Sunflowers provide excellent forage for native bees. These ubiquitous, road-side beauties attract bees such as this long-horned bee (Mellisodes sp), but also a number of different insect which feed on the petals and pollen. You can actually see some petal damage on the right side of this flower. How these other insects affect pollinators and the plant are still relatively little studied.
I am a researcher at CU-Boulder leading a USDA funded project looking at native bee diversity in agricultural landscapes of eastern Colorado. Please enjoy your visit and contact me if you have any questions.