Fig. 4. (A,B) Deilephila-based relative quantum catches for the five different stimuli viewed under various sunset, twilight and nocturnal illuminants. Filled circles represent quantum catches of stimuli at sunset and twilight (solar elevation from 11° to –11°). Solar elevation decreases as data moves from right to left. Quantum catches under the nocturnal illuminants are to the right of those for sunset and twilight and consist of the following: open circles, quantum catches of stimuli under full moonlight; open triangles, quantum catches of stimuli under light polluted night sky; asterisks, quantum catches of stimuli under starlight only. (C) Quantum catches of the five stimuli assuming that D. elpenor has von Kries color constancy and is adapted to a background of green leaves under each illuminant (hence the central location of all the green stimuli). With the exception of light-polluted night skies (triangle), all the data have the same symbols for clarity.