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Fig. 2. Maxwell's triangle of D. elpenor. The corners of the triangle
represent colours that excite only one of the three receptor types (UV, B, G).
Loci within the triangle represent colours exciting all three receptor types.
The line with wavelengths represents monochromatic colours in the colour space
of the hawkmoths. For calculation of colour loci, see text. Diamonds, colour
loci under white illumination; open circles, loci under yellow illumination;
triangles, colour loci under blue illumination. (A) The loci of the colours
used in experiments 1 and 2. The lines connect the same colour loci under the
different illuminations. In experiment 1, the loci are very close and do not
change much between the white and blue illumination. (B) The turquoise (T),
green (G) and lime (L) colours were used in dual-choice tests under white (Tw,
Gw, Lw; filled diamonds) and yellow (Ty, Gy, Ly; open circles) illuminations.
y marks the locus of the yellow illumination.