Foraging insects can see wave-lengths that flowers reflect (ranging from 300 nm to 700 nm[14][15]). Pollination being a mutualistic relationship, foraging insects and some plants have coevolved, both increasing wave-length range: in perception (pollinators), in reflection and variation (flower colors).[3] Directional selection has led plants to display increasingly diverse amounts of color variations extending into the ultraviolet color scale, thus attracting higher levels of pollinators.[6]