Table 1.

Glossary of terms used in this review.

Term	Definition
Achromatic stimuli	Visual stimuli that vary only in the total intensity of reflected light.
Actinomorphy	Two or more planes of symmetry; radial symmetry.
Chromatic stimuli	Visual stimuli that vary only in the spectral (wavelength) composition of the reflected light (color).
Color distance	A metric indicative of perceptual color difference between two stimuli in animal color spaces (graphical models based on photoreceptor properties and sensitivities).
Color-opponency	Combination of differential neuronal outputs of color-sensitive photoreceptors to create a signal in the processing of color.
Floral integration	Covariation in flower parts.
Flower constancy	Tendency for an individual pollinator to visit flowers of a single species within a foraging bout.
Geitonogamy	A type of self-pollination, in which a flower is fertilized by pollen from another flower of the same individual plant.
Nectary	Specialized cells that are usually part of a flower, which secrete sugary fluids.
Photopigment	A chemical that undergoes a chemical change when exposed to light. In vision, these are primarily the visual pigments or other opsin-based molecules.
Poricidal anthers	Anthers packed with loose pollen grains, dehiscing by a pore at one end of the thecae.
Trichromacy	A color-vision system based on three classes of color receptors.
Visual acuity	The minimum angular separation between two objects in the visual field that are perceived as distinct, at a given distance from the viewer.
Visual field	The limits of the space around the eyes from which visual information is obtained.
Zygomorphy	A single plane of symmetry; bilateral symmetry; one half of an object mirrors the other half.