of interest that Zack Falin's detailed discussion of Ripiphoridae in
(1) includes remarks on
Macrosiagon stating "eggs are laid on undersides of leaves, in crevices in soil, and on flowers of Asteraceae" (see bottom of page
here). The beetle flew off soon after I snapped two quick photos. I don't think any of us noticed the eggs at the time...as we were distracted in trying to track our fleeing quarry.
I ran this ripiphorid through the keys in Rivnay
(2)(1929), Vaurie
(3)(1955), and Linsley & MacSwain
(4)(1951) and cross-referenced with the discussions there, the description
here, and resources elsewhere. Based on studying those ref's, and BugGuide images and comments, I'm fairly confident this is
Macrosiagon pectinatum. The rounded vertex and black head here rule out
M. sayi...in that species females have red heads; the vertex is truncate; and (key character) the distal end of first segment of hind tarsus is produced...or obliquely truncate...depending on the angle of view (see Fig. 18t
here).
Rivnay (1929) listed
numerous synonyms for
M. pectinatum, and Vaurie
(3)(1955), Linsley & MacSwain
(4)(1951), and Falin
(1) emphasize that
M. pectinatum is a highly variable species...or likely a "species complex" that will eventually be sorted into more than one taxon.