Flowers that appear red to humans are of three types
(Chittka and Waser, 1997). Some species have an
additional peak that stimulates the blue receptor of bees;
for example, the red flowers of Dianthus carthusianorum
L. are perceived as blue by bees, as this species has
a reflectance peak that stimulates the blue receptor of
bees. The red flowers of field poppies (Papaver rhoeas L.)
have a reflectance peak below 400 nm and are perceived
by bees as ultraviolet.