In their Holly monograph, G. F. Peterken and P. S. Lloyd stated:
Entomophilous. Apis mellifera L. is the commonest insect visitor, but the following bees have been observed in southern England (O. W. Richards): Andrena wilkella Kby. (Andrenidae), Osmia rufa L. (Megachilidae) and Bombus lucorum L. (Apidae). B. lucorum and syrphid flies have been seen at the flowers in northern England. Nectar is secreted from tissue at the base of the ovary.
A honeybee visiting the flowers.
An Red Mining bee at the left of the flowers with scopa full of yellow holly pollen