We examined structures of acarinaria and phoretic mite faunas of the large carpenter bees Xylocopa amamensis, X. flavifrons, X. albinotum, and X. ogasawarensis from Japan, and compared them with those of X. tranquebarorum and X. ruficeps from Taiwan. While the first three Japanese Xylocopa bees had acarinaria both on the mesosoma and on the first metasomal tergum like the common Japanese large carpenter bee, X. appendiculata circumvolans, X. ogasawarensis did not have distinctive mesosomal acarinaria. Xylocopa tranquebarorum, which nests in bamboo, did not have either kind of acarinarium. Of the species examined, only X. ruficeps had a distinctive metasomal acarinarium, which was a deep, round cavity that opened on the first metasomal tergum. All mites except for Dinogamasus were collected from host's mesosoma, wing base furrows, mesosomal acarinaria and the metasomal acarinarium. We collected mites of two Sennertia spp. (alfkeni, japonica) and Horstia helenae from the Japanese bees. The Taiwanese bees also carried Sennertia and Horstia mites but probably of different species. Only X. ruficeps carried mesostigmatid mites (Dinogamasus sp.) in the metasomal acarinarium. We suggest that Sennertia deutonymphs are well adapted to be phoretic on the large carpenter bees with specialized body structures such as attachment organs and hook-like pretarsal claws as seen in other astigmatids phoretic on bees. In contrast, putatively beneficial mites, such as those of the genus Dinogamasus, have possibly been specialized to settle in the distinctive acarinaria in the course of mutualistic evolution with the host.