Unearthing the overlooked inhabitants of ant nests: mites (Acari) associated with the ants (Formicidae) of Ohio

Ants (Formicidae) have long been an insect group of great interest to the scientific world, whether for their ecological roles, feeding strategies, or social behaviors. They form complex colonies, harboring resources that can potentially be exploited by myrmecophiles (organisms living in association with ants). Myrmecophily has been studied in detail for Coleoptera, but mites (Acari), the most frequent of ant guests, remain largely unstudied. Previous work has focused primarily on descriptions and has provided little ecological information. This study provides a robust list of the mite inhabitants of ant nests focusing in Ohio and ecological factors influencing their diversity. A survey of Ohio ants was conducted from April 2008-March 2010. Phoretic mites were individually removed from ants and debris from 273 colonies. Mite collections totaled 198 morphospecies: 151 species phoretic and at least 47 mite species in non-phoretic relationships within the ant nests. Phoretic mites consisted of representatives of the cohort Astigmata (Histiostomatidae, Acaridae), the cohort Heterostigmatina (Scutacaridae, Pygmephoroidea), and the suborder Mesostigmata (Laelapidae, Uropodina). Most phoretic mite species were host specific and attachment site specific. An unusually large number of mite species were found to be associated with the ant genus Lasius, possibly the result of social parasitism. Statistical analyses show significantly greater mite diversity in colonies when 1) in the ant subfamily Formicinae, 2) the colony is in the woods, 3) the nest substrate is wood, 4) the colony is populous, 5) the ants are large, and 6) the ant species establishes its nest parasitically.