A simple field method for manipulating ultraviolet reflectance of flowers

It has been difficult to manipulate the ultraviolet (UV) reflectance of flowers independently of other wavelengths to study the response of insect pollinators to this trait. One effective solution is to paint flower corollas with human sunscreen that absorbs UV wavelengths. Honeybees (Apis mellifera scutellata) foraging on the strongly UV-reflecting flowers of Hypoxis hemerocallidea Fisch. & C.A. Mey. rejected flowers that had UV reflectance eliminated by a sunscreen coating, but continued to visit control flowers painted with sunscreen solution that did not contain the UV absorbing compound. The sunscreen technique could be useful for determining the response of a wide range of pollinators to the UV component of spectral reflectance in flowers and could be used to test the functional significance of UV-contrasting nectar guide patterns.