Hummingbird flower mites (Rhinoseius Baker & Yunker and Tropicoseius Baker & Yunker, and certain Proctolaelaps Berlese species; Acari: Mesostigmata: Ascidae) feed on nectar and pollen, mate, and oviposit in the inflorescences of hummingbird pollinated plants and are phoretic in the nasal cavities of hummingbirds. Unlike many phoretic mites, males as well as females of most of these species disperse on the phoretic host (hummingbirds). Theory suggests that male dispersal may increase mating success in species in which breeding groups are small and males can seek groups with a more favorable (more female-biased) sex ratio by dispersing, a process we call sexual sorting. Laboratory experiments in which mites were confined to a lattice of interconnected capillary tubes, some with nectar present to simulate flowers, showed that both Proctolaelaps kirmsei Fain Hyland, & Aitken and Proctolaelaps sp. nov. #1 from La Selva, Costa Rica, demonstrate significant sexual sorting. Field census data from the same site for P. kirmsei showed that, consistent with theory and the laboratory results, sexual sorting also occurs in nature among incipient mite breeding groups on inflorescences, when these groups are small.