Table 1.

Structural parameters of the multilayer structure of the eight differently coloured areas named from C1 to C8 as shown in figure 1. (The mean thicknesses of the cuticle and air layers, d_c and d_a, respectively, and the maximum number of the cuticle layer N_max within one scale is determined from observations using a TEM. It is found that in several areas (C1, C2, C7 and C8) the number N_max differs, depending on the scale examined. The wavelengths λ_p are theoretically estimated by the interference condition mλ_p=2(n_cd_c+n_ad_a) for the different order m of the optical interference, where the refractive index of the cuticle layer n_c and air layer n_a are assumed to be 1.55 and 1.0, respectively. The wavelengths λ_p are also determined experimentally from the spectra shown in figure 4 except for area C5, where the spectrum of figure 3 is used for the determination.)

area	colour	Nmax	dc (nm)	da (nm)	λp (nm; estimated)	m	λp (nm; experimental)
C1	pale blue	7–8	100	100	510	1	570
C2	pale green	5–6	110	130	601	1	580
C3	orange	6	140	100	634	1	670
					787	1	800
C4	purplish red	6	170	130	394	2	420
					1097	1	1110
C5	green	4	270	130	549	2	545
					366	3	357
C6	dark red	6	160	150	796	1	750
					398	2	420
C7	orange	5–6	140	130	694	1	600
C8	green	5–6	110	110	561	1	590