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J. Eur. Opt. Society-Rapid Publ. 22, 12( 2026)
Figure
6. The visual systems of Calliphoridae species( blow flies), Parus caeruleus Eurasian blue tit, Zootoca vivipara lizard and Vespula vulgaris wasp are all highly sensitive to Lucilia richardsi’ s visual appearance, as shown here in terms of quantum catches. Due to its reflectance peak at 537 nm, L. richardsi’ s colour gives rise to a high absorption by the LWS photoreceptors of the Eurasian blue tit, the blow fly and the common wasp as well as by the MWS photoreceptors of the common lizard.
Figure 7. The photonic structures occurring in Calliphora vicina and Lucilia richardsi’ s cuticle were modelled by multilayer periodic reflectors made of a stack of two different kinds of layers with thicknesses d i and d j, magnetic permeabilities l i = 1 and l j = 1 as well as dielectric permittivities e i = 1.68 2 and e j = 1.55 2 [ 75 ]. The incidence medium and the substrate have, respectively, magnetic permeabilities l inc = 1 and l sub = 1as well as dielectric permittivities e inc = 1.00 2 and e sub = 1.68 2 [ 75 ]. Vector ~ k represents incident wave vector.
Indeed, in TEM images, both kinds of layer are much less contrasted in the middle multilayer than in the top multilayer. The layers in the middle multilayer have therefore a more homogeneous electron opacity than in the top layer. The materials in these layers could be relatively similar, with a weak refractive index contrast. For C. vicina, the 98-nm and 20-nm layers were assigned refractive indices( RI) of 1.68 and 1.55, respectively; for L. richardsi, the 78-nm and 82-nm layers were assigned RI values of 1.68 and 1.55, respectively. These dispersionless values are good compromises between published values for butterfly scales and beetle cuticle [ 76 – 80 ] and correspond to the RI measured in the layers of Chrysochroa rajah beetle [ 80 ]. The RI of the incident medium and the substrate were taken equal to 1.00 and 1.68. The same structural models were used for both reflectance spectra and photonic band structures. However, for the calculation of the photonic band structures, the number of bilayers was assumed infinite. The simulated reflectance spectra and photonic band structures( Fig. 8) are in accordance with the experimental results. In the case of C. vicina and L. richardsi, the simulated reflectance peak and photonic bandgap( PBG) are located at 395 nm and at 517 nm at normal incidence, respectively. Both results are in accordance with the experimental results( experimental errors are smaller than 10 %). Both the simulated reflectance peak and PBG blue-shift to 337 nm and to 436 nm at grazing incidence, for C. vicina and L. richardsi’ s models, respectively. The predicted weak oscillations in the reflectance spectra are due to Fabry-Pérot interferences. They are related to the total multilayer thicknesses. They are not observed experimentally since the multilayer interface are not perfectly parallel in the actual dipteran cuticles and the multilayer