I poked around for information on Cypripediums and found this study:
'Enhancing the trap of ladys slippers: a new technique for discovering
pollinators yields new data from Cypripedium parviflorum' by Case &
Bradford. The Cypripediums are 'trap pollinators' with the only way out
through a trap door in the back.
The researchers cleverly closed the back door with a paper clip so they
could ascertain who the pollinators are. Here's what they mention in the
abstract: 'Ten species of hymenopteran visitors in the families
Andrenidae, Apidae, Halictidae and Megachilidae were observed, with two
female Andrena tridens and one male Adrena perplexa successfully removing
pollen.' Andrenas seemed to be the star performers. Honeybees need not
I think we'll try this locally this summer; we have a lot of Cyprepedium
> I searched and Illinois Wildflower Society cites that it has been
observed to be pollinated by Andrenoid Bees.