Thanks so much, Edward, for adding the additional 5 wonderful(!) images!! They show the detail I was hoping for, and are in many ways are much more clear and easy for me to study than the real specimens I was working with recently!

After seeing your 5th and 7th images above, I'm more confident now that what I was seeing in my image below...

...is indeed the "hairy elongate projection on the inner side of the front coxae" that Vaurie(1) was referring to. I've made two labelled crops of your 5th and 7th images to indicate what I believe are the locations of the coxa and trochanter, see thumbnails below:



So your images really helped resolve my doubts about "where the coxa is" on these Ripiphorus. (Though I still may be in error...I now think that's less likely :-)

However, the issue of how to clearly and cleanly distinguish R. rex from R. vierecki seems as murky as ever to me. I'll comment on the forum post when I get a chance. Until then, if you have a decent chunk of time, you may want to peruse the recent posts I made of Ripiphorus specimens seen during a visit to the Cal Academy last Friday afternoon. The commentary is long! (I apologize for my loquacious posts...but that's my nature :-)

By the way, I also want to express my unabashed awe at the amazing detail and focused resolution of your images here! As well as my appreciation for the significant amount of careful effort, skill, and time that must go into setting up the equipment, the specimen (the lateral pinning technique is quite nifty...allows for a less encumbered ventral view!), the spacings of the many(!) different images, and the post-processing of all those images. Thank you for sharing your wonderful work. Bravo! :-)

(And last but not least...nice bug huh! Glad you found it :-)