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The status of the genera in the small microtrombidiid mite tribe Hexathrombiini is reevaluated. Type specimens representing all genera were studied and diagnostic characters for Hexathrombiini are reviewed, summarized, and new data and a key to the genera in the tribe are provided: Alhamitrombium, Beronium, Hexathrombium and Hoplothrombium. Hexathrombium is the most speciose genus in the tribe and species recorded from South America are compared, as well as those with a divided pygidial plate. A provisional key to species assigned to Hexathrombium is provided. Finally, Hexathrombium abirami was captured in Peru parasitizing a bright metallic tiger beetle (Tetracha fulgida). A total of 361 larvae were removed parasitizing a single carabid host; this is the highest load of parasites reported in terrestrial Parasitengona mites associated with arthropods. This capture represents a new record of Hexathrombiini mites for Peru. A redescription of He. abirami using all specimens available to date is included.

An unusually large acariform mite is described as Immensmaris chewbaccei gen. et sp. nov. from the Cretaceous (ca. 100 Ma) Burmese amber of Myanmar. With an idiosoma plus gnathosoma more than a centimetre long, it represents the largest unequivocal fossil mite ever recorded and approaches the maximum size of the largest living Acariformes today. Although some details of the dorsal idiosoma are equivocal, the new fossil appears to belong to Smarididae (Prostigmata: Parasitengona: Erythraeoidea) and also represents the largest erythraeoid mite ever discovered, indicating a clade of giant, possibly arboreal, mites in the Late Cretaceous of southeastern Asia.