either Bombus bimaculatus or B. griseocollis female - Bombus griseocollis -
Pella, marion County, Iowa, USA May 20, 2016 Size: 20-28 mm
infrequent visitor to Baptisia minor and B. australis. Hair on metasomal segment 2 or 3 seems worn off but narrow like that of B. bimaculatus but also appears brown as in B. griseocollis