Beard tongue flowers have a large, hairy staminode on the lower half of the tubular flower which restricts access to bees to the flower and helps in pollen deposition. Small to medium sized bees are the most frequent visitors.
Tall Beard Tongue flowers can be white to light pink, sometimes with darker pink to purple stripes which act as nectar guides for bees.
Small Carpenter Bees (Ceratina spp.) visit Tall Beard Tongue flowers primarily to feed on pollen. Their small size allows them to easily climb over the staminode into the tubular flowers to access the pollen on the anthers.
As they feed on pollen, they often inadvertently contact the stigma. The hairs on the staminode keep their bodies held closer to the stigma, resulting in more contact and pollen transfer.
Look for small holes chewed at the base of the flower. Mason Wasps will chew holes to reach the nectar reward without having to enter the flower. Smaller bees will take advantage of these nectar thievery holes.
Attracting Native Pollinators: The Xerces Society Guide, Protecting North America's Bees and Butterflies
The Interaction between Pollinator Size and the Bristle Staminode of Penstemon digitalis (Scrophulariaceae) Gregg Dieringer and Leticia Cabrera R. American Journal of Botany , Vol. 89, No. 6 (Jun., 2002), pp. 991-997