The associations of phoretic mites (Acarina: Chelicerata) with sand-hoppers (Amphipoda: Crustacea) on the South Wales coast

Mites of the genera Halolaelaps and Phaulodinychus (Gamasida), together with Histiostoma (Acaridida) (Acarina: Chelicerata), occur amongst tidal debris strandlines on the sandy shores of the South Wales coast. Phoretic deuteronymphs of all three mites are dispersed between strandlines via talitrid amphipods (Talitridae: Amphipoda: Crustacea) which provide two principal advantages over the insect hosts used by most other phoretic Acarina. First, amphipods migrate between strandlines throughout the year allowing continual phoretic mite dispersal, and second, even juvenile Talitridae are sufficiently large to transport several mites. The highly aggregated populations of all three mites are distributed independently of amphipod age, sex and species, suggesting that host selection is primarily influenced by other factors. The most likely factors are those related to host behaviour and, in particular, monthly/diurnal quiescence when the mites encounter, and are boarded by, the desiccation-sensitive phoretic mites. The discrete site selection exhibited by each mite species is at least partly influenced by attachment mechanisms.