The visible spectral range for humans, as noted, spans 380–780 nm, covering the wavelengths perceived as color to Homo sapiens. In this range and for this observer, color can be precisely measured and characterized within human perception, enabling studies of variability within a species and potential environmental influences. The vision of arthropods has been discussed in Chapter 5 . Their spectral range can be very different, extending further on either side of the human range, into the UV and/or the near infrared. The study of human vision offers imprecise indications of what the members of arthropods themselves can perceive, as well as their prey or predators. The functions of colors will be discussed in Chapter 7 (Fig. 6.1).