Fig. 1. (A) The spectrum of the white cage illumination without filters. (B) The transmission of Schott filters FG-3 (blue) and FG-13 (yellow). (C) Reflectance of colours used in the first multiple-choice experiment with D. elpenor (experiment 1). Blue (b), blue-green (bg), green (g), violet (v) and blue-violet (bv). (D) Reflectance of colours used in the second multiple-choice experiment (experiment 2). Yellow (y), yellow-orange (yo), orange (o), dark green (dg) and light green (lg). (E) Reflectance of green, turquoise and lime used in the dual-choice experiments with D. elpenor and M. stellatarum (experiments 3-5). (F) The sensitivity curves of the ultra-violet (UV), blue (B) and green (G) receptors of Deilephila elpenor. The curves were calculated from the recorded sensitivity maxima (Höglund et al., 1973) using the Stavenga-Smits-Hoenders rhodopsin template (Stavenga et al., 1993) and normalised in such a way that the integrals equal 1.