David :
You wrote : "Also in northeast Tennessee, Bletialla striata is also found to be commonly pollinated. I've never seen bees or butterflies on the flowers but have noticed ants on them. Perhaps this is the pollinater?"
In An Atlas of Orchid Pollination - America, Africa, Asia and Australia, Cingel indicates :
"Bletilla striata...
Ishiwaka & Tanaka ... (1995) have recorded honey bees, Apis mellifera, to visit and take away pollinia.
Sugiura (1995) observed 26 species of hymenopteran, dipteran and lepidopteran visitors on the flowers in Kobe ...
The flower is nectarless and the species seems to deceive by food deception of a generalised character. Seven species of aculeate Hymnoptera were able to pollinate because of their body seize [sic] fitting the space between column and labellum. From the bees with appropriate size (i.e. intermediate) male longhorn bees, Tetralonia nipponensis, were the most effective ones, by abundance of visitation and legitimate intrafloral behaviour. The females of this species and the other six bee visitors contributed to a lesser extent, because of lower visiting frequency, as well as by grooming and thus removing pollinia. Mean fruit set was near 25% for individual scapes, with 20% bearing no fruits at all." (p. 189)
Well, Japan is not Tennessee but I would suspect that bees might also be pollinators for Bletilla striata in your part of the world.
Regards,
Viateur
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