Figure 1

For illustrative purposes the O. cacaliae (green phenotype) beetle shown here was manipulated by painting the right-hand side elytron only with a matt clear-coat varnish. One square on the background paper represents 1 mm². In the experiment, the whole beetle was either painted or left untouched (see section 2(c)). A beetle was photographed from above with the incident light (light source) positioned at an elevation of 80° (red arrows indicate the direction of the light) and an azimuth of 180° from the beetles head. The beetle was positioned with its posterior towards the light source (a) and then with the right (b) and the left (c) hand sides facing towards the light. Note the specular reflection does not appear or is greatly reduced after manipulation (left side of beetle in panel b). The elytra appear almost matt black when not in favourable lighting geometries suitable to reflect light. (d) Standardized (between zero and one) average reflectance of three manipulated (dark green line) and non manipulated (light green line) beetle elytra (black dotted lines represents ± standard deviation) measured in their maximum reflectance angles. (e) Reflectance spectrum of the green background placed in the petri dishes used during the behavioural assays (f). Reflectance spectrum of a green leaf.