All else being equal red and striped flowers attract more bees, at least in snapdragons.
Nuffield Bursary students spent successive summers observing the foraging patterns of bumblebees on snapdragon plants grown on a plot near Norwich. The students compared the number of visits by bumblebees to various cultivars of the common snapdragon and the number of flowers visited per plant. Red flowers and those with venation patterning were visited significantly more frequently than white or pink. More flowers were visited per plant too.
“Stripes provide a visual guide for pollinators, directing them to the central landing platform and the entrance to the flower where the nectar and pollen can be found,” said Professor Martin.
“We examined the origin of this trait and found that it has been retained through snapdragon ancestry. The selection pressure for this trait is only relaxed when full red pigmentation evolves in a species.”
Bumblebees are the main pollinators for snapdragon because the weight of the bee is needed to open the closed flower. Pollinators learn and memorize floral signals, such as flower shape, scent, colour and patterns of pigmentation. They return to flowers from which they have previously found food. Simple changes due to single gene changes can have dramatic effects on which pollinators visit and how often.