Observed this pair on a trail not here in Clifton but at River Bend park near Great Falls.  

Clif Fairweather, a Naturalist with Audobon Naturalist Society, responded to this post  suggesting “that the little beetle might be taking cantharidin from the blister beetle toincorporate into its own chemical defense” Whatever the intent was of the little beatle attached to larger one it struck me as some sort of strange symbiosis