Fig. 5.
Sexual dimorphism in J. evagoras: reflectance, color and degree of polarization. (A) Male (left) and female (right) specimen images of J. evagoras. Red circles indicate the approximate patches measured for spectral reflectance. (B) Reflectance spectra of J. evagoras wings for 12 females and 13 males. Spectra were measured on forewings (solid lines) and hindwings (dashed lines) at normal incidence (θ=0) and an oblique detection angle (ϕ=55 deg). (C) Degree of polarization (DoP) in UV (λ=360 nm), as a function of θ+ϕ (‘angular contrast’) for male and female butterflies. Here, θ ranges from −60 to 70 deg and ϕ from 10 to 70 deg, both in steps of 10 deg. DoP is defined as abs[(IH−IV)/(IH+IV)], with IH and IV calculated by integrating the intensity of the butterfly images in Fig. S1 in the polarization photos at certain θ and ϕ. (D) DoP in blue (λ=450 nm) as a function of angular contrast for male and female butterflies. The largest DoP is achieved at angular contrasts of around 120 deg and is slightly larger for the female butterfly under both UV and blue illumination. In B–D, the means and standard error ribbons are plotted for illustration purposes. (E) Jalmenus evagoras wings in tetrahedral color space. The tetrahedral color space represents the relative stimulation of each of the four rhodopsins indicated by the labeled vertexes: ‘u’ for UV, ‘s’ for short wavelength (blue), ‘m’ for medium wavelength (green) and ‘l’ for long wavelength (red) (see Materials and Methods). Points locate individual specimen wing spectra in the color space, and the bounding box denotes locations of specimen spectra in overall color space. Color coordinates of specimen spectra are shown on an expanded scale on the right to show differences between males and females for the forewings (FW) and hindwings (HW); colored arrows indicate the direction of the tetrahedron's vertexes, with magenta indicating UV.