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Records of insects visiting the flowers of Penstemon haydenii (S. Wats.) are supplied. The flower-visitor fauna was different at the two sites censused. Primary pollinators appeared to be four species of megachilid bees which consistently visited the flowers for pollen. While bees exhibited high fidelity to flowers of the genus Penstemon, analysis of the pollen carried by females suggests that crossing over between Penstemon species on a particular foraging trip may be common. Opportunities for interspecific hybridization almost certainly occur.