Macrocheles mycotntpetes and M. peltotrupetes K. and M. were found to exhibit marked specificity in choice of scarab ’hosts’ when provided with a variety of candidate species in the laboratory. Overwhelming preference of the mites for their natural geotrupine associates (Mycotrupes gaigei Oison and Hubbell, Peltotrupes profundus Howden and Geotrupes egeriei Germar) over non-geotrupine candidates was illustrated in their initial olfactory responses, boarding and pre-attachment behavior, and in choice of final attachment sites.