Differences in ultraviolet wing patterns in the New Zealand lycaenid butterflies Lycaena salustius , L. rauparaha , and L. feredayi as a likely isolating mechanism

The dorsal and ventral surfaces of fore‐ and hind wings in Lycaena salustiu s, L. rauparaha , and L. feredayi were examined under visible and ultraviolet (UV) light. Differences between the males and females of all three species, invisible to the human eye, appear under UV‐radiation. Males of L. salustius exhibit extensive UV‐reflecting regions on the dorsal sides of both wing pairs. On female L. salustius , these UV‐reflecting areas are reduced to tiny submarginal spots. Males and females of both L. rauparaha and L. feredayi are UV‐absorbing. Scales examined under the scanning electron microscope confirmed the correlation between scale‐ultrastructure and UV‐reflectance or absorbance known from other butterflies. The geographical distribution of the sexually UV‐dichromatic L. salustius and either the UV‐absorbing L. rauparaha or L. feredayi (rarely both) overlap, and the latter two are not found together on their own. Therefore I suggest that the UV‐pattern is an isolating mechanism, similar to the one found in the well‐studied American sympatric UV‐reflecting pierid Colias eurytheme and the UV‐absorbing C. philodice . Intermittant “flickers” of UV‐patterns, as generated by beating wings, possibly combined with a certain degree of polarization of the reflected light, provide an insect eye with a powerful stimulus useful in mating and territorial ritual displays.