Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 101. (Budapest 2009)

Bálint, Zs., Moser, A., Kertész, K., Biró, L. P. & Parker, A. R.: A supposition: structural colours resulting from both natural and sexual selection on an individual wing in the butterfly genus Cyanophrys (Lepidoptera: Lycaenidae)

64 Zs. Bálint, A. Moser, K. Kertész, L. P. Biró & A. R. Parker INTRODUCTION Members of the neotropical lycaenid butterfly genus Cyanophrys CLENCH, 1

961 (type species: Strymon agricolor BUTLER et DRUCE, 1872) have attracted the attention of biologists due to the stark contrast between their dorsal and ventral wing colourations. The green colour of the ventral wing surfaces is shared by many species, and has been used to imply phylogenetic relationship. The genus was considered to be related to the lycaenid genus Callopbrys BLLLBERG, 1820 (type species: Papilio rubi LINNAEUS, 1758) because it displays the same matt green colour in the ventral surfaces of the wings (

cf. SCOTT 1975: 297). The structures producing physical colour were examined by GHIRANDELLA (1989) also in the species "Thecla herodotus" (= Cyanophrys herodotus (FABRICIUS, 1793)), but the biological role of the colours was not tackled. Later the genera Cyanophrys and Callophrys were considered to be monophyletic on the basis of structural characters ("Callophrys Section" of ROBBINS 2004; in this context see JOHNSON & KRUSE 1997: 5), but the intrageneric relationships within the group remain unresolved (ROBBINS & DUARTE 2005: 413). ROBBINS & DUARTE (2005) recognized 15 species of Cyanophrys during a cladistic revision, using 14 characters provided by the bodies (frons in the head and genitalia in the abdomen) and wings (androconia, shape and venation) of the imagines. In this paper it was mentioned that "exposure to humidity, particularly during preparation, or to physical abrasion can change scale colour from green to brown" (ROBBINS & DUARTE 2005: 400 and 411), suggesting that the colour is structural. Recently KERTÉSZ et al. (2006) revealed the physical properties of the contrasting wing surfaces of a single individual of Cyanophrys remus (HEWITSON, 1868). It was demonstrated that both dorsal and ventral wing colourations are generated by photonic crystal-type structures of the scales that varied in architecture on the nanoscale. The physical mechanism of the colour change from green to brown was also explained, where individual light waves reflected from the various optical interfaces interfere constructively. When one of the two materials in the scale, i.e. chitin and air, changes, i.e. from air to water, the refractive index difference is also changed, and this affects the optical properties of the structure. No publications dealing with Cyanophrys or the optical phenomena generated by wing scales present any data for understanding how synchronic Annls hist.-nat. Mtis. natn. hung. 101, 2009