Ripiphorus rex has distinctive conical projections, or "coxal processes", emanating from the inner bases of the fore-legs that are densely hairy. There are also smaller such coxal processes at the bases of the mid-legs (see Champion's original description). In this photo, on the beetle's left side (i.e. to the right in the photo), the tips of both the fore- and mid-coxal processes are subtly visible as tufts of pale-yellow hair against the black underside of the beetle. [See full-size image, and look a little more than an "eye's-length" directly below the eye on the right (i.e. the beetles left eye :-)]

Moved from Ripiphorus.

Moved from ID Request.