My main research interests are in the systematics and evolution of mites. Within the general area I have migrated from trying to understand the quite specific host associations in sarcoptid mange mites, to biogeographical patterns in ticks, to basal systematics of the entire order Parasitiformes. I try to approach these questions from several directions, combining morphological and molecular data sets in order to develop well corroborated hypotheses. More recently I have started some projects on diversity of soil Mesostigmata in Ohio as well as in Southern Mexico and Belize.

In addition I am also co-organizer of the Acarology Summer Program, one of the world's premier training programs in systematic acarology.